MANUAL OF PHOTOGRAPHY. 
 
MANUAL 
 
 OP 
 
 PHOTOGEAPHT 
 
 INTENDED AS A 
 
 TEXT BOOK FOR BEGINNERS AND A BOOK OF REFERENCE 
 FOR ADVANCED PHOTOGRAPHERS. 
 
 Br 
 
 M. CAREY LEA. 
 
 SECOND EDITION, 
 
 KP] VISED AND ENLARGED. 
 
 PHILADELPHIA: 
 PRINTED FOR THE AUTHOR 
 1871. 
 
Entered according to Act of Congress, in the year 1871, by 
 M. CAREY LEA, 
 in the Office of the Librarian of Congress, at Washington, All rights reserved. 
 
 PHILADKLPHIA : 
 OOLLINS, PRINTEK, 706 JAYNE STREET. 
 
 / 
 
• 
 
 PREFACE TO THE SECOND EDITION. 
 
 In preparing a second edition of this manual, rendered necessary 
 by the early exhaustion of the first, the author has endeavored as 
 far as possible to include all the information useful to the working 
 Photographer. A very considerable portion of the matter in the 
 first edition has been cancelled and rewritten, and over a hundred 
 pages have been added, so that fully one-half of the book is new. 
 The number of engravings has been also nearly doubled: all 
 have been engraved expressly for this manual, and, with two or 
 three exceptions only, all have been made from original drawings 
 of the author. 
 
 The present edition also contains the results of several trains 
 of investigation by the author, hitherto unpublished. Some of 
 them he hopes will be found of material practical importance, 
 especially those relative to "permanent" printing-paper and to 
 water-proof negative varnishes. The arrangement adopted in the 
 first edition has been continued in this. The first part gives a 
 short and clear course of instruction for beginners. In the 
 subsequent parts the various subjects are treated of in detail. 
 
 June, 1871. 
 
CONTENTS. 
 
 PAET I. 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 PAGE 
 
 CiiArTER I. Selection of Materials . 9 
 
 II. Making the Negative 17 
 
 III. Printing 44 
 
 IV. General Rules for Beginners 47 
 
 PART II. 
 
 PHOTOGRAPHIC OPTICS AND THEORY OF PERSPECTIVE. 
 
 CirAPTEK I. General Optics 52 
 
 II. Of Lenses 56 
 
 III. Faults incident to Spherical Lenses . . • . . . 58 
 
 IV. Focal Lengths of Lenses 66 
 
 V. Photographic Objectives 78 
 
 VI. Photographic Perspective 97 
 
 PART III. 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 C}{APTEE I. The Dark Room 107 
 
 II. The Glass Room 114 
 
 III. Pyroxyline and Collodion 126 
 
 IV. The Negative 147 
 
 V. Ambrotypes and Ferrotypes 188 
 
 VI. Portraiture 190 
 
 VII. Landscape and Architectural Photography .... 208 
 
VIU 
 
 CONTENTS. 
 
 t 
 
 PAGE 
 
 Chap. VIII. Composition 234 
 
 IX. On Copying 251 
 
 X. The Stereoscope 256 
 
 XI. Micropliotograpliy and Microscopic Photography . . 258 
 
 XII. Development on Paper 260 
 
 XIII. Silver Printing 269 
 
 XIV. Failures in Photographic Operations 301 
 
 XV. Out-door Photography 344 
 
 XVI. Dry Plate Photography 351 
 
 XVII. Dry Processes 364 
 
 XVIII. Negative Varnishes 375 
 
 XIX. Treatment of Residues 379 
 
 XX. Photography on Glass and Enamel, and Collodio-Chloride 
 
 Printing, &c 383 
 
 XXI. Carbon Printing 898 
 
 PAET IV. 
 
 THEORETICAL CONSIDERATIONS. 
 
 Chaptee I. General Observations 404 
 
 II. Action of Light on Silver Compounds .... 406 
 
 III. Action of Various Portions of the Spectrum . . , 413 
 
 PABT V. 
 
 Chapter I. Photography in its Relations to Health .... 415 
 
 II. Chemical Manipulations 420 
 
 Addenda ...» 43 1 
 
MANUAL OF PHOTOGRAPHY. 
 
 PART I. 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 CHAPTEE 1. 
 SELECTION OF MATERIALS. 
 
 § 1.— Selection of Photographic Lenses. 
 
 The information first wanted by the beginner will be as to bis 
 materials, and especially as to bis lenses. They are to form the 
 image which it will be his part to render permanent, and, unless 
 they are right, his work will never be satisfactory. And they 
 must not only be good in themselves, but expressly suited for 
 the work which he proposes to do. 
 
 Such a thing as a universal lens does not exist. One combi- 
 nation is best for one purpose, another for another. 
 
 For Landscapes the best lenses are the View Lens, the Rapid 
 Rectilinear, and the Steinheil Aplanatic. If architectural subjects, 
 or any others, are introduced, in which straight lines must be 
 preserved, the view lens will be unsuitable, because it slightly 
 distorts, and although this distortion is of no consequence when 
 buildings are not introduced, it will be a sufficient reason, when 
 such are included, for using a lens of which the stop, or dia- 
 phragm, is central^ that is, between two lenses, as in the case of 
 the second and third of the above-mentioned objectives. 
 
 The view lens has also this fault, that it includes but a small 
 angle of view, or, in other words, but a small portion of the 
 scene at which it is exposed. This defect has been remedied in 
 Dallmeyer's wide-angle view lens, of which the writer thinks 
 very favorably ; it is, however, not adapted for architectu^?al sub- 
 jects, for the reason already given. / 
 2 ./ 
 
10 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 The lens, whether single, double, or triple, is termed an Objective. 
 The single lens has its stop in front, that is, on the object side, 
 and the concave side of the lens must always be turned also 
 towards the object. Sometimes, in cleaning the lens, it may hap- 
 pen that it is set back wrong side foremost, the effect of which is 
 very injurious. In all cases when any lens is taken to pieces to 
 clean, the utmost care must be used to replace everything exactly 
 as before. 
 
 For Portraits there is but one lens proper, and that is the 
 "portrait combination," invented by Petzval, and made by many 
 excellent opticians in all parts of the world. For groups the 
 Steinheil aplanatic is the best lens ; it is often applied also for 
 taking portraits, which may be obtained of large size with com- 
 paratively small lenses, at the expense, however, of rapidity of 
 action. Triplets were formerly much used for groups, but are 
 now superseded by the lens just named. 
 
 For copying engravings, plans, maps, &c., any lens with central 
 stops may be used, except the portrait combination, which, as 
 well as the view lens, is unsuited for such work. In copying, a 
 stop with small opening will be proper. 
 
 A great mistake is often made by those who interest themselves 
 in photography, in practising too much economy in their lenses. 
 One lens cannot be made to do the work of another, except at a 
 sacrifice of excellence of result. Every lens has a certain size of 
 picture for which it is suited ; if used for a smaller size, it will 
 give a less angle of view, and work more slowly, than the lens 
 made for that size; if strained to cover a larger plate than that 
 which the maker intended, a sufficient sharpness of focus can 
 only be got by using too small a stop. And the beginner cannot 
 too soon learn what is too often overlooked, that, where solid 
 bodies are to be depicted, a stop of a fair size is essential if the 
 best efiects are desired. It is only where flat objects, such as 
 maps, engravings, or plans, &;c., are to be copied, that small stops 
 are right. 
 
 If the" student intends at first to provide himself with one lens 
 only, that had probably better be a Steinheil aplanatic. This 
 and the Dallmeyer " rapid rectilinear" are the nearest approaches 
 to a universal lens that we have. 
 
 . In te^MMENCiNG photographic work, the student, whether he 
 intends devoting himself chiefly to portraiture or to landscape 
 
SELECTION OF MATERIALS. 
 
 11 
 
 work, whether as amateur or professional photographer, will find 
 it most convenient to begin by taking views, or, in other words, 
 he will point his camera out of the windows and practise on 
 whatever scene presents itself. He will endeavor in this way, 
 firstly, to learn to make dean work, that is, to get negatives free 
 from failures, such as stains, fog, comets, &c., and secondly, to 
 secure harmonious effects. The first will be soon accomplished, 
 but to obtain the latter in a good degree will require effort and 
 experience. The high lights must be dense enough not to print 
 through before the shadows are dark enough, and there must be 
 detail everywhere. That is, the high lights must never show a 
 flat white surface, but must be relieved by faint half tint, except, 
 perhaps, in some very minute portion. The shadows must not 
 show a black mass, but the shape and form of the objects in 
 shadow must be everywhere perceptible. 
 
 Portraiture may next be attempted, and, in default of a sitter, 
 a white plaster bust may be used, with different colored draperies. 
 A white bust with black drapery makes a very difficult subject, 
 and to obtain at once a well-shaded face and preserve the folds 
 in the drapery, will be no easy task, but will aftbrd excellent 
 practice. 
 
 Care and cleanliness in the operations, and a thoughtful and 
 close study of results, and comparison with their cause, will ac- 
 complish more in a month, than rapid, careless work in two or 
 three. 
 
 In undertaking landscape photography, it is not well to begin 
 with views too small or too large. The smaller the pictures are, 
 the more easily they are taken in every respect ; difficulty in- 
 creases vastly with the dimensions. On the other hand, small 
 prints are apt to be too trifling and insignificant to repay for the 
 trouble expended upon them. Therefore the beginner will do 
 well to start with "half size" plates, and go from that to whole 
 size, after becoming perfectly familiar with all the manipulations. 
 Eventually he will probably prefer to advance to 8 x 10 and per- 
 haps larger work. Generally speaking, the most artistic effects 
 are got with plates of from 6|x SJ up to 12 x 14. Larger prints 
 are apt to be less pleasing, however technically perfect. It is no 
 advantage whatever to have a lens embrace an unnecessarily wide 
 angle, except, indeed, where architectural objects have to be 
 
12 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 taken in positions where the photographer cannot recede beyond 
 a certain point. An angle of 50° to 60° is generally best. 
 
 In undertaking portraiture^ the beginner will naturally (after 
 having just practised as above explained) commence with card 
 portraits. For this work a " card lens" will be wanted, which is 
 simply a small-size portrait lens. Of these, the French " Jamins" 
 are the lowest in price ; they are often very fair in their perform- 
 ances, though not equal to the best English, American, or German 
 lenses. 
 
 Lenses should be kept with the greatest care — never wiped 
 with anything except clean, soft old linen cambric, and even with 
 this only when necessa'iy. The exquisite polish on the surface is 
 of the highest importance, and it is easily injured. 
 
 Do not begin by buying second-hand lenses, but go to respon- 
 sible dealers and purchase the work of makers of reputation. 
 
 In choosing amongst a number of lenses by the same maker, 
 view a piece of perfectly white paper through the lens, holding 
 the latter close to it. If the appearance shows that the glass of 
 which the lens is made has any color, especially if that color be 
 brownish, the lens should be rejected: it may be expected to be 
 slow. So, too, if, when carefully examined by reflected light, it 
 shows any strias, or hair-like lines. Very small bubbles, or 
 white spots, if not exceeding one or two, are unimportant, and 
 often occur in excellent lenses, though, of course, they are better 
 absent, and, indeed, are rarely, if ever, found in lenses of the best 
 makers. 
 
 These brief remarks are perhaps as much as the beginner can 
 advantageously act upon. Other points will be explained later. 
 
 I 2.— Selection of Camera. 
 
 "Without a thoroughly good camera, no first-rate work can be 
 done, and the beginner cannot make a greater mistake than that 
 of purchasing a cheap one. Any camera that is not thoroughly 
 good is absolutely worthless. 
 
 A camera is to be tested as follows: — 
 
 1. Observe if all the wood-work is sharply cut and closely 
 fitted. 
 
 2. Try the rack and pinion movement, to notice that it works 
 easily aitjd regularly, and not by jerks. 
 
 3. Eack the back forwards until all the bellows body is closed 
 
SELECTION OF MATERIALS. 
 
 13 
 
 in ; then continue to rack up till the back wood-work just comes 
 into contact with the front. Observe attentively if this contact 
 takes place everywhere at once — top, sides, and corners. If it 
 does not, the camera is worthless, for the sensitive plate will in 
 such a case not occupy a position perpendicular to the optical 
 axis of the instrument. 
 
 4. These points having all been found satisfactory, it remains 
 to ascertain whether the sensitive plate, when in place, occupies 
 the exact position of the focussing screen of ground glass. 
 
 This is the most essential point of all, and is precisely that in 
 which cameras, even of good makers, are apt to be defective. 
 The fault, if it exists, is easily detected with a little attention. 
 
 Take a piece of plate glass of the size which the dark slide is 
 intended to carry, set it in place, close the door, set the slide on 
 the table, door undermost, and draw out 
 the shutter. Lay across the middle of the Fig. 1. 
 
 slide a perfectly flat and rigid ruler, a 
 draughtsman's straight edge, or a long, 
 thick, narrow piece of plate glass. Take 
 a piece of smooth hard card, rest one end 
 of it on the plate-glass, pressing the side 
 close up to the ruler, and with a sharp 
 
 , , •IT ^ • ^• 1 l^ i The bottom of the card ^4 rests 
 
 hard pencil draw a hair-lme where the card j,,^ g,^,,_ t,,^ ..^.t, 
 touches the ruler. Next repeat this exactly agaiust the ruier b a, aud the 
 
 . ... peucil line is drawn where the 
 
 With the focussing slide, ground side ot the edge s c touches the card ^. 
 glass uppermost. If the camera is well 
 
 made, the two hair-lines will exactly coincide to make but one. 
 If they do not, the camera will require to be fitted over again by 
 the maker. Care aud attention are necessary to make this trial 
 effectual, but it is essential to make it with every new camera. 
 
 An absolute coincidence of the two lines must be insisted on. 
 At the same time, the experimenter must be sure that he is doing 
 the measuring correctly, and not producing an apparent discord- 
 ance by careless manipulation. 
 
 The next point requiring attention will be the inside of the door 
 of the slide. This is always blackened in order that the light 
 which passes through the sensitive plate during exposure may 
 not be reflected back upon it, but this blacking is often very in- 
 sufficiently done. It is not sufficient that the surface be perfectly 
 black, it must also be perfectly dead, must have no appearance 
 
14 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 whatever of shining when held with the light falling upon it in 
 any direction. 
 
 If any reflection is visible, and the maker be accessible, he 
 should be required to render the surface perfectly dead. If the 
 owner, however, finds it necessary to attend to this himself, he 
 can mix 
 
 Powdered gum arabic 1 draclim. 
 
 Brown sugar i " 
 
 Fine lampblack 2^ draclims. 
 
 and rub them well together with a little hot water to a thick 
 paste. This is to be applied with a flannel rag, and rubbed in 
 well and evenly. But if the black appears to have been origi- 
 nally applied in the form of black varnish, it will be well to 
 remove this polish in a great measure by rubbing with a rag 
 moistened with a mixture of alcohol and ether. If the above 
 mixture shines when dry, there was too little lampblack. If it 
 soils the finger when rubbed, too much. 
 
 Carriers are small frames constructed to enable one with any 
 given camera and slide to take a smaller plate than the proper 
 plate of the camera ; large cameras are often supplied with a set 
 of these to enable the owner to take a whole series of sizes with 
 the same instrument. They are certainly very convenient ; they 
 have the objection, however, that they sometimes yield a little 
 to the pressure of the spring of the back of the slide, and allow 
 the plate to advance too near the point, by a little distance, 
 which may, however, displace the focus. Therefore the above 
 system of testing should be repeated with each carrier. This 
 method has the advantage that the plates receive the same pres- 
 sure, and are under exactly the same conditions, as when receiv- 
 ing the image. 
 
 Of course, in testing, the plates set into the slides must be per- 
 fectly flat, or erroneous indications will inevitably result. 
 
 Although carriers will be often useful, yet, as far as practi- 
 cable, it will be better to use the slide with the size of plate 
 for which it was made. 
 
 Prevention of Stains. — Stains often occur from the absorption 
 of more or less decomposed nitrate of silver from the slide, left 
 there on occasions of previous use. Saturating the whole inside 
 of the slide with some repellant substance has been found useful 
 as a prb.ventive. Parafl5ne or lard may be used. If paraffine be 
 used it must be melted and the different parts of the slide plunged 
 
SELECTION OF MATERIALS. 
 
 15 
 
 in successively. Lard has the advantage that it raay be rubbed 
 in cold. Either the application should be made when the slide 
 is new, or it should be well washed and all old stains scraped 
 carefully away. If paraffine be used, each portion of the holder 
 should remain in it about ten minutes, that it may be properly 
 absorbed. 
 
 The Cut-off. — All slides should have a cut-off, a wooden spring 
 inside the slit through which the shutter passes, and which closes 
 the opening light tight when the shutter is withdrawn. 
 
 t 
 
 § 3.— Selection of Stand. 
 
 For out-door work, a folding tripod is employed. For in-door 
 work many forms are in use. Those in which the table is sup- 
 ported by a single cylindrical stem are very objectionable, for 
 want of steadiness. The most absolute steadiness is requisite, 
 and a large proportion of the stands in the market fail to fulfil 
 this requirement. A stand cannot be judged if almost unloaded. 
 Place a heavy camera on it, strike it a gentle blow, and observe 
 if any vibration follows. 
 
 § 4. — Selection of Chemicals. 
 
 Few photographers have sufl&cient chemical knowledge to be 
 able to apply tests of purity to their chemicals. Perhaps the 
 very best advice that can be given to a beginner is to observe 
 who amongst his friends is most regularly and completely suc- 
 cessful, and then to obtain materials from the same place. In 
 fact, the demands of photography are now so enormous, that good 
 materials can be obtained almost anywhere. The substance most 
 likely to give trouble, in the hands of a learner, is nitrate of 
 silver. This last should always be purchased prepared expressly 
 for photography — never from the druggist. Without the best 
 and purest neutral nitrate, the negative bath cannot be expected 
 to work well. 
 
 The same remark is to be made respecting alcohol and ether, 
 which are needed of the very test quality and higher grade than 
 usually sold by even the best druggists. The photographer ^will 
 need to have alcohol and ether always at hand to thin his qbllo- 
 dion with ; for, after coating a plate, the excess of collodion that 
 is poured off (into a separate bottle) is always much thicker than 
 
16 
 
 INTRODUCTIOX TO PHOTOGRAPHY. 
 
 the stock in the bottle, and will probably need to be thinned as 
 well as filtered before using again. This thinning work needs to 
 be done chiefly with ether, sometimes with the addition of a little 
 alcohol. 
 
 § 5.— Selection of Glass for Negatives. 
 
 Of all matters connected with photography, the selection of the 
 glass is that which is most habitually overlooked. 
 
 Plate glass has some evident advantages over blown. Its sur- 
 face is a true plane; the material of which it is made is generally 
 whiter, and it is free from blebs and other faults and irregularities. 
 On the other hand, it is found that the artificial surface of the 
 plate glass, produced by polishing, does not hold the collodion 
 and varnish so well after a lapse of years as the natural surface 
 of the blown, and that with time the film is more apt to crack 
 and sufier. The surface of plate glass is also more porous than 
 the natural surface of blown glass, and holds back stains more 
 strongly. 
 
 In consequence of the high price of plate glass in America, 
 blown glass is almost exclusively used. But in this blown glass 
 there is great variety of quality. 
 
 1, A good surface, free from knots and blebs, is important, and 
 no glass that has not this characteristic should be employed, A 
 smooth collodion film cannot be got on an irregular surface. 
 
 2, Glass varies greatly in thickness. It is a great advantage to 
 have stout glass; the loss from breakage of negatives in the 
 printing-frames is less, and the operator may venture to apply a 
 strong pressure in his frames where his glass is strong : he thereby 
 gets a sharper and cleaner print. 
 
 3, Blown glass varies extremely in curvature. Much of it is 
 very flat; much, again, greatly curved. All that is much curved 
 should be rejected. See also Part III., Chap. IV. 
 
MAKING THE NEGATIVE. 
 
 17 
 
 CHAPTER II. 
 
 MAKING THE NEGATIVE. 
 
 1. — Absolute Cleanliness. 
 
 All photographic work depends upon the delicate turning of 
 nicelj-balanced affinities, which a slight alteration of the condi- 
 tions may completely reverse. It is necessary, therefore, that the 
 operator should not only follow closely the directions given, but 
 that he should learn to constantly maintain a perfect cleanliness. 
 
 All the vessels which he uses must be irreproachably clean ; 
 and, as far as practicable, each should be restricted to some par- 
 ticular use, so that if slight vestiges of substances escape the 
 attention, such may be less hurtful. The hands, especially, must 
 be constantly washed ; there is no way in which small portions of 
 material are so readily transferred as by adhesion to the fingers. 
 In all these respects too much precaution cannot be taken, and 
 many failures, perfectly unaccountable to the beginner, may be 
 traced to trifling neglects of this sort. Nothing will so well 
 repay its trouble as a systematic and invariable attention to hav- 
 ing the hands and all the utensils clean beyond suspicion. 
 
 Unless the glass be perfectly clean, a regular development can- 
 not be hoped for. Perhaps the best method of cleaning glass is 
 one introduced into photography by the writer a few years ago, 
 and which has since been extensively used. 
 
 Provide a large glass pan, in which make a mixture in the 
 following proportions : — 
 
 Bichromate of potash 3 ounces. 
 
 Siilplmric acid 3 flnidounces. 
 
 Water 25 fluidounces. / 
 
 Place the pieces of glass in the pan alternately, one at each end, 
 so that their ends shall overlap a little, and allow the free pas- 
 sage of fluid between them. For new glass half a day will be 
 
 § 2. — Preparing the Glass. 
 
18 
 
 INTRODUCTION" TO PHOTOGRAPHY. 
 
 sufficient to destroy tlie greasiness. Old glass that has been used 
 before, should have a day, and, if it has been varnished, even 
 longer, or a mixture containing only half the above proportion 
 of water. 
 
 So long as this bath is yellowish-brown, it is active. When it 
 acquires a violet color, it is spent, and will want renewing. 
 
 After a suitable immersion in the cleaning bath, place the 
 glasses one by one in a pan under a water-faucet, and, as fast as 
 the water fills the pan, lift one end, and empty it. Eepeat this 
 half a dozen times at least. Then take up the first plate, let the 
 stream of ivater run some seconds, first on one side, then on the other, 
 until every possible trace of the cleaning bath is removed, and 
 then rub dry with soft blotting-paper— wo^ with cotton rags, as 
 so universally directed. Cloths always leave fluff, which has to 
 be carefully brushed away afterwards — paper does not. 
 
 It is usual to roughen the edges of the plates, and thus diminish 
 the chances of having the film slip off during the work, and also 
 to lessen the risk of cutting the fingers. A coarse file is com- 
 monly used, but the writer greatly prefers a coarse whetstone, 
 such as is used for sharpening scythes. It cuts faster and more 
 evenly, doing better work in less time, and is good until wholly 
 worn away, whereas the file quickly becomes clogged and smooth. 
 The whetstone, or file, is to be drawn three or four times along 
 each edge, holding it so that it shall rest more on the face than 
 on the edge. The roughing should precede the cleaning. After 
 cleaning the glass must be handled as little as possible ; its face 
 must never be touched by a finger, or there will probably be a 
 finger mark developed on the negative. Grlass when cleaned 
 should be laid away, each piece in a fold of soft clean blotting- 
 paper, in which it may lie even for months without injury, if set 
 in a box kept out of the reach of dust and vapors. The writer 
 has used glass which, after cleaning with the bichromate bath, 
 had been kept eighteen months; it gave good results. When 
 glass is to be kept for more than a few days, it should rest on its 
 edges, and not lie flat, otherwise there is a possibility (the writer 
 has seen this happen) that folds in the paper between two sheets, 
 may show in the development. 
 
 Nitric acid may be used for cleaning, or caustic alkali ; but the 
 above is not only the easiest and most economical, but is perhaps 
 the only one with which an old picture never reappears in the 
 development of a new one. 
 
MAKING THE NEGATIVE. 
 
 19 
 
 Plates that have been varnished are necessarily more difficult to 
 clean. They will need a stronger bath and a longer immersion 
 in it. Or the varnish may be easily and completely removed by 
 soaking in a bath of caustic soda. It is best to wait till a quan- 
 tity accumulate, and then to dissolve a pound of " concentrated 
 lye" in a half pailful of hot water, and put the plates in, one by 
 one, leaving them in till they easily rub clean ; after rinsing off, 
 put them into the bichromate bath for a few hours. When com- 
 mon photographic glass is used, varnished plates scarcely repay 
 for the trouble of cleaning, especially as, if the cleaning is not 
 done carefully, the negatives will not be satisfactory. 
 
 § 3.— The Negative Bath. 
 
 ' Of all that the photographer works with, nothing exceeds in 
 importance the negative bath. Its preparation is exceedingly 
 easy, and, if thoroughly good nitrate of silver be used, it cannot 
 fail to work well, if no mistake or oversight has been made in 
 its preparation. 
 
 A vertical glass lath is to be procured ; there is none other which 
 is perfectly safe. In a porcelain bath, if there is the slightest 
 flaw in the glazing inside, the solution will penetrate it, and 
 gradually saturate the whole of the porous biscuit which makes 
 the body of the vessel, between the inside and outside glazing. 
 This not only involves a great loss* of expensive silver solution, 
 but after a time the outside glazing also probably cracks, and 
 some day the operator finds his bath empty. In many cases 
 porcelain baths last for years, but there is never a certainty about 
 them, as there is with glass. The "photographic ware" has been 
 much complained of in the same way. 
 
 A glass bath requires to be supported in some way, and the 
 simplest is to place it in a box sufficiently wide to give the bath 
 a proper inclination, laying a wooden or pasteboard cover over 
 it, when not in use, to exclude the dust; or boxes may be pur- 
 chased provided with covers, and with an iron foot at the back 
 to enable the box to stand at a proper inclination (see beyond, 
 Fig. 6, p. 24). 
 
 A "whole-size" bath, for plates 6|x8^-, will be found a con- 
 venient one for the beginner, as, even if much smaller plates are 
 worked with, it is not worth while to use a smaller bath — it holds, 
 too little solution and' changes too rapidly. The " whole-size" 
 
20 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 baths require about 25 ounces of solution to charge them. This 
 solution is to be made as follows : — 
 
 Dissolve 2 ounces of nitrate of silver in 25 ounces of water, 
 which need not be distilled water. Leave the solution in a glass 
 bottle in the sunlight for several hours, or in cloudy weather for 
 a day or two near a southerly window. Separate this into two 
 equal portions. Take 3 grains of iodide of potassium or iodide 
 of ammonium, dissolve it in a few drops of water, and pour it 
 into one of the halves ; stir up well and let stand half an hour, 
 or longer. Filter the other half into a clean bottle, and then filter 
 into it the second half, that to which the iodide of potassium was 
 added. 
 
 Observe: The two portions are not to be mixed until after they 
 are filtered, and the portion to which the iodide was added is to 
 be filtered last, if the same filter be used for both. 
 
 Next, take a clean six-ounce stoppered vial ; place in it one 
 fluidrachm^ of pure nitric acid, fill it up with water, and label it 
 " Dilute nitric acid, ten minims to the ounce." To the twenty- 
 five ounce bath add one flaidrachm of this dilute acid. 
 
 If this does not prevent fogging, the fault is probably in the 
 collodion. It will therefore be advisable to add to it enough 
 tincture of iodine to bring it up to a light sherry wine color. 
 Tincture of iodine (which must not be confounded with " Lugol's 
 Solution") may be purchased ready made, or be prepared by dis- 
 solving a quarter of an ounce -of iodine in four ounces of alcohol ; 
 it should be prepared and kept on hand, as it does better after 
 standing for a time. If with a collodion of a sherry wine color, 
 and the acidification already mentioned, which is in the propor- 
 tion of about a drop of nitric acid to twenty ounces of bath, the 
 fogging continues, it shows that there is something very much 
 wrong. The operator may try the effect of a further addition 
 of acid, but he may be assured that either he has made some mis- 
 take, or is working with bad materials. More acid may force a 
 clean picture, but will fail to give delicately graded shadows and 
 half tints. (See also Chapter on Failures.) 
 
 The negative bath should always be kept covered to exclude 
 dust and dirt. Constant care must be taken to let no extraneous 
 
 ' The photographer should provide himself with graduated measures of one 
 pint, 6f two ounces, and a minim glass for measuring a drachm and its frac- 
 tions. Onemi-nim of water weighs one grain nearly, and corresponds approxi- 
 mately with a drop. Sixty minims make the fluidrachm. 
 
\ 
 
 MAKING THE NEGATIVE. 21 
 
 matter get into it, and to place it in nothing, and nothing in it, 
 that is not perfectly clean. 
 
 When the bath by use will no longer work Avell, add bicarbo- 
 nate of soda till the bath just turns red litmus paper blue, boil it 
 down to one-half, expose it for a day to sunshine, filter, dilute, 
 and add just enough dilute nitric acid to get a clean picture, with 
 a collodion known beforehand to give good results. Of course 
 nitrate of silver must be added from time to time to keep up the 
 strength, which is rapidly diminished by sensitizing plates. 
 
 Litmus Paper is useful to indicate whether solutions are acid, 
 alkaline, or neutral. An acid solution turns Hue litmus red ; an 
 alkaline turns red litmus blue ; a neutral solution is without influ- 
 ence on either. The paper should be cut into narrow strips, and 
 kept in a wide-mouthed vial, corked. 
 
 § 4. — The Developer. 
 
 Make the developer as follows : — 
 
 Proto-snlpliate of iron 400 grains. 
 
 Acetic acid, No. 8 1^ ounce. 
 
 Alcohol 1^ " 
 
 Water 20 " 
 
 The developer, if kept corked, will keep for a couple of months. 
 It is ready for use as soon as the solution of the sulphate of iron 
 is complete and the whole has been filtered. As it grows older 
 it becomes reddish, but, so long as kept clear by filtration, the 
 reddening is rather beneficial than otherwise. 
 
 § 5. — Collodionizing the Plate. 
 
 Holding the clean glass plate by pressing a finger or two of 
 each hand at the edges of the plate (the fingers must never touch 
 the face), hold it up to the light, and look along the long edge to 
 see which is the convex and which the concave side. The choice 
 between these is a matter involving a variety of considerations 
 which will be stated in full farther on. The beginner will find 
 it best to generalize as follows : for portraits and for buildings, 
 coat the hollow or concave side ; for landscapes, the convex side. 
 Next brush it off with a broad (two-inch) soft camel's hair bj?^ish, 
 which must be kept clean and free from dust, and be used for no 
 other purpose. It should not even be left in damp air, oi* it may 
 
22 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 Fig. 2. 
 
 leave streaks of dampness on tlie plate, producing stains in de- 
 velopment. It is an excellent plan to have a tin box, three or 
 four inches deep and an inch larger in breadth and length than 
 the plates which thus lie in it between folds of clean blotting- 
 paper. Any impurity in the paper is transferred infallibly to the 
 glass. The writer has seen glasses between which newspapers 
 had been laid, take off a complete copy of the print. If the 
 glasses remain for a long time unused, the box should be turned 
 on its edge that the plates may not rest on each other. The brush 
 should lie in this box, ready for use. When the brush is drawn 
 over the surface of the glass, it should slip over with a peculiar 
 facility. The careful operator will occasionally notice an absence 
 of this facility : the difference is so slight that only experience 
 enables one to appreciate it, but when once observed it is unmis- 
 takable. This always indicates that the plate, though it may 
 have been well cleaned, has not been sufficiently rubbed in dry- 
 ing. A quick rubbing with clean dry blotting- 
 paper will at once remove this, and enable the 
 brush to pass easily and lightly over the sur- 
 ftice. But rubbing just before coating is always 
 objectionable : the glass becomes electrical, and 
 attracts and holds motes of dust that may be 
 floating through the air. 
 
 After brushing, gently but thoroughly, take 
 the plate in the left hand, three fingers sup- 
 porting it underneath, the thumb pressing on 
 the corner, and the narrow end towards you. 
 Fold up a piece of blotting-paper, and put it 
 between the bottom of the plate and the finger 
 ends. For want of this there will occasionally 
 appear curious mottled markings at the points 
 where the fingers touch the under side. 
 
 Take the collodion bottle in the right hand, 
 having previously removed the cork and wiped 
 the lip to remove dust or fragments of dried 
 collodion. {Never neglect this, and repeat it 
 between every plate.) 
 
 Pour the collodion slowly and steadily on, 
 lettl^ng it come upon the plate at a spot a little further from you 
 than \the middle — say equi-distaut from the end and the two 
 
 Hold at 3, pour on at 
 A, or even a little below 
 the dot, and off at 4. 
 
 Fig. 3. 
 
 V 
 
MAKING THE NEGATIVE. 
 
 23 
 
 sides (see A, Fig. 2). Pour on till the pool covers rather less 
 than half the plate. 
 
 Incline the plate till the pool extends itself to corner No. 2 
 (see also Fig. 3), then to corner No, 1 (see Fig. 4). Then bring 
 it down to the lower end, reaching, however, 
 corner No. 3, where the thumb is, before cor- Fig. 4. 
 
 ner No. 4, at which it is to be poured off (see 
 Fig.6)._ 
 
 This is all to be done quite coolly, and yet 
 without loss of time. The collodion must go 
 up full to the edge of the plate all round, and 
 with a little practice this is accomplished A¥ith 
 great ease and without spilling a drop. When 
 the operator has learned to do this with ease, 
 he will find it a good plan to send hack the 
 collodion from 4 to 1 before pouring off, by raising corner 4 ; as 
 soon as the wave reaches 1, corner 4 is lowered again, and the 
 excess poured off' there. This makes a more even plate. 
 
 Fig. 5. 
 
 It is best not to pour back the collodion into the bottle from 
 which it came, but have a separate bottle ready, uncorked. 
 
 The operation of pouring off requires the operator's best atten- 
 tion. The plate must be slanted but very little, otherwise the 
 collodion runs off too fast, and leaves too thin a film, especially 
 at corner No. 1. At the same time the operator rocks the plaie, 
 that is, turns it backwards and forwards, one quarter round, 
 
 / 
 
24 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 without changing the inclination (see Fig. 5, in which the dotted 
 line shows the direction taken by the upper left-hand corner). 
 If this be neglected, the film will be full of crapy lines. If the 
 plate be properly rocked, it will dry as smooth as the glass itself. 
 
 The writer has endeavored here to give as clear a description 
 of the method of collodionizing a plate as possible; at the same 
 time it is unquestionably one of those manipulations which it is 
 almost necessary to see done, in order to execute properly one's 
 self. 
 
 No formula for making collodion is given here. The beginner 
 is strenuously advised to introduce no unnecessary difficulty by 
 such attempts, but to procure a reliable collodion from some pro- 
 fessional photographer or trustworthy dealer. "When he has 
 mastered the manipulations, he may advantageously make his 
 own collodion, for which a number of good formulas will be 
 given further on. The nitrate bath, the developer, and the fixing 
 solution, on the other hand, every one must learn to prepare for 
 himself from the outset. 
 
 § 6. — Sensitizing. 
 
 The collodion coating quickly sets — in half a minute or less in 
 summer, whilst a minute may be necessary in winter. The be- 
 ginner may judge of its condition by gently touching it near 
 corner No. 4 with the tip of the finger ; if the film does not wet 
 
 Fig. 6. 
 
 the finger, but receives a slight depression from it, which remains 
 after the finger is removed, it is called " tacky," and is now 
 ready^or immersion in the bath. Up to this time the rocking 
 motionis to be steadily continued, pausing only for a second, if 
 
MAKING THE NEGATIVE. 
 
 25 
 
 necessary, to ascertain the condition of the film. When this has 
 attained the proper state of setting, the plate is to be rested upon 
 the dipper firmly and steadily. The operator next lowers the 
 dipper, carrying the plate with it, into the bath, by a gentle, con- 
 tinuous, and uninterrupted motion. For if he pauses for any 
 fraction of time, however short, the part of the film which at that 
 moment corresponded with the surface of the bath will show a 
 distinct line, ruining the negative. No unnecessary delay should 
 occur in putting the plate in the bath, or the risk of marbled 
 stains is increased. 
 
 Dippers are made of porcelain, glass, and gutta-percha. If glass 
 ones could be got of a right pattern, they would be preferable, 
 but made of rods they are too fragile. The porcelain are good, 
 and the gutta-percha also, provided they are well made, and con- 
 sist wholly of gutta-percha, without any metallic support in the 
 centre. The porcelain dipper may rest in the bath when not in 
 use ; the gutta-percha dipper must never be left in the bath. The 
 porcelain is the best and safest. It has, moreover, this recom- 
 mendation, that if the plate slips off, and goes down to the bottom 
 of the bath, the porcelain dipper can be easily worked under it ; 
 at least this can be done with glass baths, the bottoms of which 
 are always a little rounded and hollow. 
 
 If the plate whitens too rapidly in the bath, it is an indication 
 that it has waited too long between coating and immersing, has 
 become too dry, and its sensitiveness will be impaired. The 
 plate should wait only long enough to prevent splitting in 
 the bath, or turning mottled in the part least dry, both of which 
 results are liable to follow too quick an immersion. This mot- 
 tling must, however, not be confounded with the mottling at the 
 pouriug-off corner, which results from a collodion too thick, or 
 containing too large a proportion of alcohol, or alcohol not up 
 to 95 per cent. 
 
 It has just been said that the collodion poured off from the 
 plate must be received into a different bottle. This is because it 
 is apt to carry with it motes and particles of dust, which appear 
 on the next plates. The collodion is, however, perfectly good 
 for subsequent use, but it will not only need to be filtered, but 
 thinned^ because the evaporation which takes place from /the 
 moment that the collodion is on the plate, causes the portions 
 poured off" to be much thicker than the original stock. As the 
 ether evaporates more rapidly than the alcohol, the thinning is 
 3 
 
26 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 best done altogether witli ether. Neglect to thin the collodion 
 will produce ridgy plates, and especially in hot weather, tend to 
 the production of small transparent spots, known as pin-holes, 
 appearing anywhere on the plate, but oftenest in the dense parts, 
 particularly in skies of landscapes. 
 
 (The sources of trouble in photographic operations have been 
 collected together by the author, and will be found in a "Chapter 
 on Failures," farther on, in which they have been classified for 
 easy reference by the photographer whenever occasion may call 
 for it.) 
 
 The plate having been placed in the bath will be left quiet for 
 a couple of minutes, and then must be moved up and down from 
 time to time ; and a side motion is also beneficial, especially if 
 the plates show a tendency to form lines in the direction of the 
 dip, a trouble of which much complaint has been made by some 
 photographers, though it has never been experienced by the 
 writer. Until the plate has been in some minutes it should not 
 be raised in moving so as to be partly uncovered by the silver 
 solution. 
 
 The time requisite for stay in the bath cannot be fixed in 
 minutes with any positiveness, as it depends somewhat on the 
 temperature, the nature of the collodion, and the condition of the 
 bath. From three to five minutes is about the time. The plate 
 is ready when, on withdrawing from the bath, no oily lines form 
 on the surface, but the whole face presents a uniform moist film. 
 The plate should never be left longer than necessary in the bath, 
 as by so doing the film tends to dissolve, thus choking the bath 
 with excess of iodide, and rendering the plate irregular. Worse 
 still, there is a great tendency in such plates to give flat and dull 
 images, at least in collodion containing bromides. 
 
 There is, of course, always a little latitude allowable. And it 
 is to be remarked that a plate removed from the bath as 
 soon as the oily streaks are gone is in condition to give the 
 cleanest plates; if left a little longer, it gains in sensitiveness, but 
 also there is a little more tendency to veil. 
 
 The plate is now to be removed from the bath and rested on 
 several thicknesses of soft blotting-paper, changing its position 
 every few seconds, until it no longer wets the paper. A thorough 
 draining in this way is very important, and cannot be neglected 
 withcHit danger of streaks and other irregular action. At the 
 same time the back of the plate is to be carefully wiped dry with 
 
MAKING THE NEGATIVE. 
 
 27 
 
 soft paper. This wiping and tliorougli draining must never be 
 omitted ; neglect of these precautions will tend to produce 
 streaks and stains. It is a very good plan to keep ready pieces 
 of thick soft red blotting-paper, half an inch smaller than the 
 plate all round ; and after it has been wiped clean to apply one 
 of these pieces moistened with clean water, but not too wet, to 
 the back. This precaution, though recommendable, has not yet 
 come into general employment. Its use is to diminish internal 
 reflections or hlurring^ as will be more fully explained hereafter. 
 
 In all these operations the face of the plate must never be 
 touched by the fingers, and with the same precaution the plate 
 is to be lifted and gently set into its place in the dark side, taking 
 care that the shutter is in its place. The door is then closed. 
 
 From the time that the plate is lifted from the bath the same 
 edge must carefully be kept undermost ; that is, the side which 
 went undermost into the bath must be kept undermost — must be 
 that which rests on the blotting-paper-^must be kept undermost 
 in the transfer to the dark slide, and the slide with its plate in it 
 must be carefully kept with that edge downwards, not only during 
 exposure, but in carrying backwards and forwards and up to the 
 moment of development. This is essential; neglect of it will 
 almost certainly result in streaky lines and irregular deposits 
 along the outside of the plate, running up in places some distance 
 into the plate. If the small size of the bath renders it necessary 
 to set the plate in end down, when the side is to be down in the 
 slide, the plate must be turned immediately on taking it from the 
 bath, and the draining and blotting done whilst it is in the same 
 position which it is to have in the slide. In this way no harm 
 results from the change of position. 
 
 Particular descriptions of the dark room and glass room must 
 be omitted for the present. Here it is sufiicient to say that all 
 the operations of sensitizing and developing must be performed 
 by yellow light. A very simple way of converting an ordinary 
 room into a dark room for photographic work consists in pro- 
 curing some of the very thickest and stoutest brown paper made 
 for envelopes, and pasting pieces of it over the panes of the win- 
 dow ; a great deal of light will come through this, sufficient for 
 all the operations, and yet, if the paper be good and thick and of 
 fine grain and quality, there will be no danger of fogging; ]f, 
 however, the sun shines directly, at times of the day, upon the 
 window, it will be well to have a bufi'curtain on rollers inside the 
 
28 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 window, so that when the light is too strong it may be properly 
 tempered. 
 
 If the room used as a dark room has two windows, it will be 
 found preferable to cover the panes of one only, and to have 
 closely fitting inside shutters to the other, over the joints of which 
 black muslin must be pasted or tacked. In this way the room 
 may be lighted at any moment, and may serve for other uses than 
 merely as a dark room. 
 
 However the dark room be arTsmged, provision must he made for 
 its thorough ventilation^ the fumes of collodion tending to produce 
 headache, nervous exhaustion, and to undermine the health. 
 This subject will be recurred to hereafter; it should never be 
 lost sight of by the photographer who values his health. 
 
 § 7. — Focussing. 
 
 The photographer first covers the camera with a black cloth, 
 and places his head beneath it. The cloth should be ample to 
 exclude all white light ; even a few scattered rays of light will 
 greatly diminish the brilliancy of the image as seen on the ground 
 glass, and interfere with a proper judgment. The picture should 
 be composed and arranged with the largest opening of the lens, 
 and after this is done the proper stop is next substituted and the 
 focus carefully taken. 
 
 Few persons have unassisted sight so sharp as to enable them to 
 take a thoroughly good focus, although a delusion to the contrary 
 is very wide-spread. It is always better to examine the image on 
 the ground glass through a microscope, as a better focus can be 
 got more quickly, and with less strain upon the eyes. The 
 microscope should consist of two lenses in the same tabe, at least 
 an inch in diameter. The difference of fatigue to the eyes in 
 using large and small lenses is enormous. A magnifier, with 
 lenses of one and a half to two inches in diameter is the best ; its 
 expense is small, as it is not absolutely necessary that the lenses 
 should be achromatized. The little doublets used by engravers 
 are good, and larger ones can be got of any optician of the same 
 pattern. The writer does not advise the system of focussing on 
 clear glass with an adjusted eye-piece. 
 
 TJie operator is not to take his focus on any point of the picture 
 indigently, but according to the following rules: — 
 
MAKINQ THE NEGATIVE. 
 
 29 
 
 In taking a single portrait, focus on the face as the most im- 
 portant point. 
 
 In taking two heads equidistant from the centre, focus on 
 either head, not on any more central object. 
 
 In taking a group, focus on one of the heads occupying a posi- 
 tion midway between the centre and the extremity of the group. 
 
 In focussing a landscape, care must be taken that the fore- 
 ground is in good focus, and at the same time that suf&cient 
 sharpness is preserved all over the picture. The largest stop 
 with which this result can be obtained, must always be used. It 
 is, however, not necessary that very distant objects should be as 
 sharp and clean cut as the foreground must be; to accomplish 
 this would require the use of a stop so small as to flatten the 
 whole picture. Many, however, do this, and the result is that 
 their pictures have no effect of distance or atmospheric per- 
 spective. On the other hand, if the focus be not taken with 
 judgment, the result will be a failure. A swing hack (hereafter 
 to be described) aids materially in getting a whole view into 
 good focus with a large stop. 
 
 These directions are important, and cannot be disregarded with 
 impunity. Careless focussing is almost the worst fault that a 
 photographer can have, and will counteract every care or pre- 
 caution that he can take in other parts of the process. 
 
 Where buildings of any description form part of the subject, 
 it will be necessary to level the camera, otherwise the perpen- 
 dicular lines of the edifices will not be 
 perpendicular in the negative, but will 
 converge or diverge. This levelling the 
 camera often prevents the upper part of 
 the building from appearing upon the 
 ground glass. Material help can be gained 
 by raising the sliding front (see Fig. 7). This, 
 however, must be done with circumspec- 
 tion, or the upper corners of the negative 
 will be transparent (and print black) by 
 being outside the circle of light given by 
 the lens. It must be also remembered that 
 the definition is always best at the centre, 
 that when the lens is shifted in position by / 
 raising the front, the upper parts of the objects will not be^^-'quite 
 so sharp as when the lens is in its usual place; nevertheless, the 
 
30 
 
 INTRODUCTION TO PHOTOGRAPHY'. 
 
 plan is a useful one. The swing-hack is also useful, but will need 
 an intimate acquaintance with photography to avail one's self of 
 it ; its operation will be explained hereafter. 
 
 § 8. — Exposure. 
 
 The time of exposure for a wet plate may vary from a fraction 
 of a second to half an hour. 
 
 With a portrait combination, medium stop, and good light 
 from three to fifteen seconds, or even more, may be required. 
 "With landscapes taken by a view or a doublet lens and medium 
 stop, from ten seconds up to several minutes may be given, ac- 
 cording to the light. With a bright light, and by having the 
 chemicals in exact order, a picture may be got in a fraction of a 
 second with a short focus lens, using a large stop. The operator, 
 however, will do well to leave instantaneous photography until 
 he succeeds regularly and without difficulty in ordinary ex- 
 posures. 
 
 The slide should always be set into the camera steadily and 
 gently, not with a jerk or snap, lest any dust be set in motion and 
 settle on the sensitized plate, the result of which will be seen in 
 comets ov pin-holes. 
 
 § 9. — Development and Redevelopment. 
 
 The operator brings back the dark slide, without loss of time, 
 to the dark room, never forgetting for an instant to keep that part 
 of the slide down which was lowest in the camera, and in all pre- 
 vious stages. Holding the slide with the left-hand edge in his 
 left hand, he opens the door with his right, places his thumb on 
 the upper edge of the plate, with the fingers touching it lower 
 down, and, by inclining the slide a little backwards, brings out 
 the plate. This is now transferred to the left hand, always keep- 
 ing the lower edge downwards. He now turns the plate up nearly 
 to a horizontal position ; a proper quantity of the developer (about 
 an ounce for a whole-sized plate, or, for a beginner, a little more) 
 has previously been placed in a suitable glass vessel — Fig. 8 
 represents a good shape; this the operator takes in his right 
 hand, and holding it a little inclined, and at the upper edge of 
 the plate near the left hand, pours out the liquid, at the same 
 time drawing the vessel towards the right, so that the liquid may 
 
MAKING THE NEGATIVE. 
 
 31 
 
 spread rapidly and evenly over the whole surface of the plate. 
 Some dexterity is required to do this, except with very small 
 plates. Just as the developer spreads over the plate 
 and reaches the lower edge, the plate is carried to a ^' 
 horizontal position, for it is an object not to let more 
 than can be helped run over. The developer becomes 
 mixed on the surface of the plate with the bath solu- 
 tion with which the film is impregnated, and this mix- 
 ture provokes the development. If much is wasted 
 by washing over the side, the image will come out less strong, 
 and a redevelopment will be more likely to be necessary. 
 
 The rapidity of development under the action of the developer 
 will depend on what has been the exposure. If the image flashes 
 out instantly, the exposure has been too long, and the picture 
 will want contrast. If the picture comes out slowly, reluctantly, 
 so that after a minute or two only the strongest marked points 
 of the subject are visible, the exposure has been too short, and 
 the picture will probably be too full of contrast, wanting in 
 detail, and hard and blocky. If the picture soon begins to show 
 itself, and, instead of flashing out too suddenly, grows steadily 
 and even rapidly in strength, a good result may be anticipated. 
 As the development goes on, the operator inclines the plate a 
 little in different directions, so as to render the developer regular 
 and even in its action. When the plate has come pretty well 
 out the operator pours off the developer from one corner into its 
 vessel again, and, as he drains the last drop, he raises the plate 
 perpendicularly between himself and the light, and judges of its 
 strength and character. If these appear satisfactory, he stops the 
 operation by washing off the plate; if not, he pours on the deve- 
 loper again (provided this last has remained active and clear), 
 and keeps it on a few moments longer. But if it seems to have 
 ceased its effects, and still more, if the slightest tendency to fog 
 manifests itself, or. if the developer looks in the least muddy, the 
 operator quickly washes the plate, and if on a further careful 
 inspection he finds that it still wants strength, he proceeds to 
 redevelop. 
 
 Care will always be needed that the developer is used in suffi- 
 cient quantity to cover the plate quickly and easily. Too much 
 is always better than too little, though with too much developer 
 the silver will always be too much diluted and washed away, and 
 
 / 
 
82 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 there will be more probability of a redevelopment being needed. 
 (Very full information in all the details of development will be 
 found in the second part.) 
 
 Another point will require special attention. The developer 
 is apt not to mix easily with the bath solution contained in the 
 film ; as long as the plate is level the tendency does not appear. 
 But when the plate is raised to judge of its strength by looking 
 through, and part of the surface liquid drains off, the indisposi- 
 tion to mix shows itself by the formation of oily lines resembling 
 those upon a plate removed too soon from the negative bath. 
 Now these oily lines that form on the plate when raised to look 
 through, consist of the developing liquid which collects in that 
 form, consequently the development of the plate goes on under 
 these lines, and checks elsewhere. There results a set of streaks on 
 the plate that wholly ruin it. There is no more fruitful origin 
 of trouble to beginners than this, and its source is often wholly 
 •unsuspected. Nor is it easily avoided. If the negative bath 
 have been a good deal used, the addition of alcohol to the deve- 
 loper to the proportion of an ounce or two to the pint will some- 
 times help. 
 
 Redevelopment may be done either before or after fixing, the 
 difference is but slight in the final result; as far as it goes, it 
 may be stated as follows : If the contrasts are likely to be a little 
 too great, or tend that way, redevelop before fixing ; if the con- 
 trasts are scarcely sufiicient, fix first and redevelop afterwards. 
 Not much, however, in the way of a curative agency can be ex- 
 pected in this way, and pictures which are either too harsh or too 
 uniform, are best wiped out at once and taken over. 
 
 The operator will always bear in mind, in deciding when his 
 development or redevelopment is carried far enough, that the 
 apparent strength of the picture, as he then sees it, will be con- 
 siderably reduced in the operation of fixing, and for this he must 
 make due allowance. 
 
 A close watch must be kept on the plate, and if the slightest 
 tendency to form oily lines shows itself, the plate must be in- 
 stantly held under the tap, or better, be plunged into a pan of 
 clean water ready for the purpose. And if it proves on careful 
 examination to want density, this must be got by redevelopment. 
 
 Negatives that come out of the right strength by the first de- 
 velopment are the best. If under-exposed, they are apt to become 
 
MAKING THE NEG-ATIVE. 
 
 83 
 
 hard and crude in the process of redevelopment ; and if over- 
 exposed, the evil is incurable. A brilliant print can only be got 
 from a brilliant negative. Much will depend upon the collodion, 
 or, rather, the pyroxyline from which it is made. Highly sensi- 
 tive collodions, and those newly prepared, are more likely to 
 need redevelopment : more intense pyroxylines and older collo- 
 dion less likely. 
 
 Eedevelopment may be effected in various ways. The most 
 usual is with pyrogallic acid, and that is the plan which I shall 
 here describe. 
 
 To redevelop with pyrogallic acid, the operator keeps in a 
 stoppered vial the following solution: — 
 
 Nitrate of silver 60 grains. 
 
 Citric acid 120 " 
 
 Water 6 ounces. 
 
 And in a well-corked vial: — 
 
 Pyrogallic acid J ounce 
 
 AlcoLol 4 ounces. 
 
 Both these solutions will need filtering ; both keep for months. 
 
 When the iron development has done what it can, and before 
 any disposition to fog sets in, the plate is to be thoroughly well 
 washed oft'. In a convenient developing vessel the operator puts 
 water, about an ounce or a little less for a 6| x 8^- plate, and pro- 
 portionately for other sizes. He next adds a little pyrogallic 
 solution, about twelve or fifteen drops for the ounce of water, 
 with which it immediately mixes. He then adds a few drops, 
 say fifteen or twenty, of the silver and citric acid solution to the 
 ounce of water, mixes well, and pours the mixture over the plate. 
 The image immediately begins to grow in strength, and, by keep- 
 ing the silver and pyro on, any desired degree of strength can be 
 obtained. The redeveloper soon darkens to a wine color, and in 
 that condition its action is still powerful. But if it becomes in 
 the least muddy, it must be rapidly washed off the plate. So 
 long as the solution remains transparent and bright, even if port- 
 wine color, it is not easy to fog the picture. Still, even the pyro- 
 gallic developer is not to be trusted too far, or fog may set in in 
 brown spots. When redeveloping is done after fixing, the hypo- 
 sulphite must first be washed oft" most thoroughly, lack as^'well 
 as front. ■ / 
 
34 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 When it is intended to redevelop plates tliat liave been fixed 
 and dried, a little more care is necessary. It is best to redevelop 
 in a pan. And as there is here more danger of spotting and 
 staining, it is best to add a little acetic acid besides the citric. 
 The operator watches the operation, keeps the developing bath 
 continually moving by tilting the pan, and examines the progress 
 of the work at intervals. Plates after drying take density more 
 slowly than when redeveloped immediately after the first develop- 
 ment. When plates have been allowed to dry, and are afterwards 
 found to need redeveloping with pyro, they are apt to show a ten- 
 dency to split in drying after the redevelopment ; it is therefore 
 a good plan to flow them over with the following solution: — 
 
 Clean gum arabic . . , . . . .2 ounces. 
 
 Water 20 " 
 
 Carbolic acid ^ drachm. 
 
 The carbolic acid enables the gum solution to be kept indefi- 
 nitely without moulding or souring, A little of the solution is 
 poured over the plate, worked in by moving the plate so that it 
 shall spread over the whole surface, which can easily be judged 
 of by catching the light upon it. This is drained off by holding 
 up the plate, and the operation repeated with a fresh portion of 
 solution, after which the plate is reared up to dry. Different 
 collodions vary very much as to tendency to split in drying, and 
 to their need for this protection. (This operation does not take 
 the place of varnishing ; plates that have been gummed must be 
 varnished the same as others.) 
 
 A pyrogallic development may be used in the first place instead 
 of the iron. In this case the pyrogallic acid solution is added to 
 water, about eight drops to the ounce, a little acetic acid is added, 
 and the mixture is poured over the plate as it leaves the frame. 
 This is a very easy development, and gives bright, strong pic- 
 tures. But the iron development is preferable, because softer 
 pictures are got, more full of detail, and shorter exposures are 
 sufficient. 
 
 The vessels used for developing must be kept scrupulously 
 clean. If the remains of the developer be left in them a few 
 minutes, it becomes turbid, and a gray-black precipitate of metal- 
 lic silver collects round the sides and bottom. Any of this left 
 in wip tend to render the next lot of developer muddy, and 
 therefore must be completely removed, 
 
 \ 
 
MAKING THE NEGATIVE. 
 
 35 
 
 I am in the habit of keeping beside me the following solution 
 in a beaker or wide-mouthed bottle : — 
 
 Concent, solution bichromate of potash . . .1 fluidounce. 
 Sulphuric, or better, hydrochloric acid . . • i " 
 "Water 3 fluidounces. 
 
 It is only necessary to pour this solution into the dirtiest de- 
 veloping vessel, and then immediately out again, when it will 
 be found perfectly bright and clean. It is scarcely necessary to 
 say that it must be well rinsed. 
 
 The same solution is very useful for removing silver stains 
 from the fingers. If got into cuts or abrasions of the skin, it is 
 to some violently irritating, to others quite indifferent, except a 
 momentary smarting. It is much preferable to the use of cyanide 
 of potassium, a most dangerous chemical, and the indiscreet use 
 of which is injurious to health, and may become destructive to 
 life. Or they may be rubbed with strong tincture of iodine 
 (alcohol 1 oz., iodine 40 grs.); and when the stain has become 
 yellow (not before), it will dissolve in a strong solution of hypo- 
 sulphite of soda. 
 
 Of these methods, the first will generally prove the most effi- 
 cacious ; it should be followed by washing with hyposulphite. 
 All silver stains, however, should be attacked before they are set 
 by exposure to light, otherwise the difiiculty of getting rid of 
 them is greatly increased. 
 
 § 10. — Fixing, Washing, and Drying. 
 
 The negative fixing-bath consists of a strong solution of hypo- 
 sulphite of soda, in the proportion of five or six ounces to the 
 pint of water. Some pour the solution over the plate until it is 
 clear. But this involves a loss of time. It is better to keep the 
 fixing-bath in a horizontal pan, and carefully to slide the nega- 
 tive into it. When the yellow opaque appearance of the iodide 
 and bromide has completely disappeared, the plate is fixed. The 
 same bath may be used for a number of negatives, but should 
 not be kept too long. A yellowish feathery appearance through 
 the film indicates insufficient fixing, and may be removed by 
 another immersion in the fixing-bath. 
 
 The plate thus fixed is to be set under a tap and thoroughly 
 washed by allowing a stream of water to fall upon it, wMlst the 
 
 / 
 
86 INTRODUCTIOlSr TO PHOTOGRAPHY. 
 
 plate is supported at such an angle that the ripple is seen to 
 spread in all directions, and keep the water in continual motion 
 over the whole surface of the plate. To accomplish this, the 
 plate must be kept in such a position that the stream of water 
 which falls upon it will flow off in every di- 
 rection. The writer finds the most conve- 
 nient mode of accomplishing this to consist 
 in having, two cones of zinc, as represented 
 in the margin. The lower and larger is six 
 inches in diameter at bottom, and five at top; 
 stands seven inches high. The upper is six 
 inches diameter at top, three at bottom, and 
 five inches high. Both are open at top and 
 bottom, and small notches are cut at the base 
 of the larger. The negative rests on the upper rim ; it will 
 be found easy to give it any slant in any direction, and with the 
 advantage that it will retain that position with entire steadiness. 
 After setting the plate upon this or any other support during the 
 washing, the operator must never fail to catch a reflection of light 
 upon the surface of the plate to assure himself positively that 
 the water is in motion all over the surface, otherwise the washing 
 will not be well done. The above dimensions will answer for 
 all sizes of plates up to 8 x 10 and even 10 x 12. 
 
 Ten to fifteen minutes is the right time for washing a negative, 
 although much less is often given by hasty operators. It is 
 almost as important to wash the hack as the face, although the 
 latter requires only simple rinsing off. If this be neglected, por- 
 tions of the hyposulphite bath will remain there, and, when the 
 plate is set up to dry, will run down to the edge, and thence be 
 drawn up by capillary attraction into the film, preparing the way 
 for spots and stains at some future time. 
 
 The plates are next allowed to dry, either reared up corner- 
 wise in a drying-frame, or simply supported in a vertical posi- 
 tion, resting on several thicknesses of blotting-paper. Fig. 10 
 represents a very convenient rack made by simply attaching 
 upright pieces to a flat board. Eacks can be purchased of the 
 dealers to hold a much larger number of negatives ; the form in 
 the figure is, however, very convenient, and safer. 
 
 Frdm the time that the plate enters the fixing-bath the plate 
 may bo, exposed to the light without injury. 
 If it ikintended to redevelop the plate after instead of before 
 
MAKING THE NEGATIVE. 87 
 
 Fig. 10, 
 
 fixing, the washing must be equally careful after the fixing solu- 
 tion is applied, or the application of the redeveloping solution 
 will cause brown stains. 
 
 Sore hands produced by contact with chemicals sometimes give 
 a good deal of trouble. "Where a tendency of the sort exists, the 
 photographer should endeavor to keep his hands as much as pos- 
 sible out of contact with chemical solution, and should thoroughly 
 wash them immediately after any such contact. At the close of 
 the day's work the hands should be well scrubbed with soap and 
 a nail brush, and then be moistened with cologne-water to which 
 one-eighth of its bulk of glycerine has been added. This will 
 strengthen the skin, and at the same time retain its softness and 
 pliability. Carbolic acid, five drops to the ounce of water, has 
 been found useful. 
 
 § 11. — Varnishing the Negative. 
 
 To varnish a negative well will require both care and attention 
 on the part of the beginner, until by habit and practice a com- 
 plete control over the operation is obtained. 
 
 Choice of Varnish. — First as to the selection of varnish. The 
 beginner should never attempt to make his own, but always pro- 
 cure a reliable commercial varnish. The experienced photogra- 
 pher should always make, never buy ; not so much for economy, 
 though the saving is material, but in order to be certain that he 
 has exactly what he wants — a hard, tough varnish, made out of 
 the very best materials. Suitable directions will be found in the 
 latter part of this manual for preparing negative varnishes/ 
 
 The commercial varnishes may be divided into two clashes — the 
 
 / 
 
 i 
 
38 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 benzine and the spirit varnishes. The former will sometimes 
 dry clear, even if used cold; the latter always require the aid of 
 heat. On the other hand, the benzine varnishes (so far as the 
 writer's experience goes) always reduce the strength of the nega- 
 tive considerably, whilst the spirit varnishes do not; and the 
 latter are every way more reliable. Either sort that the ope- 
 rator becomes accustomed to he will consider the more easy, 
 and it is best to adopt some particular varnish, and use it always. 
 The writer prefers the spirit varnishes. The two different sorts 
 can always be distinguished by the odor. 
 
 Applying the Varnish. — First dust off" the plate, either ver.y gently 
 with a very soft, broad camel's-hair brush, or by blowing with a 
 bellows. With plates developed with iron, or redeveloped, the 
 latter is the better plan. To apply a spirit varnish, warm the 
 plate gently ; in winter a coal stove will be convenient, in summer 
 a gas stove is most commonly employed. Try the temperature 
 by holding it at one corner with the left hand, and moving the 
 right hand under it and applying the side of the hand and back 
 of thumb to various places to see if the heat be uniform. To be 
 right, the temperature should be quite warm, but not in the least 
 hot; there should be a distinct, pleasant sensation of warmth, but 
 no more. If too hot, set aside a few minutes to cool. If used 
 too hot, there is danger of getting lines, as will be presently de- 
 scribed. If used too cool, the varnish will probably " dry dead." 
 A benzine varnish requires rather less heat than a spirit varnish. 
 Some use it cold when the weather is clear and dry. The writer 
 prefers to use heat with all varnishes. Taking a convenient posi- 
 tion in front of a window so as to watch b}'' the reflection all the 
 movements of the varnish, pour it on precisely in the same way 
 as with collodion. Having put on a liberal supply, slant the plate 
 towards you and bring the pool of yarnish towards you, in a full^ 
 slow vjave, keep its border as squa7-e as possible, making it advance 
 slowly and quietly ; if one edge gets a little the advance, incline 
 the plate the other way to bring it up. With too little varnish 
 or too much tilt to the plate, long arms will start out, and whilst 
 you are slanting the plate this way and that to get it covered on 
 some part of the border, the wave will stop moving, and a line 
 may result. 
 
 Haying now got the whole plate covered, keep it quite level 
 or even tilt it backward, so as to send a returning wave clear up 
 to the far end of the plate. The varnish should rest on the whole 
 
MAKING THE NEGATIVE, 
 
 89 
 
 plate some seconds before hegimiing to pour off, otherwise it will 
 not soak in sufficiently, and so dry dead. 
 
 The length of time necessary for the varnish to rest on the plate 
 varies a good deal. The more a plate has been redeveloped the 
 longer it will need the varnish to remain upon it ; the thicker 
 the varnish, the less time is required. A thick varnish with a 
 close film will need only seven to ten seconds. A very thin var- 
 nish with a spongy film may need fifteen to twenty. Generally 
 speaking, eight or ten seconds will be a proper time ; a few 
 trials on rejected negatives will show what is needed. The time 
 here spoken of is to elapse after the negative has been completely 
 covered. 
 
 Having let it soak in sufficiently, incline it very little^ so that it 
 will run off at the right-hand near corner into the "pouring off 
 bottle" held there to receive it. After it has run slowly for a 
 couple of seconds, the plate being of course nearly level, hring it 
 suddenly up hy a quick movement till it is vertical, and there hold it 
 for half a minute or more that it may drain and set. Eock it 
 from right to left precisely as in the case of a collodion plate. 
 Let it drain until it almost ceases to drop, and then hold it prettv 
 close to a hot stove until perfectly hard, but not longer than 
 necessary for this. The heat of the stove should be about as 
 great as the hand can bear in holding the plate. 
 
 The varnish must of course not be returned into the same bottle 
 as that from which it was poured off, otherwise it will soon have 
 bits of collodion, dust, etc., on it. The writer invariably manages 
 as follows : Take two clean six-ounce vials, fill one with filtered 
 varnish, put on the neck of the other a funnel of about two and 
 one-half inches in diameter, with a paper filter in it. Pour off 
 from the plate into this filter ; in this way there will be less 
 varnish lost, and less trouble in getting the stream from the plate 
 into the bottle. The varnish having run through the filter, is of 
 course clean, and when the first bottle is empty, the funnel is 
 transferred to it, and the operation reversed. The funnel with 
 the filter in it may stand permanently in the neck of the bottle, 
 to which it supplies the place of a cork, and so is always ready. 
 
 The varnish which has been poured off from plates has of 
 course lost alcohol by evaporation, and is thicker than at first. 
 Therefore before the pouring-off' bottle is used for varnishing 
 with, a little alcohol must be added — one-sixth or one-eighth its 
 bulk, in round numbers, but this is a point of which the operator 
 
40 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 must learn as quickly as possible to judge for himself. If varnish 
 is too thin it is apt to dry dead, and does not properly protect the 
 plate. A negative film varnished with a very thin varnish can 
 be easily rubbed up by the finger. Such negatives are of course 
 very perishable, and are soon destroyed in printing. If too thick 
 it is less easy to work with, and removes the film too far from 
 the paper in printing, thus (especially in shade-printing) diminish- 
 ing the sharpness of the print. 
 
 Some varnishes require heat only before their application; 
 generally, however, they should be dried by heat, as well as be 
 applied on a warm plate. The drying by heat expels the vola- 
 tile portions more thoroughly, and renders the varnish less liable 
 to become soft and sticky in printing. 
 
 The main points are to get the corners covered immediately 
 after you begin to pour, to put on enough, and to bring it down as 
 above explained to a full, slow, square wave. The learner cannot 
 pay too close an attention to these directions. By doing so he 
 will get a smooth, even plate. Neglecting them, he will find : — 
 
 Ridges. — These start from some point at the edge of the plate 
 and extend some distance over the face of, or even all across the 
 negative. If strong enough to be likely to show in the printing, 
 the plate must be flowed with alcohol, drained, and revarnished. 
 
 Lines result from a momentary stopping of the wave of var- 
 nish. The varnish dries a little on the hot plate during the 
 pause, and the result is a line exactly marking the position it 
 then had. The hotter the plate, the more apt lines will be to 
 appear. If a line has been made and is seen before you begin to 
 pour off, it may be lessened, and sometimes entirely removed, by 
 keeping on the varnish a few seconds longer than usual before 
 beginning to pour off*. Fine parallel lines may come from omitting 
 to rock the plate. 
 
 Drying Dead. — This results in the production of a film looking 
 like ground glass — sometimes fine, sometimes coarse. If fine, it 
 may not show at all in the printing ; if coarse, it will. This may 
 arise from several sources : — 
 
 From Dampness of the Film. — After the film is surface dry, it 
 takes a long time to dry through, and the drying must be thorough 
 before the varnish is applied. So, too, the film is very absorbent 
 of atkiospheric moisture, and even after thorough drying and 
 standing for weeks, may easily in damp weather absorb enough to 
 
MAKING- THE NEGATIVE. 
 
 41 
 
 affect the varnisliing. It is therefore better, so far as convenient, 
 to varnish in clear dry weather, or at least after the plate has 
 remained some time in a warm dry room. 
 
 Too thin a varnish may also cause drying dead, or too little ap- 
 plied. If, as soon as the plate is covered, the varnish be poured 
 off again, it will almost certainly dry dead, because the surface 
 only was moistened ; this presently soaks in and leaves the film 
 only half saturated with varnish. This is perhaps the commonest 
 of all causes of drying dead, and often (by the beginner) the last 
 suspected. Therefore the writer advises, if the operator is 
 troubled by this difficulty, to proceed as follows : Put on an 
 abundant supply of varnish after covering the plate, send back a 
 ■wave to the far end, and then hold the plate quite level and 
 motionless for at least twelve seconds quietly counted. At the 
 end of this time, incline the near right-hand corner until a steady 
 stream runs into the bottle, and then, as before directed, bring 
 the end up with a quick motion. 
 
 Negatives will be found to vary; some will dry smooth with the 
 very same treatment that gives, perhaps with the very next one 
 varnished, a dead film. This depends upon the amount of re- 
 development they have received ; the more redeveloped, the more 
 apt to dry dead, because there is more silver powder to soak in 
 the varnish. If found necessary, the varnish may be kept on 
 even for fifteen or twenty seconds, to penetrate thoroughly. 
 
 Special care should always be taken not to allow the varnish 
 to get over the edges upon the back of the plate, not only 
 because it is troublesome to clean it off, but because if a stream 
 of varnish runs across the back of the plate, it will often happen 
 that the corresponding part of the face will dry dead, the evapo- 
 ration going on at the back keeps the corresponding portion of 
 the face cool, and thus prevents the drying smooth. 
 
 Breathing on the plate may at times, and under some circum- 
 stances, lead to spots of deadness. 
 
 Often a deadness of the surface will not affect the printing. 
 An experienced operator will be able to distinguish at once 
 whether the evil is great enough to bring about this result. If, 
 when the plate is examined by allowing the light to fall through 
 it, the deadness is not at all or very slightly perceptible, the nega- 
 tive will probably print well. - / 
 
 Revarnishing. — But if the roughness is quite distinct, a retnedy 
 must be applied. Since the first edition of this work was printed, 
 4 
 
42 
 
 INTRODUCTION TO PHOTOGRAPHY, 
 
 it occurred to the writer to remove the varnish at once by hot 
 alcohol, and this proves to be much the best method. 
 
 The defective plate is to be warmed precisely as for varnishing, 
 and then instead of varnish, an abundant quantity of ninety-five 
 per cent, alcohol is poured on and well worked over the plate ; this 
 is then poured off and a second portion used to wash off residue. 
 The plate is then allowed a few moments to become quite dry, is 
 heated again, and varnished precisely as with a new plate. This 
 operation, when carefully performed, leaves nothing to be de- 
 sired in its results. 
 
 Ridges, that is, lines of greater thickness extending across the 
 plate, may be easily got rid of in the same way. 
 
 When it is intended to print a very large number of positives 
 from one negative, two coats of varnish may be applied. Mr. G-. 
 W. Wilson always gives two coats, touching out defects between 
 the two. In this case, the varnish should be thinner than when 
 one coat only is applied. 
 
 It is a good plan, as soon as the face of the varnished plate is 
 dry, to draw a piece of blotting-paper along the lower edge of the 
 glass ; this prevents the production of a thick ridge there, which 
 would have a tendency to lift up the paper in printing, and pre- 
 vent a close contact with the adjoining parts. 
 
 § 13. — Ambrotypes and Ferrotypes. 
 
 If the development of a negative be stopped as soon as all the 
 details are out and considerably before printing density is reached, 
 we have a picture called an Ambrotype when made on glass, and 
 a Ferrotype when made on a thin plate of varnished iron. The 
 high lights appear white by reflected light, because of the white- 
 ness of the silver deposit of which they are made ; the transparent 
 portions are rendered black by black varnish applied on the back, 
 in the case of the ambrotype, and by the black face of the metal 
 in the case of the ferrotype. 
 
 All negatives, therefore, in an early stage of their develop- 
 ment, are ambrotypes. But to get the best effects, it is found ad- 
 vantageous to use in the negative bath a little more acid, and to 
 employ an old and ripe collodion, for it is necessary to keep the 
 shadows perfectly transparent and free from the least tendency to 
 veil, which would destroy their depth and richness. 
 
 An ordinary negative collodion may be used if it is thoroughly 
 
MAKING THE NEGATIVE. 
 
 43 
 
 ripe ; if not, tincture of iodine may be added till it is sherry wine 
 colored. (Tincture of iodine may be purchased, or may be made 
 by dissolving iodine in alcohol. Thirty grains of iodine to the 
 ounce of alcohol is a convenient strength.) 
 
 Some photographers prefer a special collodion containing iodide 
 of potassium, now rarely used in negative collodions. Mr. Thomas, 
 of New York, uses the following proportions : — 
 
 Iodide of potassium 50 grains. 
 
 Bromide of potassium 30 " 
 
 Dissolve these salts, with the aid of heat, in 8 ounces of alcohol, 
 Take 60 grains of pyroxyline, dissolve it in 5 ounces of ether and 
 2 of alcohol. Then add the above while still hot. 
 
 The developer is to be the same as for negatives, taking care 
 that it be sufficiently acidified, for which purpose one-half more 
 acetic acid may be added than for negatives. 
 
 § 13. — General Remarks. 
 
 Avoid doing anything which may cause dust in the dark room. 
 Keep the dark slide clean and well wiped. 
 
 Notice the camera from time to time to assure yourself that the 
 wood work is close and tight. 
 
 See that the focussing slide sits tight and close up. The spring 
 that holds it to the body of the camera will sometimes get out of 
 order and affect the two slides differently, so that one comes up 
 more closely than the other. The result of this -^ill be that the 
 focussing surface no longer corresponds with the sensitive film, 
 and no matter how carefully the focussing be done, the pictures 
 will not be accurately sharp. 
 
 Make sure that the camera-stand is absolutely steady and not 
 given to trembling. 
 
 See that the dark room is thoroughly ventilated, so that whilst 
 at work you are not inhaling noxious vapors, and as little as 
 possible of the fumes of collodion. 
 
 Removing stains from hands. — Fresh stains come away much more 
 easily than those that have been exposed to light. Dilute hydro- 
 chloric acid, to which a little solution of bichromate of potash is 
 added, is very effectual. It should be followed by an applica- 
 tion of a vegetable acid, tartaric, citric, or better yet, binqxalate 
 of potash, which last is also convenient for removing ink' stains. 
 One or more of these substances should be kept at hand in solii- 
 
44 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 tion to use after the bicliromate solution, which otherwise leaves 
 behind a yellow stain and disagreeable odor; the injurious effect 
 upon the skin is also diminished. Perchloride of iron, which has 
 been recommended, the writer has not found to answer. Cyanide 
 of potassium should not be used. Silver stains on clothes are best 
 removed by solution of corrosive sublimate, which destroys them 
 effectually and without injuring either the texture or the color. 
 
 CHAPTER III. 
 PRINTING. 
 
 § 1. — Sensitizing. 
 
 As alhumenized paper is now almost exclusively used in positive 
 printing, it will be the only method described in this introduction ; 
 others will be hereafter given. 
 
 Those who operate upon a large scale sensitize their sheets 
 whole, others divide them into halves or quarters, and one corner 
 
 is to be folded backwards for 
 ■^^S- 11- half an inch or three-quarters. 
 
 The piece is then held at its 
 two ends, is folded into a loop 
 by bringing the hands some- 
 what together so that the cen- 
 tre will be lowest, and the 
 albumenized surface under- 
 most. The centre of the sheet 
 is made to touch the bath first, 
 and then, by opening the hands 
 and lowering them, the whole 
 surface is regularly opened out on the bath. In this way air- 
 bubbles are avoided. Should an air-bubble remain under the 
 paper, its place will be marked by a white spot in the print. 
 
 Laying the sheet ou the piiutiug bath. 
 
 Positive Bath. 
 
 Water 
 
 Nitrate of silver 
 
 22 ounces. 
 3 " 
 
 Th^j)aper remains on it about four minutes in winter, and two 
 in sumVier. It is then lifted oft' by the corner turned up, and 
 
PRINTING. 
 
 45 
 
 pinned to a rod or string to dry. A convenient method is to take 
 a long strip of wood, and glue on it at spaces corks, into which 
 to stick the pins. 
 
 When the bath turns dark, shake it up with half an ounce of 
 kaolin. Let it stand some hours, with occasional shaking, and 
 filter. 
 
 Examine the bath from time to time with red and blue litmus 
 paper, and keep it as nearly neutral as possible. If the blue 
 litmus turns red, the bath is too acid, and may be neutralized 
 with a grain or two of bicarbonate of sodium. If red litmus 
 paper turns blue, the bath is alkaline, and a little dilute nitric 
 acid must be carefully added. It is best to have the solution an 
 inch deep in the glass or porcelain bath. Too shallow a bath 
 tends to irregular action. 
 
 See that the paper is thoroughly dry before printing it. A 
 dense negative prints best in the sun, a thin one in the shade. 
 That is, it is to be exposed at a window to a good light, but not 
 to sunshine. A negative too thin to give a good result in any 
 other way, may often be successfully printed by laying a sheet 
 of tissue paper over it. 
 
 Printing frames are made in many different patterns. The 
 writer recommends the bar frame (Pig. 12) to the exclusion of all 
 so-called improvements on it, which 
 generally fail to bring the paper 
 closely up to the negative, unles the 
 pressure is dangerously increased. 
 The padding behind the paper should 
 be of soft woollen material, felt, or 
 best of all, piano-cloth. 
 
 Print till the highest lights just 
 hegin to color. By this time the 
 dark shadows ought to show the 
 greenish, almost metallic, look 
 known as " bronzing." 
 
 Examine the print from time to 
 time, taking the frame to a darker 
 part of the room, open the back 
 gently, taking care not to shift the print, bend it back, and judge 
 of the degree to which the printing has gone. 
 
 As fast as the exposure is finished, throw the prints into'a dark 
 drawer. 
 
46 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 When all are ready, proceed to wash them by putting them 
 one hy one into a basin of water, where they lie ten minutes. 
 This water is to be carefully added to the residues, as it is rich 
 in silver. Change the water two or three times, then tone. 
 
 As the printing-bath will continually lose in strength, it should 
 be kept up by adding crystals of nitrate of silver, remembering 
 that each sheet of 18 x 22 will remove about a drachm and a 
 quarter of nitrate of silver. 
 
 § 3.— Toning Bath. 
 
 Water 16 ounces. 
 
 Chloride of gold 4 grains. 
 
 Acetate of sodium 1 ounce. 
 
 If mixed with warm water, it will in two or three hours be 
 ready for use, otherwise it is best kept till next day. In very 
 cold weather, a little more gold must be used ; and the bath, 
 except in hot weather, should be warmed till it is tepid. 
 
 Put in only a few prints at a time, and keep them constantly 
 moving about. When they reach the shade desired, let them 
 remain a little longer, as they will afterwards recede a little in 
 color; then take them out, pass them through clean water, and 
 proceed to fixing. This bath will give rich warm tones, but not 
 black ones, for which, if desired, the carbonate bath, or better, 
 the chloride of lime bath (see beyond), must be used. 
 
 Prints that look blue when finished, have been over-ioned by too 
 
 long an immersion. 
 I 
 
 § 3. — Fixing Bath. 
 
 Water . ' 33 ounces. 
 
 Hyposulphite of sodium 4 " 
 
 Keep the prints moving about in this, and leave them in fifteen 
 minutes. The above bath will suffice for two whole sheets, and 
 must be increased in proportion if more are to be toned. Never 
 use on any subsequent day a baih that has had even only one single 
 print fixed in it, or the print so toned will surely fade in time. 
 
 § 4. — Washing. 
 
 A very thorough washing is needed to prevent fading. Prints 
 thrown into a tank into which a tolerable stream of moving water 
 falls, will be sufficiently washed in six to ten hours, provided 
 there are not too many of them. When the number is large, the 
 tank must be continually emptied of water and refilled. 
 
A FEW GENERAL RULES FOR BEGINNERS. 
 
 47 
 
 CHAPTER lY. 
 
 A FEW GENEEAL RULES FOR BEGINNERS.' 
 
 1. Invariably wash the fingers under the tap immediately 
 after they have been in any solution, but most particularly after 
 hyposulphite. Neglect of this will transfer portions of one solu- 
 tion to another, and lay the foundation for long series of failures, 
 which may prove utterly distressing and perplexing. 
 
 2. Do not be actuated by an ambition to commence with diffi- 
 cult work. Point the camera out of the window, and take the 
 view, such as it is, until it is done with certainty and success. 
 After that will be time enough to try portraiture— last of all, 
 copying. 
 
 3. Begin with small plates, and do not try large ones until 
 the smaller are mastered. Half-size will be the largest proper to 
 begin with. 
 
 4. Do not undertake to make collodion before its use is learned. 
 Be satisfied to purchase that which some experienced friend re- 
 commends. 
 
 5. Do not tend towards intensifying thin pictures by after-treat- 
 ments. When photography was less understood this was oftener 
 necessary. It is better to wash off and begin again, and generally 
 less trouble to get a better result. 
 
 6. The quickest way to learn is this : take any simple object 
 as above, a brick house, for example, and try it again and again, 
 varying the length of exposure and the length of development, 
 until a negative is got that prints exactly right. This will teach 
 more in a few mornings than as many weeks of random work. 
 
 7. Successes that come by chance are worthless, and prove 
 nothing as to ability. Try to know exactly the causes of success 
 and of failure. 
 
 8. The right exposure may often be got the first time, but not 
 
 ; 
 
 1 At the end of this volume will be found descriptions of those simple j^hemical 
 manipulations which are used in photography, and with which thybeginner 
 will do well to make himself early familiar. / 
 
48 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 certainly ; yet a careful examination of the first trial ouglit to 
 enable one to make sure of the second. 
 
 9. If the camera needs to be placed in the sunshine, throw the 
 focussing cloth over it before the shutter is drawn out to make 
 the exposure. The direct light of the sun may find its way 
 through cracks too small to admit diffused light. 
 
 10. Once in a while wipe out the camera with a damp cloth to 
 remove dust, which by settling on the plate may cause pin-holes 
 or comets. 
 
 11. Treat the lenses with the utmost care. Never leave them 
 about ; never wipe them with anything but the softest old linen 
 cambric, perfectly clean, and not even so except when needed. 
 
 12. Do not unscrew the tubes unnecessarily to wipe the inside 
 surfaces of the lenses, or for any other purpose, and always do 
 this in dry weather, or damp air will be admitted, which will be 
 apt later to leave a dew on the lenses. If any of the lenses are 
 set loosely in the tube, be sure they are replaced with the same 
 side front as before. 
 
 13. Do not let either the lenses or the camera stand in the sun, 
 the result will be warping and splitting of the wood, and discolo- 
 ration of the lens. 
 
 14. Be sure that the camera stand is free from vibration. Un- 
 cover the lens very gently so as not to shake the camera in the 
 least, or the definition will be impaired. 
 
 15. Unless the ground glass is of the best, the focus cannot be 
 taken with accuracy. Much of the ground glass in cameras made 
 for sale is very poor. The glass should, in fact, not be ground at 
 all, but only "grayed," that is, have its surface removed by 
 "rubbing with fine emery powder. Focus a brick house 200 feet 
 oft' with a short focus lens, and if the white lines of the mortar 
 cannot be seen, either with the naked eye or with a magnifier, 
 the glass is too coarsely ground ; and it is to be expected that all 
 the work done with it will be inferior. 
 
 16. Focussing with a microscope is less trying to the eyes, and 
 gives sharper work. The larger the lens of the microscope used, 
 the less the eye is strained. An engraver's glass set in horn 
 is good, but a similar one, an inch and a half or two inches in 
 diameter, tires the eye still less. 
 
 17. |jearn exactly how to make a negative bath, and then avoid 
 doctoring. For the most part it will only be injured. Add a 
 very little carbonate of soda, and sun it, if out of order, for some 
 
 '\ 
 
A FEW GENERAL RULES FOR BEGINNERS. 
 
 49 
 
 hours in direct sunlight, then filter and acidulate as directed for 
 a new bath. Filter first, then acidulate. 
 
 18. Decaying organic matter, foul smells, sulphuretted hydro- 
 gen, and fames of ammonia may be expected to produce fog. 
 
 19. Do not think it necessary to have the dark room too dark. 
 There may be light enough to work with perfect comfort, and 
 the strain on the eyes in going backwards and forwards will be 
 so much the less : an important consideration. 
 
 20. Have nothing to do with cyanide of potassium. It is a 
 substance of which the photographer has no real need. If used at 
 all, it should be left to those who have learned their experience 
 on less dangerous materials. 
 
 21. Eemember that most chemicals are poisons, and that if the 
 fingers are not washed immediately after being plunged in them, 
 or if, even with this precaution, they are kept long in the solu- 
 tions, mischief may ensue. What this mischief may be is of so 
 gradual and insidious a nature, as to be ascribed to any other 
 cause than the right one. 
 
 22. Eemember also that most fumes are injurious. Yapors of 
 ammonia disorganize and paralyze the blood corpuscles. Yapor 
 of ether is very injurious to the nervous system, produces head- 
 ache, and depresses the whole tone of the body. Nitric acid is 
 highly poisonous ; its fumes, when inhaled for a sufficient length 
 of time, will cause death. 
 
 23. Therefore make every provision for thorough and complete 
 veiitilatiom. And do not fancy (as many most unwisely do) that 
 because the senses become habituated to such fumes, and cease 
 to be inconvenienced by them, that the system is therefore not 
 suffering. 
 
 24. Adopt invariably the maxim, that whatever is worth doing 
 is worth doing well. Practice never makes perfect without care, 
 and thoughtful and intelligent observation. Some will do a thing 
 all their lives, and always badly. 
 
 25. Acquire the habit of rinsing out all the vessels as soon as 
 emptied, and of not leaving the adhering portions to dry on the 
 bottom and sides, when it will take five times the trouble to get 
 it out. 
 
 26. Make it a rule to wash every vessel before you put it away, 
 and again before using it. Never trust to anything being clean, 
 but make it so. If there is any one thing that is ess^tial in 
 photography, it is care of this sort. The delicate reactions on 
 
50 
 
 INTRODUCTION TO PHOTOGRAPHY. 
 
 whicli photograpliic processes depend are sufficiently exacting, 
 without further embarrassing the processes by introducing foreign 
 matter of unknown nature. 
 
 27. Never forget that no vessel is rendered clean (even if what 
 it has contained has been merely an aqueous solution) by simply 
 pouring water in and throwing it out. 
 
 Hold therefore the vessel, whether beaker, bowl, bottle, or 
 whatever it may be, under the tap, so that the water may run 
 over every part, inside and out. Outside, because it is never 
 certain that a glass vessel is clean inside unless it has also been 
 made so outside. Eemember that if a vessel be hastily rinsed 
 out, there may be left drops of the old solution adhering to the 
 sides above the part washed, and that a single drop so left may- 
 spoil the following operation. This direction may be thought so 
 much a matter of course as to be superfluous; it is not so. 
 
 In all cases, except where the old contents are very easily 
 removable by water, employ the bichromate cleaning solution, 
 which for this purpose may be made of double or treble strength, 
 so as to work more energetically. 
 
 28. In the field, before making the first exposure, take pains 
 to make sure that everything is right. (See especially sections 3 
 and 4 in chapter on Landscape Photography.) 
 
 29. Make it a fixed rule that every failure shall be made the 
 stepping-stone to some new advance. If by accident any work is 
 destroyed or injared, make it a rule that it shall be replaced with 
 better. The result will be that, instead of feeling that time has 
 been lost in merely remedying an accident, there will be a feeling 
 of congratulation that that very mischance was converted to an 
 advantage. 
 
 Again, instead of falling into a routine of work from time to 
 time, consider whether there may not be some better mode of 
 operating, and if a probable improvement suggest itself, or is 
 suggested by qthers, give it a fair trial. 
 
 On the other hand, beware of capriciously changing about from 
 one process to another. There are often several good ways of 
 doing some one thing, any one of which well done is better than 
 any other unskilfully carried out. It is best, therefore, to acquire 
 a thorough knowledge of some good means of managing each 
 operation — this gives firm foothold. Experiments in other di- 
 rections; then will be compared carefully with the regular plan, 
 
A FEW GENERAL RULES FOR BEGINNERS. 
 
 51 
 
 whicTi will never be abandoned until by repeated trial tbe new 
 method has shown itself distinctly superior. 
 
 30. Success will very often depend upon the willingness to 
 make another trial, for want of which many barely fail. 
 
 31. Finally, the beginner in Landscape Photography is earnestly 
 recommended to act upon a definite system. For example, let 
 him not run from one lens to another, but rather, having provided 
 himself with one thoroughly good one, let him study out its capa- 
 bilities and learn exactly how to use it. Different lenses work 
 so differently, that, to the beginner, they are very confusing, and 
 tend to conceal from him the sources of the mistakes and faults 
 that he must necessarily make. Only in one way can he usefully 
 employ himself with several lenses, and that is by using them in 
 succession to take the same view, and observing and studying 
 closely the differences in the results. 
 
 The secret of success lies in taking up separately each different 
 portion of the work and mastering it by careful study. First 
 take the view from any convenient window until you can do it 
 with regular and complete success. Next select some attractive 
 landscape, and try it upon different points, and with varying 
 lights, and longer and shorter exposures, until you have done 
 with it the best that it admits of, and until you know why such a 
 result is the best that can be attained. One such piece of nega- 
 tive-making, worked thoroughly out, will teach as much as thrice 
 the time spent in random view-taking. The student should bear 
 steadily in mind that whilst a thoroughly good negative is very 
 valuable, there is nothing more worthless than a tolerable one. 
 A tolerable negative is not worth the trouble of printing, and is 
 consequently worth nothing at all. 
 
PART II. 
 
 PHOTOGRAPHIC OPTICS AND THEORY OF 
 PERSPECTIVE. 
 
 CHAPTER I. 
 
 GENERAL OPTICS. 
 
 § 1. — Reflection and Refraction. 
 
 "When a ray of light (this expression will be more convenient, 
 although wave of light would be more correct) falls upon any 
 surface, a part is reflected and a part transmitted. 
 
 Let the ray A 0 (Fig. 13) pass from the rarer medium on one 
 side of the surface into the denser on the other ; for example, 
 
 out of air into glass. Part of the 
 ray will be reflected and part re- 
 fracted. In order to study these 
 phenomena, we draw a line per- 
 pendicular to the surface E F z.i 
 the point of incidence 0. This 
 line iVO is the normal, and the 
 angle A OiV between the incident 
 ray and the normal is the angle 
 of incidence. 
 
 We find that the reflected ray makes the angle of reflection BON 
 equal to the angle of incidence AON. 
 
 The refracted ray is bent out of its course toioards the normal. 
 In place of continuing on in its direction A 0 I/ii is deflected 
 towards the normal NN', in some direction 0 and the quan- 
 tity of deflection depends upon the character of the substance. 
 The grqater the deflection, the higher the refractive power is said 
 
 to be. 
 
 In thelpregoing we have considered the case of a ray passing 
 
REFRACTION. 
 
 53 
 
 from a rarer medium into a denser. In the converse case the 
 converse result takes place. If in the above figure we suppose 
 the directions to be reversed, and that the ray B 0 passes at 0 
 from the denser medium into the rarer above it, then the ray E 0 
 will be bent away from the normal to precisely the same extent, 
 and will follow the path 0 A. 
 
 It therefore follows from this that when a ray passes from a 
 rarer medium into a denser, and then through the denser again 
 into the rarer, it will emerge in a direction parallel to that in which 
 it entered, provided that the denser medium has parallel sides. 
 
 The ray A D (Fig. 14), in passing through the denser medium, 
 takes the course D B, being deflected towards the normal, and, 
 on emerging, again assumes a direction B G parallel to A D. 
 
 Fig. 14. Fig. 15. 
 
 But if the sides of the denser medium are not parallel, the ray 
 will not emerge from the second surface parallel to its first direc- 
 tion. Thus the sides 0 B F {^ig. 15) of the denser medium 
 not being parallel, the ray A 0, in passing through the surface 
 B takes a different direction B G. 
 
 Different substances refract the rays of light very difierently, 
 and are therefore said to difi^er in refractive power. 
 
 We have a very convenient method of measuring refractive 
 power, which is as follows: — » 
 
 In Fig. 16 let 8' &" be the boundary line between an upper and 
 rarer substance and a lower and denser one. Let any ray of light 
 B 0 pass at 0 out of the rarer into the denser, and let the line 
 0 B' represent its deflected direction. 
 
 "With any distance (9 J. as a radius, draw the curve A N' B' . 
 Draw at the point 0 the normal N N' , and from the intersection 
 A let drop the perpendicular A S, similarly from B' the perpen- 
 dicular B^ S. 
 
 A S will be the sine of the angle of incidence and B' S the sine 
 
54 
 
 GENERAL OPTICS. 
 
 s 
 
 s- 0 
 
 A 
 
 
 
 1 
 
 / 
 
 
 S"\ 
 
 N' 
 
 
 Fig. 16. of the angle of refraction. Each 
 
 of these angles will be conve- 
 niently measured by its sine. 
 
 Now it is found that when any 
 two given substances constitute 
 the rarer and the denser me- 
 dium, the proportion between 
 the lengths oi A 8 and R' S is 
 invariable, whatever be the an- 
 gle of incidence. If the upper 
 medium be air and the lower a 
 certain quality of glass, the sine of refraction S will always be 
 exactly two-thirds the sine of incidence A S, let the ray fall upon 
 the dividing line S' S" at what angle it may. 
 
 The ratio of the sines is then invariable for any given substance, 
 and this ratio is called the index of refraction. In the case just 
 mentioned A jS being to S always as 3 to 2, the index of re- 
 fraction of such glass is said to be | or 1.5. 
 
 The path which will be taken by any ray in passing from one 
 medium into another can easily he traced as follows: Let the ray 
 B 0 pass out of air (or rather out of a vacuum, but the difference 
 is unimportant here) into glass of refractive power 1.5. Draw 
 the normal iV iV' through the point of incidence and perpendicu- 
 lar to the surface. Set off any distance 0 S', and, taking this as 
 unity, make 0 equal to the index of refraction. In this case 
 0 S" will stand to 0 >S" in the proportion of 1.5 to 1. Draw the 
 perpendiculars B', S" A. Putting one leg of a compass at 0 
 and the other at A (the intersection of S" A with 0 B) draw the 
 curve A B\ the intersection of this curve with S' B' when con- 
 nected with 0 gives the path of the refracted ray. 
 
 § 3. — Dispersion. 
 
 In the foregoing section we have reasoned as if light were 
 homogeneous. But white light is made up of rays of very differ- 
 ent refrangibility, so that when a ray of white light A D (Fig. 17) 
 passes at D into the denser medium bounded by the line B C, 
 these rays are differently affected. The more refrangible rays 
 are ber|t more out of their course, following the direction D F; 
 the less^take the direction I) E. 
 
 On reaehing the second surface B Z>, if this surface is not 
 
DISPERSION". 
 
 55 
 
 parallel to the first, but inclined to it, these different rays will 
 have their divergence greatly increased, and will be spread out 
 as there represented. 
 
 Fig. 17. 
 
 We find that a difference of color accompanies a difference of 
 refrangibility, the most refrangible being violet, and so proceeding 
 in the order, violet, indigo, blue, green, yellow, orange, and red. 
 Under very favorable circumstances, and with well-exercised eyes, 
 a commencing disposition to repeat this gamut, like octaves in 
 musical sounds, is observable, far beyond the red a crimson tint 
 has been seen, and beyond the violet, a lavender. 
 
 But, independently of these, the existence of non-luminous 
 influences beyond the limits of the visible spectrum is easily 
 detected. Beyond the red rays, rays of dark heat are made 
 evident by the thermometer, and beyond the violet there exists 
 rays also invisible, but having a powerful chemical effect, so that 
 in a portion of space completely dark, sensitive paper is rapidly 
 impressed. 
 
 "Whilst rays, invisible to our eyes, are thus capable of exerting 
 powerful actinic action, other rays, plainly and even brilliantly 
 visible, exercise little or no actinic influence. The yellow and 
 red rays, in which the chief illuminating power of light resides, 
 scarcely act upon sensitive substances. The green rays exert an 
 influence on some and not on others. 
 
 It is not a little remarkable that sulphate of quinine possesses 
 the power of lowering the refrangibility of the rays beyond the 
 violet, and thus rendering them visible to our eyes. If sulphate 
 of quinine be dissolved in water acidulated by sulphuric acid, and 
 the solution be placed in the dark rays beyond the violet, these 
 become visibly blue. 
 
66 
 
 GENERAL OPTICS. 
 
 CHAPTER II. 
 
 OF LENSES. 
 
 § 1. — Nature of Lenses. 
 
 A LENS may be plane on one side and convex on the other — 
 plano-convex. (Fig, 18.) Plane on one side and concave on the 
 other-»-plano-concave. (Fig. 19.) Convex on both sides — double 
 convex. (Fig. 20.) Concave on both sides — double concave. 
 
 Fiff. 18. 19. 20. 21. 
 
 22. 
 
 23. 
 
 (Fig. 21.) Concave on one side and convex on the other — menis- 
 cus. The meniscus may be of two sorts. If the radius of the 
 convex side is the shorter, the lens is thickest in the middle, and 
 is called a positive meniscus. (Fig. 22.) If the concave curve has 
 the shorter radius, the meniscus is thickest at the edges, and is 
 termed a negative meniscus. (Fig. 23.) 
 
 To understand the action of a lens on rays of light, let us select 
 
 a plano-convex lens and con- 
 Fig. 24. . n . 
 
 sider its properties. 
 
 When a ray of light L A falls 
 
 upon any curved surface at any 
 
 point J., we draw a tangent B 0 
 
 at the point and we may 
 
 then consider the solid body 
 
 A as far as the ray L A is 
 
 considered, not as a body hav- 
 
 a curved surface, but as a prism 
 
 B O for it will act towards the ray L A precisely as if it were 
 
 such a prism. The ray L A passing out of it will be sent away 
 
 from the normal in the direction A II, and will intersect the axis 
 
 I) H at a point H. 
 
 L 
 
 
 
 0 
 
 
 
 \ C H 
 
OF LENSES. 
 
 57 
 
 Let us now consider several rays of light L L\ &g. (Fig. 25.) 
 L strikes at the centre of the curve, where the tangent is parallel 
 to the plane side A B, and is therefore influenced precisely as if 
 
 Fig. 25. 
 
 T' 
 
 T 
 /> 
 
 
 
 
 
 
 
 
 
 
 
 
 
 B 
 
 
 T T r 
 
 it passed through a piece of plane glass, and emerges in the same 
 right line. L' is bent on leaving the curved surface, and tends 
 towards F. Other rays strike the curve still higher from the axis, 
 where the tangents are still more inclined, and are therefore still 
 more deflected. This greater deflection makes up for the fact 
 that the original path of that ray was farther from the central 
 ray, and thus all the rays approximately tend to gather together 
 at a point called the focus. 
 
 What is true of the plano-convex lens, is true of all lenses that 
 are thickest in the centre, of double convex and of positive 
 meniscus lenses. Those lenses which are thinnest at the centre 
 are called negative. They do not collect parallel rays to a focal 
 point, but cause them to diverge. They have no real focus, but 
 only a virtual one. Such lenses taken alone would be of no use 
 in photography, but they are often employed in connection with 
 others. 
 
 If matters passed exactly in the manner above described, the 
 construction of photographic objectives would be far more simple 
 than it is. But the spherical lenses which we use are li?ible to 
 faults, which will next be considered. 
 5 
 
68 
 
 GENERAL OPTICS. 
 
 CHAPTEE III. 
 
 FAULTS INCIDENT TO SPHERICxiL LENSES. 
 
 There are five distinct sources of inaccuracy in the image 
 formed by a spherical lens. These are, Spherical Aberration, 
 Chromatic Aberration, Astigmation, Curvature of the 
 Field, and Distortion. 
 
 § 1. — Spherical Aberration and the Modes of Remedying it. 
 
 All lenses in use at the present day have their curves, parts of 
 spheres. Now it is a property of all spherical curves A Fig. 
 26, that they do not bring the rays exactly to a point at F. Just 
 in proportion as the parallel ray L' is farther from the central 
 axis Z-, so is that ray, after passing through the lens, brought 
 down to the central axis at a point nearer to the lens. The focal 
 length F' for the ray L' is shorter than the length of F for the 
 ray Z, and so on. 
 
 It will be seen, then, that for the spherically curved lens A B 
 there is no real focus, but a succession of foci all the way from 
 i^to F\ and although the fault is intentionally exaggerated in the 
 £gure, it is still so great as imperatively to require attention. 
 
 Fig. 26. 
 
 A 
 
 
 
 V 
 
 
 
 
 
 
 I 
 
 B 
 
 
 Spherical aberration may be destroyed, or at least diminished, 
 in two ways. Either lenses may be so combined that their aber- 
 rations will be in opposite directions, and so compensate and 
 destroy^ach other, or else diaphragms may be employed. 
 
 Correct^n ly Diaphragms. — The ray B" A which would come 
 
FAULTS INCIDENT TO SPHERICAL LENSES. 
 
 59 
 
 to a focus at a point F' nearer to the lens than F (see Figs. 26 
 and 27) is cut off bj the diaphragm CD. We thus greatly in- 
 
 Fig. 27. 
 
 
 
 
 R' 
 
 F 
 
 
 R 
 
 G 
 
 
 / 
 
 
 F 
 
 D B 
 
 crease the sharpness of definition by the use of a stop, though of 
 course at a great sacrifice of light. Thus, if the lens is two inches 
 in diameter, and the aperture of the diaphragm is a quarter of an 
 inch, then, as the areas of circles are at the squares of their dia- 
 meters, the loss of light is gf, or only one sixty-fourth part of 
 the whole light which would reach the sensitive film, if a full 
 aperture could be employed, is left available. 
 
 Although this loss of light is a most serious evil, it is necessa- 
 rily submitted to, and we gain that the image, before dull and 
 hazy, becomes at once sharp and crisp. Before, the lens seemed 
 to have no true focus; now, for any given object, the focus can 
 be found with exactitude. 
 
 § 2. — Chromatic Aberration and Mode of Correction. 
 
 Spherical aberration is independent of the nature of the light 
 employed ; it results wholly from the form of the lens, and occurs 
 even with homogeneous light. We have next to consider a sort 
 of aberration arising from the different indices of refraction of 
 the different rays of which white light is composed. 
 
 When considering the subject of dispersion, we saw that when 
 light fell upon a prism, it was spread out into a spectrum, in 
 which its different constituents were arranged in the order of 
 their refrangibility. And as a lens may be taken to represent a 
 number of small prisms, it follows that the same spreading of 
 the colors wall there take place. 
 
 If, as in Fig. 28, a perpendicular ray of light strikes a plano- 
 convex lens at J, it passes into it unchanged; but at B the dis- 
 persion of the rays takes place according to their refrangibility, 
 and the focus of the violet rays is nearer to the lens th%tf that of 
 the less refrangible rays at the red end of the spectrum. The 
 
60 
 
 GENERAL OPTICS. 
 
 distance between these two foci Fand R is called the chromatic 
 aberration, which in the figure is necessarily exaggerated for 
 clearness. 
 
 Fig. 28. 
 
 A 
 
 
 
 
 
 
 This fact may be easily rendered visible by holding such a lens 
 in the sunlight. Eays of white light L L (Fig. 29) are divided, 
 
 Fig. 29. 
 
 L 
 
 L 
 
 and the violet rays find their focus at F, the red at P. If a 
 white screen be interposed anywhere between the lens and the 
 point /, there will be a circular image of the sun with a red 
 border ; beyond /, where the violet rays cross the red and pass 
 outside, the image will have a violet border. The distance VP 
 along the axis between the foci of the red and violet is termed 
 the longitudinal aberration, and that at // the lateral aberration. 
 1 lis the place at which the least circle encloses the whole of the 
 rays, it is therefore the best focus. 
 
 To understand clearly how the chromatic aberration is cor- 
 rected, it is necessary to bear in mind that the refractive power of 
 substances and their dispersive power are not proportionate to each 
 other. For substances may exist of equal refractive power, and 
 different dispersive, and conversely. 
 
 Let us, then, take two sorts of glasses, and construct a double 
 convex lens of that sort that has the least dispersive power. Next 
 let us form a negative lens {i. e. one thinnest in the middle) of a 
 sort of glass having a much greater dispersive power, and let us 
 
FAULTS INCIDENT TO SPHERICAL LENSES. 
 
 61 
 
 SO regulate its curves that it shall exactly compensate and de- 
 stroy the dispersion of the first lens (by introducing an equal dis- 
 persion in an opposite direction). As the 
 negative lens had a higher dispersive power 
 than the double convex, it will, whilst re- 
 moving wholly the dispersion of the latter, 
 leave it a residue of refraction. So that the 
 compound lens (Fig. 30), although its disper- 
 sive power has been destroyed, is still capa- 
 ble of converging rays to the focus. This is now an achromatic lens. 
 It is not necessary that the negative lens should be double concave, 
 as in Fig. 30. It may be plano-concave, and may be combined 
 with a plano-convex (Fig. 31), or a double convex (Fig. 32). 
 
 § 3. — Astigmation. 
 
 Astigmation is produced in those pencils of light that fall 
 obliquely upon the lens. 
 
 Let G D E F represent the face of a lens, not a section as 
 usually shown in the figures. Let R i?, B' B\ B" be rays of 
 
 Fig. 33. 
 
 light coming from an object so distant that they are parallel. 
 Let the central ray R" pass through the optical centre of the 
 lens; it will emerge parallel to its original direction; itp; prolonga- 
 tion in the direction ^ will constitute a secondary axig. Let E F 
 
62 
 
 GENERAL OPTICS. 
 
 be a diameter of the lens, perpendicular to the axial ray B", 
 and G D another diameter at right angles with the first. Now 
 the rays i?', which reach the lens at ^ and F, strike it under 
 absolutely the same conditions. They will, therefore, undergo 
 equal refraction, and will meet the secondary axis at some 
 point P'. 
 
 But this is not at all the case with the rays E R, which fall on 
 the ends of the other diameter C D. They will strike the curved 
 surface of the lens under very unequal angles, and will be very 
 differently refracted. R D will reach the axis at some point P, 
 C at some point p} 
 
 But the use of a diaphragm cuts off R D and the neighboring 
 rays. Of the rays that are left, R C and the neighboring rays 
 have their focus at whilst R' R' F have their focus at p'. 
 
 It follows, therefore, that oblique pencils have no true focus. 
 For if ^ be taken as the focus, then the rays R' R' F will have 
 crossed at^', and at^ they will have widened out again, and the 
 image of the radiant point, instead of being a point, will be an 
 ellipse, having its major diameter in the direction E F. Con- 
 versely, ifp' be taken as the focus, R G and the neighboring rays 
 will not have converged to a focus, and their section on the focus- 
 sing screen will form an ellipse, having its major diameter in 
 the direction G D. In neither case will the point have its image 
 as a point, hence the name astigmation. (a, no, and anyfi^, point). 
 The image of the point will appear as an ellipse, whose greatest 
 diameter will change its direction according as the focussing 
 screen is farther or nearer to the lens. 
 
 Eays incident perpendicularly upon the lens, do not produce 
 astigmation. If, then, we examine the case of a pair of lenses 
 having convex surfaces outside, and a stop between them, we 
 shall see that if this stop be placed at the centre of curvature of 
 the outside surfaces, then only rays of incidence nearly perpen- 
 dicular to the surfaces of the lenses will be permitted to pass 
 through the stop. Lenses with central stops, will have less or 
 more astigmation, according as their central stop corresponds 
 more or less nearly with the centre of curvature, and as its open- 
 ing is smaller. 
 
 1 The unequal refraction of B G, B D is the cause of coma, which will be 
 presently treated of. 
 
FAULTS INCIDENT TO SPHERICAL LENSES. 63 
 
 In the single meniscus view lens, the astigmation will be less 
 in proportion to the depth of concavity of the front surface. It 
 will also be controlled by the position of the front stop. The 
 nearer this is placed to the centre of curvature of the front con- 
 cave surface, the more nearly will the incidences be perpendicu- 
 lar, and consequently 
 
 the less the astigma- ^^S- S4. 
 
 tion. 
 
 Coma. — Spherical 
 aberration is much 
 more easil}'' removed 
 for direct rays than 
 for those that strike 
 the lens in an oblique 
 direction. Let the 
 rays E B' B" strike 
 the plano-convex lens 
 in an oblique direc- 
 tion. One ray, B' ^ 
 
 which, after refraction at the first surface of the lens, passes 
 through the optic centre C, emerges in a direction parallel to 
 that which it originally took. This line G P' is the axis of the 
 refracted pencil. The ray B" meets the axis at P, whereas the 
 ray B meets it at P' farther on. Thus whilst the rays 
 corresponding with B are gathered at the point P', 
 those corresponding with B" are spread out below it 
 constituting coma. (Fig. 35.) 
 
 This incorrectness, like so many others, is kept 
 within bounds by the use of the diaphragm, which in 
 the above case would cut off" the ray B, and permit only such 
 to pass as would converge on the axis (7 P to a single point, P, 
 or to a sufficiently near approximation. 
 
 § 4. — Curvature of the Field. 
 
 If we suppose an object of some size placed before a lens, we 
 shall find that its extremities do not come to focus on the same 
 plane as its centre. 
 
 The arrow G is supposed to be so distant that its ends and 
 centre may be regarded as equally far removed from the lens. 
 Now if the centre of the arrow G has focus at C, its extremities 
 will have their focus not in a plane perpendicular to the axis of 
 
64 
 
 GENERAL OPTICS. 
 
 Fig. 36, the lens, but at points nearer to the 
 
 lens. The whole image, therefore, 
 will not fall upon a plane, but upon 
 ^' a concave surface. As it is necessary 
 that it should be rendered flat, we 
 shall consider the means of doing 
 this by the conjoint operation of the 
 diaphragm and the correction of the lens. 
 
 Diaphragms. — If a diaphragm or stop were placed immediately 
 in contact with a lens, it would virtually reduce the lens to one 
 the size of the diaphragm. But the diaphragm is always placed 
 some distance away, and then every part of the lens concurs in 
 forming the picture, but each part is only permitted to act upon 
 those rays for which it is intended. 
 
 Fig. 37. 
 
 By the interposition of the diaphragm, the dotted oblique ray, 
 for example, which would reach its focus at a much nearer point, 
 is cut off, and only those rays are permitted to pass which meet 
 at a focus as nearly as possible in the plane in which the central 
 rays find their focus at F. Here is at once a valuable approxima- 
 tion towards a plane field. 
 
 Moreover, by virtue of the stop the rays which form the image 
 meet with a very small angle, and it is evident that the focussing 
 screen may be brought into such a position that all parts of the 
 image will be very good focus at the same time. 
 
 This is flattening the field hy use of the diaphragm. 
 
 Correction. — But the field may also be flattened in the same 
 manner that the correction for chromatic aberration is apphed. 
 
FAULTS INCIDENT TO SPHERICAL LENSES. 
 
 65 
 
 In the simple lens the field is very curved. If we now add the 
 correcting negative lens to remove the color, we shall lengthen 
 out the oblique pencils more than the central. 
 
 This is flattening the field hy correction of the lens. 
 
 ? 5. — Distortion. 
 
 The mathematical conception of a lens regards it as consisting 
 merely of its bounding planes, and destitute of thickness. If 
 lenses actually possessed this form, the images produced by them 
 would correspond strictly with the principles already laid down. 
 But all lenses necessarily possessing a definite thickness, the image 
 is thereby deformed, unless special measures be taken to correct 
 such distortion. 
 
 Every right line, no matter what be its inclination, if it be 
 directly in front of the lens, so that the prolongation of the axis 
 of the lens passes through it, is imaged on the screen as a right 
 line, whether perpendicular, horizontal, or inclined, because of its 
 symmetrical position with respect to the different parts of the lens. 
 
 But if the line be not symmetrically placed, that is, if the pro- 
 longation of the axis of the lens do not pass through it, then the 
 image of such a right line will be curved, with its concavity 
 turned towards the axis of the lens, and a square, 
 for example, will be represented as in Fig. 38. Fig. 38. 
 
 This is termed barrel distortion^ and is seen in 
 the single view lens. 
 
 The position of the diaphragm has necessarily 
 a strong influence on distortion. When the dia- 
 phragm is in front of the lens, as in the case 
 of the view lens, the crossing of the rays takes 
 place in front of the lens, and the lower part of the lens receives 
 the rays from the upper part of the object, and the distortion is 
 barrel-shaped. If the diaphragm be placed behind the lens, the 
 crossing of the rays takes place behind the lens, and the lower 
 part of the lens receives the rays from the lower part of the ob- 
 ject. If now we take the case of two lenses with a stop between, 
 as in photographic doublets, the one compensates the other, and 
 the distortion disappears completely if the lenses be exactly 
 similar and the stop be placed equidistant from each. 
 
 Falling off of Intensity at Edges. — In addition to the foregoing 
 faults incident to lenses there is the defect introduced by the dia- 
 
66 
 
 GENERAL OPTICS. 
 
 Fig 
 
 89. 
 
 D 
 
 
 \ 
 
 / 
 
 
 \/ 
 
 / \ 
 
 
 \ 
 
 /' 
 
 \ 
 
 N 
 
 D 
 
 phragm that the light is strongest at the 
 centre, and falls off at the edges instead 
 of the illumination being everywhere 
 equal. 
 
 For if D D be a diaphragm, it is evi- 
 dent that the pencil of rays that enter it 
 at right angles will be much larger than 
 the pencils that take an inclined posi- 
 tion, as represented by the dotted rays. 
 The diminution of light in the pencils 
 from the sky, is rather an advantage 
 than otherwise ; but the contrary is the 
 case with the pencils from the fore- 
 ground. 
 
 Several ingenious contrivances have 
 been made to counteract this tendency. 
 Thus a conical piece is arranged to 
 set in the opening of the diaphragm 
 D D, within it is an inclined diaphragm. 
 This evidently allows a larger pencil to 
 pass from the foreground than the centre, 
 and the pencil admitted from the sky is still smaller. With 
 badly illuminated foregrounds this arrangement is advantageous, 
 but in ordinary landscapes the distribution of light is found to 
 be sufficiently good in the regular image. 
 
 CHAPTER IV. 
 FOCAL LENGTHS OF LENSES. 
 
 § 1. — Images of External Objects. 
 
 If an opening be made in a shutter A of a dark room, there 
 will be formed on the opposite wall an image of external objects. 
 The rays of light coming from an object B G will cross each other 
 at the opening A ; will form an image E D on the opposite wall, 
 which image will have the following characteristics: — 
 
 will be reversed, because the rays cross at A, and that which 
 was lowest {G) in the object, becomes uppermost (E) in the image. 
 
FOCAL LENGTHS OF LENSES. 
 
 67 
 
 Tf the opening A he small, the image Fig. 41. 
 
 will be very faint, but moderately 
 sharp. 
 
 If the opening he large, the image 
 will be better lighted, but will be 
 confused. 
 
 There will he no focus. E D may 
 
 be at any distance from A. 
 
 The fact that the confusion of the image can only be removed 
 by an excessive diminution^ of the opening, and consequent re- 
 duction of the light, renders it useless for photography. The 
 cause of this confusion is shown in Fig. 42. Let P be any point- 
 Fig. 43. 
 
 of any distant object, as the point (7 of the arrow in the preced- 
 ing figure. The rays that emerge from it, after passing through 
 the opening A B, are spread out upon the wall at A' B', whereas 
 they should be collected at the point F'. 
 
 This collecting of the rays and conveying them to the point 
 is effected by placing a lens at the opening A B. 
 
 But now a new condition comes in with the lens. Without it 
 images were formed though the wall were at any distance from 
 the opening. But with the lens the surface that receives the 
 image must be at a fixed distance from the lens. This distance 
 is its focal length. Measured from the back surface of the lens, 
 it is called the "back focus," an extremely rough and erroneous 
 mode of measurement. Measured from the true point (the centre 
 of emission, hereafter explained) it is the ahsolute focus, also 
 called the principal focus or equivalent focus. 
 
 I With an excessive diminution of tlie opening, another difficulty presents 
 itself, that of diffraction. The lines of light are bent by the edges of the 
 opening. 
 
68 
 
 GENERAL OPTICS. 
 
 ^'ig- 43. If rajs from an external object 
 
 fall upon the lens Z, Fig. 43, and 
 an image is formed at the focal 
 length would be the distance from 
 i^to the lens at Z, supposing the 
 lens to have no thickness. But 
 as all lenses have thickness, the 
 question immediately arises, from what point or part of the lens 
 or lenses is the measurement to be taken ? 
 
 To answer this question it is necessary that we should get a 
 clear idea of certain remarkable points belonging to lenses, single 
 or compound. 
 
 7 
 
 
 
 p 
 
 
 
 § 2. — Optibal Centre. 
 
 All lenses have a remarkable point, to which the above name 
 has been given. All lines that pass through the lens and also 
 
 through this point, are termed 
 ^^ig- 44. transversals, and have the remarka- 
 
 ble property that all rays which 
 pass through the lens along their 
 path, emerge from the lens parallel 
 to the direction in which they en- 
 tered it. 
 
 If Cbe the optic centre, any line 
 ' G T passing through it will be a 
 
 transversal. If now a ray of light strike the lens at T at such 
 an angle that it follows the path T T' it will, on emerging at T\ 
 follow the direction T' P parallel to its original course. 
 
 The optical centre of any lens is easily found. It is only ne- 
 cessary to draw parallel radii from the two centres of curvature, 
 to connect the points at which these radii meet the curves, and 
 to prolong this line till it intersects the axis. 
 
 From the centre G of the one curve draw any radius G B. 
 From the centre G' of the other curve draw another radius G' R\ 
 parallel to the first. Connect the points R R\ prolonging, if 
 necessary, the line of connection R i?', till it intersects the axis 
 G G' . The point of intersection 0 will be the optical centre of 
 the curve. In a double convex lens (Fig. 45) the optical centre 
 falls inside the lens, in the meniscus (Fig. 46) outside of it. In a 
 
FOCAL LENGTHS OF LENSES. 69 
 Fig. 45. Fig. 46. 
 
 double convex lens, whose surfaces are of equal curvature, the 
 optical centre will coincide with the centre of the lens. 
 
 § 3.— Centres of Admission and Emission. 
 
 Fig. 47. 
 
 These centres play too important a part in photography to be 
 here passed over. 
 
 Let 0 be the optical centre, as before, of a double convex lens; 
 then any lines drawn through it, as 
 T T, T' T\ are transversals, and any 
 rays that strike the points TT' at such 
 angles of incidence as to follow the 
 course of the transversals, will, as be- 
 fore explained, emerge at T T'^ on the 
 other side of the lens, and follow paths 
 parallel to their original direction. 
 
 If, now, all the entering rays be pro- 
 longed in their original directions, they 
 will converge to a point P on the axis 
 of the lens. This is the centre of admis- 
 sion. If the emerging rays be likewise 
 prolonged, they will meet at a point P'. 
 This is the centre of emission. 
 
 This statement is rigorously true only for rays very nearly 
 parallel with the axis, for others it is simply an approximation. 
 
 Now, if in Fig. 48 we have a bi- 
 convex lens, and A B be an object 
 before it, G D its image, the focal 
 length of that lens must be mea- 
 sured from P, its centre of emission, 
 that being the point to which all 
 the rays, (7 P, F P, D P, converge. 
 And similarly, if we wish to take 
 
 Fig. 48. 
 
70 
 
 GEXERAL OPTICS. 
 
 into account the distance of the object from the lens, it is to be 
 computed neither from the exterior of the lens, nor from its 
 centre, but from the centre of admission P'. Consequently, 
 when we speak of the conjugate foci belonging to the lens for an 
 object AB^ and its image G these focal lengths are the lines 
 F' P\ FP. 
 
 In the following figure of a meniscus lens, the transversals are 
 seen centering at 0, the optical centre of the lens. The respective 
 
 rays B R R R are those that 
 Fig. 49. undergoing refraction at the 
 
 surface A • follow the 
 courses of the transversals 
 /J through the lens. Emerg- 
 ing they take directions T 
 i?', &c., parallel to those 
 _ which they originally had, 
 and all cut the axis at P, 
 the centre of emission. 
 
 The focal distance of any 
 object in front of this lens 
 will therefore be measured 
 to the centre of admission 
 P'. And the focal distance of any image will be measured from 
 that image to the centre of emission P. 
 
 If the first surface of the lens AB\>q plane, the lens becomes 
 a plano-convex, and the points 0 and P both recede to the inter- 
 section of the curve G D with the axis OP', where they coincide. 
 
 § 4. — To Determine Focal Lengths by Actual Measurement. 
 
 Equivalent Focus. — This term is constantly misapplied, and 
 most of the popular explanations of it are erroneous. The 
 whole matter is, however, very simple, and may be explained as 
 follows : — 
 
 In a plano-convex with its plane side to the object, the focal 
 length is the distance between the ground glass B' (Fig. 50) and 
 the bach surface of the lens, therefore A' B'. This distance is 
 easy to measure, and offers a valuable aid towards determining 
 the focal lengths of other forms of lens. 
 
 Suppose now that we have a doublet M N, 0 P, and that a very 
 distant object is focussed correctly when the ground glass is in 
 
FOCUS LENGTHS OF LENSES. 
 
 71 
 
 the position C D. The question Fig. 50. 
 
 arises, are we to measure from the 
 ground glass at B to what point ? 
 the back lens, the front lens, or 
 what point between ? 
 
 Let us suppose that we find a 
 plano-convex lens E S, which, 
 when placed in the same position 
 as the doublet, and focussed on 
 the same distant object, makes its 
 image C D' exactly the same size 
 as the image C D of the same object 
 given by the doublet. Then these lenses have the same equivalent 
 focus^ and the easily measured focal length A' B' of the plano- 
 convex is also the true (equivalent or absolute) focal length of 
 the doublet. The rays A C, A D, which form the image in the 
 case of the doublet, diverge as if they came from a point A, which 
 point is the centre of emission. 
 
 It follows from the foregoing that all lenses that have the same 
 equivalent focus, will, when focussed on some distant object, 
 produce images of it that have the same size, the one as the others. 
 
 And further, which is important, that lenses of different focal 
 lengths will, when focussed on the same distant object, produce 
 images of it whose size is proportionate to the respective focal 
 lengths. 
 
 If A B, Fig. 51, be any distant object: different lenses placed 
 at L will give images of it having different sizes, but these sizes 
 will always be proportional to 
 the focal length P' F, P' F', &c., 
 and will be larger or smaller 
 in the exact proportion of the 
 focal length of the lens that 
 forms them. A lens having 
 twice the focal length of ano- 
 ther, will, when placed in the 
 same spot, and focussed upon 
 the same distant object, produce an image having twice the linear 
 dimensions of the image given by the first. If, therefore, in 
 order to find the focal length of a doublet, we compare it with 
 a plano-convex as in Fig. 50, it is not essential that the two 
 should give images of the same size, which might in practice 
 
72 
 
 GENERAL OPTICS. 
 
 be difl&cult to attain. But having easily measured the focal 
 length of the plano-convex, we simply compare the size of the 
 two images, the proportion between which establishes the focal 
 length of the doublet. If the image given by the doublet is 
 one-fourth longer, we know that its focal length is necessarily 
 one-fourth longer, and so on. And having thus determined the 
 exact focal length of one doublet, we may use it (just as well as 
 the plano-convex) to determine the focal length of any other de- 
 scription of lens, by the same system of comparing the linear 
 dimensions of the image formed. 
 
 Another practical method of determining the focal length of 
 any form of photographic objective has been indicated by Mr. 
 Gr'ubb. 
 
 Mark the centre of the focussing screen by drawing diagonals 
 from opposite corners. Set the camera on a large sheet of 
 white paper ; place the camera so that the images of two well- 
 marked distant points shall be equally distant, one on each 
 side of the centre. Measure the distance of these two points 
 from each other on the screen. Now turn the camera so that 
 one of these points shall fall exactly upon the centre. Having 
 done this, run a pencil along the side of the camera, ruling a 
 
 to half the length of the space measured on the ground glass be- 
 tween the points. From (7 draw 6^ ^ parallel to A B. The 
 distance on F H its intersection H from F will be the abso- 
 lute focal length of the objective used. 
 
 This having been once correctly done for any one lens, it will 
 serve as a standard for the easy determination of others by the 
 method above described,^ 
 
 Fig. 52. 
 
 lineon the paper underneath. Now 
 turn the camera around again, till 
 the other point falls on the centre 
 of the focussing screen, and draw 
 another line on the paper. 
 
 c 
 
 Let A B and G D be the lines 
 so drawn; continue them till they 
 meet at E. Bisect the angle AEG 
 by the line E F. At any point F 
 erect the perpendicular F G equal 
 
 ' Another method is the following : Focus two objects, so that their images 
 will fall upon the ground glass equally distant from the centre, as before de- 
 scribed ; then measure with a theodolite the angle which these objects subtend. 
 
FOCAL LEjSTGTHS OF LENSES. 
 
 73 
 
 It is remarkable that tlie method of determining the focal 
 length of a lens by focussing an object so that the size of its 
 image shall be equal to its own, and then taking one-fourth of 
 the distance between the object and its image for the focal length, 
 after having been repeatedly shown to be inaccurate, has been 
 constantly brought forward again. The error lies in the misap- 
 plication of the formula J ~ y + ^ which it is attempted to 
 
 afford a proof. This formula neglects the thickness of the lens, 
 which, in compound lenses (^. e. doublets, &c), is often very con- 
 siderable, and thereby introduces an error. Nor can this error 
 be avoided by computing these focal distances from the optical 
 centre of the lens, since they must be computed from the centres 
 of admission and emission to render the formula applicable.^ 
 
 § 5. — To Calculate the Focal Length of a Lens from its Dimensions. 
 
 In the following formulae, it will be taken for granted that the 
 lens is made of glass, having its refractive power equal to 1.5. 
 The more general expressions will be given in foot-notes. The 
 focus in all cases is determined for sunlight or parallel rays fall- 
 ing parallel with the axis of the lens.^ 
 
 In the case of a glass sphere the focal length is IJ times the 
 radius, measured from the centre of the sphere. It falls there- 
 fore beyond the sphere at the distance of half the radius from 
 the surface.^ 
 
 Calling this angle a, and the distance measured on the ground glass, the focal 
 length will be found by the expression — 
 
 d 
 
 /= « 
 
 2 tan— 
 3 
 
 ' If it were required to make a correct determination by the method of fo- 
 cussing equal size, it would be necessary to determine for any lens the distance 
 which separates its centres of admission and of emission. Calling this S and 
 
 the distance between object and image, D, we have /= — ^ , the positive sign 
 
 applies when the centres cross each other, the negative when they do not, as in 
 the photographic objectives. 
 
 2 These calculations are all based (except when otherwise specified) accord- 
 ing to custom, and for simplicity, upon the supposition that the lens has no 
 thickness. 
 
 3 The general expression is as follows : Let r equal index of refraction, B the 
 
 r 
 
 radius, / the focal length, then f=R ^^^ 
 
 6 
 
74 
 
 GENERAL OPTICS. 
 
 Double Convex Lens} — If the curves on both sides are equal, 
 the focal length will be equal to the radius. 
 
 If unequal, multiply the radii together, and divide by half 
 their sum. If the radii are respectively 5 and 7 inches, the focal 
 length will be ^ inches or 5§ inches. 
 
 Plano-convex Lens. — Where the plane side is exposed, the focus 
 will be twice the radius, measured from the convex side. Where 
 the rays fall on the convex surface f the thickness of the lens 
 must be deducted from twice the radius, and this will be mea- 
 sured from the plane side. 
 
 Meniscus Lens. — Multiply the radii, and divide the result by 
 half the distance of the radii. For example, if a meniscus has 
 its positive curve with a radius of 5 and its negative 7 inches, its 
 
 35 
 
 focal length will be ^77^ — or 35 inches. 
 2 I ' — ^Jj 
 
 If the concave surface had a radius of 5 and the convex of 7, 
 
 the focus would be the same, but 
 it would be a virtual focus^ an im- 
 aginary one in front of the lens. 
 
 So in Fig. 63, the parallel rays 
 R R R are spread out by the 
 negative meniscus, so that if their 
 direction were continued back- 
 wards, they would meet at the 
 virtual focus. 
 
 Although this focus has only an imaginary existence, it be- 
 comes important in compufing the effect of introducing di negative 
 lens, as in several forms of photographic objectives. 
 
 Ficr. 53. 
 
 § 6.— Focal Lengths of Combined Lenses Computed from their 
 
 Elements. 
 
 Where two lenses of known focal length are combined to- 
 gether, it is easy to determine the focal length of the combina- 
 tion. It becomes here necessary, however, to take into account 
 the distance at which the two lenses are separated, as the focal 
 length always increases as this separation increases. 
 
 1 The general expression for the focal length of any lens in terms of its radii, is 
 the positive sign belonging to the biconvex lens, the negative to the 
 meniscus. 
 
FOCAL LENGTHS OF LENSES. 
 
 75 
 
 Add the two focal lengths together, and subtract the distance 
 of separation. Multiply the two focal lengths together, and di- 
 vide this last quantity by the first, which gives the focal length.^ 
 This formula, which, like the preceding, depends on the suppo- 
 sition that glass with a refractive power of 1.5 forms the material 
 of the lenses, is that which is employed by opticians in their 
 calculations. 
 
 Two lenses of 6 and 10 inches focal length respectively, sepa- 
 
 6x10 
 
 rated one inch, will have their combined focal length ^ 
 
 or 4 inches. 
 
 If these lenses when combined are to have a focal length of 5 
 inches, this can be effected by giving them a separation of 4 
 
 inches, because ^ is 5 inches. 
 
 § 7. — Conjugate Foci. 
 
 Up to the present point we have considered parallel rays only. 
 But when divergent or convergent rays fall upon a lens, its focal 
 length is thereby necessarily altered. 
 
 Thus the lens A B having its focus at i^for parallel rays, may 
 have it at D for diverging, and at E for converging rays. 
 
 If D' be a point from which diverging rays emanate and these 
 converge again after passing through the lens, at these two 
 points D and D\ are termed conjugate foci. If D' be an object, 
 it will have its focus at D, These points are interchangeable, 
 so that if the object be placed at D, its focus will be at D'. 
 
 ■ If / and/'' are the respective focal lengths, and d the distance of separa- 
 
 //' 
 
 tion, then the combined focus will be — 
 
76 
 
 GENERAL OPTICS. 
 
 Fig. 55. 
 
 To observe this better, let us take 
 a plano-convex lens, with its plane 
 side to the object, 
 
 The object D' has its focus at D. 
 If the principal focus (that for paral- 
 lel rays) be called /, and the distance 
 D' C, u and G v, then we shall 
 have this relation : — 
 
 1 1 
 
 / u 
 
 or V 
 
 u—f 
 
 This equation will permit, if the principal focal length is 
 known, to determine the position of the image D of any object 
 situated at any point D'. If, for example, the lens have a focus 
 of 6 inches, and the object D' is 10 feet or 120 inches off, we shall 
 have — 
 
 6x120 720 .„,- 
 
 " = 120=6 = m = 
 
 The focus of such a lens will, therefore, be a little over three- 
 tenths of an inch longer for an object at the distance of ten feet, 
 than for a very distant object, that is to say, for parallel rays. 
 
 It will be seen that this formula gives a very simple rule for 
 calculating focal lengths. If the principal or absolute focal dis- 
 tance of a lens be known, and we place an object nearer to the 
 lens, and require to know what will be the focal length of the 
 lens for such an object, we have only to take these two quanti- 
 ties — the absolute focal length and the distance of the object. 
 First multiply them and then subtract them, and divide the first 
 number by the second, as in the example where 120 was multi- 
 plied by 6, and divided by 120 less 6. 
 
 It is a very important point, and one that has been too often 
 overlooked in treating the subject elementarily, that the formula 
 111 
 
 = - + - neglects the thickness of the lens. In practice it 
 is necessary either to introduce a correction for this quantity,^ or 
 
 ' The most general form of expression for conjugate foci is 
 
 u \ n r r' — (w — 1) i r' K-\-t r r' 
 
 v = i I 
 
 u (n — 1) (r + rO — (n — 1)^ t j- + (w — 1) t r — n r r' 
 
 Tliere t is the thickness of the lens, rr' the radii, and n the index of refraction. 
 — Secretan, Sj/stemes Optiques Convergents, 54. 
 
FOCAL LENGTHS OF LENSES. 
 
 77 
 
 else to consider the various focal lengths as measured from the 
 centres of admission and emission already described (p. 69). In 
 the case of a plano-convex lens, these centres fall together at the 
 centre of the convex curve, and the focal lengths are correctly 
 measured from the point G in the figure. 
 
 Although, exactly speaking, the focal length of the image 
 always varies with its distance from the lens, yet there is practi- 
 cally a distance for each lens beyond which all objects are simul- 
 taneously in focus. If, for example, we say that a difference of 
 focal length not exceeding g'^ of an inch may be neglected, then 
 "we may fix for every focal length of lens the distance beyond 
 which all objects are practically at once in focus. 
 
 fu 
 
 We had on the last page the formula v = -. Now, if the 
 
 u •/. 
 
 limit of u is that it shall not be more than -g\ of an inch longer 
 than the principal focus, put u = f ~ and we have 
 
 As / is inconsiderable in comparison with the other members 
 of the equation, it may practically be neglected, and it may be 
 said that all objects that are distant over fifty times the square 
 of the focus, are simultaneously in focus. 
 
 Consequently : — 
 
 For 
 
 lenses of 3 inches focal length the distance is 
 6 " " 
 
 10 
 12 
 16 
 
 37| 
 150 
 300 
 417 
 600 
 1065 
 
 feet. 
 
 Objects at these distances may be said to have practically the 
 same focal length as those at any greater distance. To get objects 
 at these distances into focus simultaneously with those at less 
 distance, we must depend upon the depth of focus'''' of the lens, a 
 very precious quality possessed by different lenses in very various 
 degrees. 
 
 When the image is formed by rays which meet at a very small 
 angle, as at i^. Fig. 37, it is evident that the focussing screen can 
 be racked a little in or out without much injury to the definition, 
 and thus a good uniform average focus is obtained. 
 
78 
 
 GENERAL OPTICS. 
 
 CHAPTER V. 
 
 PHOTOGRAPHIC OBJECTIVES. 
 
 Tn this claapter will be briefly considered the various forms of 
 photographic objectives now chiefly used. 
 
 Fig. 56. 
 
 § 1. — The View Lens. 
 
 By a view lens is understood a single achromatic combination, 
 -usually consisting of two pieces, forming a meniscus or a plano- 
 convex lens, witb the concave or plane face, as the case may be, 
 turned to the light. This form of lens is figured at page 61, Figs. 
 30, 31, 32. The combination of a double convex of crown and a 
 double concave of flint glass is the usual method employed. 
 
 Latterly Dallmeyer has produced a wide angle view lens, con- 
 structed of three pieces, as shown in the margin (Fig. 56). 
 
 A flint negative meniscus is inclosed between two menisci of 
 
 crown glass. In these two latter 
 the crown glass is not of equal 
 refractive power, the rear lens 
 having a somewhat less index of 
 refraction than the front. 
 
 In this way a most excellent 
 lens is formed. It has, of course, 
 the fault common to all lenses not 
 centrally stopped, that straight 
 lines are more or less curved on 
 the image. It is therefore only 
 suited for landscapes in which 
 architectural subjects are not in- 
 serted, or where these are small 
 and inconspicuous. But for all 
 cases in which it can be properly used, and these are very nume- 
 rous, the writer thinks very highly of it. If this lens be criti- 
 cally compared with the Steinheil aplanatic, it will be found that, 
 in respect of that very important quality, depth of focus, the wide 
 angle view lens has a distinct advantage. It also covers satisfac- 
 
 F F. Flint negative meniscus, 
 c c. Two positive menisci of crown glass 
 d. Diaphragm. 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 79 
 
 torily a wider angle. Thus the 8| wide angle cpvers a 6|x8^- 
 plate, whereas with the aplanatic the 9J-inch is required. It is 
 true that the seven-inch is sold for this purpose, which, however, 
 it does not properly accomplish. The 9|-inch Steinheil used 
 on a 6Jx8| plate gives, of course, a rather less angle of view 
 than the 8| view lens, but, on the other hand, gives a better mar- 
 ginal definition and straight lines. 
 
 The wide angle view lenses more than cover the plates for 
 which they are advertised, and admit of a little pushing up or 
 down of the camera front, without producing black corners. The 
 writer has not found any more serviceable lens for view-making. 
 
 § 2. — The Portrait Lens. 
 
 The form of objective represented at Fig. 57 is that at the pre- 
 sent time exclusively used for portraiture. It was the result of 
 
 Fig. 57. 
 
 f 
 
 f 
 
 0, 0. Double convex crown glass lenses. 
 
 F, F. Negative flint lenses ; tlie front, plano-concave, the back, negative meniscus. 
 /,/. Flange 
 D. Diaphragm. 
 
 the labors of Petzval, of Vienna, who calculated this combina- 
 tion, and by its immense improvement over the systems pre- 
 viously in use for portraiture gave a vast impetus to that branch 
 of photographic art. A glance at the figure will at once explain 
 the nature of the arrangement. 
 
 As the portrait is most natural and effective when the sitter 
 
80 
 
 GENERAL OPTICS. 
 
 has not been compelled for a length of time to retain his position, 
 and as the chances of moving are greatly increased with the 
 length of the exposure, the great object of the portrait combina- 
 tion is to throw as strong a body of light into the camera as 
 possible. Considerations of depth of focus, correction for sphe- 
 rical aberration, &c., have been necessarily, to some extent, sub- 
 ordinated to 'the one great need. 
 
 It follows that, instead of having many planes in excellent 
 focus simultaneously, as in the case of the view lens, the portrait 
 lens is very restricted in this respect, and hence cannot be 
 appropriately used except for the purpose for which it is 
 intended. 
 
 Some portrait lenses, especially the Jamin (Darlot) lenses, are 
 arranged to permit of the front portion, consisting of the double 
 convex and plano-concave, to be unscrewed, and after reversing, 
 be screwed into the same flange for use as a view lens. This is a 
 very convenient system; it is, however, liable to the objection 
 that the front surface of the view lens thus made is plane, instead 
 of concave. Now, to get the best results, not only the front sur- 
 face should be concave, but this concavity should be consider- 
 able. Such a view lens cannot, therefore, be expected to give 
 strictly first-rate results, though it may do good work. It can- 
 not be too clearly understood by the student, that the whole 
 system of photographic objectives is a system of compromises 
 between conflicting troubles; that these compromises can always 
 be best adjusted for some definite end, and that consequently 
 when one sort ot objective is made to do another's work, such 
 work is always done at a disadvantage. 
 
 Mr. Dallmeyer gives the following information relative to the 
 character of portrait lens best suited for given sizes of plates, 
 supposing the camera to be placed at a distance of 18 to 20 feet 
 from the sitter, as he advises. 
 
 The equivalent focal length of the lens for a given sized plate 
 should be about double its largest side ; that is for card size, 
 4^x31, the focal length should be 8 to 9 inches; for cabinet 
 size, 6x5, 12 inches; for 8x10 plates, 20 inches. Salomon's 
 success confirms these views; his 8x10 plates are made with a 
 lens of 20 inch focus. 
 
 Next arises the question as to what diameters these lenses 
 should have. It is useless to expect that the highest degrees of 
 rapidity, flatness of field, and depth of focus can be combined, 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 81 
 
 because these qualities are essentially antagonistic. So that two 
 lenses, both perfectly corrected for spherical aberration, and of 
 the same focus, the one of two inches diameter, will have double 
 the depth of focus of the other, whilst the latter, on the other 
 hand, is four times more rapid. 
 
 Or again, comparing two lenses, both having the same ratio of 
 diameter to focal length, consequently of equal (or nearly equal) 
 rapidity, the greater the length of focus the less the " depth" of 
 focus. Thus, for example, a card lens of 9 inches equivalent 
 focus and 2| diameter, producing a card picture at 20 feet, will 
 sufficiently define accessories at eighteen inches in front of, and 
 behind the principal object having thus a " depth" of 3 feet, 
 whereas a lens of twice the focal length, placed at the same distance 
 of 20 feet^ will have -but half the " depth," viz., 9 inches before 
 and behind the object, but will produce an image four times, i.e. 
 twice linear, the size. 
 
 These lenses were first manufactured by the well-known firm 
 of the Yoigtlsenders. Now they are made by opticians generally. 
 
 § 3.— Steinheil's " Aplanatic" and Dallmeyer's "Rapid Rectilinear." 
 
 Several years ago two lenses were invented, the one in Eng- 
 land, the other in Germany, which are remarkable in their per- 
 formances, and in a certain similarity to each other. 
 
 Fig. 58. 
 
82 
 
 GENERAL OPTICS. 
 
 Steinheil's aplanatic, of whicli a figure is given below, for which 
 the writer is indebted to Dr. Liesegang's Archiv, has already 
 become a great favorite in this country. It is a " symmetrical 
 doublet," that is, the front and back lenses are alike. Each con- 
 sists wholly of flint glass, but the respective portions being com- 
 posed of flint glass of different refractive powers, correct each 
 other, so that the lenses are achromatized ; in this is an essential 
 difference from any other lens hitherto constructed. 
 
 It is an advantage in the Steinheil lens that when used with a 
 large diaphragm, although the exterior portions of the image 
 lose their sharpness, the central portions are still tolerably good. 
 As the rapidity of a lens increases greatly with the increase of 
 the diaphragm, we may thus employ the aplanatic as a portrait 
 lens, if we reject all but the central portions. It does not, how- 
 ever, in this wa}' attain the rapidity of a good portrait lens. For 
 groicps, it and the Dallmeyer rapid rectilinear are probably the 
 best of all lenses. 
 
 The Dallmeyer rapid rectilinear greatly resembles the Stein- 
 heil aplanatic in its form. Its symmetrical lenses are not, how- 
 ever, made of flint glass only, but of flint and crown achroma- 
 tized in the usual manner. Although less known in this country, 
 they are equal to the Steinheil; indeed, there is, as far as the 
 writer's experience goes, no choice between them. 
 
 One important point in the comparison should be noted. Simi- 
 lar as these lenses are, their makers have taken different views as 
 to their powers, and the Steinheil lenses are advertised to cover 
 a plate one size larger than the Dallmeyer. Thus the Steinheil 
 having about 9 inches focal length, is advertised for use for 
 8x10 plates, whilst the corresponding lens of Dallmeyer is 
 advertised for 6|x8| plates. This might naturally lead to mis- 
 conception, in the supposition that the lenses covered different 
 angles and had different powers. The fact is that the nine inch 
 lens will with a little straining cover (in either case) an 8x10 
 plate, and may be used with it, but generally will be found best 
 suited for a 6|x8|. In other words, the nine inch focus lens, 
 when worked with a fair-sized stop, has hardly power enough 
 for the 8 x 10, and rather more than power enough for the 
 6Jx8|. 
 
 These lenses fall off a good deal in illumination towards the 
 edges. At the centre, the definition cannot- in the writer's opinion 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 83 
 
 be easily surpassed, but as we pass from the centre, it rapidly 
 falls off, unless sharply stopped down. 
 
 For architectural work both these lenses have no superiors, and 
 the same may be said as to groups. They are useful for instan- 
 taneous work, though not so rapid as a first-class portrait lens, 
 and the same is true of portraiture. For copying they are ex- 
 cellent. When width of angle of view is important, they are 
 exceeded by several lenses, by Zentmayer's 
 lens, by Dallmeyer's wide-angle rectilinear, by 
 Steinheil's pantoscope, &c. 
 
 SteinheiVs Uncorrected Lens. — Previous to 
 the discovery of the lens above described. 
 Prof. Steinheil devised a lens consisting of 
 two uncorrected menisci, which were remark- 
 able for the great size of plate covered by so 
 small a lens. The adjoining figure gives an 
 idea of its construction. It is now superseded 
 by his achromatized doublet or aplanatic. 
 
 A useful maxim, familiar to experienced photographers, is 
 never to strain a lens. Some who purchase a lens intended to 
 cover a given size of plate, and who find that by using a very 
 small stop, good definition can be got over a materially larger 
 plate than that for which the lens was advertised, think they 
 have made a useful discovery, and perhaps avail themselves of it 
 habitually. The work so produced will never have the boldness, 
 atmospheric effect, gradation of distance, and transparency of 
 shadow given by a lens used with a larger opening. 
 
 On the other hand, it is a mistake to use a lens intended for 
 larger views, in taking small ones. Lenses for large views are 
 unavoidably slower, and the extent of angle included in a small 
 view, taken by a longer focus lens, is too small. An exception 
 to this is when a lens, like the triplet, is used for instantaneous 
 effect, and where it is worked with a large stop, rejecting all but 
 the centre of the image. 
 
 § 4.— The Triplet. 
 
 The triplet lens consists of two large achromatized menisci, 
 between which is placed a small negative lens as near as possible 
 
84 
 
 GENERAL OPTICS. 
 
 to the diaphragm. The length of the focus is thereby increased, 
 but at the same time marginal definition is obtained. 
 
 The triplet is a lens which, although possessing great merits, 
 has been somewhat over-praised. It is a useful lens undoubt- 
 
 Fig. 60. 
 
 0, O. Double convex crown glass lenses. 
 
 F, F. Double concave flint. 
 
 C. Double concave crown. 
 
 F'. Double convex flint. 
 
 B. Diaphragm with its opening at F'. 
 
 /,/. Flange. 
 
 edlj, but since critically examining its power, the writer finds 
 himself led to the following comparison : — 
 
 For architectural objects it is surpassed by the Steinheil, the 
 Dallmeyer rapid rectilinear, and by Zentmayer's lens, the last 
 mentioned of which gives lines equally straight, and includes a 
 very much larger angle. Where angle is no object, where we 
 have free open space in the desired direction about the archi- 
 tectural object, there only the triplet may be conveniently em- 
 ployed. 
 
 For copying, it is surpassed by the same lens. 
 
 For views not embracing architectural objects, or where these 
 are not near the margin, and are inconspicuous, it is undoubtedly 
 surpassed by the view lens, especially by Dallmeyer's wide angle 
 view lens. 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 85 
 
 For portraiture, it is inferior to the portrait lens, being much 
 slower. By removing the central negative lens, however, its 
 action is increased ; but the centre of the image only is sharp 
 enough for use, as in the case of portraits to be vignetted. 
 
 § 5. — The Globe Lens. 
 
 Fig. 61. 
 
 The globe form of lens was devised in this country by Mr. 
 Schnitzer, and was manufactured by him in connection with the 
 late Mr. Harrison. Its character- 
 istic feature lies in this, that the 
 exterior curves, back and front, 
 form part of one and the same 
 sphere, the diaphragm being 
 placed at the centre of that 
 sphere. Consequently it follows 
 that the incident ray i?, Fig. 62, 
 which passes through the centre, 
 has a nearly perpendicular inci- 
 dence upon the outside surface. 
 It therefore undergoes but little 
 deviation at either of the four 
 surfaces, but necessarily encoun- 
 ters some, and is bent from its 
 original direction R P down to 
 D. A grave objection to this lens 
 lies in its tendency to form a 
 
 D 
 
 C, 0. Positive menisci of crown glass. 
 F, F. Negative menisci of flint glass. 
 
 D. Diaphragm. 
 /,/. Fiauge. 
 
 Fig. 63. 
 
 thicker spot at the centre of the image, called flare, or ghosi, the 
 cause of which will be explained further on (see p. 91). 
 
86 
 
 GENERAL OPTICS. 
 
 6. — The Zentmayer Lens. 
 
 Fig. 68. 
 
 Mr. Joseph Zentmayer, of this city, has succeeded in making a 
 photographic objective of a single sort of glass, his lenses being 
 both uncorrected menisci. Nevertheless, in these objectives the 
 chemical and visual foci are practically coincident. This single 
 fact would be enough to invest the lens with interest, but its 
 performances are sufficiently remarkable to indicate that this 
 
 lens will be adopted for all those 
 descriptions of work to which it is 
 especially suited. 
 
 Fig. 63 will give a clear idea of 
 the system of construction. The 
 front and back curves of each lens 
 stand to each other in the relation 
 of 12 to 13, and the two lenses to 
 each other in the ratio of 2 to 3. 
 The stop is advanced a little nearer 
 to the front lens than the centre of 
 curvature of the exterior surface of 
 the larger lens. 
 
 It is evident that by having a 
 series of lenses of difi'erent sizes, the 
 larger lens of one pair may serve 
 as the smaller lens for the next larger pair. On this principle 
 these lenses are manufactured. The complete sets embrace six 
 lenses, capable of forming five pairs, having a great range of 
 focal lengths. Smaller sets are made, in which four lenses form 
 three pairs. 
 
 These lenses include a wonderful angle — fully as much as can 
 ever be advantageously used, and much more than covered by 
 the globe lens. The architectural effects attained are good, and 
 bolder than would be expected from the small size of the stop 
 that must be used. The reflecting surfaces which the ray meets 
 in this lens are fewer than in any other centrally stopped objec- 
 tive, and this gives brilliancy as well as diminishes the propor- 
 tion of light lost. For copying these lenses are at least as good 
 as any. They are, in the opinion of the writer, unsuitable for 
 landscape work, by reason of the small stop required. 
 
 D. Diaphragm. /, /. Flange. 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 87 
 
 § 7 —Ross's Doublet. 
 
 Mr. Eoss's form of doublet, Fig, 
 64, has been favorably spoken of. 
 It is intended for views and archi- 
 tecture, of which last it preserves 
 the straight lines, and for copying, 
 A material convenience is afforded 
 with this lens, an internal shutter, 
 sliding across the opening of the 
 diaphragm, instead of covering and 
 uncovering the lens in the usual 
 way with a cap. This feature has 
 been also introduced into Zentmayer's 
 lenses. 
 
 Eoss's lenses may be separated, 
 and each can be used as a single 
 landscape lens. 
 
 Fig. 64. 
 
 L, L. Positive menisci, corrected. 
 D. Diaphragm. 
 
 § 8 — Other Forms of Photographic Lenses. 
 
 OrtJioscopic Lens. — This form which, like the portrait lens, we 
 owe to Petzval, has been extensively used, especially in this 
 country. Harrison manufactured many good objectives of this 
 form ; but on introducing the globe lens, he stopped making the 
 orthoscopic, and this lens is now but little used here. In Ger- 
 many it seems to have kept its place better. 
 
 The orthoscopic is an excellent copying lens, but slow, owing 
 to its long focus, and the small stop generally used with it in 
 copying. For taking views, a stop of considerable size may be 
 employed ; and, as it has a considerable depth of focus, it is by 
 some much prized for landscape work; though this is rather in 
 Germany than here. Small pictures of landscape scenery are 
 well taken by the smaller orthoscopic lenses, because in them 
 the focal length is not far from corresponding with that of the 
 eye. But large pictures made with the orthoscopic require a lens 
 of very long focus; and it results that planes of distance are not 
 well rendered, the foregrounds become indistinct and inconspic- 
 uous, and distant objects look unnaturally near. The remarkable 
 influence exerted by the focal length of a lens upon the resulting 
 image will be fully explained a few pages further on. 
 
88 
 
 GENERAL OPTICS. 
 
 BuscKs Pantoscope consists of two corrected lenses with a cen- 
 tral stop. It includes a very large angle of view, and has been 
 highly spoken of. A very carefully constructed camera appears 
 to be necessary for it. 
 
 Blunts Hemispherical Lens. — Mr. Blunt, of New York, con- 
 structs a lens of this name, which is spoken of in very high 
 terms by Mr. Hull and other competent judges. Mr. Hull affirms 
 it to be equal to any other lens for landscape purposes, without 
 exception. It is also suited for architecture and for copying, 
 
 Dallmeyer's Rectilinear. — This lens is less rapid than the 
 " Rapid" and the Steinheil aplanatic, but covers a very large 
 angle, about 100°. It gives straight lines. 
 
 Panoramic Cameras. — The theory of this very ingenious instru- 
 ment, by which such beautiful results have been obtained, is as 
 follows : — 
 
 Let t/be the centre of emission of the cone of rays coming out 
 
 from any objective, single, double, 
 '^^ or triple, which finds its focus on 
 
 the screen S S'. 
 
 If now the lens be made to rotate 
 horizontally, on J as a centre, the 
 position of objects in the image 
 formed on the focussing screen will 
 not change. If the image of any ex- 
 terior object, for example, falls at 
 the centre i^, the rotation of the lens 
 will not cause the image of that 
 body to move, but it will remain accurately at F until the lens 
 rotates so much that it passes out of the field of view. 
 
 Now, to avail ourselves of this property, we must remember 
 that when the lens is rotated so that its axis passes from the di- 
 rection J"^ to the direction J A\ its image is no longer in focus 
 on the screen at A'^ but at the point F' ; because the central ray 
 is now in the direction J A, and its focal length will be the same 
 it originally was, viz., J F or J F' , 
 
 The first idea for applying these principles would evidently be 
 to "Use a sensitive plate of a cylindrical form, corresponding with 
 the curve F" F F\ and by means of a mask with a vertical slit, 
 to conceal all the plate but a high narrow strip at the centre ; 
 then if the plate F" F F' remained stationary, and the lens rotated 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 89 
 
 carrjnng the mask witli it, every part of the plate would be ex- 
 posed successively. 
 
 But in the instrument now in use, this is otherwise managed. 
 The sensitive plate occupies the position SS', and is flat. It is 
 masked, with a narrow opening at F, extending from top to bottom. 
 As the lens rotates, the plate S is shifted sideways by a system 
 of clockwork, which makes its movement exactly correspond 
 ■ with that of the lens, whether it be slow or fast, as the light may 
 require. 
 
 As a curved plate, F' F F" would receive a perfect image from 
 the rotating lens, masked as above explained, all that is necessary 
 is that the flat plate S 8' should "be shifted in such a way that 
 when, for instance, the lens has moved so that its axis is in the 
 direction J F' , then the plate shall have been brought up to F' , 
 there to receive its image at its correct focus. And, evidently, 
 if the plate be long enough, and the camera be rotated to a full 
 circle, an entire panorama may be obtained. 
 
 This picture will be found to differ materially from one obtained 
 in the ordinary camera. It will be in panoramic, instead of plane 
 projection. The picture will not be an harmonious whole, which 
 the eye sees whilst regarding its perspective centre, but as if the 
 eye were directed always opposite to it, in whatever direction it 
 chanced to look, or, to speak more exactly, as if the eyes were 
 directed in succession at all the vertical lines in the picture. 
 
 Another difference will be, that from end to end (but not from 
 top to bottom) the picture, no matter how large, will be in equally 
 good focus. At the right and left extremities the picture will 
 be as sharp as the middle. This is because the central part of 
 the image only is used. Each part becomes successively the 
 centre. 
 
 Again, the vertical slit at F may be made narrow at bottom 
 and wide at top, so that the foreground will get a larger exposure 
 than the sky ; and this difference may be regulated at will, giving, 
 if desired, to the sky an exposure of one-tenth or less than that 
 which the foreground receives. It is this which has enabled 
 Braun to produce such wonderful cloud pictures in his Swiss 
 scenery, and to get good definition of snow mountains against 
 the sky and clouds. 
 
 The most successful application of this principle is at present 
 Johnson's panoramic camera. It is patented, but the patent can- 
 not cover the principle, which was understood many years before 
 7 
 
90 
 
 GENERAL OPTICS. 
 
 his application of it, and was applied to the construction of pano- 
 ramic cameras.^ 
 
 § 9. — General Remarks on Lenses. 
 
 Portraiture. — The portrait lens is so far superior to all others 
 for this purpose that none other is habitually used. The Stein- 
 hoil aplanatic is the form that comes nearest in effioiency ; it is 
 now occasionally used for portraits, and is probably unsurpassed 
 for taking groups. 
 
 For card portraits the focal length needed for the lens will 
 depend upon how much is to be included. For full lengths, very 
 short focus lenses are commonly employed. For such as show 
 part of the body, and even including the hands, lenses of six to 
 eight or nine inches focal length will be proper. For "cabinet 
 size" lenses of eight to twelve inches focal length will be needed. 
 For 6| X 8 J plates and half-length portraits, a lens of from ten to 
 sixteen inches will be suitable. For very short exposures, espe- 
 cially in taking children, " extra rapid" lenses are made, with 
 very short focal lengths. Some makers make a difference in their 
 lenses according as they are wanted for full lengths and for vig- 
 netted heads. In the latter case every effort is made for perfect 
 definition at the centre; in the former a good definition all over 
 the plate is aimed at. 
 
 Generally, the shorter the focal length, the less exposure will 
 be needed, and the facility of getting all portions of the image 
 into focus will be greater; but the longer the focal length, the 
 less exaggeration there will be in those parts that project, the 
 hands especially. 
 
 Very ingenious arrangements have been adapted to the portrait 
 lens, with the object of changing the focus during exposure, in 
 the effort to get a diftusion of focus, and, instead of having one 
 part sharp to the exclusion of the rest, to maintain a certain 
 average of sharpness over the whole. Even lenses have been 
 made in which a certain amount of spherical aberration has been 
 left uncorrected, in order to diffuse the sharpness. The late Mr. 
 Claudet brought this whole matter prominently forward shortly 
 before his death, and opinions are very much divided on the 
 subject. 
 
 1 See Secretan, De la distance focale des Systemes Optiques conver gents. Paris, 
 1855. 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 91 
 
 Landscapes. — As already said, for such cases where it is appli- 
 cable, the single view lens, especially the wide-angle form, is 
 exceedingly satisfactory. The small angle included by the com- 
 mon view lens is often a great objection. The rapid rectilinear 
 of Dallmeyer, and the aplanatic of Steinheil, are exceedingly use- 
 ful in landscape work, are quick, clean, free from flare, and cover 
 a very satisfactory and sufficient angle. Between the two there 
 is little choice. In using the aplanatic, the photographer is advised 
 to employ a lens of one size larger than that advertised for the 
 size of plate which he has in view. With the other this is not 
 necessary. 
 
 There seems to exist a curious distinction between the effects 
 of these forms of lenses which has been little noticed. The wide 
 angle view lens produces a remarkable amount of detail — every 
 stone in a wall, every pebble on a shore, seem individually 
 brought out, distinct from the rest. The aplanatic gives less of 
 this individualization, but perhaps more general harmony. These 
 effects have nothing to do with the sharpness of the image, for 
 the distinction exists with lenses of equal focal length, equally 
 stopped down, and producing equally sharp definition. If any 
 difference exists, the image of the aplanatic is the sharper of the 
 two, at the centre. In depth of focus the view lens has the ad- 
 vantage. 
 
 Flare or ghost in the camera is an indistinct image of the dia- 
 phragm. Let C be the centre of curvature of the second surface 
 
 of the lens, whose thickness is here intentionally exaggerated, in 
 order to make the lines visibly distinct. A ray passing through 
 the diaphragm, strikes the first surface, is refracted, and passes 
 to the second at A. Here it is divided — most passing onwards in 
 a direction R' to form the true image, but a part suffering reflec- 
 tion and returning to the first surface. Here most is transmitted, 
 but a part is reflected again and returns to the second surface. 
 Here again the greater part is transmitted, after passing three 
 
92 
 
 SPECIAL OPTICS. 
 
 times through the thickness of the lens, and, undergoing refrac- 
 tion, is bent down to the axis at some point F', producing the 
 flare. 
 
 Comparing Lenses. — A great deal of unintentional injustice is 
 done by photographers in comparing lenses, for want of taking 
 the necessary precautions to make the test a just one. 
 
 It should invariably be borne in mind that the performance of 
 a lens depends entirely upon its stopping down. Of two lenses com- 
 pared, the inferior one may easily be made to seem the better, if 
 it be used with a smaller stop, and no account be taken of the 
 time of exposure. 
 
 It may be taken for granted that the sharpness, depth of focus, 
 and size of good picture obtained will always increase as the size 
 of the stop is diminished. This has led many landscapists to the 
 use of extremely small stops habitually, esteeming it of little 
 consequence to wait longer for the impression to be made. Several 
 evils result from this practice. 
 
 1. It may be taken as an invariable rule that the larger the 
 stop used, the more detail in the shadows will be obtained, always 
 supposing that each trial has been made with a correctly timed 
 exposure. Let us say that, with a half-inch stop, fifteen seconds 
 have been found exactly right. Now, using a quarter-inch stop, 
 we must expose for one minute or rather more.^ The exposure 
 will be correct; the picture will be the best obtainable with that 
 size of stop, but the detail in the shadows will not be so good as 
 in the former case. 
 
 2. A large stop gives a bolder picture and spaces it out better. 
 The planes of distance are better made out. A small stop tends 
 to produce a map-like effect. One-thirtieth of an inch is about 
 the limit for the diameter of the stop for landscape work, and 
 one twenty-fifth is much better, and ought to be generally used. 
 That is, if the lens have a 10-inch focus, the stop should not be 
 less than f inch, or at farthest not less than ^ inch. A small stop 
 tends to produce pictures destitute of atmosphere, the distant 
 objects look too near. 
 
 3. A long exposure in the case of portraiture is a serious evil. 
 Even with landscapes it is not unimportant, for, although the 
 
 ' Theoretically the exposure should always be inversely proportioned to the 
 area of the stop, and this area is proportional to the square of the diameter of 
 the stop. But in practice, it is found that the increase of exposure must be 
 considerably more than in this proportion. 
 
PHOTOGRAPHIC OBJECTIVES. 
 
 93 
 
 contrary has been affirmed, the difficulty of catching foliage still 
 always increases with the length of the exposure. 
 
 The comparison, therefore, between lenses of equal focal length 
 must always be made with stops of equal opening. Between 
 lenses of different focal lengths no true or just comparison can 
 be made at all. Some approximation may be reached by trying 
 them with stops whose diameter is exactly proportionate to the 
 focal length, but even then, the smaller lens will always work 
 the quickest and otherwise appear to be the best. The truth is 
 that the difficulties both of the optician in making, and of the 
 photographer in using, increase so rapidly with the size of the 
 picture, that between different sizes a just comparison is all but 
 impossible. A photographer who has for a long time worked 
 with any one size of plate, and then changes to a larger size and 
 corresponding lens, becomes at once aware of the increased dif- 
 ficulties in his way. He must exclude more foreground, or he 
 cannot get his whole picture well in focus. He must use a smaller 
 stop also to the same end. His image on the ground glass is not 
 nearly so brilliant, and his exposures must be materially pro- 
 longed to get a harmonious negative. 
 
 Selection of Lenses. — The color of a lens is always important. 
 Place the lens on a perfectly white sheet of paper — any brown- 
 ness of tint is a serious objection. In an old lens this may arise 
 from the Canada Balsam, with which the separate portions are 
 cemented together, turning yellow. If this be thought to be the 
 case, the lens should be taken to an optician to be separated, 
 cleaned, and re-attached. The photographer is not advised to 
 attempt this himself, 
 
 Buhhles in the glass are objectionable, because they tend to 
 throw rays in abnormal directions, and to impair the brilliancy 
 of the image. One or two small ones are not important, nor a 
 sufficient cause for rejecting an otherwise satisfactory lens. But 
 it indicates carelessness in the maker, as these bubbles are always 
 visible in the disk from which the lens is made, and such disks 
 should be rejected. 
 
 Strise, hair-like or thready transparent lines, are very objec- 
 tionable, and at once a sufficient cause for rejection. 
 
 Scratches. — Lenses will sometimes come from the maker with 
 scratches, the result of careless handling of tools in setting, or 
 of bad packing. Such of course are returned. 
 
 Centering. — To every lens there belongs an optical axis, a line 
 
94 
 
 SPECIAL OPTICS. 
 
 perpendicular to the surface of the lens, and passing through its 
 centre of curvature. Every achromatized lens consists of at 
 least two portions, and it is necessary that these should be so 
 arranged when attached together by the balsam used for that 
 purpose, that the optical axis of each should exactly correspond. 
 When two lenses or more are united -to form an objective, not 
 only must the parts of each be properly disposed, but the front 
 lens must have its axis coincident with that of the back lens. 
 This will depend upon correct mounting. 
 
 The usual way in which opticians test the correctness of the 
 centering, is by making the tube containing the lenses revolve in 
 an upright position, that is, with the lenses horizontal. If, now, 
 a candle be placed at a little distance, and the eye be placed at a 
 convenient position, the candle will be seen reflected from the 
 surface as a bright point. Every surface of every piece of glass 
 in the tube will send back a reflection. Next the tube is caused 
 to rotate. Each lens that is correctly centered will continue to 
 send its reflection back perfectly fixed and immovable ; but any 
 surface that is out of centre will cause its reflection to deviate 
 more or less, according to the amount of error. It is evidently 
 not necessary that all the reflections should be seen at once, but 
 they may be observed successively. This method of observing 
 evidently renders it easy to fix which, if any, of the surfaces is 
 erroneously placed, and in which direction is its error. 
 
 Another mode of observation is more convenient for the pho- 
 tographer, as not requiring the apparatus needed for the method 
 just described. 
 
 The observer places himself in a dark room with a single can- 
 dle. Standing five or six feet from it, he looks at it through the 
 objective, inclining the latter a little until he sees a series of 
 bright points, which are the images of the candle, produced by 
 successive reflections from the different surfaces of the lens. 
 When a lens has four pieces of glass in its construction, as in the 
 case of the portrait, globe, orthoscopic, and some other lenses, 
 the number of possible images is very considerable. These can- 
 not generally be all found at once, but eight, ten, or more can be 
 counted; a little practice, and altering the inclination of the lens 
 materially aids in increasing the number. 
 
 If now the centering is perfect, it will be found that, by care- 
 fully adjusting the position of the lens, all of these reflections 
 can be made to range themselves in a straight line. But if any 
 
PHOTOG-RAPHIC OBJECTIVES. 
 
 96 
 
 one or more of the component parts is out of centre, this will be 
 found impracticable. One or more of the bright points will re- 
 main obstinately out of line ; and, when a little movement is 
 made which brings them in, it will be found that some other 
 image, previously in line, has slid out of it. When the observer, 
 after very careful trial, finds that it is positively impossible to 
 make all the images range, he will be justified in concluding that 
 there is a fault in the centering. 
 
 Whilst this test is so easy that any intelligant observer can 
 apply it at once, there is no doubt that it is a very severe one. 
 A lens may perform quite fairly, and yet such an examination as 
 this may reveal a defect. But there is no doubt that first-rate 
 excellence is incompatible with such defectiveness. 
 
 It is also evident that the fewer the pieces of which a lens is 
 composed, the less difficulty the optician will find in getting them 
 all in correct line. 
 
 Quickness. — When lenses of equal focal lengths are tested 
 with equal stops, their comparative quickness will depend upon 
 the whiteness of the glass, the fewer number of surfaces that 
 enter into their formation, and on the curves given by the op- 
 tician : careful testing, and this alone, can settle the point. 
 
 Chemical Focus. — The correction for chromatic aberration is now 
 greatly better made than formerly. To test whether a lens is 
 properly corrected, select a newspaper printed with sharp-cut 
 type, and paste a piece a foot or fifteen inches square upon a 
 smooth piece of board. Set this up before the camera, with the 
 columns vertical, but inclined in a slanting direction, so that one 
 side, the right, for example, shall be a couple of inches nearer 
 the camera than the left, keeping the board, however, exactly up- 
 right. Focus carefully along the central upright line, and copy 
 it full size, or thereabouts. 
 
 Next examine the hair-strokes of the letters on the negative 
 with a microscope. If the lens is properly corrected, the central 
 line should be in the sharpest focus. If, however, it be found 
 that a portion to the right or left of the central line is in better 
 focus than the centre, then the correction has evidently been 
 faulty. If the sharpest image is of a part nearer to the lens than 
 the centre, the lens is under -corrected ; if of a part further from 
 the centre, the lens is over-corrected. In either case, it is said to 
 have a chemical focus,^' that is, its chemical and visual focus 
 
96 
 
 SPECIAL OPTICS. 
 
 does not correspond, a fault of the first magnitude, and sufficient 
 cause for rejecting the lens entirel3^ 
 
 Flanges.— The flange is the brass circle, which is permanently 
 attached to the camera front, and into which the lenses screw. 
 It is greatly to be desired that opticians should adopt a regular 
 set of sizes and threads for flanges, so that all the lenses habit- 
 ually used with one camera should screw into one flange, and 
 thus one camera front only be necessary. This has long been 
 done in the case of microscopic objectives, which, no matter 
 where made, screw at once into any instrument, though the 
 latter have been made thousands of miles away. A similar 
 system is greatly needed in photographic objectives. Dallmeyer 
 has made some approximation to it, his lenses of different sorts 
 all screw into the same flange, except where the lenses are of 
 widely different focal length. But a universal adoption of this 
 system is what is wanted. 
 
 § 10.— Care of Lenses. 
 
 A few words on the preservation and care of these beautiful 
 products of science and art will not be inappropriate here. 
 
 When lenses have been out of use for some time, or have been 
 carried to a distance, they should be carefully unscrewed and 
 wiped out with a soft old linen handkerchief, or a piece of chamois 
 leather. Nothing else should be used. 
 
 If the lenses have stood only for a short time, they may only 
 require wiping on the exterior surfaces. They should first be 
 examined, and if free from dust, it is better not to wipe them. 
 Toojnudodiiing is as bad as too little, and it may be set down 
 as a general principle, that the less lenses are touched wWi any- 
 thing the better ; especially the fingers should never touch them. 
 
 With many forms of lenses, convenient caps of morocco lined 
 with velvet are now furnished. This is an excellent arrange- 
 ment, as dust is excluded, and the amount of wiping is diminished. 
 These caps are also very convenient for covering and uncovering 
 the lens. Such should be made and furnished with all photo- 
 graphic objectives. Something similar, or a light brass cap, to 
 protect the back lens, would also be very useful with all lenses 
 intended for field use. 
 
 It is a disadvantage to keep the lens in a cold place, and then 
 perhaps, suddenly remove it to a warm one. A dew may form.' 
 
PHOTOGRAPHIC PERSPECTIVE. 
 
 97 
 
 on the lens while the image is being impressed, or before, and 
 may escape observation. This may even happen by a mere 
 change of position in taking views, by the photographer remov- 
 ing his apparatus from a cool position to a warmer and damper 
 one. 
 
 Lenses should never be left lying where the sun, or even a 
 bright light, can fall upon them, as strong light has a tendency 
 to darken the color of the glass and increase the exposure ne- 
 cessary. For this reason, where steoroscopic lenses are occasion- 
 ally used separately, this use should be divided between the two. 
 If one of the pair is always used on such occasions, it will tend 
 gradually to work more slowly than the other, so that the two 
 can no longer be used advantageously together. 
 
 The care of the lens should also be extended to the brass 
 mounting. If this is allowed to become dented, or is in any way 
 roughly treated, there is danger that the centering may be inter- 
 fered with, and the working of the objective thereby impaired. 
 Second-hand objectives should always be severely tested before 
 purchasing, and no one should be induced to acquire a lens in 
 this way, unless he feels fully capable of judging the objective on 
 its own merits by a careful trial. 
 
 CHAPTER VI. 
 PHOTOGRAPHIC PERSPECTIVE. 
 
 § 1. — Nature of the Image formed by a Lens, 
 
 When it was first found that the image of the camera could 
 be fixed, and that thus representations of natural objects could 
 be produced with critical exactness, the enthusiasm that resulted 
 was unbounded. Gradually this was mixed with severe disap- 
 pointment. The representations produced were, for the most 
 part, destitute of beauty even where the subjects themselves 
 were very beautiful. Everything was present in the picture, the 
 delineations were correct, or nearly so, and yet the result was 
 most unsatisfactory. 
 
 It soon appeared that good apparatus and a competent know- 
 ledge of the process constituted only a very small part of what 
 
98 
 
 SPECIAL OPTICS. 
 
 was needed for obtaining a pleasing picture. A natural sense of 
 the beautiful, and a sufficient acquaintance with the rules of art, 
 proved to be at least equally necessary. Without these last, the 
 best point of view at which to place the camera could not be 
 selected, the time of day for securing the best aspects of light 
 and shadow could not be known, nor how much to include on 
 the plate, nor where to place the horizon line, &c. &g. The more 
 intelligent photographers gave earnest attention to these points, 
 and in proportion as they mastered them, their works found 
 favor. Those who disregarded them quickly sunk out of sight. 
 
 Even the nature of the image formed by a lens cannot be well 
 understood without some knowledge of perspective. It will well 
 repay any earnest landscape photographer to study this science 
 in the text-books specially devoted to it. Here, the limit assigned 
 by the author to this manual will permit of a very brief descrip- 
 tion only. 
 
 Perspective is the science of representing solid objects upon 
 a flat surface. 
 
 If between the object to be represented and the eye, we inter- 
 pose a plate of glass, and keeping the eye steadily fixed in position, 
 we draw lines upon the glass corresponding with the objects, we 
 shall obtain a representation of these objects in correct per- 
 spective. 
 
 Let us select a building for example, and on the plate of glass 
 mark the point at which we see all the corners and intersections 
 of the lines of the building. Then connecting these by drawing 
 lines on the plate we shall obtain a representation such that when 
 held up in its proper position between the eye and the building, 
 every line on the glass shall cover the corresponding line of the 
 building. This will be one drawing of the building in correct 
 perspective. 
 
 But we shall immediately notice that if we change in the least 
 the distance of the eye from the plate, the correspondence of lines 
 instantly ceases. Still keeping the eye exactly opposite the 
 centre of the pane, let us draw back, so as to be farther from the 
 window; at once every line of the building has started out, 
 beyond the corresponding line of the original drawing, and we 
 obtain a larger picture than before. 
 
 By altering the position of the eye, any number of different 
 pictures will be obtained of the same object, and these corres}Jond 
 
PHOTOGRAPHIC PERSPECTIVE. 
 
 99 
 
 ivith the pictures obtained from lenses whose absolute focal lengths are 
 equal to the distance of the eye, in each casejrom the pane of glass. 
 If the arrow A J3, Fig. 67, represent the edifice, P' P' the pane 
 
 Fig. 67. 
 
 £ 
 
 of glass, and U the eye, the edifice as represented on the pane 
 will have the height P P. If the eye be withdrawn to the 
 image will be enlarged to P' P'. 
 
 Now, if the eye be replaced by a lens whose focal length is 
 the same as the distance of the eye from the pane, the image 
 formed by that lens will be precisely the same as seen by the 
 eye — reversed, of course. 
 
 The lens L forms on the screen an image /' (Fig. 68) of the 
 arrow precisely as large as the image / seen by the eye when 
 placed at L, upon the pane at /, the 
 distance of the eye to the pane being Fig. 68. 
 
 the same as the focal length of the 
 lens ; that is, the distance from L to 
 the centre of the arrow. 
 
 If now, keeping the eye at we 
 move the plane /, backwards and for- 
 
 wards, we shall obtain any number of 
 
 images of the object A B. By drawing lines from L to all parts 
 of A B, it will be seen that the triangles are always similar; that 
 is, any triangle E A B (Fig. 67) will always be similar to the 
 corresponding triangle E P P. All parts of the image P P will 
 therefore have the same proportion to the corresponding parts of 
 the object A B. If any one dimension be altered, or if P P be 
 increased to P' P' by drawing back the eye to E', all others will 
 be proportionately changed. It follows, therefore (and this is 
 very important), that all these images of the object will vary in 
 size only ; that is, they will be magnified or reduced images of 
 each other ; and as these images are identical with those formed 
 
100 
 
 SPECIAL OPTICS. 
 
 hy lenses placed at i:(Fig. 68), having focal lengths respectively 
 equal to any distance from the eye to the pane, we draw the 
 conclusion that similar lenses of different focal lengths, placed at 
 the same spot, give representations which differ from each other in 
 size only. If the picture given by a small lens be magnified (for 
 example, in a solar camera) to the size of the picture given by a 
 large lens, the resulting picture will be identical with it, sup- 
 posing the lenses to be perfect instruinents. The perspective 
 angles will be the same. But this is only true when the lenses 
 have been placed all successively on the same spot. 
 
 On the other hand, changing the position of the lens, or of the 
 eye, makes a complete difference in the nature of the image 
 formed, li A B C ]) he the side of a house seen obliquely, the 
 
 top and bottom lines, if continued, 
 will meet at a vanishing point F, 
 and the perspective angle B V A 
 will be greater or smaller, ac- 
 cording as we place ourselves 
 nearer to or farther from the 
 building. The nearer we ap- 
 proach, the nearer the point V 
 comes in, and the more abruptly the apparent size diminishes 
 from AB to G D. As any good photographic lens placed in the 
 same position as the eye gives the same result, it follows that the 
 nearer we go with our lens to the edifice, the sharper will be the 
 perspective angle at B. 
 
 As the influence of these two conditions, viz., the focal lengths 
 of lenses, and the distance at which they are removed from the 
 
 Fig. 70. 
 
 Fig. 69. 
 
 objects should be very clearly understood, the writer has endea- 
 vored to further illustrate it by the accompanying diagrams. 
 Fig. 70 he has drawn in exact proportion, so that it exemplifies 
 exactly, and not merely approximately, the mode of rendering 
 
PHOTOGRAPHIC PERSPECTIVE. 
 
 101 
 
 of two given objects by each of two lenses of very different focal 
 lengths. 
 
 Let us imagine two trees of equal height standing the one 
 somewhat farther than the other, and considerably to one side. 
 Let us assign to both the height of 50 feet, and let us first place 
 our camera so that the nearer tree is distant 600 feet. Let us 
 first take a lens of twelve inches focus. The tree will have the 
 exact height A B, or one inch, upon the ground glass. 
 
 Let us now suppose that the second tree is distant 1000 feet, 
 or 400 more than the first.^ Its image on the ground glass will 
 measure six-tenths of an inch in height, and it will occupy the 
 precise position C D, as shown in the figure. 
 
 Next let us for comparison substitute a lens of very much 
 longer focus, thirty inches. And let us recede to such a distance 
 that the image of the nearer tree shall occupy precisely the same height 
 A i? as it did before. To accomplish this we shall be obliged to 
 recede to the distance of 1500 feet. How will now the second 
 equal tree be represented ? 
 
 Instead of measuring six-tenths of an inch, as in the previous 
 case, it will be found to be .79 inch, or very nearly eight-tenths. 
 It neither stands in the same relation of height, nor does it occupy 
 the same position, but is represented at E F. 
 
 Let us next substitute a lens of four inches focal length. In 
 order to produce an image of the first tree of the same height as 
 in the first case, we shall be obliged to advance to within 200 
 feet of the first tree. And then the second tree will be found to 
 have a height on the ground glass of only .33 inch, or one-third of 
 an inch. Its place will also be totally changed ; and it will be 
 found at G J, showing only that apparent height which it has in 
 the figure. 
 
 If now we consider the equal height and the relative position 
 of these trees, we shall see that the image formed by the first lens 
 of twelve inch focus preserves a truthful relation between these 
 objects, and conveys it to the eye. 
 
 On the contrary, the long focus lens brings the second tree so 
 far forward, and gives it so nearly the height of the first, that we 
 do not at all realize that it is so much farther away. The eye is 
 completely deceived. And this fault is incident to all lenses of 
 
 ' These distances are always measured upon the line of sight E C, Fig. 76, 
 and will be presently explained, and the mode of determining apparent sizes 
 explained. 
 
102 
 
 PHOTOGRAPHIC PERSPECTIVE. 
 
 very long focus, that they do not preserve the relative planes of 
 distance^ but drag objects that belong to the middle distance, into 
 the foreground. 
 
 The fault of the very short focus lens is in an exactly opposite 
 direction. The second tree is so excessively reduced in size that 
 the eye to account for this is driven into one or other of two 
 errors, either it misconceives the height of the second tree, and 
 imagines it to be smaller, or it misconceives the distance, and 
 imagines the object to be much farther. 
 
 So the vanishing point which in a correct representation is at 
 the point V, is, in the short focus lens, drawn in to V, and, with 
 the long focus lens, carried far beyond the limits of the diagram. 
 
 The author has chosen trees to illustrate this point, but the 
 principle is of course universally true. So the side of a house, 
 seen at a suitable distance, and with a lens of moderate focal length, 
 may present the appearance A B CI), Fig. 71. When we approach 
 nearer, and, as before, substitute a lens of smaller focal length. 
 
 Fig. 71. 
 
 V 
 
 so as to keep some one line ^ ^ of the same height as before, 
 the image assumes the appearance ABc b. 
 
 There is a certain subtlety in applying these principles to prac- 
 tice, which requires close attention. Although the character of 
 the image, as distinguished from its mere size, depends upon the 
 distance to which we go from the object, and not upon the lens, 
 yet, nevertheless, lenses of small focal lengths give almost always 
 very incorrect pictures, because such lenses are brought too near 
 to the objects, and the sharp perspective angle c B A results, 
 which is always ofiensive, and may legitimately be termed incor- 
 rect, because it gives incorrect conceptions of the object deli- 
 neated. In some cases where an excessively sharp perspective 
 angle is introduced, the building will actually seem to be falling 
 forwards, and this may happen just as easily with a draughts- 
 man's sketch as with a photographic view. In the latter case a 
 longer focus lens should be used, and taken to a greater distance. 
 
PHOTOGRAPHIC PERSPECTIVE. 
 
 103 
 
 If, for example, it be required to photograph a large edifice, so 
 that the image shall be only three inches high, and we take a 
 four-inch lens and go to such a distance as will secure the size 
 required, we shall get a picture with the sharp angle GB A \ but 
 if we take a lens of eight to ten inch focus, and go to such a dis- 
 tance that the image is reduced to the same height, three inches, 
 we shall get a natural, angle C B the actual apparent height 
 A .5 remaining the same in both cases, precisely as exemplified in 
 the cases already considered. 
 
 As the principles here involved are of much importance in ob- 
 taining satisfactory representations of buildings of all descriptions, 
 the author subjoins some illustrations that will exemplify them 
 strikingl3^ Fig. 72 gives a view of Girard College as repre- 
 
 Fig. 72. 
 
 Girard College. — View exemplifying the exaggerated perspective produced by very short focus 
 
 lenses. 
 
 sented by a very short focus lens. The sharpness of the upper 
 angle will be remarked, and also the unnatural effect given to the 
 building in consequence of the vanishing points being so much 
 drawn in. 
 
 On the other hand. Fig. 73 shows the same building as repre- 
 sented by a much longer focus lens, not planted on the same spot. 
 
 Fig. 73. 
 
 Girard College. —View sliowiug tbe correct perspective produced by longer focus lenses. 
 
104 
 
 PHOTOGRAPHIC PERSPECTIVE. 
 
 for then the result would have been a much larger picture, with 
 the same angles as the former. But when the longer focus lens 
 is made to produce a picture of about the same size as the other 
 by removing it to a greater distance, we then get the effect shown 
 in Fig. 73, in which the perspective is natural and agreeable to 
 the eye. 
 
 In order to illustrate the principle more fully, the author sub- 
 joins two oblique views of a Gothic front, the one (Fig. 74) show- 
 
 West Front of St. Mark's Church, Philadelphia. — Exaggerated perspective of short focus lens. 
 
 ing the exaggerated and unpleasing effect of the short focus, by 
 which the correct relation between the nearer and farther por- 
 tions is destroyed. 
 
 Fig. 75. 
 
 St. Mark's. — Correct perspective of longer focus lens. 
 
 On the other hand. Fig. 75 shows the same front seen from the 
 same direction, but as represented by a longer focus lens placed 
 at a greater distance. 
 
PHOTOGRAPHIC PERSPECTIVE. 105 
 
 The practical application of these rules is farther somewhat 
 complicated by the fact that it is necessary to take into consider- 
 ation the actual size of the picture ; for it is an unquestionable 
 fact that the eye will support perspective angles in a large picture^ 
 that it will not in a small one. 
 
 If, for example, we take a small picture 0 B A (Fig. 69), and 
 magnify it considerably, we shall find that the perspective angles, 
 too sharp before, lose this effect, and seem more natural. (The 
 experiment is a surprising one, and must be tried to be appreciated.) 
 This is one reason why the small photographs taken with very 
 short focus lenses are so much improved by magnifying them. 
 Their caricatured, or, as it is technically termed, violent, perspec- 
 tive, intolerable in such small pictures, becomes more endurable 
 in the large one. On the other hand, a large picture, in which 
 the perspective is appropriate and suitable for its size, cannot be 
 reduced without injury. Even if the reduction be absolutely 
 perfect, as when executed by a copying camera, the character of 
 the design is destroyed. Engravers know this, and know that a 
 large architectural drawing cannot be reduced with advantage; 
 and the same truth is recognized by all artists. Euskin remarks 
 that true perspective is infinite and unreducible in its nature. 
 To every size of representation there is a certain size of perspec- 
 tive angle appropriate, or rather the appropriate size lies within 
 certain limits, and these are only to be fixed by judgment and 
 cultivated taste. 
 
 Farther, it is to be remarked, that as in every photographic 
 image the focal length of the lens corresponds with the distance 
 of the eye from the section on the window-pane before spoken 
 of, it follows that every photographic picture, to give a correct 
 impression, should be held from the eye at a distance equal to 
 the focal length of the lens with which it was taken. It will be 
 at once apparent that a view taken with a lens of four or five 
 inches focus, cannot be held that near to the eye of a person with 
 ordinary sight. It follows, therefore, that such lenses never can 
 give truthful delineations of scenery. They may make pretty 
 pictures, but these are wholly incorrect, as many must have 
 noticed. A garden becomes a park. The farther part of a house 
 is represented on so much smaller a scale than the nearer part, 
 that the eye, accustomed to correct representations, is deceived, 
 and imagines the farther part, by reason of its smallness, to be 
 much farther away than it is. And thus the farther part being 
 8 
 
106 
 
 PHOTOGRAPHIC PERSPECTIVE, 
 
 dragged away, the house appears to stretch much farther back 
 than it does in reality, and consequently to be much larger. 
 Distant objects are dwarfed down, mountains become hills, if they 
 but stand clear of the foreground. 
 
 As we see objects best at about 10 or 12 inches from the eye, 
 this would appear to be about the best focal length for a lens. 
 Still, as the eye does not discriminate closely in these matters, and 
 is very tolerant within limits, lenses of all focal lengths, from 7 
 to 15 or 16 inches, may be employed with advantage. Beyond 
 this, the pictures become flat and tame, and the impression of 
 solidity is insufficient. The round pillar looks like a flat pilaster. 
 
 In these cases the defect is, to some extent, corrected b}'- remov- 
 ing the picture considerably farther from the eye. We can here 
 alleviate the evil in a way that we could not with the pictures of 
 the short focus lens. Still, the effects are not good. 
 
 Portraiture. — Perspective is not without its bearing upon por- 
 traiture. All portraits taken with short focus lenses are incor- 
 rect. The nose is represented upon too large a scale for the rest 
 of the face, because it is nearer the lens. And it is still worse 
 with the hands and feet, if visible. If two or more persons be 
 included, their relative sizes are not properly preserved, unless 
 they stand exactly in line side by side. This incorrectness be- 
 comes quite striking where one person stands behind the other, 
 and a lens of 4 or 5 inch focus is employed. The fault in all 
 such cases depends upon the use of lenses of too short focal 
 length, in order to work in a short gallery, and work very 
 quickly. By using a lens of 7 or 8 inch focal length, and going 
 sufficiently far from the sitter to get the reduction desired, all 
 parts of the person will be harmoniously rendered, and the 
 different persons composing a group will be represented in correct 
 perspective proportion, whether near to, or at some distance from 
 the foremost figure. 
 
 § 2. — Plane Projection and Apparent Size. 
 
 Plane Projection. — In the foregoing we have always considered 
 the perspective as referred to ordinary or plane projection, that 
 is, the surface of the image is perpendicular to the line of vision. 
 The eye looks in the direction E C at the view A G B, which, as 
 delineated, is supposed to be projected on the screen or paper 
 A' B\ held perpendicularly to the line of sight E C. 
 
PLANE PROJECTION AND APPARENT SIZE. 
 
 107 
 
 This enables us at once to fix the apparent size that any object 
 will have in a plane projection, whether it be drawn or photo- 
 graphed. For suppose the paper 
 to be held at one foot from the Fig. 76. 
 
 eye, that is, that E C is one 
 foot. If the tree C is a hundred 
 feet from the eye, that is, one 
 hundred times E C, which is 
 now our scale, it will be dimin- 
 ished one hundred times. There- 
 fore, if it is fifty feet high, it will 
 be represented on A' B' as half 
 a foot. Precisely the same is 
 true of a photographic represen- 
 tation. If the lens is at E^ and has a focal length E Fo'l one foot, 
 the tree fifty feet high and one hundred feet distant, will appear 
 in the negative six inches in height. 
 
 If another tree of exactly the same height be situated at A, then, 
 although that tree may be distant half as far again, it will be 
 represented at A' of the same size as C. It appears at first anoma- 
 lous that two objects of the same size, at very different distances, 
 should have an equal size in the image or picture ; but this ano- 
 maly disappears by reflecting that, as the image is supposed to 
 be held square before the eye, the image of the tree A at A' is 
 farther from the eye than the image of the tree G at C, so that 
 E A' stands in the same relation io E A s^s, E C io E G, and, 
 therefore, if a sketch of a given size held at G' would exactly 
 cover the real tree (7, then a sketch of the same size held at A' 
 would exactly cover the real tree A. 
 
 It follows, therefore, that all objects of an equal size uj)on a line 
 A B, perpendicular to the line of sight E C, are represented of equal 
 size in the plane projection A' B\ whatever he their distances from 
 the eye. 
 
 An instance of this occurs in all drawings of fronts of build- 
 ings or rows of houses of equal heights, when the observer is 
 supposed to stand exactly in front. In the picture the houses 
 have the same actual height at the ends of the row, as in the 
 middle, although they may be much more distant. So in the de- 
 lineation of the front of the building, seen directly in front, the 
 roof line is parallel to the base line, and shows no tendency to 
 meet it. 
 
108 
 
 PHOTOGRAPHIC PERSPECTIVE. 
 
 § 3. — Panoramic Projection. 
 
 This form of projection is never used in architectural delinea- 
 tions, and has only lately attracted attention in photography, 
 from the introduction of the revolving camera. 
 
 In plane projection the image is projected upon a plane sur- 
 face, as the name indicates ; in the panoramic it is thrown upon 
 one that is cylindrical. 
 
 The curved surface A' C B' receives the image, and as the point 
 A' is no farther from the eye than C, it follows that of the two 
 equal objects A and C, A is represented smaller just in propor- 
 tion to the actual distance, so 
 that if the distance E A he 
 half as long again as F (7, the 
 tree A will have only two- 
 thirds the apparent height of 
 the equal tree G. 
 
 The representations afforded 
 by panoramic perspective are 
 correct only when they are 
 received on a curved surface and so viewed. If printed on 
 paper, the paper must be curved into the arc A' C B' of a circle, 
 whose radius is the focal length of the lens with which they were 
 taken. If such prints be laid flat (as they always are in practice), 
 everything is distorted. With landscapes this may be tolerated, 
 that is, the eye, if unfamiliar with the scene, may not detect the 
 falsification, and the general effect may be pleasing. But as soon 
 as this mode of representation is applied to architecture, its 
 faults become strikingly apparent. If the front of a building 
 be represented, the horizontal right line of the roof or cornice 
 becomes a curve with the ends pointing downwards. The base 
 line of the building becomes another curve, with the ends point- 
 ing upwards. All horizontal lines become curves, but vertical 
 lines still remain straight, because the projection plane was 
 curved only in a horizontal direction ; it was cylindrical, and the 
 vertical right lines in nature were all represented by vertical 
 right lines on the cylindrical surface. 
 
PART III. 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 CHAPTER I. 
 THE DARK ROOM. 
 
 § 1.— Regulation of Light. 
 
 The dark room in wliicli the operations of sensitizing and 
 development are to be conducted, is most commonly made by 
 partitioning oft' a portion of a larger room for this purpose. It 
 consequently happens not unfrequently that this room is lighted 
 only by an opening into the larger room, and has no window 
 communicating with the exterior. This is a serious evil, and 
 one to be avoided if possible. No sufficient ventilation can be 
 obtained except from a window upon the street or yard, and 
 for want of this, the operator's health is exposed to suffer severe 
 injury. 
 
 The Window. — "When access can be had to the open air, it is 
 desirable that the window of the dark room shall not be so 
 situated as to receive the direct rays of the sun. If this can- 
 not be wholly avoided, it is better to have the sun fall obliquely, 
 and later in the day, rather than perpendicularly, or in the 
 morning ; therefore a northwest exposure will be best, if it can 
 be arranged. 
 
 It is much better to have a good light in the dark room than 
 to work by a faint one, and this can always be accomplished by 
 using proper precautions. The window need not be small, if it 
 is properly protected. 
 
 There are two methods in common use: the use of yellow glass, 
 and the coloring, or otherwise guarding of common glass. 
 
 The yellow glass sold in the shops, even when the darkest 
 shades are used, is not in itself a sufficient protection. Even 
 when direct sunlight does not fall upon the window, light enough 
 
110 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 will enter to impress a plate; this the writer can assert from 
 experience. As an additional protection, a shade of brown hol- 
 land is useful, which in dark weather can be rolled up. 
 
 Pasting yellow paper, such as is made for common yellow en- 
 velopes, gives an excellent protection if the paper is stout, and if 
 the sun does not fall directly on the window, this will, in many 
 cases, be sufficient. The paper should be cut to the exact size of 
 the panes, and attached by a border of paste. In this way the 
 free open and shutting of the sash is not interfered with. The 
 yellow glass is of course preferable. 
 
 For a long time past, the writer has substituted green glass for 
 yellow. The orange-yellow shade of color imparted to light by 
 the glass in ordinary use is very trying to the eyes of many 
 persons. The green light, on the contrary, is pleasant both for 
 the operation of preparing the plates and for developing. A 
 tolerably dark, but not too dark, shade will be proper. 
 
 ^J'he light used may be (whether green or yellow glass be em- 
 ployed) either ordinary daylight, or artificial light. The latter 
 has the advantage that it may be had always of equal power, 
 which is of great use in judging of the density of a negative 
 during development. In employing daylight through colored 
 glass, more mistakes will be made as to the density of the nega- 
 tive than when an artificial light of uniform strength is used. 
 
 If a window is used for illumination, it should not be too 
 small, so that the light, after being thoroughly divested of its 
 actinic elements, may still be sufficiently abundant 
 Fig. 78. to render all operations easy. Ordinary print 
 should be read with ease in the dark room, and 
 this is not inconsistent with absolute immunity 
 from fogging, if the precautions just mentioned 
 have been suitably taken. 
 
 But a window for occasional opening, is not in 
 itself, hy any means, a sufficient mode of ventila- 
 tion. In the roof of the room, a five or six-inch 
 pipe should be set, the exterior part of which is 
 bent twice at right angles, so as to point down- 
 wards ; in this way neither light nor rain can enter. 
 An opening communicating with the outer air, 
 near the floor, for the admission of air, is also very desirable. 
 A slanting board is nailed against it, which freely lets pass the 
 air, but excludes the light. 
 
THE DARK ROOM. 
 
 Ill 
 
 Or a Ventilating Box may be employed. Sach a box is repre- 
 sented in Fig. 79. It is easily put together out of a few boards. 
 A hole is cut into the partition of 
 the dark room, corresponding in Fig. 79. 
 
 size to the opening G at the right 
 hand end of the box, from which 
 one side A B C D, is here supposed 
 to be removed, in order to show the 
 interior arrangement, and then the 
 box is fastened close over the hole. 
 The air enters at the opening H, in 
 the bottom of the box, and passes 
 through the partition, whilst the 
 light is effectually excluded by the cross pieces E and F. Two 
 such boxes should be used, one for the ingress, the other for the 
 egress of the air. The former is better placed so as to commu- 
 nicate with the outside air. If this cannot be done, and both 
 must be placed inside, one should be near the floor, the other 
 near the ceiling. 
 
 § 3. — Arrangement. 
 
 The arrangement of the room will depend so much upon its 
 size and shape, that it is difficult to give any general directions. 
 But it may be said, that the place for developing should be in 
 front of the window, and that near by it should be a sink with a 
 tap for washing. The tap, in fact, should be so at hand that 
 water can be made to flow over the negative at any instant to 
 stop its development. This is very urgent, and any arrangement 
 that does not accomplish this is exceedingly defective. 
 
 A good plan is to have a shelf eighteen inches wide round 
 three sides of the room. The height of the shelf will depend 
 upon whether the operator develops sitting or standing. If the 
 former, the shelf should be just high enough to put the knees 
 under, and no more. If standing, it should have a somewhat 
 greater height. 
 
 If vertical baths are used for sensitizing, they should not 
 stand on this shelf, but should be let into it, so that the top of 
 the bath will be level with the shelf; at least this is advisable if 
 it is intended to do this part of the work seated. 
 
 If the fixing is done in the dark room, the fixing bath and all 
 utensils connected with this part of the work, should be as far as 
 
112 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 possible from the sensitizing baths, and the utmost care should 
 be taken to avoid the introduction of the minutest portion of the 
 hyposulphite into the silver bath, to which it would be fatal. 
 
 The figure below represents an arrangement adopted by the 
 author, where it was a great object to save space. A wide shelf 
 
 Fig. 80. 
 
 w 
 
 
 A 
 
 
 to be used as a table, runs round three sides. At A are the 
 sensitizing baths, and near ^ is a small window of yellow glass, 
 to coat the collodion and manage the sensitizing by. (This win- 
 dow is by no means essential.) Opposite to B is the principal 
 window, looking north, and opening to the open air. In front of 
 it at is the tray or sink over which the developing is done. 
 This window comes down so that the bottom of the lowest pane 
 is level with the top of the table. A window with a high sill in 
 a dark room is a great nuisance. At Cis the sink with a tap of 
 water over it. At Z) is the fixing bath of hyposulphite. 
 
 A double-kneed pipe is set into the roof, and fresh air is in- 
 troduced at the floor from the outside, as before described. 
 
 The dark room should be kept clean and free from dust. The 
 chemicals that emit fumes should be kept elsewhere, and care be 
 taken to avoid spilling hyposulphite solutions about, because 
 whatever substances are scattered over the floor in solution soon 
 dry, and are ground off into dust by the feet. This dust may 
 rise and settle again in vessels and solutions. All such foreign 
 matter is injurious, and nothing more so than hyposulphite. 
 
 Too much shelf space in the dark room is undesirable ; it is an 
 invitation to leave things there that are better away. No worse 
 mistake can be made than that of keeping chemicals in the dark 
 room. It happens that most of the substances used for after- 
 intensifying emit vapors fhat tend strongly to produce fogging, 
 and especially sulphide of potassium (liver of sulphur) and 
 Schlippe's salt. Old solutions containing vegetable or other or- 
 
THE DARK ROOM. 
 
 113 
 
 ganic matter liable to turn sour or putrefy, are very injurious.. 
 A long succession of failures was once traced by a professional 
 photographer to a bottle of sulphocyanide of ammonium, either 
 originally impure, or into which something had been dropped 
 that had set up a decomposition. In a word, there are so many 
 suspicious substances, and injury when it comes is so intensely 
 vexatious and so dif&cult to trace out, that it is best to be on the 
 safe side, and to absolutely interdict the presence of anything in 
 the dark room that is not needed for the coating, sensitizing, and 
 developing, to the exclusion of all other operations. 
 
 It is still worse when the dark room is used as a work room 
 for chemical operations, and when torrents of gases are gene- 
 rated that permeate the wood work and plastering, and slowly 
 ooze out again for weeks. 
 
 Foul drains, or pipes communicating with sewers may intro- 
 duce gases that will interfere with the work. The presence of 
 turpentine and of fresh paint have been affirmed to interfere with 
 negative work very seriously. 
 
 But the simple exclusion of these sources of trouble is not in 
 itself sufficient. A complete ventilation is required, and a 
 copious admission of pure air into the dark room is a matter 
 upon which the photographer's health, possibly even his life, may 
 depend. The recklessness shown by many in these respects is 
 incredible, and can only be explained by an entire want of know- 
 ledge of the dangers incurred. It is a fact familiar to physicians 
 that a daily exposure, even for a limited time, to an atmosphere 
 impregnated with noxious fumes will do serious mischief, even 
 when no inconvenience is felt at the time. Our senses rapidly 
 familiarize themselves with injurious emanations, and cease to 
 give us notice of them, even when they are silently and steadily 
 doing their work of destruction. 
 
 Nor should any photographer require an assistant or person 
 employed to do work which he would avoid himself by reason 
 of its insalubrity. This, however, is often done, and is always 
 thoroughly unjustifiable. Frequently the person so exposed is 
 ignorant of his own danger. 
 
 It is desirable that the temperature of the dark room should not 
 differ very raaterially from that of the glass room. 
 
lU 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 CHAPTER II. 
 THE GLASS EOOM. 
 § 1. — General Remarks. 
 
 No subject concerns the professional photographer more deeply 
 than the glass room. Chemicals, lenses, and cameras he can 
 always obtain of excellent quality from dealers of reputation, 
 but in the construction of the glass room he must depend to a 
 large extent upon himself, acting under such information and in- 
 struction as he can obtain. It is certain that a very clever ope- 
 rator will occasionally obtain good pictures in almost any glass 
 room ; this is not, however, what is wanted. The disposition of 
 light should be such as to facilitate to the utmost the really diffi- 
 cult task of regular success. 
 
 If any intelligent observer will place himself in a room lighted 
 from several different directions, and taking a looking-glass in his 
 hand, will observe his own face, as he stands in very different 
 parts of the room, with very different illuminations, he will see 
 a wonderful change as regards feature, character, and expression. 
 Now, the object of the glass room is to obtain from each face its 
 best, and at the same time, also, its characteristic expression. 
 
 If the observer with his hand-glass carefully notices the effects 
 of different lights upon his features, he will be especially struck 
 with the three following facts : — 
 
 1. That a level light, coming directly in hon%, flattens all the 
 features. 
 
 2. That a light directly from above produces an opposite effect, 
 exaggerating the projection of the brows and nose, rendering 
 the eyes cavernous, and drawing out the cheek bones. 
 
 3. That a level light from one side produces a most unpleasant 
 effect, causing what is known as a " hatchet" expression of face. 
 
 Pursuing his trials further, he will find that the right light to 
 use consists in a combination of the three into a front upper-side 
 light. To produce this light is the great object of the disposition 
 of the glass room ; bearing in raiiid that for different sitters a 
 variation of light must be at command, and that as the position, 
 strength, and character of the light vary at different hours of the 
 day, the means of compensating for, and correcting these changes, 
 must be at hand. 
 
THE GLASS ROOM. 
 
 115 
 
 Selection of Glass for Glazing .—^\iQ experiments of Mr. Gaf- 
 field and others have shown that very pure white specimens of 
 glass are more apt to change color by the continued action of 
 sunlight, than those that are a little colored. The explanation 
 appears to be that the freedom from color is obtained by the 
 addition of manganese in the making of the glass, and that glass 
 to which manganese has been added is apt to change by sunlight 
 I to a color which is sometimes purple, sometimes golden; in 
 ■ either case greatly obstructing the passage of the active rays. 
 It was found that fine white plate glass was the most liable to 
 change of all the sorts examined. A light bluish-green window- 
 glass is that which is most suitable for glazing the glass room. 
 It would be desirable if glass manufacturers would furnish glass 
 expressly for glazing photographic rooms, guaranteed free from 
 manganese. 
 
 § 3. — Ridge Roof Construction. 
 
 By far the best light for the portraitist is the pure, soft, diffusive 
 light that comes from a northern exposure. An abundant supply 
 of this light is of the highest value. It is best, therefore, that 
 the length of the glass room should be east or west, and that the 
 north light should be received on one side. The best photo- 
 graphers all over the world are now pretty generally agreed in 
 preferring what is known as the Eidge Eoof System of Construc- 
 tion, a section of which in various forms is shown in the figures. 
 
 Fig. 81. Fig. 82. Fig. 83. 
 
 The single line represents the glazed parts; the double line, ordi- 
 nary walls, ceiling, &c. 
 
 Of these forms A is the preferable one. Great differences of 
 opinion exist as to the best pitch to give the light side of the 
 roof. Two different inclinations are shown in Fig. 81 by the line 
 above, and that below, G. Some, however, make it still flatter 
 
116 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 than the flattest of these, even as little slope as two inches to the 
 foot. Others again will give it a pitch of thirty degrees or more. 
 Fig. 84 shows a perspective view of the interior of this con- 
 struction. The principal length 
 from front to back is, of course, 
 east and west, the glazed side 
 being towards the north. The 
 glazing is carried half way or 
 thereabouts ; at least it is better 
 that it should not go farther, 
 in order that the camera may 
 be well protected from the light. 
 It will be necessary, or, at least, 
 far better, to have a screen so 
 interposed as to shut off useless 
 and injurious light from strik- 
 ing the camera from the glazed 
 portions. It is, indeed, a most 
 excellent canon, that the eye^ if placed in the position which the lens is 
 to occupy, shall not see any uncovered glass. It should never be for- 
 gotten that neglect of this will diminish the brilliancy of the image. 
 
 The relation between the dimensions of the glass house will 
 be better understood by the perspective drawing of its exterior 
 
 Fig. 85. 
 
 view, Fig. 85. If a perpendicular be dropped from the top line 
 of the glass to the floor, its height, A B, represents the extreme 
 height of the glass. A line C D is drawn at right angles to it, 
 and the angle C D B is that of the inclination of the roof. The 
 glazing begins at the height E H from the floor. H D is the 
 height from the floor at which the top light commences. 
 
 The pitch of the upper skylight is usually measured by giving 
 the angle B D 0. But as few carpenters are able to lay off a roof 
 
THE GLASS ROOM. 
 
 117 
 
 at a given angle, the following table will be found useful. It 
 gives the actual height B C for any desired angle, taking the 
 breadth D C as 10, from which the height is easily found for any 
 other breadth, greater or less. 
 
 TABLES OF INCLINATION" IN FEET FOR A GIVEN ANGLE OF PITCH. 
 
 Table I. 
 
 Angle of pitch of roof = 
 
 10° 
 
 ; if depth C D 
 
 = 10, height B C 
 
 = 1.76. 
 
 Angle " " = 
 
 12° 
 
 u u 
 
 (I 
 
 u 
 
 
 = 2.13. 
 
 Angle " " = 
 
 15° 
 
 u u 
 
 (( 
 
 u 
 
 u 
 
 = 2.68. 
 
 Angle " " = 
 
 20° 
 
 U (( 
 
 u 
 
 u 
 
 u 
 
 = 3.64. 
 
 Angle '■ , " = 
 
 25° 
 
 U (1 
 
 il 
 
 
 u 
 
 = 4.66. 
 
 Angle " " = 
 
 30° 
 
 li 11 
 
 (1 
 
 (( 
 
 u 
 
 = 5.77. 
 
 Angle " = 
 
 35° 
 
 U (( 
 
 (C 
 
 u 
 
 11 
 
 = 7.00. 
 
 Angle " " = 
 
 40° 
 
 U (( 
 
 u 
 
 u 
 
 li 
 
 = 8.40. 
 
 That is, with a pitch of 10°, the roof will rise 1.76 (If nearly) 
 feet in ten, and so on for other inclinations. To exemplify the 
 use of this table : Suppose it be intended that the skylight shall 
 have a pitch of 20°, that the room is 22 feet wide, and that the 
 skylight shall come perpendicularly over 12 feet of these 22, 
 what perpendicular height must the carpenter give the upper 
 edge B of the skylight above its lower edge D G ? or, in other 
 words, if 0 D is to bo 12 feet, what height must B C have that 
 the roof may pitch 20°? 
 
 Eeferring to the table, we get for 20° the height corresponding 
 
 to 10 feet of base, viz. ' . 3.64 
 
 For each additional foot we add one-tenth of this, viz., for 
 
 2 feet .73 
 
 And find 4yVu feet, or 4 feet 4i inches nearly . . 4.37 
 
 The following table shows the perpendicular height for differ- 
 ent angles when the length of slant line B D is given : — 
 
 Table II. 
 
 Angle of pitch 
 
 = 10°, 
 
 slant line B D = 
 
 10, the height BC = 1.73. 
 
 Angle " 
 
 = 12° 
 
 u u 
 
 " " " =2.08. 
 
 Angle " 
 
 = 15° 
 
 (( u 
 
 " " " =2.59. 
 
 Angle " 
 
 = 20° 
 
 ii li 
 
 " " " =3.42. 
 
 Angle " 
 
 = 25° 
 
 a li 
 
 " " " =4.22. 
 
 Angle ' ' 
 
 = 30° 
 
 11 11 
 
 " " " =5.00. 
 
 Angle " 
 
 = 35° 
 
 11 li 
 
 " " " =5.73. 
 
 Angle " 
 
 = 40° 
 
 li il 
 
 " " " =6.43. 
 
118 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 As an example, suppose it be intended to build a skylight 
 fourteen feet square, and to give it a pitch of 15°, what perpen- 
 dicular elevation must be given to the top ridge ? 
 
 Consulting Table II. we find for 10 feet and angle of 15° 2.59 
 For the four additional feet of the 14 we add four-tenths of 
 
 2.59 1.04 
 
 And find Sj%% feet, or 3 feet 7| inches nearly . . 3.63 
 
 The form A, Fig. 81, may be still otherwise varied. A " lean 
 to" roof may be substituted, that is, the glass G may be continued 
 all the way with the same pitch till it reaches the side wall, 
 which is then much higher, and the roof E is thus superseded. 
 
 Mr. Fennemore's glass room is arranged upon a different plan, 
 as will be seen by the adjoining figure. Its dimensions are : — 
 
 Top light, width 19 feet. 
 
 " length 12 " 
 
 Side light, width 13 " 
 
 Greatest height 12 " 
 
 Lowest " . 7 " 
 
 The pitch of the top light is five feet in twelve, or five inches 
 to the foot. Eeference to Table II., p. 117, will show that this 
 corresponds to an angle of between twenty-four and twenty-five 
 degrees. 
 
 Fig. 86. 
 
 Mr. "Wenderoth's skylight is in form somewhat like that of 
 Mr. Fennemore's, that is, it is -4, Fig. 81, widened out. But the 
 sitter has his back to the west wall, and the line from the camera 
 to the sitter has the usual east and west direction. He has, in 
 
THE GLASS ROOM. 
 
 119 
 
 addition, arrangements for admitting light at the ends, and also 
 a narrow line of opening just at the top of the south wall. This 
 last, without the most careful management, must lead to cross 
 lights, and is probably of no real use. 
 
 Sarony uses a longer ^room, with glass at each end, in order to 
 carry on two sets of operations at once. Both ends have light 
 from the northward. The roof-light is 13 feet long, and 13 feet 
 along the slides slanting upwards, which have an angle of thirty 
 degrees. The side light commences at a distance of five feet 
 from the floor, and meets the roof three feet above this; it has 
 the same length, thirteen feet, as the roof-light that joins it. The 
 construction is, therefore, very similar to Fig. 85, if we sup- 
 pose another glazed portion added to the farther end. The 
 height B H is five feet, the glazed side has a height D E of three 
 feet. The upper skylight is square, the lengths, B D, D K, being 
 each thirteen feet. The pitch or angle B D C is thirty degrees. 
 It is easy, by Table II., p. 117, to find the perpendicular height 
 of the top of the skylight from the floor. The table gives for the 
 absolute height, C B, of the sash, 6 feet 6 inches, and as D H is 
 here 8 feet, the whole height, A B, is 14 feet 6 inches. 
 
 Gurney's new studio is 18x30, with a top light 15x13, the 
 side light 15 feet long and 7 high, beginning at a height of 2J 
 feet from floor. The top light is at its junction with the side 
 light 9 feet 6 inches from floor ; at its highest point 11 feet 8 
 inches. Its inclination is, therefore, 2 feet 2 inches in 13, or 2 
 inches to the foot. This is 1.67 feet in 10 feet of slant line. Ee- 
 ferring to Table II., p. 117, we see that this corresponds with an 
 inclination a little under ten degrees, or not quite one-third as 
 much as that of the last-mentioned studio. 
 
 In a new studio, recently completed, Loescher and Petzch, of 
 Berlin, continue to use the ridge roof form, but built in somewhat 
 different proportions from their former studio, described in the 
 first edition of this manual. Their light fronts north, and the 
 skylight is protected from the direct sunlight by higher build- 
 ings south of it. The glass room is 35x17 — the lower side of 
 the skylight is 10 feet from the floor, the higher 14, the inclina- 
 tion is, therefore, 4 feet in 17. The whole side of the room, and 
 about three-quarters of the roof, are glazed. This plan involved 
 so great an exposure of side light, that especial means were found 
 necessary to exclude perfectly all that was not needed.^ 
 
 ' For fuller details and figures see Phila. Photog., 1870, pp. 89 and 117. 
 
 i 
 
120 
 
 PHOTOGKAPHIO MANIPULATIONS. 
 
 The particulars of the construction of the glass room of a cele- 
 brated Parisian photographer, Reutlinger, have been given to the 
 pujplic. On the north side there is a perpendicular glazed por- 
 tion, 22 feet long and 12 high. The glass roof has only 14 feet 
 of width, protected by an awning controlled by pulleys inside, 
 to cut off direct sunlight. The glass overhead is ground glass, 
 and so are the sides as high as the eyes. The entire length of 
 the room is about 44 feet.^ 
 
 Salomon, of Paris, uses a system corresponding for the most 
 part with Fig. 85. But as one of his essential peculiarities lies in 
 the use of a diagonal background, a sketch of the interior of his 
 glass room will be given in the section on backgrounds. 
 
 Any one of the forms of glass room which have been here par- 
 ticularly described, will, in good hands, give good work. The 
 whole system used by Loescher and Petzch seems that most in 
 accordance with sound principles, and without meaning in the 
 least to detract from the excellence of the others, is that which 
 is most strongly recommended here. 
 
 Whatever system is adopted, the following precautions will be 
 found useful : Keep the end at which the camera is placed dark, 
 and avoid having much illumination in the space between the 
 camera and the sitter, because the slight dust that always floats 
 in the air of a room reflects back a portion of any light that falls 
 upon it, and so takes from the clearness and brilliancy of the 
 work. As to the power of dust to do this, any one may convince 
 himself by observing how visible the path of a sunbeam in a 
 dark room is rendered by the dust that floats in the air, and it is 
 a general rule that whatever is capable of sending hack light to the 
 eye will also send it to the camera. Dust in the glass room is in 
 every respect a serious evil, and should be carefully prevented. 
 
 Closely allied to this principle is that the direction of the light 
 that is admitted should be towards the sitter and not towards the 
 camera. 
 
 It cannot be expected that any one system of illumination 
 should be best for all purposes. Groups are best taken in a well- 
 diffused light, affording to all parts an equable illumination, 
 whereas for many sorts of portraits, such a light is unmanage- 
 able: in fact, many skilful operators, in making single portraits, 
 try to suppress all strong light except that which falls directly 
 
 ' P7iotographisc7ie Mittheilungen, No. 41, p. 130. 
 
THE GLASS ROOM. 
 
 121 
 
 on the head. Groups also are best managed in a tolerably large 
 room, whereas experience seems to show that single heads are 
 best taken in rather small glass rooms, and there is no doubt that 
 in a small room the pose is more rapid than in a large one ; light 
 becomes more diluted in a large room, and the sitter is farther 
 from the glass. 
 
 Length of the Glass Room. — This will be determined by the 
 character of the work to be done. The shortest length in which 
 a full-length card portrait can be taken is 21 feet, full-length 
 cabinet 24, full-length whole size 40. These requirements are 
 those that will fix the length, because heads and half-lengths can 
 always be taken within a shorter space. The breadth of the 
 room will need to be approximately half its length. 
 
 The quality of the glass needed for the skylight has already 
 been discussed. As to its management, it may be either the 
 simple, clear glass, ground glass, or blue frosted. Some persons 
 are under the belief that the blue color increases the actinic 
 power of the light. This is a complete error : any skylight will 
 work faster without than with such an application. The ad- 
 vantage of the frosting lies in very greatly diminishing the glare, 
 so that a larger amount of active light may be admitted without 
 inconveniencing the sitter. Ground glass is little used here, it 
 greatly softens the light, but also greatly diminishes it strength. 
 It has been found that whilst ordinary (clean) glass holds back 
 but about five per cent, of the light, ground glass stops one-half. 
 Nevertheless ground glass is largely used in France, and with 
 great success. The blue stippling is the favorite method here, 
 and is extending to Germany. 
 
 To apply it, blue frosting is first brushed on with any ordinary 
 flat brush. Then a thick round painter's brush is tied up with twine 
 to about an inch of the end, and is tapped against the moist 
 frosting until the effect is obtained. 
 
 Ventilation. — Some portion of the glass side should be arranged 
 to slide, or there should be somewhere a window that can be . 
 raised. It is true that its use will be somewhat limited : the 
 photographer cannot of course run the risk of having a puff of 
 wind derange drapery, and even when opened between exposures 
 there is danger of the introduction of dust. But in weather in 
 which there is no dust in the atmosphere, it is highly desirable 
 to get the benefit of the freshness of the exterior air. Nothing 
 9 
 
122 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 tends more to give a portrait an old and faded expression than a 
 hot close atmosphere, the depressing effects of which are apt to 
 tell quickly upon the expression. 
 
 § 3.— Control of Sunlight. 
 
 An important consideration presents itself with respect to all 
 the forms of roof and glazing just shown in section. Even if 
 the roof looks directly to the north, it is impracticable to give it 
 so high a. pitch that the sun shall not shine over the ridge at 
 midday, and it must also shine over the ends morning and even- 
 ing, unless higher walls abut against them. Various efforts have 
 been made by different photographers to obviate this difficulty. 
 Some select a position where the walls of adjoining houses afford 
 a screen, some use awnings moved by pulleys, others trust to 
 excluding the sun by curtains and shades inside. These, indeed, 
 are of course always necessary to regulate the amount and direc- 
 tion of light, independently 
 of direct sunbeams. An 
 effectual course, in the ab- 
 sence of protection from 
 other parts of the build- 
 ing, or of adjoining build- 
 ings, is to construct a frame- 
 work of boards, as shown 
 in Fig. 87. This is valu- 
 able not only as respects 
 light, but checks the over- 
 heating of the glass room. 
 The same figure is intended to show a system of construction 
 sometimes adopted in this city ; it is easy to make and cheap, but 
 less advantageous than some others. 
 
 Some, however, trust so entirely to inside shades to exclude the 
 sun, as to prefer a southern exposure, softening the sunlight by 
 shades, and getting it under management as best they may. The 
 solitary advantage that this system possesses is, that in dull 
 weather the southern light is stronger than the northern. 
 
 Some, in order to get every variety of light, use a ridge roof, 
 with equal slopes north and south, both glazed, so that the prin- 
 cipal light may be taken from either side, as may be found best 
 £uited to the weather and the sitter. But this has a most serious 
 
 Fig. 87. 
 
THE GLASS EOOM. 
 
 123 
 
 objection in the intense heat caused by it. The glass room be- 
 comes in hot weather a veritable hot-house. The sitters suffer— 
 the chemicals do not work well. 
 
 To maintain a moderate temperature in the glass room is at 
 best a difficult matter, even when not complicated by a southern 
 exposure. A brick wall on the south side is a great protection, 
 and there should be, if possible, a space between the southern 
 ^ slope of the ridge and the ceiling on that side. An excellent 
 arrangement on all these grounds is represented in Fig. 88. At 
 the upper angle of the ceiling A, a girder supports a wooden 
 studding B. This allows an interspace D on the south pitch of 
 
 Fig. 88. Fig. 89. 
 
 the roof— very effectual in diminishing the heat. The wall B 
 tending to keep off" the noon sun from the glazing A G. 
 
 It is evident that if the south wall supports a higher building 
 adjoining, as shown in Fig. 89, somewhat the same result is at- 
 tained. Such a form of construction requires especial care to 
 render it water-tight at the junction of the roof and wall. The 
 gutter in the angle must have a rapid pitch from back to front 
 (which cannot be shown in the section), and must be thoroughly 
 tinned by a good workman. 
 
 It will be important to keep the glass, especially its outer sur- 
 face, clean, and an arrangement for scattering water over the 
 top light will have the double advantage of affording an easy 
 means of washing, and a method of cooling the room in hot 
 weather. 
 
 Keeping the glass clean has an importance even greater than 
 might be supposed. It has been ascertained by careful trial that 
 the best and newest colorless glass stops orie-iwewiie^A of the light; 
 
124- 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 a moderate accumulation of dust, perhaps spread and splashed 
 by ram and dew, may increase this source of loss five or tenfold. 
 
 § 4. — Secondary Lights. 
 
 In all these sections the sitter is supposed to be at the far end, 
 and looking towards the spectator. He will thus receive on his 
 left side a powerful light from the glass roof, whilst his right 
 side will be comparatively dark. 
 
 Now, a difference in light on the two sides is desirable, and 
 even necessary, but this difference must not exceed a certain 
 moderate measure. And the dark side of the face requires a 
 secondary light, to give transparency to the . shadows upon it. 
 Three different methods are used for this end. 
 
 First, and most common, reflectors are used. Generally, a large 
 screen covered with white paper, or white cloth, is placed on the 
 side of the sitter, opposite the light. Some have used screens 
 covered with silver paper ; others, large mirrors. 
 
 Secondly, some have opened a window on the south side, and 
 let in light directly on the dark side. 
 
 Thirdly, some object that these methods give false lights, es- 
 pecially affecting the expression of the eye, and, therefore, prefer 
 to keep the south side of the room of a sufficiently light color to 
 throw back a volume of soft white light, adequate to light up 
 the shadows. 
 
 The brilliancy of the picture is always aided by excluding all 
 extraneous light. The camera, therefore, should always be under 
 an unglazed portion of the roof, and screens should be so ar- 
 ranged that, if the eye be placed where the lens is to be, it shall 
 see no uncurtained glass. Too much glass is very objectionable, 
 especially toward the direction of the camera. The air of a room 
 always contains dust. The more strongly the dust between the 
 sitter and the lens is illuminated, the more it will affect the pic- 
 ture, and always by taking from its brilliancy. 
 
 The Tunnel System is not to be recommended, though it is 
 certain that good work has been done in this form of house, still 
 the system is every way inferior to the ridge roof. In it, one 
 end of the room, that in which the camera is placed, is lower than 
 the other, and the vertical *space between the two ceilings is 
 glazed. Thus the strongest light is full in the sitter's eyes, at 
 
THE GLASS ROOM. 
 
 125 
 
 the same time that its quantity is almost always deficient, seri- 
 ously incommoding the operator in dull weather, and producing 
 effects inferior to the ridge roof, in good. 
 
 It has been said that few photographers succeed in their first 
 attempts at building a glass house ; that they require the expe- 
 rience of a first failure to attain subsequent success. Failures of 
 this kind are expensive, and infinitely vexatious. They are best 
 avoided by obtaining beforehand a clear conception of what are 
 the conditions essential to success, and then carefully and thought- 
 fully applying them to the position which their glass room is to 
 occupy. Sometimes splendid success comes by mere chance, 
 Mr. Hughes gives an instance in which the portraits produced 
 by a photographer in a country town in England were so excel- 
 lent as to induce him to travel a long distance to see the maker. 
 He proved to be a man of limited intelligence, who, however, 
 had chanced to erect an excellent room, where an abundance of 
 soft, pure light from the north was received to the exclusion of 
 cross lights. The photographer knew that his work was excel- 
 lent, and ascribed it all to his personal skill, neither understand- 
 ing nor appreciating the merits of his room. Encouraged by 
 success, he erected a new gallery in another town, intended to be 
 far better than his old one, but was confounded to find that in it 
 he could not make anything worth having. 
 
 One material difference that will be found between a well and 
 ill -planned glass room is, that in the former work can be con- 
 tinued till a late hour in the afternoon, and, even then, brilliant 
 and well-modelled portraits can be got. It is, therefore (and this 
 cannot be too clearly understood), no proof of a good construction 
 that the operator can show a piece of first-rate work made in it. A 
 glass room can hardly be so badly planned but that in some sort 
 of weather, and at some hour of the day, good work, may be done 
 in it. The well-planned room is one that is always in a condition 
 to meet the operator's needs. 
 
126 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 CHAPTER III. 
 
 PYKOXYLINE AND COLLODION. 
 ? 1. — Pyroxyline. 
 
 The manufacture of this substance has passed so much, in fact, 
 so completely into the hands of those who make it their business, 
 and who employ special methods, that it scarcely requires atten- 
 tion here, except in a brief way. 
 
 When any form of cellulose, such as cotton, paper, linen, &c., 
 is exposed to the action of mixed nitric and sulphuric acid, a 
 substitution takes place by which one or more molecules of NO^, 
 hyponitric acid, are taken up by the cellulose. Several different 
 compounds are thus formed, and often simultaneously. When 
 the acid mixture is too weak, the cellulose is dissolved with 
 abundant disengagement of red fumes. When it is somewhat 
 stronger, and used before the heat generated by the mixture of 
 the acids escapes, pyroxylines suitable for photography are pro- 
 duced, thoroughly soluble in mixed alcohol and ether. With 
 lower temperatures and stronger acids, the more explosive form 
 of pyroxline is produced, which does not dissolve well in the 
 usual solvents. 
 
 The proportions most commonly employed in these later years, 
 are to take equal bulks of the two acids, using sulphuric acid of 
 full commercial strength (1.83 to 1.84), aud nitric acid, sp. gr. 
 1.42. For each ounce of cotton, about twelve fluidounces' of 
 each acid will be required. When this relative proportion of 
 acids is varied from, it is more usual to increase the sulphuric 
 acid than the nitric. The proportion of 12 sulphuric to 10 nitric 
 is often used, and indeed the sulphuric may be increased until it 
 
 ' As it is more convenient to measure liquids tlian to weigh tliem, it is com- 
 mon to talte them in "fluidounces" — tliat is, a quantity equal to a measured 
 ounce of water. Of course, with heavy acids, the quantity may largely exceed 
 an ounce in weight. A fluidounce of sulphuric acid will weigh not far short 
 of two ounces, one of nitric acid 1.42, nearly an ounce and a half. So in collo- 
 dion formulae the ounce of alcohol or ether means always a measured ounce, 
 and consequently much less than an ounce in weight. 
 
PYROXYLINE AND COLLODION. 
 
 127 
 
 is threefold the bulk of the nitric. Some hold that this excess 
 of sulphuric acid tends to increase the intensity of the pyroxyline 
 produced. The mixing of the acids produces considerable heat. 
 If the thermometer plunged into them rises above 150°, the mix- 
 ture is allowed to cool ; if it stands below, heat is applied. "When 
 the temperature is right the cotton is immersed in tufts, is pushed 
 quickly under the liquid so as to become soaked immediately 
 (otherwise red fumes may burst out from it, which, however, will 
 be checked by a complete immersion). The whole cotton is got 
 in as rapidly as possible, and is well worked round to insure 
 equality of action. After eight or ten minutes of immersion, the 
 cotton is drawn up with two stout glass rods, pressed against the 
 sides, and then thrown into a bucket of water. Without a mo- 
 ment's delay the operator separates it out so that the water may 
 penetrate it instantly. This can only be well done with the 
 fingers, and as they would be corroded and stained yellow by the 
 acids, it is best to use India-rubber gloves. 
 
 The pyroxyline then receives a very thorough washing in run- 
 ning water, is squeezed out and dried at ordinary temperatures 
 and not near a stove or other source of heat. The washing must 
 be sufficient to remove every trace of acid. Some, therefore, 
 wash it with very dilute ammonia or solution of carbonate of 
 soda, one ounce to the gallon, which must itself be washed out 
 of the cotton with clean water. 
 
 As commercial nitric acid varies very much in strength, it is 
 often found convenient to substitute nitrate of potash, and to 
 increase the quantity of sulphuric acid, inasmuch as part goes to 
 separate the nitric acid from the potash. It is also affirmed that 
 pyroxyline made with nitrate of potash dissolves more easily, 
 and gives a clearer solution, than that made with nitric acid. 
 
 Mix 200 parts of sulphuric acid of 1.84 (the full commercial 
 strength) with 100 parts of dried and pulverized nitrate of potash, 
 and keep them at a temperature of 147° to 150° F., which must 
 be maintained during the -operation. Stir with a glass rod till 
 the lumps disappear. Then add six to eight parts of perfectly dry 
 carded cotton. Agitate the mixture from time to time with a 
 glass rod. After the action has continued for from ten to forty- 
 five minutes, empty suddenly into a large pan of water. Wash 
 thoroughly and rapidly with plenty of water ; finally with boil- 
 ing distilled water. 
 
 During the whole operation the temperature must remain over 
 
128 
 
 PHOTOGEAPHIC MANIPULATIONS. 
 
 147° or the pyroxyline is of inferior quality, and if over 160° 
 the cotton is partly dissolved, and becomes shorter in fibre.^ 
 
 But, as already said, the manufacture of pyroxyline as a busi- 
 ness is now so thoroughly understood, that it is no longer neces- 
 sary for the photographer to prepare it for himself in order to 
 have it good. On the contrary, it is probable that it would cost 
 him much labor and some experience, to get it of as good quality 
 as that which he can readily purchase. 
 
 It has been found that the quality of the original cotton used 
 has much to do with the resulting pyroxyline, and that in general 
 the best cottons make the best pyroxyline — especially the Ameri- 
 can Sea-Island. Also, that different cottons require different 
 treatment ; the same mixtures of nitric and sulphuric acids, or of 
 nitre and sulphuric acid, which give the best results with one 
 description of cotton, will give inferior results, or perhaps fail, 
 with another. It seems to be well attested that a small quantity 
 of chlorine in the nitric acid adds considerably to the intensity of 
 the cotton, but diminishes its adhesiveness to the glass. The 
 writer has observed that the introduction of a chloride into the 
 collodion is attended with the same results, increased strength in 
 the picture, accompanied with a tendency of the film to slip from 
 the plate. 
 
 As to the keeping properties of pyroxyline, especially at tem- 
 peratures above the common, there exists a great difference of 
 opinion. It has been affirmed that pyroxyline exposed for several 
 days to a temperature of 150° F. became uniformly decomposed, 
 and that at the temperature of boiling water, some specimens 
 explode. On the other hand, another experimenter declares, that 
 pyroxyline was sealed up in a glass bottle and exposed in his 
 garden for a year, the temperature of the interior of the bottle 
 having frequently exceeded 150° F., and was found at the expira- 
 tion of the time to be unaltered. 
 
 That pyroxyline does easily decompose there can be no doubt. 
 And, also, that that decomposition is greatly aided by light — 
 even by diffuse light. The writer prepared at one time several 
 different pyroxylines, which were placed in glass bottles and 
 corked. One of these bottles was partly used just before leaving 
 town for the summer, and was by oversight left on the table, 
 where it remained for nearly three months. The room received 
 
 ' Belitzky, Br. J. XII., 4. 
 
PYROXYLINE AND COLLODION. 
 
 129 
 
 a nortli light only, and no sunlight. At the expiration of the 
 time just mentioned, the pyroxyline was converted into a moist, 
 sticky, spongy substance, not one-fifth the bulk of the original 
 cotton; the vial was filled with red vapors of hyponitric acid, 
 and the cork much eaten away. Other bottles left in a closed 
 closet had not suffered. 
 
 For this reason pyroxyline should always be kept in opaque 
 cases. It is also found that it keeps better when not too closely 
 kept from the air. Pasteboard boxes are the most suitable, and 
 the most usually employed. 
 
 M. Blondeau has published some interesting views on the 
 subject of pyroxylines, which may be briefly expressed as 
 follows : — 
 
 He considers pyroxyline to be a definite compound of fulmi- 
 nose, a substance isomeric with cellulose, and nitric acid. Of this 
 fulminose little is stated except that it is decomposed at 140° F. 
 into vapor of water and carbon. In the case of pyroxyline, the 
 nitric acid which is in combination with the fulminose oxidizes 
 the carbon to carbonic oxide, so that the products of explosion 
 are carbonic oxide, nitrogen, and vapor of water. 
 
 M. Camuzat affirms that when collodion is poured into water it 
 separates into three portions, a powder which sinks, a flaky 
 portion that swims, and a third, which dissolves. In his opinion, 
 the flaky portion is the only one which is essential or useful in 
 photography. It seems almost certain, however, that the nature 
 of the image must depend also upon any soluble organic matter 
 present. In one hundred parts he found — 
 
 Flaky part . Powdery part. Soluble part. 
 
 Best cotton .... 31 15 54 
 
 Ordinary .... 27 13 60 
 
 Powdery .... 27 7 66 
 
 Papyroxyl .... 60 5 35 
 
 Dr. Leisegang strongly recommends the substitution of tissue 
 paper for cotton in preparing pyroxyline. The tissue paper is 
 cut into strips and plunged into the acid mixture, which per- 
 meates it more rapidly and evenly. There is, therefore, less 
 tendency to decomposition, and, it is afl&rmed, the product is 
 more- regular and uniform in its chat-acter. It is also claimed 
 that it gives a remarkably smooth and uniform film when poured 
 out upon the glass. Of this papyroxyline 4 to 5 grains only are 
 dissolved in the ounce of solvent. 
 
130 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 A variety of pjroxyline, called " alcoholic," has been intro- 
 duced, but has been found of little use, even in our hottest sum- 
 mer weather, with the thermometer ranging from 90° to 100°. 
 The ordinary pyroxylines, made up with perhaps a little more 
 alcohol than in cooler weather, are preferred. 
 
 Xyloidine is a substance analogous to pyroxyline, produced by 
 the same mixed acids, when made to act upon starch. It dries 
 from its solutions as a dead^ and not as a transparent film. Nitro- 
 glucose will be discussed in Chapter XII. ■ 
 
 The careful study which every department of photography has 
 received during the past years has taught us the almost unlimited 
 influence exercised upon photographic operations by the nature 
 of the pyroxyline used. And especially that this affects the image 
 obtained even more than the salts dissolved in the collodion. So 
 that it is impossible to say that any particular salting is best for 
 any particular photographic process. All we can say is, that a 
 particular salting does best with some particular pyroxyline. 
 
 It has not been found practicable in cottons made for the wet 
 process, to combine great sensitiveness and great intensity. The 
 most sensitive cottons mostly give rather thin soft images, de- 
 ficient in intensity, needing re-development, whilst those that 
 give easily a full and bold image need a longer exposure. 
 
 These tendencies of the cotton necessarily affect the salting. 
 A very intense cotton will do best with a good deal of bromide, 
 a treatment very inappropriate for one tending to give a thin 
 soft image. 
 
 Nothing but actual trial will determine the quality of a cotton : 
 the indications which some rely on are mostly fallacious. A 
 yellowish color has been supposed to indicate intensity, but in 
 reality depends upon the wash water having contained traces of 
 muddiness. Some think that a short fibre indicates intensity ; 
 this is likewise a mistake, as is the supposition that a powdery 
 cotton is intense. These indications may, or may not, accompany 
 intensity. 
 
 Nor can manufacturers produce at will, with any exactness, 
 any particular quality of cotton, or even re-produce one that 
 they have already made. The best that they can do is to avoid 
 any wide variation. 
 
PYROXYLINE AND COLLODION. 
 
 131 
 
 § 2.— Collodion. 
 
 When pyroxyline is dissolved in acetic ether, it makes a per- 
 fect solution, but dries opaque. The solution of good negative 
 cotton in a mixture of alcohol and ether has the inestimable 
 quality of leaving behind it in drying an absolutely transparent 
 film, not to be distinguished from the glass on which it lies.^ It 
 is, moreover, acted upon in some way by nitrate of silver, with 
 the effect of adding greatly to the ordinary sensibility of iodide 
 and bromide of silver, so that in the " wet collodion process" a 
 fraction of a second is sufficient, under favorable circumstances, 
 to impress a latent image, full of gradation and detail, in the 
 camera. • 
 
 Formerly, the plain collodion was generally prepared sepa- 
 rately, the salts were dissolved apart in a portion of the alcohol, 
 and added subsequently. But as more care was taken in the 
 manufacture of pure materials,, and as the proper constitution of 
 collodions came to be better understood, it became possible to 
 prepare them so much more stable, that now it is more usual to 
 prepare at once the collodion in the condition in which it is to be 
 used. A good sound collodion, placed in a cool cellar, will keep 
 two years, and is then by many preferred to fresh. 
 
 Influence of Alcohol, Ether, and Water on Collodion. — Alcohol 
 and ether have been used in very different proportions in collo- 
 dion. Water is present in quantity depending upon the strength 
 or weakness of the other two substances. 
 
 The tendency of ether is to make a close, skinny, and tongh 
 film. Therefore, where it is intended to transfer a film, it is use- 
 ful to employ a collodion with an abundance of ether. 
 
 Alcohol loosens the film and renders it porous. By rendering 
 the permeation of the developer easy, the development is more 
 rapid, and intensity is gained. 
 
 The action of water, or in other words, of alcohol and ether of 
 low grade, is mostly injurious, except that when there is much 
 tendency to make silver stains, water in the collodion seems to 
 check them. With too much water there is a tendency to crapy 
 lines, to form ridges, and especially to make a peculiar mottled 
 appearance at the corner at which the collodion is poured off. 
 
 • Some varieties leave a "dead" film, which is rendered transparent in the 
 varnishing, and this is by some operators preferred. It is doubtful if such a 
 film is as strong as a clear one. 
 
132 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Proportions. — Formerly ether was used to excess, about 3 parts 
 ether to 2 of alcohol. For some time past the practice of em- 
 ploying equal parts of each has gained ground. 
 
 Washing with, or steeping in, Alkalies. — Pyroxyline is often 
 treated with ammonia, which has the effect of destroying any 
 acid that may either have been left in it by the maker, or have 
 been generated by a disposition to decompose. A more regular 
 action is thereby obtained, and a certainty of avoiding the in- 
 sensitiveness which acidity of the cotton inevitably causes. 
 
 The ammonia treatment is applied by diluting ordinary liquid 
 ammonia with four times its bulk of water. Into this the cotton 
 is plunged, and the solution well worked through it by alternate 
 soaking and squeezing. The cotton is then to be well washed, 
 squeezed, and dried, at ordinary temperature, or by a furnace 
 flue, but not near a stove or open fire. 
 
 It is desirable that the drying should be complete to avoid in- 
 troducing water into the collodion. The plan used by some of 
 getting the cotton ready at once by moistening with alcohol, 
 squeezing out, and repeating this several times, is not to be re- 
 commended, partly because the water is not thus completely re- 
 moved as supposed, but principally because some sorts of cotton 
 are somewhat soluble in alcohol. The writer has himself seen 
 alcohol that has been used for this purpose gelatinize in drying, 
 so much cotton had been taken up by it. 
 
 The proportion of pyroxyline to that of solvent varies, accord- 
 ing to the character of the pyroxyline itself, from 4 to 8 grains; 
 5 to 6 is the most usual with average pj'-roxylines. Some cottons, 
 however, make a collodion so dense that the proportion must be 
 lessened ; others make it so thin that 6 grains are insufficient. 
 Something will depend upon the character of the work to be 
 done — for instance, negatives require a denser collodion than 
 positives (ambrotypes). 
 
 Relation of Salting to Development. — The very important influ- 
 ence exerted by the nature of the pyroxyline has been already 
 dwelt on. The tendency of photographers at the present day is 
 not to accept pyroxylines on the authority of the makers, but to 
 try specimens and see what can be done with them, before mix- 
 ing quantities of collodion with which it may prove impracti- 
 cable to get the very best results. 
 
 It consequently becomes important with any particular cotton 
 to ascertain exactly what it will do, and this cannot be found by 
 
PYROXYLINE AND COLLODION. 
 
 133 
 
 mixing it according to any routine formula to be followed by a 
 routine development: this will only ascertain the suitableness of 
 the cotton for such treatment, and not its real value. 
 
 The question is not to find a routine formula, but what salting 
 will do best with the particular specimen. Some will yield with 
 ^ grain of bromide as much softness and detail as others with 2|, 
 It is a good plan to make up a new sample in several portions, 
 with varying quantities of bromide, until that which is best has 
 been determined. And then having found the best salting, we 
 must depend upon a proper development to get the best combina- 
 tion of half-tone and intensity, 
 
 A collodion giving a very weak image with plenty of detail is 
 .generally very sensitive, and will bear a very weak developer 
 which deposits silver slowly and heightens contrasts, especially 
 if the plate is kept in motion during development. This will 
 be the proper treatment for a collodion tending to give weak 
 negatives. 
 
 A collodion giving strong contrasts should have a strong de- 
 veloper which (as the writer long since pointed out) tends to 
 soften the picture by a more equal deposit of silver. This action 
 may be heightened by using so much developer as to wash off 
 the plate a certain portion of the bath solution with which it is 
 soaked. 
 
 Although a developer of 15 to 30 grains of sulphate of iron 
 to the ounce will do very well for regular use and suit most cases, 
 it will be a great mistake to assume that it will suit all collo- 
 dions, or to persist in using it when the character of the image 
 indicates the need of a different treatment. To avoid the trouble 
 of keeping many developers on hand, one may keep besides the 
 regular mixture, one of double strength. When a stronger de- 
 velopment is called for, part of this may be added, or when a 
 weaker, the regular developer may be diluted with water, and 
 must at the same time have an addition of acetic acid propor- 
 tionate to the water added. 
 
 The object of the worker with the wet process will always be 
 to secure a very sensitive collodion with a reasonable amount, 
 but not an excess, of intensity, and having found a cotton which 
 with some appropriate salting, will answer this need, he will 
 regulate the development so as to make up for whatever defi- 
 ciencies the character of his images may tend to show. 
 
134 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 3.— Selection of Bases. 
 
 The selection of bases to which the iodine and bromine shall 
 be united, is a matter of very great interest to tke photographer. 
 And this has been so well recognized that even exaggerated im- 
 portance has been ascribed to it. The following will, it is be- 
 lieved, be found to be the sum of what is actually known on the 
 subject. 
 
 It appears that the most permanent collodions are obtained 
 when the iodine and bromine are combined with only a mode- 
 rately powerful base. The alkalies tend to provoke decompo- 
 sition, perhaps by attacking the hyponitric acid contained in the 
 pyroxyline, whereby iodine is liberated, or at least enters into 
 other forms of combination. Of the moderately strong bases, 
 cadmium has been found to give such excellent results that it is 
 very extensively used. 
 
 On the other hand, freshly-mixed collodion does not give as 
 good results as that in which certain reactions, little understood 
 as yet, have taken place between the constituents; and these re- 
 actions take place much more rapidly when an alkaline base is 
 present. For this purpose ammonia is greatly preferred. Po- 
 tassium is liable to the objection that its bromide is comparatively 
 insoluble in the mixture of alcohol and ether used as a solvent. 
 And even if the potassium appears in the form of iodide, yet as 
 a bromide must be employed also, it follows, according to the 
 well-known chemical law, that if the constituents present are 
 capable of forming a combination insoluble in the solvent used, 
 that combination will be formed. Therefore, if with bromide of 
 cadmium we mix iodide of potassium in such proportion that if 
 by the combination of all the potassium with its proportional 
 amount of bromine, there will be more bromide than the liquid 
 present can dissolve, then that excess will inevitably be formed 
 and precipitated. 
 
 A grain, or possibly two, to the ounce of bromide of potas- 
 sium can, however, be kept in solution in an ordinary collodion. 
 To get it dissolved, all the salts should be placed together in a 
 large test-tube or a flask, alcohol be poured over them, and the 
 whole boiled for some minutes. Fresh alcohol is then to be 
 added to the undissolved part, and the operation repeated till 
 complete solution is effected. It should be clearly understood 
 that the bromides of potassium and ammonia are more soluble in 
 
PYROXYLINE AND COLLODION. 
 
 185 
 
 a solution of bromide or of iodide of cadmium than in plain 
 alcohol. They form double salts of greater solubility than the 
 unmixed alkaline bromide. This fact explains why some ope- 
 rators can prepare a collodion partly with potassium, and some 
 cannot : all depends upon the manner of operating. 
 
 Much also depends upon the solvents. The less high the 
 grades of the ether and alcohol, the more easily will the bromide 
 of potassium be kept in solution. The writer is much disposed 
 to think that when two grains of this salt are used to the ounce 
 of good solvents, a portion of it is sooner or later precipitated, 
 and if the collodion be used whilst this precipitate is tending to 
 form, pin-holes will result. 
 
 Sodium forms a more soluble bromide than potassium, and the 
 use of bromide of sodium, or of iodide of sodium, in the presence 
 of bromide of cadmium, has been highly praised, but has never 
 attained general acceptance. 
 
 Lithium forms a very soluble bromide, and its use in collodion 
 has been very highly spoken of. Its higher price prevents its 
 being more extensively used. Its action is similar to that of 
 potassium. 
 
 A curious difference exists between the actions of alkaline salts 
 and of cadmium compounds in this: that the alkaline iodides 
 and the bromides tend to render collodion thin and fluid, whilst 
 the corresponding cadmium compounds render it thick and 
 viscid. 
 
 For the various reasons here given, it is almost invariably 
 customary to combine in collodion and alkaline and a metallic 
 base. 
 
 Collodions made for sale must have good keeping properties, 
 therefore in such the proportion of cadmium largely prepon- 
 derates. Those mixed by photographers for their own imme- 
 diate use, bear a larger proportion of ammonia, and this compo- 
 sition is generally preferred by portraitists. 
 
 Before touching upon the influence of iodine and bromine, 
 which will form the subject of the next section, I must remark 
 here that it is by no means indifferent in what form we add the 
 respective substances to the collodion. It is a general law in 
 chemistry, that when different salts are all completely dissolved 
 in a solvent, the resulting combination will be independent of the 
 form in which the substances were added. For example, if an 
 equivalent of nitrate of potassium and one of chloride of sodium 
 
136 
 
 PHOTOGEAPHIC MANIPULATIONS. 
 
 be dissolved in water, the result will be absolutely the same as if 
 one equivalent of chloride of potassium and one of nitrate of 
 sodium had been used. In each case the afi&nities are independ- 
 ent of the original form of the compounds. 
 
 It would be a great mistake to apply this principle to the 
 preparation of collodion, as some might be disposed to do. The 
 admixture of one equivalent of iodide of ammonium and one of 
 bromide of cadmium would produce a quite different collodion 
 from that afforded by the mixture of one equivalent of bromide 
 of ammonium and one of iodide of cadmium. This is a point 
 that cannot be too well understood. 
 
 The explanation is, that bromide of ammonium is a very stable 
 salt, so, likewise, are bromide and iodide of cadmium; but iodide 
 of ammonium is not. As received from the manufacturer it is 
 apt to be yellowish, and to have a penetrating smell, apparently 
 of iodine. It reacts quickly on the collodion and brings it soon 
 to an orange shade, as is observable in collodions made with 
 iodide of ammonium and iodide and bromide of cadmium. Whereas 
 collodions made with bromide of ammonium and iodide of cad- 
 mium retain a pale straw-yellow color (if the pyroxyline has 
 been quite neutral) easily for a year, and even more. 
 
 Mr. Blanchard has published some remarkable experiments 
 which show the difference of the action of alkaline and metallic 
 bases. He found that in some cases a bath rendered alkaline and 
 exposed to the sun, fogged, and that acidifying only made it 
 worse. If such a bath, showing a decided alkaline reaction, was 
 used to sensitize a film in which ammonium salts predominated, 
 each plate showed less fog, until presently perfectly clean ones 
 were obtained. Under the same circumstances, cadmium collo- 
 dions gave dense fog, without a trace of an image. 
 
 This probably has something to do with the fact that the ten- 
 dency of late years has been to use less and less cadmium, some 
 even omitting it entirely (see formula 5). 
 
 To resume, then. For all practical purposes, ammonium and 
 cadmium are the great resources of photography as bases. Where 
 the bromine is combined with the ammonium, and especially 
 when the proportion of ammonium compound is not over the 
 fourth parts of that of the cadmium, a collodion is obtained which 
 ripens within ten days or a fortnight, and then continues of excel- 
 lent quality for many months, or, in a cool place, for years. 
 
PYKOXYLIISrE AND COLLODION. 
 
 137 
 
 When the iodine is combined with the ammonium, and espe- 
 cially when this is used in larger proportions than above men- 
 tioned, collodions are obtained that ripen rapidly, and are fit for 
 use in two or three days, or even in a few hours ; but which 
 become dark colored and insensitive, and give harsh pictures 
 when kept. Whilst these are in their best condition, they are 
 by some considered as giving the best possible results, and supe- 
 rior to those of the other class. It is only, however, when there 
 is a regular and uniform consumption of collodion that this form 
 can be employed without waste, or the risk of having a quantity 
 of material on hand that has passed its best condition. 
 
 Collodion which contains an iodide assumes in a few days, 
 often in a few hours, an amber colol*, whereas collodion made 
 with bromides only (for certain dry processes) remains as color- 
 less as water, or rarely takes a perceptible yellowish shade. 
 
 Where it is desired that new collodion shall ripen rapidly so 
 as to be fit for use as soon as possible, it should be kept in a 
 warm room and in a strong light. On the contrary, when it is 
 intended to keep it for a length of time, it should remain in the 
 dark, and in a cold room, best in a cellar. 
 
 § 4. — Effects of Iodine and Bromine. 
 
 At first iodides were used alone in connection with collodion. 
 But as photographers were familiar with the influence of bromine, 
 bromides were shortly after used with collodion. Experience led 
 (by surprisingly slow degrees, however) to the recognition of the 
 fact that they were invaluable. 
 
 The manner in which bromides act is, however, still a point 
 not thoroughly settled. It is a familiar fact that iodide of silver 
 solarizes very easily, that is, the maximum effect of light is quickly 
 reached, after which its action is reversed. So that with a certain 
 degree of exposure, for example, the brightest lights may produce 
 less impression, and come out in the development less strongly 
 than others of inferior intensity. Bromide of silver has much 
 less of this tendency, and a collodion containing bromide has 
 much less tendency to solarize. 
 
 It has also been generally held that the use of iodides was 
 favorable to the effects of force and contrast, whilst bromide 
 tended to softness and the correct rendering of half tone. 
 
 Some careful experiments made by the writer brought him to 
 10 
 
138 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 the conclusion that this view requires a certain limitation, for 
 that when bromides were added to collodion in large excess, that 
 collodion used in the wet process, gave harsh pictures, so that 
 softness of effect and correct rendering of half tone depend upon 
 the judicious combination of the two. For example, two grains 
 of bromide and four of iodide gave a soft and well-modelled 
 picture. More bromide Was found to make the picture too soft 
 and deficient in contrast, up to a certain point. Then the con- 
 trary effect set in, and when four grains of bromide were used to 
 two of iodide, the picture was harsh. 
 
 Another important function of bromide of silver is that of 
 keeping the plate clean. It is certain that a bath which will no 
 longer work with a pure iodide collodion, will give good pictures 
 with one containing bromide. So with careless manipulation and 
 impure chemicals, clean pictures may be got with a collodion 
 containing bromide, when this would be impossible with a simple 
 iodide collodion. 
 
 In the older formula employed for collodions, a great variety 
 of substances were employed, and in some not only iodides and 
 bromides, but also chlorides and fluorides. Then came a tendency 
 to reject everything but iodides. Next this was modified by in- 
 troducing bromides, and it is by no means impossible that we may 
 yet find it advantageous to introduce a portion of chloride into 
 our collodions. 
 
 The writer expresses this opinion, not with any positiveness, 
 but as an idea which we may yet see realized. He has made 
 many experiments on the development of positive prints on 
 paper, and has been much struck with the superiority of chloride 
 for this purpose. He believes that, at least when he first pub- 
 lished this view, it was contrary to the prevailing opinions, 
 according to which mixtures of iodides and bromides were pre- 
 ferred. But he found chloride of silver, though less sensitive 
 .and needing a rather longer exposure, to work far more evenly 
 and regularly than the others, and he has little doubt that a grain, 
 or perhaps half a grain to the ounce of chloride of copper, would 
 be found an improvement. A collodion containing three grains 
 of chloride of copper, ten of bromide of ammonium, and twenty- 
 five of iodide of cadmium, to two and a half ounces each of 
 alcohol and ether, and twenty-five grains of pyroxyline, would 
 constitute a collodion which would probably be found to have 
 superior qualities. 
 
PYROXYLINE AND COLLODIOlSr. 
 
 139 
 
 (Since the foregoing was written, the writer has shown that a 
 perfectly invisible image upon chloride paper can be perfectly- 
 developed with as full detail as one upon bromo-iodized paper. 
 And that the use of chloride of silver in connection with bromide 
 in a particular form of dry process (chloro-bromide process) 
 gives most excellent results.) 
 
 Experiments made by the writer with collodion containing a 
 chloride and a bromide in equivalent proportions, resulted in 
 showing that such a collodion gave faint images and foggy plates, 
 with a bath working well with ordinary collodions. He con- 
 cluded, therefore, that an iodide is an essential constituent of col- 
 lodion for the wet process, at least with baths as used at present. 
 Herein is a remarkable distinction between wet and dry processes. 
 On the other hand, neither chlorides nor bromides are essential 
 to the wet process, but good plates may be obtained with iodide 
 of silver alone, or in connection with either bromide or chloride 
 of silver. 
 
 By some it has been argued, that the beneficial effects of the 
 addition of bromide of silver are due to the fact that, as has been 
 stated, bromide of silver is sensitive to less refrangible rays than 
 iodide. That whilst iodide of silver was affected by only the 
 violet and bluish-violet rays, the bromide was sensitive to the 
 blue, and even, to some extent, to the green. 
 
 The writer pointed out, as far back as 1865, that the action of 
 the green color of leaves upon the collodion film was very 
 trifling and of little importance, and that leaves impressed them- 
 selves upon the film, not by the agency of their green, but of 
 their white light. 
 
 In bodies generally we distinguish two sorts of light as ema- 
 nating from them. One reflected from the surface, which is white, 
 whatever be the color of the body, and the other emanating from 
 the interior of the body, which is characterized by color. In 
 some cases one of these may predominate almost to the exclusion 
 of the other. Perfectly black objects send us only surface light, 
 and in perfectly white objects the interior color is white as well 
 as the surface color. 
 
 Now this surface light, which we scarcely take into account at 
 all in our ordinary observation of bodies around it, so completely 
 is it masked by the colored light, is, in fact, as the writer h^s else- 
 where pointed out,^ all that is really effective to the photographer, 
 
 ' Philadelphia Photographer, July, 1867. 
 
140 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 with the exception only of blue or violet-colored bodies. All 
 bodies of blue-green, green, yellow, orange, and red colors im- 
 press themselves on the collodion film solely by virtue of the 
 white surface light that accompanies, unperceived to us, the 
 colored emanations which they give forth. 
 
 It follows from this that there is little use in endeavoring to 
 find collodion that has a little greater range of impressibility. 
 "What we want is a film sensitive to the very faintest rays of 
 white light, so that every faintest emanation of surface light shall 
 act upon it by virtue of the violet rays which it includes. This 
 high sensitiveness is rarely accompanied with a great intensity, 
 so that it is precisely the most sensitive collodions that are most 
 apt to need a redevelopment. 
 
 Yogel has published some interesting experiments, from which 
 he concludes that iodide of silver is more sensitive to strong 
 lights, is more quickly impressed by them than bromide, but, on 
 the other hand, that bromide is more sensitive to weak rays. 
 Schrank and others have since called this view in question. 
 Schrank gives as the result of special experiments made by him, 
 that the beneficial influence of bromide depends upon its ab- 
 sence of tendency to solarization. 
 
 In view of this diversity of opinion, and still more, of the in- 
 fluence of the pyroxyline itself, it is not surprising that the rela- 
 tive quantity of bromide to iodide, which gives the best result, 
 is still unsettled. It has been positively ascertained that the 
 bromide should not form less than 20 nor more than 50 per cent, 
 of the whole salting. It may be said, however, that the propor- 
 tion of bromide recommended has steadily increased for several 
 years- past, and with its increase has been a well-marked gain in 
 the artistic effect of the photographs produced. The addition, 
 moreover, of bromide has the effect of rendering the process far 
 more certain. The bath will continue to work with a well-bro- 
 mized collodion long after it has ceased to give any good result 
 with a simply iodized collodion. The tendency to stains, fog, 
 and other troubles in development is far less with a bromo-iodized 
 collodion. On the other hand, too much bromide leads to the 
 production of flat and monotonous pictures, unless, indeed, the 
 proportion of bromide be very much exaggerated, when the 
 result again becomes too harsh. Too much bromide also tends 
 to give a granular crystalline precipitate wanting in fineness. 
 
PYROXYLINE AND COLLODIOISr, 
 
 141 
 
 It now remains to give a few general directions as to the pre- 
 paration and management of collodion, and then will follow some 
 of the best formulae in use. 
 
 To make the collodion, the cotton should first be weighed and 
 placed in the bottle. Three-fourths of the alcohol are then to be 
 added, and shaken up with the cotton. Next the ether is added, 
 and the whole shaken till the cotton dissolves. If the cotton is 
 exactly right, little or no visible residue will be left — a few fila- 
 ments through the liquid, which, however, will not be clear. 
 
 This constitutes plain collodion^ which may either be kept as 
 such, or at once be sensitized (which is the better plan) by dis- 
 solving the salting in the remaining one-fourth of alcohol. 
 
 In preparing a collodion, the photographer will always be 
 guided by the purpose for which it is destined. It is true that 
 collodions can be made which will answer well for almost any 
 use ; but not so thoroughly well as a collodion especially intended 
 for that particular employment. 
 
 Thus for portraiture there is a general preference given for 
 collodions containing from one to two grains of a bromide. Here 
 the main object is rapidity and delicacy. The light is under 
 almost complete control by the shifting of blinds and shutters, 
 and harsh contrasts can always be avoided by that control. 
 
 With landscapes the case is very different. We take the light 
 as we find it, and must enable ourselves to control our chemicals. 
 Collodions suitable for portraiture would give excellent results 
 in landscape work in dull weather, but in bright there might 
 with some be difficulty in getting harmonious effects. These. we 
 secure by increasing the bromide, if the collodion in question be 
 deficient in it. Where the contrasts constitute the main difii- 
 culty, as in taking interiors of buildings, or copying old paint- 
 ings, the proportion of bromide may be increased to one-half. 
 The writer proved some time ago that if we go beyond this point, 
 in place of obtaining a still farther increase of softness, a contrary 
 effect sets in, and we get increase of contrast. 
 
 A difference will also be made in the formula, according as the 
 collodion is needed for immediate use, or can be put aside for 
 some time to ripen. 
 
142 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Formula 1. Portrait Collodion. 
 
 For immediate use. 
 
 Alcohol and ether, equal parts 1 ounce.' 
 
 Iodide of ammonium 5 grains. 
 
 Bromide of cadmium to 2 " 
 
 Pyroxyline 6 " 
 
 This collodion can be used as soon as it assumes a straw-color, 
 or immediately, if a little tincture of iodine be added. 
 
 Formula 2. Portrait Collodion. 
 
 To be kept for several months before using. 
 
 Alcohol and ether in equal parts 1 ounce. 
 
 Bromide of ammonium . . . . . . ^ to 2 grains. 
 
 Iodide of cadmium 5 " 
 
 Pyroxyline 6 " 
 
 Formula 3. Portrait Collodion. 
 
 To be kept six months in a cellar before using. 
 
 Alcohol and ether, equal parts 1 ounce. 
 
 Bromide of cadmium 1^ to 2 grains. 
 
 Iodide of cadmium 5 " 
 
 Pyroxyline 6 " 
 
 The tendency to the use of the more rapidly ripening collodions 
 made chiefly with ammonium (Formulas 1, 4, 5, 6) rather than the 
 slower ones in which cadmium preponderates (Formulas 2, 3, 8), 
 seems to be on the increase, though, many good workers still prefer 
 the more stable sorts. Collodions, like No. 3, if kept in a cool 
 place, are good in six months, better at a year, and still good at 
 eighteen months. 
 
 In addition to the foregoing the writer gives the collodions of 
 some of the most successful portraitists in various countries. 
 
 Formula 4.^ Reutlinger (Paris). 
 
 Ether 6 ounces. 
 
 Alcohol 4 " 
 
 Cotton 50 to 60 grains. 
 
 Iodide ammonium 30 " 
 
 " cadmium 20 " 
 
 Bromide of ammonium 5 " 
 
 ' It is important to understand that in these and all other photographic for- 
 mulse the ounce means a fluidounce as measured in a graduate, and never a 
 weighed ounce. The expression is evidently an incorrect one, but its use is 
 universal. See also foot-note to p. 126. 
 
 2 This formula calls for the addition of " a little pure sodium." 
 
PYR0XYL1N"E AND COLLODION. 
 
 143 
 
 Formula 5, Sarony. 
 Ether and alcohol, equal parts. 
 
 Iodide of ammonium, to ounce 4i grains. 
 
 Bromide of potassium " 2 " 
 
 Pyroxyline 5 to 7 " 
 
 The pyroxyline to be treated with ammonia. (See Sec. 2 of 
 this chapter.) 
 
 Formula 6, Ourney. 
 Ether and alcohol, equal parts. 
 
 Iodide of ammonium, to ounce 5 grains. 
 
 Bromide of cadmium " I2 " 
 
 Bromide of ammonium " 
 
 Pyroxyline 5 to 7 " 
 
 Nos. 1, 4, 5, and 6 work best when from ten to thirty days old. 
 
 Formula 7. Landscape Collodion. 
 
 Alcohol 15 ounces. 
 
 Ether . . . 15 " 
 
 Bromide cadmium 35 grains. 
 
 Iodide " ....... 80 " 
 
 Bromide ammonium 30 " 
 
 Iodide " 60 " 
 
 Pyroxyline 180 " 
 
 This ripens more rapidly than the following, in consequence of 
 containing iodide of ammonium. 
 
 If softer effects are desired, the bromide may be moderately 
 increased, but too much of it will result in flat pictures and a 
 coarsely grained deposit. 
 
 Formula 8. Landscape Collodion. 
 
 To be kept some weeks, or else mixed with other ripe collodion. 
 Alcohol and ether, equal parts. 
 
 Bromide of ammonium 3 grains. 
 
 Iodide of cadmium 4^ " 
 
 The sensitizing is done by placing the weighed salts in a test- 
 tube for small quantities, or a flask for larger, and pouring over 
 them the remaining fourth of the alcohol, not at once, but in 
 successive portions, allowing each to take up what it will before 
 pouring it off. It is generally expedient to employ the heat of a 
 
14:4 PHOTOGRAPHIC MANIPULATIONS. 
 
 Bunsen burner or spirit lamp to get the bromide into sojution. 
 It is not worth while to filter the solution — the simplest plan is 
 to pour it into the plain collodion, shake well, and filter or de- 
 cant afterwards. 
 
 Bromide of cadmium dissolves very easily in alcohol; bromide 
 of potassium and of ammonium, with much difiiculty. But these 
 alkaline bromides dissolve much more easily in a solution con- 
 taining already bromide of cadmium (because double salts are 
 formed, whose solubility is greater than that of the alkaline salt). 
 Therefore it will always be found easiest to place all the salts 
 together in the test-tube or flask and dissolve them together. 
 
 Great care must be taken of fire, in all operations with 
 ether which may readily ignite from a flame at a considerable 
 distance. Ether evaporates very easily, and its vapor rapidly 
 spreads through the atmosphere— this vapor may easily become 
 dense enough to carry the flame. For this reason the utmost care 
 is needful, and accidents with the heedless are very common. 
 The danger is all the greater that as ether has little affinity for 
 water, water does not easily extinguish it, the ether floats on the 
 surface and continues to burn. Wet sand is the best application. 
 If a quantity of ether is spilled by the breaking of a large vessel, 
 the first care should be to extinguish every light and fire in the 
 building. The next to provide buckets of wet sand, in case of 
 kindling. If happily this is avoided, no fire or match should be 
 lighted until the whole house has been so thoroughly ventilated 
 that the smell of ether has disappeared. 
 
 Many operators regularly add a little solution of iodine to all 
 their collodion, and there is no doubt that that system is the 
 one that obviates the most completely all danger of fogging. 
 Others .prefer to depend upon the aging or ripening of the 
 collodion. 
 
 Those who adopt the former plan of adding iodine to the col- 
 lodion, should be extremely careful about acidifying the nitric bath • 
 Perfectly neutral nitrate of silver should alone be employed, and 
 before adding any acid to the bath, a plate should be tried with 
 the collodion intended to be used, and if it works cleanly, then 
 no acid must be introduced into the bath, or the sensitiveness of 
 the film will be materially diminished. This point will also be 
 adverted to in the remarks on fogging. 
 
 A collodion that gives a thin image will often be cured of this 
 
PYROXYLINE AND COLLODION". 
 
 145 
 
 defect bj adding to it pjroxyline in the proportion of a grain or 
 two to the ounce. On the other hand, coarseness indicates the 
 presence of too much pyroxyline. 
 
 § 5. — Clearing Collodion. 
 
 When time can be given, the simplest and much the best 
 method of clearing collodion is by subsidence and decantation. 
 The collodion is set aside for any time not 
 less than a month, and the clear part Fig. 90. 
 
 poured off. It will be found, however, 
 that the operation of pouring quickly stirs 
 up the sediment at the bottom, consequently 
 the method of transferring represented in 
 Fig. 90 should invariably be employed. 
 Two holes are pierced through a cork, one 
 carries a short bent tube A, and through 
 the other is passed the shorter leg of the 
 siphon S. By blowing gently into the 
 tube A, the siphon is started, and then 
 continues to empty the bottle to the level 
 of the bottom of the shorter leg. This 
 last should be pushed down to within a 
 quarter of an inch of the layer of sediment. 
 
 At B is represented the size and weight 
 of glass tube which will be proper. The siphon is easily made 
 by bending the glass tube over a bat-wing gas-burner : heavy tube, 
 though slower in heating, is much more manageable than light. 
 The cork should be very conical, in order that it may fit any size 
 of neck for which it may be wanted. 
 
 If filtering be resorted to, then instead of the filtering appa- 
 ratus commonly employed, in which the collodion is filtered 
 through sponge, the writer has found it far preferable to select a 
 piece of fine strong close-woven linen. This is thrown into 
 boiling water and left to soak for some hours to get rid of the 
 dressing; it is then well shaken in cold ^Sitev and dried. A 
 round piece about four inches in diameter is cut. As the collo- 
 dion runs through in a rapid stream, this will be large enough. 
 
 By preparing a yard or two of linen in this way, the pho- 
 tographer will be supplied for an indefinite time ; for one piece 
 
l^fl PITOTOGUA PIIIC MAXIPUL ATIONS. 
 
 answers over and over again. Althougli it 
 may appear to have its meshes completely 
 stopped by the solidified collodion, still it filters 
 as well as ever. 
 
 Sponge is also excellent for filtering collodion. 
 The writer takes " surgeons' sponge," or even 
 a fine quality of carriage sponge, and soaks it 
 for two or three days in hydrochloric acid di- 
 luted with eight times its bulk of water, using 
 plenty of the dilute acid. This removes the 
 calcareous matter, and renders the whole tex- 
 ture of the sponge weak and soft. It is then 
 thoroughly washed out with water, dried, and is 
 fit for use. 
 
 Whichever is used, the funnel should be 
 covered with a plate of glass, as shown in Fig. 91. With this 
 precaution the evaporation becomes inconsiderable. 
 
 1 6. — Keeping Collodion. 
 
 The ripening of collodion depends upon temperature^ and, pro- 
 bably, to some extent upon light. If, therefore, it is desired to 
 ripen collodion rapidly, it should be kept in a warm light room. 
 On the other hand, if a quantity is prepared to be used over a 
 long period, it should be placed in a cool dark cellar. Collodion 
 chiefly salted with cadmium salts keeps well and improves for a 
 long time. 
 
 It is well to understand that with time all collodions tend to 
 produce a substance having a peculiarly irritating odor, which 
 sometimes causes personal suffering to those that use it. Espe- 
 cially it attacks the eyes, and cases have been known of persons 
 obliged to give up photography for six months or a year, so ob- 
 stinate is the soreness produced in this way. 
 
THE CAMERA. 
 
 147 
 
 CHAPTER IV. 
 THE NEGATIVE. 
 
 § 1. — The Camera. 
 
 The photographic camera should be made of mahogany or 
 cherry, not of walnut, should be neatly fitted, and strongly put 
 together. Small cameras are often fitted up with a removable 
 partition, so that they can be used either with two lenses for 
 stereos, or with a single lens. The front of the camera should 
 permit of a movement up and down, and sideways, in either case 
 to be arrested and the front held firm, by a mill-head screw. This 
 is known as a Sliding Front. The focus is regulated in two 
 different ways, the camera front is racked in and out by a long 
 screw moved by a mill-head at the back, or the back is moved in 
 and out by a mill-head that turns a pinion working in a rack. In 
 the latter construction a " pinching screw" serves to secure the 
 position firmly when the focus has been taken. Every camera 
 should have a " universal level" set in, to enable the operator 
 with certainty to level his instrument. The universal level is 
 about an inch and a quarter in diameter, and contains a piece of 
 glass ground to a slight curvature somewhat like a watch-glass. 
 A single bubble of air in the spirit underneath, indicates a true 
 level by resting in the centre of the glass. This level is in- 
 serted in the camera at the back, just behind the ground glass. 
 Those who have cameras unprovided with them, can procure 
 them at a small cost from makers of surveying instruments (the 
 writer's were made by Mr. Zentmayer, Fourth St. and Harmony 
 Court, Philadelphia). To insert them a board must first be fixed 
 in a perfectly level position. A hole | inch deep must previously 
 have been made in the camera for the level. The camera is set 
 upon the accurately levelled board, the level is then so set into 
 its cavity that the bubble will be in the centre. A little cap 
 cement or bottle wax serves to secure it permanently. 
 
 The landscape camera should be lightly but strongly made of 
 the best seasoned mahogany, walnut being too apt to crack, and 
 
148 
 
 THE NEGATIVE. 
 
 should combine lightness for carrying, with solidity. Brass 
 bindings will be useful, by permitting the wood to be lighter. 
 
 Although most views require that the greatest dimension of 
 the plate should be horizontal, still there are very many cases 
 where this condition can be advantageously reversed, and, there- 
 fore, it is essential that the camera shall be arranged to screw on 
 to the tripod in either position. There is only one way in which this 
 can he properly done, that is, by having a wood or metal cross- 
 piece, as represented in the gure. That shown in Fig. 92 is 
 of wood. When brass is used, it may be much narrower, but 
 needs a third arm extending from the screw-hole A to the front 
 part of the base at C. (See Fig. 94.) 
 
 Sheet brass is wholly unsuitable. A careful brass casting is 
 needed, which must be stout and stiff. 
 
 Fig. 92. 
 
 If wood be employed, nothing will be suitable except the best 
 mahogany. The screw-plate must be set on the inside, if set on 
 the outside it will soon be pulled off. 
 
 After having given both a fair trial, the writer prefers the 
 wood, especially for large cameras. 
 
 In cameras made for sale, there will often be found, instead of 
 a cross-piece a simple screw-hole at B. It is evident that the 
 strain resulting from actual use will be so great as either to soon 
 pull the camera to pieces, or force it out of shape. On the con- 
 trary, the arrangement here described adds materially to the 
 solidity of the instrument. 
 
 The Swing-back and Swinging Lens. — The swing-back is the most 
 capita] improvement to the camera that has ever been made. Its 
 object and mode of use should be fully understood, and when 
 once mastered, this contrivance will be accepted at once as an 
 indispensable adjunct to both landscape work and portraiture. 
 
THE CAMERA. 
 
 U9 
 
 The swing-back has two objects perfectly distinct from each 
 other. The first is — 
 
 To render it possible to tilt the camera and yet avoid distortion of 
 vertical lines. — In making a view of any building, we are apt to 
 find that we get too much foreground, whilst the upper part of 
 the building is apt to be beyond the edge of the plate. To some 
 extent we can remedy this by pushing upwards the sliding front 
 of the camera. But this is insufiicient, and is open to the serious 
 objection that as the axis of the lens no longer coincides with 
 the centre of our picture, we no longer get the best definition of 
 the lens. So that only a little adjustment is allowable in this 
 way. And if we tilt the camera upwards all the vertical lines of 
 the building are intolerably distorted. 
 
 The remedy is as follows : Let E F represent a vertical line in 
 any building. If we tilt the camera 
 so as to get the whole of it upon 
 the plate, the plate will occupy the 
 inclined portion A B, and the lines 
 will be distorted. But if we can 
 shift the back so that whilst the 
 camera is tilted, the plate can be 
 kept in the vertical position 0 
 and remain parallel to E F, then 
 there will be no distortion, however 
 much we may tilt the camera. 
 
 This result is obtained by saw- 
 ing through the back of the camera and interposing a few bellows 
 folds. At a point about half way between the top and bottom 
 
 Fiff. 93. 
 
 Fig. 94. 
 
150 
 
 THE NEGATIVE. 
 
 there is a pivot on each side, on which the back swings, and on the 
 top there is a brass slot and a mill-head which secures the swing- 
 back firmly into any position that has been given it. 
 
 This arrangement is, however, incomplete without a second 
 piece exactly similar, but with its pivots at top and bottom, and 
 slot and mill-head at sides. As the first described permits the 
 plate to be adjusted vertically, it will be called for distinction the 
 vertical swing-hach. And as the second, that with its pivots at 
 top and bottom, moves horizontally, it will be called the horizon- 
 tal swing-back. The two together constitute the " double swing- 
 back," and is represented in Fig. 94. 
 
 The second and perhaps the most important function of the 
 swing-back \s>ioaidin getting different parts of a subject simultaneously 
 into focus. It is evident that with a double swing-back, the 
 different portions of the plate may be made to assume a great 
 variety of positions. Either the top, the bottom, or either side 
 may be brought nearer to the lens, or farther from it than the 
 centre. 
 
 Use of Swing-hack in Portraiture. — Often the camera needs to 
 be depressed in front to make it conveniently include the whole 
 of a standing figure. Here the first-mentioned application of 
 the swing-back comes in, and vertical lines, as columns, windows, 
 &c,, are preserved from distortion. The second application of 
 the swing-back finds its use with sitting figures, in which the 
 feet are always too near for the rest of the body, and with lenses 
 of long focus it will not be easy to get them into focus with the 
 face. Being nearer to the lens, they will have a longer focus. 
 We have, therefore, only to move the vertical swing on'its pivot 
 so as to draw the top of the plate back a little, and the difficulty 
 disappears. For this purpose the pivot A should be helow the 
 middle, in order to be opposite to the head, it being an object in 
 adjusting the swing-back not to disturb the focus on the principal 
 object, but this point is apt to be overlooked by the makers. 
 (For landscapes, the pivot is best exactly in the middle.) 
 
 The horizontal swing-back will be useful in taking groups, and 
 permit of varying the grouping in a way otherwise impossible 
 with a portrait lens. With its aid, the members of the group at 
 one side may be nearer or more distant than those at the other : 
 may be more distant than the central ones, and yet may be got 
 into focus by bringing the end of the plate upon which they fall 
 nearer to the lens. 
 
THE CAMERA. 
 
 151 
 
 Landscape Work. — For landscape work the swing-back is very 
 valuable in several ways. In almost all views the foreground is 
 the nearest portion to the camera. Its conjugate focus is longer, 
 consequently if the focus is taken so as to embrace satisfactorily 
 the rest of the picture, the foreground is apt to be wrong. 
 And if the focussing slide be racked back to bring the foreground 
 into correct focus, the rest of the picture sufiers materially. The 
 evil here spoken of is often considerably alleviated by curvature 
 of thefield^ but yet not often sufficiently, and in lenses possessing 
 a flat or nearly flat field, even this assistance is wanting. It is 
 therefore an immense aid to be able to move the top of the plate 
 a little away from the lens. 
 
 There is yet another use for this valuable contrivance. It will 
 occasionally happen in landscapes that one side of the view is mate- 
 rially nearer to the camera than the other. Here the horizontal 
 swing-back comes into play. The side on which the nearer 
 objects fall is pulled a little out from the lens, and that part 
 of the picture comes into focus without material injury to the 
 centre. 
 
 The combination of these two movements, vertical and hori- 
 zontal, will sometimes be valuable, and it is moreover to be ob- 
 served that as the camera is used sometimes on its base and 
 sometimes on its side, the functions of the two swing-backs 
 change with this change. When the camera is turned upon its 
 side, that which was before the horizontal swing-back now serves 
 to regulate the foreground. So that whatever value is placed on 
 the two modes of adjustment, neither can be dispensed with, ex- 
 changing functions as they do. It is, therefore, a serious mistake 
 to purchase a camera with a single swing-back, except, perhaps, 
 in the case of a camera to be used solely and exclusively for 
 stereoscopic work. In this case a vertical swing-back (with 
 pivots at the sides) is principally needed. 
 
 Swinging Lens. — A little consideration will show that results 
 analogous to the above may be obtained by simply so setting 
 the lens that it may turn freely in all directions. The writer 
 considers, however, that the introduction of this system as a 
 substitute for the swing-back, is a serious evil. Before explain- 
 ing this, it will be proper to exhibit the action of the swinging 
 lens. 
 
 Suppose that the tube of the lens L be jointed to the camera 
 
152 
 
 THE NEGATIVE. 
 
 SO that it can be turned in any direction whilst the body of the 
 
 camera remains fixed. It is evident 
 ^ig- 95. that the focussing screen A B, and 
 
 consequently the sensitive plate 
 rernains vertical, precisely as if the 
 lens had not moved. And remain- 
 ing vertical it cuts the cone of rays 
 from the lens, parallel to the verti- 
 cal lines of any building that may 
 stand before the lens. These are, 
 therefore, correctly represented on the screen A B, precisely as 
 if the lens L had remained in the ordinary position. 
 
 But the tilting of the lens, whilst it enabled the camera to 
 take in the higher parts of any building before it, at the same 
 time altered the position of the axis of the lens. This axis when 
 the lens is in its usual position, passes through the centre of the 
 camera, but with the tilting assumes a new position L A, and the 
 centre of the image no longer corresponds with the centre of the 
 focussing screen, but falls to A. 
 
 To remedy this the camera front, carrying with it the lens, is 
 raised until the axis of the lens takes the position B L (Fig. 96). 
 
 So that here we have accomplished 
 Fig. 96. much the same result as by the swing- 
 
 back, viz., we have tilted the lens 
 so as to embrace the higher objects 
 L and yet have kept the image per- 
 fectly vertical. With the swing-back 
 the centrality of the axis was not 
 disturbed, here it has been disturbed, 
 but readjusted. 
 
 For this object, the utility of the 
 swinging lens is probably equal to 
 that of the swing-back. 
 Next, as to adjusting the focus for the foreground. It is to be 
 remembered that the image is formed at right angles to the axis of 
 the lens, consequently when the lens is bent downward and the 
 axis takes the position L A (Fig. 97), the image is found in the 
 plane B C. But this image is not received on the focussing 
 screen at the position B C, but in that of D B. A little reflection 
 will show that this change corresponds with the moving back of 
 
THE CAMERA. 
 
 158 
 
 the swing-back. That is, that in Yig 97 
 
 both cases the image is received ^, — 
 
 on a plane which, at the top of \ 
 the camera, is farther from the lens, / '"-.^ 
 And thus in both cases, the longer 
 focus of the foreground will be ac- 
 commodated. 
 
 It is evidently a fault in the L 
 swinging lens that thus to bring 
 the foreground of a landscape 
 into focus we are obliged to tilt 
 
 the camera downwards, and so take in more foreground. But 
 this again can be cured by tilting the body of the camera 
 upwards. Let us say that we first arrange the camera in such a 
 position that we include just what we want, and have the horizon 
 line where we want it. But the foreground is not in focus. "We 
 therefore first turn down the lens somewhat, and then tilt the 
 camera upwards until this tilting brings the lens into its first 
 position. It is therefore certain that the swinging lens can, like 
 the swing-back, accommodate the focus of the foreground. 
 
 But its great inferiority lies in the way in which this is done. 
 With the swing-back we arrange the camera with the largest 
 opening of the lens until we get the picture exactly composed, 
 and then changing the diaphragm as the case may need ; if the 
 foreground is not in focus, a slight adjustment of the top of the 
 plate brings it right. 
 
 With the swinging lens we have a double adjustment to make. 
 First, the lens must be depressed. We cannot tell, however, how 
 much, but can only make a trial, then the camera is to be tilted, 
 the horizon line readjusted, and we examine if the proper amount 
 of change has been hit upon. If the foreground is not yet in 
 focus, or if, in getting it into focus, we have seriously injured the 
 focus of any other part, in either case the manipulation must be 
 tried over again. Whereas with the swing-back, we watch the 
 changes and stop it exactly at the proper point. And a similar 
 objection holds where these contrivances are used to meet the 
 case of the two sides of the picture being at different distances 
 from the lens. Here also the adjustment with the swing-back is 
 the easier. 
 11 
 
154 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 3. — Selecting the Glass. 
 
 None but very careless operators will use a lot of glass indis- 
 criminately. Every piece should be gone over and examined 
 previous to cleaning it. The high price of plate glass in this 
 country almost wholly excludes it from photographic use. If it 
 could be obtained at the same cost as in England, France, or Ger- 
 many, none other, or very little other, would be used. As it is, 
 photographers for the most part content themselves with a quality 
 of glass, usually of French manufacture, known as "photo- 
 graphic glass." 
 
 The best quality of the glass only should be purchased. It 
 comes in boxes containing fifty square feet. Opening such a 
 box, and sitting with his face to a well-lighted window, the ope- 
 rator examines every piece — 
 
 1. As to suficient thickness. Thin plates break too easily in 
 the printing process. 
 
 2. As to curvature^ by running the eye along the edges : a 
 slight curvature cannot always be avoided ; but anything over a 
 certain degree of bow is a sufficient cause for rejection. 
 
 3. As to blehs. In sun printing these are apt to show, and it 
 is generally safest to reject all plates that exhibit this defect, as 
 it is difficult to foresee how much injury may result from it. 
 
 4. As to scratches. Some lots of glass by careless handling will 
 be scratched. All pieces with scratches visible by transmitted 
 or reflected light are to be rejected. And to avoid farther danger 
 every piece after examination must have a sheet of paper laid 
 between it and the adjoining piece. And this precaution must 
 be kept up in every subsequent stage of the operations. Printed 
 paper should never be employed for this purpose, but some com- 
 mon though clean sort. If glass is left for some time in contact 
 with printed paper, a complete impression will be taken off upon 
 it, and the difficulty of cleaning will be proportionately increased 
 by the greasiness transmitted to the glass. 
 
 5. As to surface. Some pieces of glass must be rejected for 
 roughness of the surface. 
 
 A close attention on the part of photographers to these points 
 would have the effect of obliging those who manufacture photo- 
 graphic glass to work more carefully and deliver a better ma- 
 terial. 
 
THE NEGATIVE. 
 
 155 
 
 Preparing the Glass. — The cleaning of the glass has already 
 been explained in the introduction. A system has latterly gained 
 ground a good deal, of alhumenizing the glass, and thus obviating 
 the necessity of being very particular in the cleaning. Some 
 simply take white of egg and shake it up with twenty times its 
 bulk of water, in a bottle with sharp fragments of glass, filter 
 it, and make fresh for each day's use. Others mix the white of 
 egg with an equal bulk of water and a little liquid ammonia, a 
 fluidrachm for a dozen eggs. In this condition it keeps, and can 
 at any time be used by diluting it with an ounce of water to 
 each drachm of albumen. 
 
 Some prefer to iodize the albumen, obtaining in that way 
 rather more brilliant points — 2 or 3 grains to the ounce of dilu- 
 ted albumen will be sufficient. The albumen is to be extended 
 over the plate with a glass rod (by some a piece of pasteboard is 
 preferred), the excess poured off, and the plate reared up to dry. 
 
 As the cleaning of glass cannot be wholly dispensed with, the 
 writer does not see that any sort of cleaning involves less trouble 
 than the method with bichromate. And when that is done pro- 
 perly, anything further is altogether superfluous. The writer 
 has in some of his experimental trials in dry work used the same 
 plates over and over until the marks made on the back with a 
 diamond pencil indicated that they had been used 5, 6, or 7 
 times each. And never on these or any other occasions has he 
 seen indications of imperfect cleaning or the reappearance of a 
 previous image. 
 
 § 3.— The Negative Bath. 
 
 The course of proceeding recommended in the introductory 
 portion of this manual involved the use of a single bath of mode- 
 rate size. This is the best course for the beginner, because he 
 will inevitably spoil some of his first baths, either by introducing 
 foreign substances into them, or by mistaken treatment with the 
 view of improving them. But when he has attained a certain 
 familiarity with photographic operations, he will do best to adopt 
 the two-hath system originally proposed, I believe, by Mr. Wharton 
 Simpson. In this mode of operating, one bath serves to form 
 the sensitive film and receive the alcohol and ether ; the second 
 bath furnishes a nearly pure silver solution, moistening the film 
 and serving for development. 
 
156 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 The writer prefers to make these baths of widely different 
 strengths. The first bath is made strong, 40 grains to the ounce, 
 because the stronger the bath the more completely the iodide and 
 bromide remain in the film. The second is tnade comparatively 
 weak, 20 grains to the ounce. This furnishes an ample supply 
 of silver for development, and the danger of stains is materially 
 lessened. 
 
 Moreover, the writer advises ample baths — one size larger than 
 the largest size of plate habitually used, and not in any case less 
 than 60 ounces each. 
 
 The advantages of the system of working with two abundant 
 baths are so great that no one who has fairly tried it will ever 
 voluntarily use any other. They consist in extreme regularity 
 of working over a long period, so that the photographer runs 
 little risk in being deceived in his exposures, in unusual facility 
 in obtaining plates of the right density without the annoyance of 
 redevelopment, and in almost complete immunity from stains, 
 marbling, pinholes, &c. &c. The system is, moreover, an econo- 
 mical one. The impurities are concentrated in the first bath 
 for a long time, and when at last the working ceases to be satis- 
 factory, it is put into the residues and the second receives addi- 
 tional 20 grains of nitrate of silver per ounce, and takes its 
 place as the first bath with a new second bath. 
 
 The mode of making a bath, and of during a propensity to 
 fog has been explained in the introduction. It remains to be 
 said here, that although the introduction of iodine into the bath, 
 by working with a collodion to which it has been added, tends 
 to acidify the bath, yet the effect of the two treatments upon 
 the working is entirely different. The writer has known a case 
 of fogging, which could not be cured by any amount of acidifi- 
 cation of the bath, give way immediately under the addition of 
 a little iodine to the collodion. It appears from experiments of 
 Weltzien that iodine liberates hyponitric acid (not nitric) from 
 nitrate of silver, and Eeynolds ingeniously remarks that as 
 hyponitric acid by action of water splits up into nitrous and 
 nitric acid, it is probably to the production of the nitrous acid 
 that the curative influence of the iodine is due. 
 
 Be this as it may, it is certain that if, after a very slight ad- 
 dition of nitric acid to the bath (1 drop to 20 ounces of bath), 
 there appears a disposition to fog, it is far better to add iodine to 
 
THE NEGATIVE. 
 
 157 
 
 the collodion than to go on acidifying the bath. This it is im- 
 portant for the photographer to bear steadily in mind. Also 
 that a bath that fogs badly with collodion in which cadmium 
 salts predominate may not improbably do well with a collodion 
 chiefly salted with ammonium salts. 
 
 The nitrate of silver should be perfectly neutral. Most per- 
 sons prefer the crystallized ; the writer has generally used the 
 /wsec? in preference. .Crystallized nitrate^ can be converted into 
 fused by melting it in a Berlin porcelain basin over a Bunsen's 
 burner ; it should be kept in fusion for a time proportionate to 
 the quantity — five minutes for several ounces, and for quantities 
 of one or several pounds, ten minutes. It is allowed to cool in 
 the basin, and removed by inverting the basin upon a sheet of 
 letter paper placed on a board, the board is then tapped on the 
 back of a chair, and the jarring loosens the cake without break- 
 ing the basin. 
 
 A negative bath may by careful treatment be used for a won- 
 derfully long time. The writer has been informed by a profes- 
 sional photographer that he had made considerably over 2000 
 negatives, many of them 10 x 12 size, in two -i-gallon baths, and 
 had them both still in excellent order. When they ceased to 
 give good results he added carbonate of silver, boiled down, 
 filtered, sunned well, filtered again, acidulated and strengthened. 
 
 When the bath gives pinholes it must be poured into its own 
 bulk of water, filtered, and after filtering, be evaporated down 
 to its original bulk. 
 
 The writer, in working the wet process, has generally adopted 
 the principle of not wasting time and patience in trying to bring 
 faulty baths into working order, but had made it a rule to sub- 
 stitute a new bath, putting the old one aside until a proper quan- 
 tity collected. These are then to be evaporated down in a large 
 basin, large enough to hold perhaps a fifth at a time, of the 
 whole quantity. As fast as the liquid goes down, more is added. 
 When the liquid becomes small in bulk, it is transferred to a 
 smaller basin of first quality Berlin or Meissen porcelain, and 
 heat applied until all the water goes off, and a powdery mass is 
 left. The heat is then carefully raised till the whole mass passes 
 
 * One hundred and eight parts of pure silver correspond to one hundred and 
 seventy parts of nitrate. The mint value of pure silver is $1 40 in silver, 
 per troy ounce. Metallic silver is sold by the troy ounce (480 grains), nitrate 
 of silver by the ounce avoirdupois (437 j grains). 
 
158 
 
 PHOTOGEAPHIC M A A IP U L A TI 0 NS . 
 
 into quiet fusion, in which condition it is kept five or ten minutes, 
 not longer. After cooling, the cake of nitrate is broken up and 
 used for new baths, acidulating with dilute nitric acid if necessary. 
 
 Some, before evaporating, dilute largely with water to throw 
 down the iodide. This makes an immense mass of material to 
 evaporate, and in the writer's experience, has not been necessary. 
 If when the fused cake is dissolved, hot" water is used, and the 
 solution filtered at once, most of the iodide will remain undis- 
 solved. The full quantity of water needed for the bath should 
 be added to the cake at once, and not a strong solution first made 
 and then diluted. 
 
 A second bath, in first-rate order, should always be kept on 
 hand to avoid the need of hurriedly treating a bath that has 
 ceased to work well. The plan of having a second weaker bath 
 to redip the plates after the first, already described, cannot be 
 too much recommended. 
 
 Swinging Bath. — In the ordinary dipping bath, if any scum 
 forms on the surface of the liquid, it is apt to settle on the plate 
 as the latter is lifted face upward on the dipper. This may be 
 avoided by swinging the bath on pivots half way up. The plate 
 is put in, with the bath in its regular position, the bath is then 
 swung forwards until the plate tips over with its front upper 
 corners on the other side of the bath. In this way when worked 
 up and down, the face of the plate is continually washed, and 
 when drawn out, the scum attaches itself to the back of the 
 plate instead of the front. 
 
 I 4. — Making the Plate. 
 
 The mode of coating the plate has been already described and 
 illustrated with explanatory figures. (See p. 22.) In the first 
 edition of this manual, the course habitually taken by photog- 
 raphers in coating blown glass, viz., to coat the hollow side, was 
 recommended. The reasons in favor of this course are, first and 
 principal, the curvature of the field exhibited by many lenses, 
 and secondly, that when the hollow side is coated the pressure of 
 the spring of the dark slide acts to some extent as a corrective, 
 flattening the plate. 
 
 Continued experience inclines the author to believe that this 
 system cannot always be advantageously employed, but that in 
 a considerable number of cases, the reverse is the proper plan. 
 
THE NEGATIVE. 
 
 159 
 
 In most landscapes the most distant objects occupy a position 
 towards the centre of the plate ; the objects occupying the sides 
 are mostly, and those occupying the lower edge are almost in- 
 variably, nearer to the camera than the central objects. It, there- 
 fore, follows that the central objects will be apt to have a focus 
 shorter, often considerably shorter than those occupying the mar- 
 gins of the plate. This fact every practical photographer will 
 have very often noticed. And if this is so, it is clear that what- 
 ever difficulty there may be in bringing these parts simulta- 
 neously into focus upon the ground glass, the case will be yet 
 worse on the sensitive plate if coated on its hollow side, whereas 
 if it be coated on the convex side, the centre of the plate will 
 approach nearer to the lens, and consequently tend to remedy 
 the defect. 
 
 It we apply these principles to photographic subjects generally 
 we shall conclude that when the different objects included in the 
 pictures are nearly in the same 'plane^ we should coat the hollow 
 side. Therefore in portraits, and in views of architectural sub- 
 jects, the hollow face should be coated. 
 
 On the other hand, when landscapes are to be taken, with the 
 central objects farthest, it will be best to coat the convex side. 
 
 In some landscapes the nearest objects are at one side, and as 
 we pass towards the other side of the plate they continually in- 
 crease in distance. This is not a common case, and is to be 
 managed by the use of the swing-back, drawing back that part 
 of the ground glass upon which the nearer objects fall. 
 
 To the remarks already made in Part I., the following may be 
 added: — 
 
 PnemnatiG Bolder s.— These are of two sorts; the one intended 
 for collodionizing with, is made entirely of rubber. If the cup 
 portion be wetted and pressed firmly against the glass at the 
 middle of the back, it adheres and affords a convenient handle. 
 Some have a hollow chamber below (see Fig. 98), 
 by squeezing the air out of which, the adhesion is 
 improved. These holders avoid the danger of 
 mottled-marks produced by the warmth of the 
 fingers touching the under side of the glass, but 
 must be used with care. They must be wetted to 
 adhere. If set down in places soiled by spilled so- 
 lutions, these may be transferred to the back of the 
 
160 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 plate, and thence to the negative bath, to its destruction. And 
 occasionally the adhesion will give way during the pouring off: 
 the operator must be prepared for this, and if he feels the plate 
 slipping, must support it by the ends of the fingers till he can 
 get hold of the corner. 
 
 Fig. 99. 
 
 Another sort is useful for keeping the hands clean during de- 
 velopment. (Fig. 99.) 
 
 A good manipulator will find both these instruments useful. 
 
 As the film dries, the surface, which' looked before perfectly 
 smooth, will frequently show minute specks, which, by capillary 
 attraction, cause the collodion to collect round them so that they 
 form slightly raised spots. These are one of the great nuisances 
 of photography, and one which no carefulness of manipulation 
 will get rid of. The writer has even tried forcing collodion 
 through thick filtering paper by the pressure of a considerable 
 column, but the collodion so filtered produced them just as much 
 as that filtered through sponge. These specks, as far as he can 
 find, depend upon — 
 
 1. Minute filaments carried through the filter (if sponge) or 
 coming from the filter itself (if paper or cotton-wool). 
 
 2. Dust on the plate before pouring. 
 
 3. Dust falling during the collodionizing. 
 
 4. Dust on neck of collodion bottle. 
 
 Of course cause (1) is beyond helping, and is therefore the 
 most serious of all. To obviate (2) brush the plate gently with a 
 soft wide camel's hair brush, or rub gently and very moderately 
 with blotting-paper moistened with alcohol, just before collo- 
 dionizing. Not using too much friction, or it will very easily 
 become electrical and attract every mote in the atmosphere, and 
 retain it obstinately. 
 
 Cause (3) is best obviated by having a special closet in the 
 dark room for collodionizing. This is so desirable on hygienic 
 grounds alone, that it should never be omitted. 
 
 Often these specks may be floated off by pouring on a good 
 quantity of collodion, so that the excess in flowing off the plate 
 may carry the speck or mote with it. 
 
THE NEGATIVE. 
 
 161 
 
 Only experience can enable tlie photographer to decide as to 
 whether a film showing some of these specks must be wiped off 
 again. If intended for copying, it must, invariably, be rejected ; 
 and, generally, if for portraiture. In landscape work, one or two 
 small specks are not likely to show in the negative. 
 
 This is on the supposition that the particles are filaments of 
 wool, or cotton, or other inert substance. Sometimes there may 
 be chemical dust, as of hyposulphite of sodium, in the atmos- 
 phere. In this case the speck, after sensitizing, will appear 
 darker than the rest when viewed by transmitted light, and the 
 plate is, of course, worthless. 
 
 Attention to the proper moment for dipping into the bath is 
 necessary, because, if the plate be kept too long, it is insensitive, 
 and tends to marbled stains ; if plunged in too soon, it may split 
 in the bath. But even if the film does not split, it taay still not 
 have been dry enough, and may exhibit an appearance which no 
 one, without instruction, would ascribe to the right cause. Some 
 portion of the film will assume a peculiar appearance, not easily 
 described, but very observable. Perhaps a better idea can be 
 given by saying that it has something the appearance of wax, 
 the structure of a freshly-broken cake of camphor, or of fused 
 nitrate of silver ; neither exactly conveys the idea, but are per- 
 haps as good comparisons as can be found. This appearance is 
 rarely at, or carried to, the edges, which dry faster, but is gene- 
 rally to the interior of the plate, and mostly covers a few square 
 inches of surface. It rather gives the idea of some decomposi- 
 tion to the collodion, than suggests its true origin. 
 
 On the whole, it is perhaps better to remove the plate from 
 the bath as soon as the greasy marks disappear. At this stage 
 the iodides and bromides are still in excess at the bottom of the 
 film ; this bottom is therefore insensitive, and consequently the 
 sensitive portion of the film is separated by this insensitive por- 
 tion from contact with the glass, and thus the danger of stains 
 from imperfect clearing is greatly diminished. 
 
 It has seemed to the writer that short immersions in the bath 
 tend to produce images that rest on the film and are whitish 
 powdery. Longer immersion gives an image more in the film, 
 and a rich, crea;ny-looking negative. In this respect the advan- 
 tage seems on the side of a little longer immersion. 
 
162 
 
 PHOTOaRAPHIC MANIPULATIONS. 
 
 § 5. — Developers and Development. 
 
 Gallic acid, the first developing agent used, was in time super- 
 seded by pyrogallic acid, obtained from gallic acid by sublima- 
 tion, Proto-sulphate of iron was found to give a softer picture, 
 and needs less exposure than pyrogallic acid, and has by degrees 
 wholly taken its place in wet plate development. 
 
 Operators differ a good deal in their views as to the proper 
 strength of the iron developer for ordinary exposures, using from 
 ten grains of sulphate to the ounce up to forty or more. The 
 following proportion will be found to give good results. It will 
 be needful, however, to bear always in mind what has been said 
 on maintaining a due relation between the collodion and the de- 
 velopment (p. 132), and to suit the developer to the needs of the 
 film. A collodion containing much bromide will need a stronger 
 developer than one containing less, and it will also need a longer 
 development, because the deposit is more crystalline, and not so 
 close and dense ; it lets more light through, and will give a weak 
 print unless the development is carried farther than in the case 
 of a collodion containing less bromide. 
 
 No. 1. Stronger Developer. 
 
 Sulphate of iron 3 ounces. 
 
 Acetic acid 3 to 4 ounces fluid. 
 
 Water 40 ounces fluid. 
 
 No. 2. Weaker Developer. 
 
 Sulphate of iron 2 ounces. 
 
 Acetic acid 3 to 4 fluidounces. 
 
 Water 40 ounces fluid. 
 
 Aids to Development. — In developing plates, and still more in 
 redeveloping them with pyrogallic acid and silver, the hands are 
 apt to be much stained, and various contrivances have been sug- 
 
 Fig. 100. 
 
 gested for avoiding this annoyance. The author, after trying 
 such as had been proposed, with no satisfaction, devised one, of 
 which the construction is explained in the adjoining figure. 
 
THE NEGATIVE. 
 
 163 
 
 Two brass rods, one considerably longer than the other, are 
 fastened firmly into a wooden handle. At their ends the rods 
 lead at right angles, and have pieces of silver soldered on to 
 them. A rod passes through these, through one end it simply 
 turns, but fits into the other with a screw thread. A mill head 
 enables one to turn it conveniently. The plate is grasped so 
 tightly as to give a perfect security, without ever being broken. 
 
 An ingenious contrivance for the same purpose was communi- 
 cated to the author by Mr. Henderson, of Montreal. A brass 
 
 Fig. 101. 
 
 \ ^ 
 
 rod A C has a knob fixed at its end A, made by heating a piece 
 of gutta percha and kneading it into shape while hot. A notch 
 is made under it to receive the edge of the plate. A short piece 
 of lead pipe, B, slides on the rod and is held by the thumb 
 against the plate, which it holds in place. This plan is simpler 
 than the first described, but does not give equal security. 
 
 If any repellant action show itself between the developer and 
 the film, alcphol must be added to the developer, in such pro- 
 portion as will check this tendency. An ounce of alcohol to 
 eight, ten, or twelve of developer may be needed. This is a 
 matter of no small importance, because the repellant tendency 
 may at any moment lead to the formation of oily lines, and these, 
 unless the plate is instantly washed oft; almost inevitably produce 
 streaks. 
 
 When sulphate of iron is used for developing instantaneous 
 pictures, no restraining acid is employed, but simply a very strong 
 solution of the iron, 80 or 100 grains to the ounce. Such a de- 
 veloper cannot, of course, be kept on more than a very short 
 time, and the image once forced out, recourse must be had to 
 redevelopment, or to after-intensification, to bring the image up 
 to printing strength. Conversely, when a long exposure has 
 been given, a good deal of restraining acid may with propriety 
 be added. 
 
 It has been proposed at various times to place a very great 
 number of various organic substances in the developer. Expe- 
 rience has shown that almost any organic substance may take the 
 place of acetic acid as a restraining agent, and sometimes with 
 advantage; for some of these substances have a remarkable 
 
164 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 power of destroying the tendency to fog, so that the iron de- 
 veloper can be kept upon the plate like a pyrogallic developer. 
 Thus redevelopment becomes wholly superseded, and the picture 
 is always finished at a single operation. The substance that pos- 
 sesses this property in the largest degree is, as shown by the 
 writer, gelatine, that has been treated with sulphuric acid, with 
 formation of glycocine and tyrosine. The writer published several 
 formula for this purpose, and the subject attracted at one time 
 very great attention. Many experimenters went to work at it, 
 and produced formulse of their own. Since publishing, some 
 years ago, the remarks on the subject that gave the initiative to 
 what has since been written, the writer has remarked that the 
 quantity of sulphuric acid necessary to modify the gelatine is 
 absolutely so small in proportion that it exercises no hurtful 
 agency upon the development, and consequently it does not require 
 to he removed hy a subsequent neutralization. This brings the pre- 
 paration of the collo-developer to a singularly simple form, as 
 follows: Take 
 
 Common glue 6 ounces. 
 
 Sulphuric acid § fluidounce. 
 
 W^t^i" ^. .9 fljiidounces. 
 
 Boil these together for a couple of hours in a flask, replacing the 
 water as it evaporates. Then throw in an ounce of granulated 
 zinc, and boil for an hour and a half. Add water as it evapo- 
 rates, and, when done, dilute to twelve ounces. 
 
 This syrupy liquid has the most extraordinary restraining 
 power. A single drop is sufficient for three ounces of 30-grain 
 iron Solution ; one ounce, therefore, of the above gelatine solu- 
 tion is sufficient for 1500 ounces of developer. 
 
 Two essential remarks remain to be made in reference to this 
 process. It might be alleged that the restraining power is due to 
 the sulphuric acid by reason of its powerfully acid nature ; but 
 the writer has, by careful experiment, demonstrated the fact that 
 sulphuric acid does not tend to restrain development, but tends 
 to fog. It is therefore clearly not the sulphuric acid that acts. 
 
 Again, it may be alleged that by the long boiling with zinc, 
 the whole of the sulphuric acid must have been removed by the 
 excess of zinc present. But the presence of the gelatine checks 
 the action of the acid on the zinc so much that it was ascertained 
 by careful experiment that when the operation is performed as 
 above described, at the end of a boiling of an hour and a half, 
 
THE NEGATIVE. 
 
 165 
 
 only one-fourth of the sulphuric acid was neutralized. This was 
 ascertained by weighing the zinc before and after the operation, 
 and determining the quantity of sulphuric acid corresponding to 
 its loss of weight. 
 
 The action of the gelatine in this case in checking chemical 
 action, prevents a very striking analogy to its action in the 
 development. 
 
 The collo-developer, obtained by adding one drop of the gela- 
 tine solution, prepared as above, to three ounces of water and 90 
 grains of protosulphate of iron, develops rapidly and with less 
 tendency to fog than the common iron developer. By somewhat 
 increasing the quantity, the development goes on still more 
 slowly, with still less tendency to fogging. 
 
 The Sugar Developer.— ^ or the regular needs of the photog- 
 rapher no developer can be better than the sugar developer. 
 The writer uses a formula of his own which he strongly recom- 
 mends. It is as follows : — 
 
 In 32 ounces of hot water dissolve 7 ounces of protosulphate 
 of iron. This is best done by letting a portion of the hot water 
 stand over the crystals until it is pretty well saturated, pouring 
 it off, and repeating it with a second and third portion. To this 
 solution add 6 ounces of white sugar and 2| ounces of acetic 
 acid No. 8. This need not be filtered. It is the sugar developer 
 in a concentrated form, and keeps indefinitely. To prepare for 
 use take — 
 
 Above solution '^h ounces. 
 
 Acetic acid No. 8 4 " 
 
 Water ... .... 18 " 
 
 Filter. 
 
 It is perhaps an improvement to add a little sulphate of cop- 
 per. An ounce of it may be added to the 10 ounces of sulphate 
 of iron. With it, or without it, excellent results are got. The 
 strength above given is suitable for winter, and may be diluted 
 with from one-half to an equal quantity of water in summer. 
 
 Management of Development. — By close attention to the manipu- 
 lations of the development something may be done towards con- 
 trolling the nature of the image produced. Softness will be pro- 
 moted by keeping the plates still whilst. the image is coming 
 out; — contrast will be increased by inclining the plate alternately 
 at each end and keeping the developer continually in motion, 
 because in this way the silver solution which impregnates the 
 
166 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 film is mucli more washed out and mixed up with the developer. 
 The strong parts of the image will always rapidly abstract the 
 silver from the solution upon their portions of the plate ; thus as 
 the image comes out the shadows will continue to be moistened 
 with a solution rich in nitrate of silver, after that which bathes 
 the high lights has been more or less impoverished. This state 
 of things is changed by keeping the developer in motion ; more 
 silver is then carried to the high lights, and contrast is heightened. 
 
 With very large plates it will be best to develop in a pan. 
 The developer is poured in abundant quantity to the lower end 
 of the tilted pan, one end of the negative is placed in the dry 
 (npper) end of the pan. The pan is then brought to a horizontal 
 position, and at the same time the negative is let gently down 
 into it. In this way a wave of developer passes evenly over the 
 whole surface. Unless flatness of effect is dreaded, it will be 
 best to leave the negative at rest in the developer, and not to 
 work backwards and forwards. 
 
 It follows from what has been said here and elsewhere that 
 the operator must be governed in his development by a principle 
 quite different from that which guides him in exposure. For 
 whilst his exposure must be timed with a view to the worst illu- 
 minated part of the subject, the development will be guided by 
 the high lights. These two principles are of such capital im- 
 portance that they cannot be repeated too often, or mastered too 
 thoroughly. They may be expressed in two rules, as follows: — 
 
 Expose the plate for the dark shadows, leaving the lights to be 
 cared for in the development. 
 
 Develop for the high lights, keep the eye steadily fixed on the 
 very highest light (the densest spot) of the plate, and stop whilst 
 that is transparent enough to preserve its perfect moulding in the 
 print to be made from it. The shadows are not to be watched in 
 developing (except in local redevelopment^ see below) ; they have 
 been, or should have been, cared for in the exposure. Not that 
 they are indifferent, far from it, but in point of fact, watching 
 the high lights is doing the best possible for the shadows, the 
 object of continuing the development as long as possible being 
 to get out as much detail in the shadows as possible. Not they, 
 however, but the high lights are to be watched, because we so 
 ascertain the exact -moment at which the development can be 
 
THE NEGATIVE. 
 
 167 
 
 pushed no farther, but must stop under pain of producing chalki- 
 ness and fiat lights, which are simply ruinous. 
 
 Too much attention cannot be directed to this matter. It will 
 be necessary for the photographer to learn by experience the 
 appearance of the deposit when it has reached a point beyond 
 which it must not go. This cannot be expressed or described, 
 can only be learned by care and attention, and at the expense of 
 spoiled plates. It is of course to be judged of by holding the 
 plate up to the light ; by degrees the operator will learn the 
 point to which he can go safely. With practice the photographer 
 will pick out at once the high light which he must watch ; he 
 will, in fact, have seen it in the subject before he uncovered his 
 lens, and his attention will be directed to it as soon as he raises 
 the plate to the light. On this portion his attention will be 
 fixed throughout the development, and his anxiety will be always 
 that it shall not reach the point at which it must stop before he 
 gets the desired detail in the dark shadows. It has already been 
 remarked that great care will always be needed in raising the 
 plate to observe the stage reached, lest the developing solution 
 break its even film into lines, producing streaks of unequal de- 
 velopment, a trouble that besets every photographer in his earlier 
 work. 
 
 Influences controlling the Character of the Negative. — Whatever 
 influences in development tend to softness will, if exaggerated, 
 tend to fogginess, and whatever helps brilliancy will, if exagge- 
 rated, produce harshness, because harshness and fogginess are 
 the extreme terms of development. 
 
 Those, therefore, who seek for the softest effects will endeavor 
 to keep just inside the line of fogging, and by the use of a strong 
 developer will equalize the deposit of silver. Those who are 
 anxious for brilliancy will use a weak developer, which will in- 
 crease contrasts. 
 
 The anxiety for brilliancy which at one time existed has nearly 
 disappeared. The magnificent effects of half-tone which have 
 been attained by skilful photographers have produced universal 
 desire for imitation. In fact, if different series of photographs 
 be compared, it will be found that they are most pleasing in pro- 
 portion to the amount of half-tone that they contain, atid the 
 recognition of this fact, both amongst photographers and the 
 general public, is every day becoming more widespread. 
 
 If a portrait is harsh, crude, and unpleasing, with a want ot 
 
168 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 relief in its various parts; if the figure seems resting against the 
 background, and if the eye has to examine the whole to estimate 
 the relative positions of the parts, the capital fault (besides what 
 others may exist) will be want of half-tone. A landscape that 
 wants half-tone will be patchy and blocky ; it will have a certain 
 narrow and scant effect, an absence of boldness and breadth ; the 
 eye will not at a glance take in the relative position and bearing 
 of its parts, but requires some moments of observation before it 
 recognizes where everything belongs, and perceives that certain 
 parts belong to the middle distance, so that the picture is not all 
 foreground and distance, as it at first appeared to be. In such 
 work, the leaves in the foreground will be either white, if well 
 illuminated, or black, if not. It is such work that has led to the 
 epithet of unartistic, so freely bestowed by artists upon the pro- 
 ductions of photography. 
 
 How then is this invaluable half-tone to be attained ? The 
 answer is not so easy. First, it may be premised that it is the 
 use of bromides in collodion that has made it possible, the use, 
 not the exaggeration. Experience has shown that broad and ex- 
 pressive half-tones do not depend upon, and cannot be reached by 
 any particular composition of collodion or of developer alone, 
 but will depend upon a happy combination. And that in every 
 case the conditions necessary can only be discovered by careful 
 and intelligent observation. For any good specimen of pyroxy- 
 line there will be a certain proportion of iodide or bromide, and 
 a certain strength of development that will produce good results, 
 and these must be found by trials. (See p. 138.) 
 
 A serious difficulty is introduced into all photographic opera- 
 tions by the variable nature of the cotton. It seems almost im- 
 possible to repeat an operation for making pyroxyline twice, and 
 get identical results. 
 
 It will be important to bear in mind that whenever a very 
 considerable quantity of bromide has been used in the collodion 
 the tendency of the deposit is to be more crystalline. A curious 
 result follows, that in printing the plates show themselves to be 
 less dense than they appear to the eye, and consequently they 
 show less contrast. 
 
 It may consequently happen that such plates, whilst appearing 
 to a -good judge to have been developed exactly right, may yet 
 in printing yield fiat and unsatisfactory results. In changing 
 
THE NEGATIVE. 
 
 169 
 
 from one formula of salting to another it will be important to 
 bear this in mind. 
 
 The whole tendency of modern photography is to full ex- 
 posures and slow, careful developments. It follows, from what 
 has been already said, that a full exposure absolutely necessitates 
 a slow development, otherwise the negative is flat and tame, a 
 fault now much commoner than it used to be when brilliancy was 
 more sought after than half-tone. In fact, some seek so earnestly 
 for masses of half-tone that they sometimes have no high lights 
 at all in their prints: this is a fault which, though not as bad as 
 the opposite error, is nevertheless a fault; no contrasts that can 
 be produced on paper, as shown by Mr. Euskin, can fully repre- 
 sent the ordinary contrasts of nature. "We are, therefore, never 
 justified in still farther contracting our means by substituting 
 half-tone for high lights. Indeed, a certain quantity of high 
 light is essential to give to half-tone its full value and due effect. 
 
 Washing the plates should not be hurried, but ample time be 
 given to get rid of the hyposulphite, especially with valuable 
 negatives. A simple arrangement for supporting the plate 
 whilst washing is figured in the introduction at p. 36, and is spe- 
 cially recommended as facilitating a safe and perfect washing, 
 
 § 6, — Local Redevelopment. 
 
 It will occasionally happen that after the deposit on a negative 
 has reached a point such that, whilst the denser parts have re- 
 ceived all that they can bear consistently with giving full detail 
 in the high lights in the print to be hereafter taken, the thinner 
 portions, or some of them, might advantageously have more 
 strength, that is, these thinner portions, though exhibiting fine 
 details to the eye, may be too thin to print properly. In order, 
 therefore, to bring the negative into a condition to show the 
 greatest possible transparency of shadow, that is, a clear render- 
 ing of details in the least illuminated portions, it may be very 
 advantageous to resort to a local redevelopment. 
 
 This may be performed either before or after fixing. When 
 done before fixing, there is more hope of adding to the details, 
 when after, the operation can be performed more satisfactorily, 
 because the operator sees far better what he is about. In. the 
 former case, although details not before visible may be rendered 
 visible, yet it is doubtful if, within the limits of this operation, 
 12 
 
170 
 
 PHOTOGRAPHIC MANIPULATIONS, 
 
 detail so brought out can be got up to printing strength. The 
 proper hope of this operation seems, therefore, to be the bringing 
 of visible details, too weak to print, up to printing strength, and 
 this is better done upon the fixed and washed negative. I shall, 
 therefore, so describe it. It will be understood, however, that if 
 preferred, exactly the same operation may be performed upon 
 the unfixed negative, remembering that the same precaution as 
 to light must be then used as in the regular development, other- 
 wise fogging will ensue. 
 
 If the negative has been allowed to dry, it will be advisable 
 first to go round the edges with India rubber dissolved in benzole. 
 The film must then be well wetted, the plate is to be grasped by 
 the left thumb and forefinger at one of its corners, and so held 
 that those parts which are already fully dense shall be on the 
 side of the plate farthest from the operator (in a landscape nega- 
 tive this will generally be the sky side); the plate is to be tilted 
 a little, so that this far side will be a little the higher, and a solu- 
 tion of pyrogallic acid, silver, and citric acid, such as is usually 
 employed for redeveloping, is to be dropped upon those parts 
 where the additional deposit is needed. The plate being very 
 wet, this dropping of solution will produce circles that slowly 
 expand, and as they cease to expand wash down towards the edge 
 near the operator, by reason of the tilting position given as above 
 directed. As this takes place the operator holds the plate under 
 the bath and washes off the solution. If the parts nearest to the 
 operator will easily bear the additional deposit that they get as 
 the solution passes over them, the operator proceeds more delibe- 
 rately. If they are already pretty strong, he washes ofi" almost 
 as soon as the solution spreads to them. A few seconds suffice 
 to wash away the solution, when the operator recommences, and 
 this is done as often as necessary, even up to six or a dozen 
 times. 
 
 By this mode of proceeding, spots and stains are avoided. If 
 the solution were left to rest on any one part, a circular spot 
 might result which would print lighter. The pyrogallic solution 
 can be used pretty strong, but should be kept clear and colorless. 
 The whole operation turns on not allowing the solution to be for 
 a moment stationary anywhere, but washing it off as it ceases to 
 spread, and recommencing. Of course, before washing, the greater 
 part of the solution may be first drained off into the developing 
 vessel. 
 
THE NEGATIVE. 
 
 171 
 
 § 7. — After-Intensification. 
 
 The three stages by which the utmost possible density is ac- 
 quired by a negative are — development, with iron, pyrogallic or 
 gallic acid ; redevelopment^ by a second application of either of 
 the foregoing reducing agents, not necessarily or even generally 
 the same as at first employed, since iron is commonly followed 
 by pyrogallic acid ; and after -intensification, which last may be 
 effected in a variety of different ways. 
 
 Eedevelopment may be resorted to either before or after fixing, 
 and in all cases is accompanied by an addition of silver solution. 
 After-intensification is always applied after fixing, and silver is 
 never used. The object of redevelopment is always to add more 
 silver, without acting in any way upon the previous deposit. 
 After-intensification adds no silver, but always acts chemically 
 upon the original image, bringing it into a new combination more 
 opaque to light. 
 
 When it is intended to apply an after-intensification, it is not 
 usual to redevelop also, but to fix after the first development. 
 It should be thoroughly understood by all students in photo- 
 graphy that after-intensification is at best the remedy either of a 
 mistake in the exposure, or else is rendered necessary either by 
 a deficiency of illumination, or an exposure which for good 
 reason has been greatly curtailed. Therefore, whilst a good 
 knowledge of several modes of intensifying is necessary for the 
 photographer, he should resort to them as little as possible. 
 Where the exposure has proved much too short or too long, it 
 is generally better, when practicable, to take another negative. 
 It will cost but little, if any, more time ; the experience of the 
 first will enable the operator to time the second correctly, and 
 the probabilities of a fine negative are decidedly greater. The 
 following are the best methods of after-intensification : — 
 
 Iodine. — When only a little additional strength is wanted, 
 iodine may be employed. If a few drops of tincture of iodine 
 be dropped into a quantity of water, the latter acquires a pale 
 sherry wine color, and if poured over a negative gradually 
 blackens it, or rather brings it to an exceedingly deep violet 
 black. The application must be stopped at this point by washing 
 off the solution as its continued action brings the plate to a light 
 yellow color. The solution may either be flowed over the plate, 
 
172 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 replacing it with fresli as soon as it loses its color, or it may be 
 applied as a bath. 
 
 Care must be taken that there are no undissolved particles of 
 iodine present, as these may lodge on the film and produce yellow 
 spots. For this reason many prefer to add a little iodide of potas- 
 sium to the liquid, which enables it to keep more iodine in solu- 
 tion. This combination may be purchased of the druggist, under 
 the name of " Lugol's solution," which may be diluted with 
 thirty or more times its bulk of water and used. 
 
 Chlorine. — The blackening may be equally well effected by 
 chlorine. Make a solution of bichromate of potash, one grain to 
 the ounce, and add to each ounce two drops of hydrochloric acid. 
 This solution is applied like the preceding, stopping as soon as 
 a uniform dark color is obtained. 
 
 Corrosive SuhUmate. — If a saturated solution of this substance 
 be diluted with ten times its bulk of water, it may be applied 
 precisely like the preceding, and blackens the plate'^very efi'ec- 
 tually. 
 
 The foregoing applications all give a moderate degree of addi- 
 tional density to the image, though the latter acts more power- 
 fully in this respect than the others. They also act alike in this, 
 that if their influence be continued too long, the images, after 
 having become black, become lighter again ; in the first case 
 pass to a yellow shade, in the two latter, to white. In this con- 
 dition, the film is in all cases much less dense than at first. In 
 this stage, however, they are fit for additional treatment, which 
 may confer upon them a much greater density yet, as follows : — 
 
 /Sulphide of potassium will not act much upon the silver film, 
 but if by the continued action of either of the three first methods, 
 the film has been brought to the yellow or white stage, and then 
 a dilute solution of sulphide of potassium be poured over it, the 
 image acquires an intense blackness, so intense, in fact, that all 
 middle tints may be expected to disappear. Nevertheless, there 
 do exist cases in which this treatment may be applied with very 
 useful results. Negatives of line-engravings, especially such as 
 are of the full size of the original, are often very successfully 
 obtained by developing only till an ambrotype is got, and then, 
 without any redevelopment, intensifying in this way. But it is 
 to be said that, in skilful hands, equally good and quicker print- 
 ing negatives of line engravings are got by the ordinary develop- 
 
THE NEGATIVE. 
 
 173 
 
 rnent and redevelopment, though they do not give prints which 
 so easily tone to a perfect black as those yielded by the denser 
 sort of negatives. Even, however, when these denser negatives 
 are wanted, they may be still better obtained by the following : — 
 Cyanide of Potassium. — When a film has been treated with cor- 
 rosive sublimate till the white stage is reached, there is often a 
 little veiling produced, scarcely visible while the print has this 
 light color, but visibly injurious after the blackening by sulphide 
 has been effected. The writer has found it, therefore, useful to 
 substitute cyanide of potassium for the alkaline sulphide. The 
 cyanide solution must be very weak, one grain, or not exceeding 
 two, to the ounce of water. It must be flowed over evenly, or 
 applied as a bath, and must be washed off as soon as an even 
 
 [ blackness is obtained. A continued action will cause the nega- 
 tive to whiten again. 
 
 This treatment gives great intensity, and, at the same time, 
 keeps the transparent parts of the negative beautifully clear. 
 For photographic operations in processes not intended to give 
 half tones, it is exceedingly well suited, as well as for all cases 
 where clean sharp contrast is a main object. 
 
 Schlippe's Salt — Scarlet Negatives. — This method of intensifying, 
 which the writer introduced to photographic notice some years 
 ago, has been largely used where great increase of intensity is 
 needed, and with excellent results. The negative is first treated 
 in either of the three first described methods : with iodine, chlo- 
 rine, or corrosive sublimate, until the light stage is reached, and 
 then, after washing, a dilute solution of Schlippe's salt (sulphanti- 
 monite of sodium) is poured over it. The negative instantly 
 turns bright scarlet, presenting a remarkable and very beautiful 
 appearance, and becoming very opaque to active rays. 
 
 The solution of Schlippe's salt should contain about ten grains 
 to the ounce, and should be kept tightly corked. It, however, 
 gradually deposits a precipitate, but if decanted from this it still 
 acts well. The addition of a few drops of liquid ammonia pre- 
 vents the precipitate and causes the solution to keep quite well. 
 In this condition it does not give the bright-colored negatives 
 before spoken of, but beautiful russet-brown ones, which are per- 
 
 * haps as non-actinic as those obtained without the ammonia. The 
 color will also be found to vary a good deal with the extent to 
 which the first application (of chlorine, iodine, or sublimate solu- 
 tion) has been allowed to act. The full scarlet color is got by 
 
174 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 allowing the first action to reach the full light stage, and apply 
 ing the Schlippe's salt without ammonia. 
 
 Solution of Schlippe's salt is apt to stain the fingers red. A 
 little weak solution of caustic potash or soda instantly removes 
 this. 
 
 It should always be borne fully in mind that operations with 
 either sulphide of potassium or Schlippe's salt should be car- 
 ried on away from the dark room, as the sulphuretted hydrogen, 
 of which a little is diffused in the atmosphere, may tend to cause 
 fogging. It is also injurious to the health to breathe a sulphu- 
 retted atmosphere, therefore a thorough draft should be provided 
 to carry ofi" such vapors. 
 
 Permanganate of potassium has been highly recommended for 
 after-intensifying by Mr. Wharton Simpson. A dilute solution 
 is poured over the plate till the requisite intensity is obtained. 
 
 Uranium intensifying is now abandoned, because the nega- 
 tives rapidly become denser in printing till worthless; after- 
 intensification with sublimate is, to some extent, liable to a similar 
 objection. 
 
 In such cases it has been recommended to* expose them to a 
 gentle heat for a length of time, which treatment is said to lower 
 the intensity. In copies of engravings without half tint (line 
 engravings and wood-cuts, but not mezzotints, lithographs, or 
 photographs) this increase of strength is of little or no disadvan- 
 tage ; in such cases, therefore, the mercury may be used without 
 hesitation. 
 
 These processes may be divided into three classes, according 
 to the amount of effect that they produce. For a quite moderate 
 increase of density chlorizing or iodizing may be used. For a 
 rather greater, but still moderate result, sublimate solution is 
 suitable. When a very decided increase is needed, chlorizing, 
 iodizing, or mercurializing, in each case till the light color is 
 reached, may be resorted to, to be followed by Schlippe's salt or 
 sulphide of potassium. 
 
 All the mercurial treatments weaken the film and render it 
 liable to split in drying. If, therefore, a valuable negative is so 
 treated, it is a prudent course to flood it with gum-water or solu- 
 ' tion of gelatine, the former about 30 to 35 grains to the ounce, 
 the latter about 20 to 25. If intensifying is much practised it is 
 well to have a solution of this sort on hand; it may be made to 
 keep by adding either creasote or carbolic acid, one or two drops 
 
THE NEGATIVE. 
 
 175 
 
 to the ounce. The gum solution or gelatine is flowed over the 
 plate for half a minute, worked in, and then poured off again, 
 and the plate is reared up to dry. After thorough drying it is to 
 be varnished. It has been affirmed that a plate so treated can be 
 varnished cold without the varnish drying dead. On the whole, 
 the gum -water answers better than the gelatine, and does not 
 require to be warmed to liquefy it. 
 
 This mode of operating has, however, the disadvantage that 
 the varnish cannot penetrate the film of gum (or gelatine) and 
 does not reach the back of the plate. And as the gum and gela- 
 tine have no very powerful adhesion to the glass, the film is 
 liable to scale off. 
 
 To Intensify Varnished Negatives. — The usual plan is to remove 
 the varnish by soaking in alcohol or benzole, whichever has been 
 used in the making of the varnish to be removed ; then apply 
 any of the intensifiers already described. ^ 
 
 The complete removal of a lac spirit varnish by alcohol is no 
 easy thing, portions of gum remain behind and refuse to dissolve. 
 Some, therefore, intensify without removing the varnish. Mr. 
 Alfred Hughes's method is as follows: Dissolve iodine in spirit 
 varnish, one grain to the ounce, and varnish the plate with this 
 varnish, without removing the first coat. Drain it well off, dry, 
 and expose to the light, when a considerable increase of intensity 
 takes place. 
 
 When the operation has been performed by dissolving the 
 varnish, the use of an alcoholic solution of iodine, two or three 
 grains to the ounce, is to be recommended, and acts more uni- 
 formly than any aqueous solution would. Care should be taken 
 not to leave it on too long, and it must be borne in mind that the 
 alcoholic solution cannot be instantaneously removed, like an 
 aqueous one, as it takes a few seconds for the water to moisten 
 the plate evenly. 
 
 According to Mr. Winter, the simple removing of the glossy 
 surface of the varnish by a moderately strong alcohol, so as to 
 give it a dead appearance, like ground glass, greatly increases 
 the effective density of the negative. This of course applies 
 only to spirit varnishes, and probably only to those made of difii- 
 cultly soluble resin like lac. 
 
176 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 8. — Reducing Over-developed Negatives. 
 
 It will occasionally happen that a negative has been over- 
 developed, and when examined after fixing and drying, gives 
 evidence that it can be expected to yield only chalky high lights. 
 This discovery may come too late to permit of retaking the 
 subject, especially with landscape negatives taken away from 
 home, and it should be more generally known than it is, that 
 such negatives can be greatly improved by the following treat- 
 ment, which the writer believes was first suggested by Mr. 
 Hughes. 
 
 A wash of very dilute solution of perchhride of iron is applied 
 to the film, which must, of course, be wetted beforehand. It is 
 also better to apply an edging of India-rubber to make sure that 
 the film shall not loosen, though this is not essential. The per- 
 chloride of iron can be got from any druggist under the name of 
 " muriated tincture of iron." It is sold in solution, which must 
 be largely diluted; from ten to twenty times its bulk of water will 
 be needed. The first trial should always be made a rejected 
 negative. The action is extremely rapid. The film apparently 
 darkens, but on holding it up to the light, a welcome transpa- 
 rency will be found in those dense portions which previously 
 threatened to print without detail. 
 
 If the negative wants very little reduction it will be prudent 
 to use the solution still more dilute. In nine cases out of ten, 
 if the perchloride does not give satisfactory results it will be 
 from excess of strength in the iron solution. 
 
 This is the only application that has ever given the writer 
 satisfactory results, or that he would think of employing. Its 
 merit lies in that it does not eat away the image, but simply 
 thins it, and especially that its action seems to be greatest upon 
 the densest part. Thus the objectionable features of the nega- 
 tive are removed without material injury to the detail. Nega- 
 tives that must otherwise be totally rejected may in this way 
 become serviceable. This mode of operating is suitable for all 
 negatives except those taken by the bromide dry processes. 
 
 Local Reduction. — Sometimes one particular object in a nega- 
 tive will develop to complete opacity before the rest has attained 
 printing density. In such a case to apply a treatment to the 
 whole negative would virtually destroy it, the thinner parts being 
 supposed to be just thick enough. It is evident that if any re- 
 
THE NEGATIVE. 
 
 177 
 
 ducing treatment could be applied to the single object or few 
 objects that are too thick, a great advantage could be gained. 
 
 Hitherto, the writer believes, this has never been attempted 
 successfully, in consequence of the treatment inevitably extend- 
 ing to the adjoining portions of the image. It occurred to the 
 writer lately to try the effect of sizing the film with gum and 
 then applying the reducing agent. It was found that this treat - 
 ment, as foreseen, resulted in making a change in the film similar 
 to that which blotting paper undergoes by sizing, that is, that a 
 solution no longer sunk into the film and spread around, but was 
 completely localized in its action ; and, therefore, that any single 
 dense object could be reduced in a quite remarkable way. 
 
 The operation is as follows : Pour over the plate (of course 
 before varnishing) a 50 grain solution of gum arable, work it in, 
 and let the plate dry. Then take some perchloride of iron (or 
 muriated tincture of iron) and dilute it largely until it is of ,a 
 pale straw color only. Apply this delicately on the part to be 
 reduced, with a small elastic sable brush, keeping strictly inside 
 the limits of the object. This presently diminishes very satis- 
 factorily in density, and when a proper point is reached, the 
 solution is washed off. It is to be observed that if the object 
 proves not to have been sufficiently reduced, a fresh coat of gum 
 must precede a new application of the reducing agent, supposing 
 that the plate has been washed off'. For washing quickly takes 
 out the gum, and then the film returns to its blotting and spread- 
 ing condition. This mode of treatment is really useful. 
 
 § 9. — Negatives for Enlargement. 
 
 A negative intended to be enlarged from, should always be 
 taken specially for that purpose. It is undoubtedly true that 
 some negatives taken for ordinary printing are capable of being 
 used for enlarging from ; such are those that print easily in the 
 shade. Usually, however, it is found better to take negatives 
 expressly. 
 
 These must be thinner than usual, but it is not to be supposed 
 that that thinness is to be secured by a brief exposure. On the 
 contrary, because the development must be short, the exposure 
 must be full, a little longer than usually given, so that the picture 
 may flash up as soon as the developer is poured over it ; and 
 then, after a very few seconds, the plate is rapidly to be washed, 
 
178 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 lest the deposit should become too thick, Yan Monckhoven, who 
 is excellent authority on this subject, remarks that the details in 
 the shadows should be scarcely visible, and the denser parts so 
 thin that one can read through them, and see the smallest objects 
 without difficulty. Also, that negatives which are too strong are 
 best reduced by plunging them into a bath of one grain of per- 
 chloride of iron to each three ounces of water ; then, after wash- 
 ing, apply cyanide, which will reduce the .strength. The opera- 
 tion to be repeated if necessary. 
 
 The deepest shadows should be represented by perfectly clear 
 glass. Veiling that would be unimportant in an ordinary nega- 
 tive, will unfit one for enlarging. 
 
 Varnish is objectionable for many reasons. The best results 
 are got with negatives washed and dried without even a solution 
 of gelatine or other preservative. Some, however, do not hesi- 
 tate to apply protectives, but, if possible, they are to be avoided. 
 
 § 10, — Retouching the Negative. 
 
 Of late years the retouching of the negative has acquired a 
 very great importance. It has been found that well retouched 
 negatives will give prints so superior to those from unretouched 
 negatives as to receive a very marked preference from the public. 
 
 It is not every one who can do this work, and it is, moreover, 
 found to be very exhausting to the eyes, especially when done at 
 night, by artificial light. It should, therefore, be always done 
 by daylight, on a retouching desk, or, for want of this, a large 
 piece of ground glass may be rested in a somewhat inclined posi- 
 tion, and a looking-glass placed under it, and near to a window. 
 The negative being laid upon the ground glass, all its details will 
 appear distinctly. The eyes should be protected by drawing 
 down a curtain so as to admit light upon the looking-glass only. 
 In some establishments this is more completely effected by ar- 
 ranging a partition in front of and near a window. In the parti- 
 tion an opening is cut sufficient to let the light upon the mirror 
 only. 
 
 - Several modes of retouching are practised. A soft Faber's 
 pencil, B B or B B B, may be used, or water-color be applied 
 with a sable pencil. As the varnish does not take these applica- 
 tions easily, it requires a preparation. Some prefer to take off 
 the glazed surface by rubbing gently with turpentine. Others 
 
THE NEGATIVE. 
 
 179 
 
 take finely powdered cuttle bone and rub it gently with the tip 
 of the finger until the glassy surface becomes mat and takes the 
 application. 
 
 Excellent results are got both from the pencil retouching and 
 the water color. When the pencil is used, it is found advanta- 
 geous to go over it with a stump, such as is sold by the dealers in 
 artists' materials; this softens and harmonizes the effect, and 
 blends it with the neighboring tints. 
 
 Water color retouching has the advantage that it is easier 
 altered, and that, if mistakes have been made, they are easier to 
 rectify. Experience shows that the best results are got by using 
 colors that are rather transparent to the actinic rays — blue or 
 neutral tint. This is to be carefully laid on until the desired 
 effects are attained. 
 
 Too great a smoothness is not to be sought for, as the character 
 of the face is removed. But as defects of complexion, freckles, 
 pimples, or irregularities of skin, are apt to be exaggerated in 
 photographic work, the removal of these by retouching improves 
 the picture amazingly. So that those professional portraitists, 
 who have judiciously retouched their negatives, have found them- 
 selves suddenly overrun with work. 
 
 Eetouching is especially useful in removing the blockiness and 
 want of moulding that results from one part of the face printing 
 too light or too dark in proportion to the rest. It is evident, 
 however, that if a negative is already too dense, retouching is 
 scarcely applicable, because it can only increase and not diminish 
 the opacity of the image. 
 
 The effect of a retouched negative is almost always more pleas- 
 ing and more flattering than that of one unretouched. Because 
 wrinkles, deep folds at the angles of the mouth, and lines under 
 the eyes, are all apt, in photography, to be much more conspicuous 
 than in the face itself; by retouching they are subdued to any 
 extent desired, and very pleasing and even flattering prints are 
 obtained from negatives otherwise unsatisfactory. Practice and 
 some artistic skill are necessary, however ; the rounded shape of 
 the cheeks must be preserved, and the face be not too much flat- 
 tened. A little careful and systematic practice will give an in- 
 sight that no directions can. It is evident that the negative must 
 not be too dense to begin with. 
 
 Another method of retouching the negative is to work upon 
 the back. As the colors do not take well upon glass, it is usual 
 
180 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 to apply a tliin varnish, and then to take its surface off in the 
 same way as directed for preparing the film side. The interpo- 
 sition of the glass causes the retouching to print less sharply and 
 more softly than when it is put upon the face; there is also no 
 danger of injuring the image. The same modes of operating, the 
 black lead pencil or the water color, may be used. 
 
 Still another method is to attach thin letter paper to the back 
 by pasting or gumming at the edges, and then applying color, 
 &c., upon the paper ; this method has been long in use for sketch- 
 ing clouds into the transparent skies of landscape negatives. 
 
 For stopping out small holes, Indian ink is generally used, 
 A color which contrasts with the negative is always desirable, as 
 it is easier to see what is done ; therefore if a negative has been 
 blackened by any after-intensification, it is more advisable to 
 touch out holes with a red color. Vermilion is very effective, 
 and seems to stand the sun pretty well. The indefinite perma- 
 nence of Indian ink against all action of light is an argument in 
 its favor that is not to be overlooked. 
 
 To landscape work little can be added by retouching, except 
 in the way of stopping out small holes or minute defects. If it 
 be attempted to materially alter the lights and shades of a land- 
 scape negative, a peculiar and artificial character results, which 
 may perhaps be an improvement in the particular case, but such 
 work can rarely be considered first-rate. In this is an essential 
 difference between landscape photography and portraiture, that 
 the best portraits are almost always those that have been skil- 
 fully retouched, whereas the contrary is the case in landscape work. 
 
 The pasting of paper behind parts that are intended to be 
 lighter is a well-known artifice; but it only answers well when 
 the borders of the part to be influenced are pretty well defined. 
 Some curious effects of light exhibited in this city have been so 
 produced. A female face, for example, is raised upwards, and a 
 beam of sunlight falls upon it from a window, lighting it up in a 
 striking way. The beam and the effect upon the face are pro- 
 duced by pasting thin paper on the back of the negative, and 
 printing in the shade. It is scarcely necessary to say that the 
 paper must be selected with a very even grain and an absence of 
 the lightish dots so commonly found in thin papers. 
 
 Hard and blocky negatives can often be made to yield materially 
 softer prints by printing under ground glass, as will be more 
 fully explained in the chapter on printing. 
 
THE NEGATIVE. 
 
 181 
 
 § 11. — Other Artifices Connected with the Negative. 
 
 Otlier ingenious operations have been performed on negatives, 
 either to remove blemishes or to produce particuLir efi'ects. Thus 
 Mr. Notman, of Montreal, has produced prints in which the 
 effect of falling snow is very well represented. A white pigment 
 is mixed up with water moderately thick, is put on a brush and 
 flirted over the negative with a quick jerk, probably an " atom- 
 jizer" would be preferable. Snow-banks in these pictures were 
 made in the studio of common table-salt, which also, when scat- 
 tered over clothes and drapery, gives a very good imitation of 
 the effects of snow caught in the folds. Clear ice was represented 
 by plate glass resting on sheet zinc : figures in skating attitudes 
 were posed on this. The positions of rapid skating motion were 
 obtained by supporting the model in the desired position with 
 Sarony's apparatus, the stem of which was concealed behind the 
 leg of the skater which touched the ice. 
 
 One peculiarity of photography lies in the opening it affords 
 for original devices of all sorts by the ingenious. This seems 
 the proper place to mention a few of them. 
 
 Ghosts. — This name has been given to prints representing a 
 shadowy figure through which all the objects behind it are dis- 
 tinctly seen. Such pictures are obtained by causing the model, 
 after remaining standing or in a chair for a short time, to move 
 suddenly away, whilst the exposure is completed without him. 
 In such a case it is evident that the objects at first concealed by 
 him will afterwards impress themselves on the film, and be 
 visible through his figure. 
 
 Doubles. — A model may appear twice in the same print by 
 having a couple of folding doors arranged inside the camera, a 
 little in front of the film. One of these being closed, the sitter 
 is taken on the other half. This then is shut, the other door 
 opened (the lens being covered during the change), at the same 
 time the sitter is transferred to the other side, and taken again in 
 some different attitude, as, for instance, offering a glass of wine 
 to his double across a small table. By accurate adjustment a 
 man is made to shake hands with himself. The position of the 
 doors causes them to be very much out of focus, so that they do 
 not show in the image. 
 
 Moonlight Effects. — Although a negative of the moon itself can 
 be easily obtained in the camera, and although it is affirmed that 
 
182 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 a dry plate exposed under a negative for a long time to moonlight 
 gives signs of an image, yet nevertheless the photographing of 
 objects illuminated by moonlight is practically impossible. Prints, 
 however, from under-exposed and over-developed negatives often 
 have a resemblance to moonlight views. For in effect if we ob- 
 serve a view by moonlight we shall notice that there is almost a 
 complete absence of diffuse light. Objects in shadow are not 
 lighted at all. A tree seen by moonlight exhibits a bright mass 
 of light where the rays fall, with a moderate detail; in the shaded 
 foliage there is absolutely no detail at all — it is a black mass. 
 Now these effects are those that belong to badly-made negatives, 
 with all their worst faults of exposure and development. But 
 these same faults, when intentionally introduced and artistically 
 managed, are capable of producing very pleasing effects. Ferrier 
 in Paris, has been particularly happy in some of these. Th( 
 moon itself is produced by a piece of paper pasted on thi 
 negative. 
 
 Mr. Baker, of Buffalo, gives the following directions : A day 
 of floating clouds is selected, and when the sun is low and hang- 
 ing over the water surface of a river or lake, or of the sea, the 
 camera is pointed towards it. At the moment when a cloud 
 passes over the sun the exposure is made. The time given is of 
 coarse short, and the result is a "moonlight effect." The clouds 
 near the sun throw brightly-illuminated reflections upon the 
 water. 
 
 Artificial Clouds. — In cases where the sky of a landscape has 
 become much thinned by solarization, it may admit of painting- 
 in clouds. This is done by the application of transparent water 
 colors on the back, in imitation of natural clouds. No small 
 skill with the brush is necessary to produce good effects. The 
 description of clouds known to meteorologists as the cumulus, the 
 cumulo-stmtus, are those most successfully imitated. The photo- 
 grapher should bear in mind that the direction of light must cor- 
 respond with that of the picture, and also that unless the sun is 
 very low, heavy clouds are always darkest underneath. 
 
 § 12. — Combination Prints. 
 
 This term is applied to the obtaining in one print of effects 
 that cannot be secured in any one negative, and which are, there- 
 fore, taken on two separate plates and combined together in 
 
THE NEGATIVE. 
 
 183 
 
 printing. Most commonly this is applied to the introduction of 
 figures into landscapes, in some cases the figure being the prin- 
 cipal subject and the landscape subordinate ; in others it is the 
 reverse. The means employed are the same in both cases. On 
 the plate upon which the figures have been taken, everything 
 else is completely stopped out by overlaying it with opaque color, 
 so that if the negative were printed in this condition, it would 
 print nothing but the figures upon a perfectly white ground. 
 Next, upon the landscape negative, the portion of the plate 
 corresponding to the figures is stopped out in the same way. Of 
 course if this negative is printed on silvered paper it leaves a 
 white space corresponding to the figures, and upon this space the 
 figures can be next printed from the figure negative. 
 
 The difficulty of course lies in bringing the paper into the 
 exact position for the second printing, that the space left for the 
 figures shall fall exactly under the proper portion of the nega- 
 tive. To do this requires a careful and experienced printer, and 
 the trouble must be repeated for every print. This difficulty has 
 very much limited the practice of composition printing, but is in 
 a great measure obviated by the ingenious registering frames of 
 Mr. Edwards and of Col. Stuart Wortley. A printing frame is 
 constructed in which four small square grooves A B C D, Fig. 
 
 Kg. 103. Fig. 103. 
 
 103, are cut, extending down to the rebate on which the negative 
 rests. A piece of thin wood is cut with four square projections 
 A' B'C D', Fig. 102, exactly corresponding to these four grooves, 
 so that when this piece of wood is let down, the grooves act as 
 guides and bring it always exactly into the same position. A 
 wooden screw S serves to press on the negative and keep it per- 
 fectly steady and immovable. A piece of silvered paper has its 
 ends bent over the piece of wood, as shown at E and F, and 
 secured with a little gum. When it is intended to print, this 
 board is put into the frame, paper side down, the projections slide 
 down the grooves, bringing the paper always into its' proper po- 
 sition. Pads and packing are put behind the board, and the back 
 (which is not shown in the cut) is then fastened down. 
 
184 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Two frames of this sort are provided, in one of whicli the 
 figure negative is placed, in the other the landscape. Having 
 stopped out all but the figures themselves in the figure negative, 
 a print is taken on the silvered paper that has been fastened to 
 the board. This is transferred to the other frame, and the por- 
 tion of the landscape negative corresponding to the figures is 
 accurately marked and stopped out. This being done, it is evi- 
 dent that the printing proceeds without difficulty ; instead of a 
 very skilful hand being needed any ordinary printer can take off 
 hundreds of copies with perfect accuracy. Each piece of paper 
 is secured over the edges of the board and is printed, first in one 
 frame and then in the other. 
 
 § 13. — Printing in Cloud Skies. 
 
 The preceding method may be applied to printing in clouds^ 
 but as the same accuracy is not required, simpler means are suffi 
 cient. If the negatives have not an opaque sky, that portion is 
 covered with opaque paint to render it so. 
 
 A print is taken and the sky cut carefully out from it and re- 
 jected, following as nearly as possible, but in flowing lines, the 
 outline of the landscape as projected against the sky. This is 
 done immediately after the print is taken from the frame. Next, 
 expose to light, when the whole becomes perfectly black, and fix 
 without toning. 
 
 A good sky negative with suitable character of clouds and 
 direction of light is taken, and the black mask above prepared is 
 neatly attached to the back of the sky negative, the white side 
 next the glass. The sky negative is now ready for use. 
 
 Prints from the landscape negative, when removed from the 
 printing frame, are placed under the sky negative, and printed 
 again. The black mask protects all but the sky, which receives 
 the cloud image from the second negative. 
 
 Printing of this kind requires, of course, to be done in the 
 shade, otherwise the line of the mask cannot be so well concealed. 
 This object is best attained by having a border of sky in the 
 mask — that is, not cutting too close to the landscape. With 
 ingenuity and care beautiful results are got in this way, and 
 effects can be obtained that, when exhibited, puzzle even the 
 photographer who is not acquainted with the mode in which 
 they are accomplished. 
 
THE NEGATIVE. 
 
 185 
 
 For example, if a dead tree, or a tree without foliage, as in 
 winter, or with but small foliage, showing the sky through as in 
 early spring, stand well out and detached from the sky, clouds 
 may be printed in behind it, showing through the branches. 
 This is done by cutting out all that part of the tree that is thus 
 open, along with the sky, so that all such part of the tree is not 
 masked. The clouds are then printed in, and as such a tree pre- 
 sents little or no aspect of light and shade in its slender branches 
 standing against a bright sky, the second printing does not affect 
 it otherwise than to make parts a little blacker, a result that is 
 not injuriously noticeable in the finished print. 
 
 A splendid effect is produced by printing reflected clouds in 
 water. It requires three printings. A scene is chosen with a 
 wide expanse of water and sky. The sky and water are both 
 masked ; the sky first printed in, and then the cloud negative 
 turned over so that what was before the top, becomes the bottom, 
 and the film or varnished side is away from the paper. The 
 reflection of the cloud on the water is thus obtained by printing 
 through the glass, which gives it just the amount of indistinctness 
 wanted, whilst every cloud and shade of cloud in the sky is faith- 
 fully rendered in the water. The deception is so complete that 
 it is difficult to persuade one's self at first that the whole was not 
 taken at once, and the reflected clouds obtained at the same time 
 with the real ones. 
 
 The same general methods have been used for obtaining effects 
 much more odd than pleasing — as, for example, a card portrait is 
 printed of a man standing before his own tombstone, with his 
 head severed from his body, and grasped by the hair with one of 
 his hands. The trees and objects behind the portion where his 
 head would properly be, are all perfectly well made out, so that 
 the deception is complete. This is done by masking and repeated 
 printing. There are several ways in which it may be thus 
 managed, but the subject has not suflS.cient importance for the 
 space the details would occupy. 
 
 § 14. — Negatives by Magnesium Light. 
 
 Some successful applications have been made of the magnesium 
 ight to photography. Thin strands, coils, or wires of that metal, 
 when set fire to, burn with a splendid blue light, very rich in 
 actinic power ; negatives may be very well taken by it. Interiors 
 13 
 
186 * PHOTOGRAPHIC MANIPULATIONS. 
 
 and parlor groups have been photographed at night by it, and 
 pictures taken of caves, catacombs, and other places inaccessible 
 to daylight. 
 
 The chief difficulty in obtaining good interiors results from the 
 directness of the light. If one light be used, of course the shadows 
 exhibit a total want of illumination. At least two are necessary, 
 and this immediately introduces the danger of double, shadows, an 
 evil which is not known in the carefully adjusted light of the 
 ordinary glass room, and which will require special attention on 
 the part of the photographer. Objects must be so placed that 
 only one set of shadows shall be visible, and the lights them- 
 selves must also be regulated with this view. 
 
 Of the two lamps used, one must give the predominant light, 
 and the other be used to light up the shadows. The predominant 
 light should be, of course, like the light of the glass room, a side- 
 ■upper-front light. The other must be lower in height, and be 
 placed at the other side. The predominance of the first is secured 
 by burning twice as much magnesium in it, say three to five tapers. 
 
 The writer has elsewhere pointed out that as the light of thi 
 magnesium diminishes rapidly as the distance from the lamp 
 increases, the background must be much lighter, or it will show 
 too dark in the picture. 
 
 Yery ingenious lamps have been constructed for burning mag 
 nesium, especially one in which a draught of air, kept up by a 
 chimney, is made to enter in front, and thus to keep the heavy 
 white smoke of magnesia, which is generated by the combustion, 
 from obscuring the light. It is affirmed by competent observers, 
 that the eifective light produced by a given quantity of magne- 
 sium is nearly doubled by this simple contrivance. 
 
 Mr. Skaife substitutes a pyrotechnic mixture burning with a 
 very luminous flame, a mixture of magnesium filings, chlorate 
 of potash, and sulphur, which he suddenly inflames. The camera 
 has been previously focussed by gaslight, and is left open, as the 
 gaslight makes no impression. Then the mixture being suddenly 
 inflamed gives an intense light for a moment, during which the 
 image is obtained. 
 
 § 15. — Storing of Negatives. 
 
 There are three ways of storing away negatives, that are in 
 common use — plate boxes, shelves expressly made for plates, or 
 
THE NEGATIVE. 
 
 187 
 
 the plates are wrapped up in clean paper in bundles of ten or 
 twelve each. 
 
 Plate boxes are made with either single or double grooves. In 
 the latter, two plates are slid together into each groove, back to 
 back. Much trouble arises from the grooves in plate boxes not 
 being made deep enough. The plates vary a good deal in size, 
 although nominally intended to be equal, and the boxes some- 
 times shrink very much ; so that in some, after having been made 
 some time, the small plates will get loose instead of being con- 
 fined, and, in other boxes, the plates a fraction over size will get 
 fast. It has happened to the writer to be obliged to force out 
 the side of a box to get out a negative. All these troubles should 
 be avoided by making the grooves deeper. The edges of the 
 groove should be rounded, not square. 
 
 Plate boxes should never be used for putting wet negatives 
 into, both because the boxes should never be wetted, and because, 
 if the washing has been imperfect, hyposulphite may be intro- 
 duced. Nor should negatives just varnished be placed in them, 
 as the edges of varnished negatives remain sticky after the face 
 is dry. Nor should " dry" plates be dried in them ; in a word, 
 they are for storage only. 
 
 Shelves for negatives should be built very strong, and are 
 better so placed that the window shall not be opposite to, but at 
 one end of the room, on the side of which are the shelves, so that 
 as they are drawn out they can be looked through to obtain the 
 one sought. 
 
 Negatives wrapped up in paper have been found to keep better 
 than in any other way. Cases are described in which some of a 
 lot of negatives have been stored in boxes, some wrapped in 
 paper and laid flat, where those in boxes have cracked, and those 
 in paper have stood perfectly. The reason appears to be, that 
 plates sliding separately into grooves are exposed to changes in 
 the atmosphere to a much greater extent than those securely 
 wrapped up and pressed closely upon each other. 
 
 It is evident that considerable care should be exercised in the 
 selection of paper to be interposed. Printed or soiled paper 
 should be rigorously excluded. Blotting paper is too porous 
 and hygroscopic. An ordinary quality of sized paper, not too 
 hard and stiff, is the most suitable. 
 
 The outside paper should be good, strong wrapping paper. 
 
188 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Paper saturated with India-rubber varnish would doubtless be 
 better than any other. For amateurs who have but small num- 
 bers comparatively of negatives, the plate box is so much the 
 more convenient form that it will probably be always that used. 
 
 Although ambrotypes almost belong to the past, a few brief 
 remarks will be made on the subject here for the benefit of those 
 who may desire to make them. A really fine ambrotype is a 
 very beautiful thing, but for the most part, they want contrast 
 and breadth of effect. 
 
 An ambrotype is nothing but a thin negative. When a nega- 
 tive is held np to the light, those portions on which the light 
 has acted in the camera are more or less opaque, and the lights 
 and shades in the original are reversed in the negatives. 
 
 But the negative is formed of grayish-white silver powder, so 
 that if it be viewed by reflected light, and held against a black 
 background, those parts which looked dark by transmitted light, 
 appear light by reflected, and the transparent parts, which per- 
 mitted the light to pass through when viewed by transmitted 
 light, look dark in the ambrotype, because their transparency 
 permits the black background to be seen through. 
 
 Formerly, a different bath was thought necessary in the two 
 sorts of work. Now the same is generally used, although many 
 prefer to acidulate it with one or two drops more of nitric acid. 
 
 A formula for collodion (if a special collodion be desired, which 
 is not absolutely necessary) will be found in the Introduction, 
 
 The developer is the same as for negatives, a little more acidi- 
 fied. Or, when brilliant whites are wanted, take — 
 
 CHAPTEE Y. 
 
 AMBROTYPES AND FEREOTYPES. 
 
 p. 43. 
 
 Sulphate of iron . 
 Acetic acid, No. 8 
 Best granulated nitre 
 Water . 
 
 250 grains, 
 half an ounce. 
 
 30 grains. 
 20 ounces. 
 
 As the bath becomes older, add a little alcohol to cause the 
 developer to run smoothly. If there is any disposition to fog, 
 
AMBEOTYPES AND FERROTYPES. 
 
 189 
 
 increase the dose of acetic acid. Stop the development as soon 
 as the image comes out enough to be seen in light reflected from 
 the surface of the plate. 
 
 Where dead whites are wanted, omit the nitre. 
 
 Melainotypes and ferrotypes are ambrotypes taken on plates of 
 thin varnished iron instead of glass. The operation is in all 
 respects similar. They may be said to constitute the most ordi- 
 nary and least artistic of photographic products. 
 
 Opinions vary very much as to the best means of getting good 
 results. The points are these, that a very clear, clean picture 
 must be got. This of course is most easily eJffected by the aid of 
 acid. The acid may be applied in various ways. For example, 
 the bath may be made more acid than usual with nitric or acetic 
 acid, and used with the ordinary collodion and development. Or 
 an ordinary bath may be used with a very ripe collodion, or one 
 to which tincture of iodine has been added ; or a very acid de- 
 velopment may be resorted to. It naturally follows that whilst 
 very clear pictures are got in this way, there is an absence of 
 detail often observable. The right plan is just to carry the 
 acidification far enough to get clean glass in the darkest shadows 
 and no farther. Of course the slightest veiling is fatal to the 
 ambrotype. 
 
 Collodion made with alkaline iodides and bromides ripens 
 quickly ; some therefore omit entirely the cadmium salts from 
 collodion intended for ambrotypes. Others employ cadmium and 
 ammonium and add iodine, and others, as mentioned in the In- 
 troduction, consider potassium essential. 
 
 Alabastrine Positives. — The body of both the negative and 
 ambrotype is composed of nearly pure silver, which has a gray- 
 ish tint, and is deficient in brilliancy. This defect injures the 
 light and shade of the picture, and recourse is sometimes had to 
 mercury in the form of corrosive sublimate to whiten them. 
 
 The following formula may be used : — 
 
 Corrosive sublimate 40 grains. 
 
 Protosulphate of iron . 20 grains. 
 
 Common salt 15 grains. 
 
 Water 2 ounces. 
 
 The first effect is to make the picture grayer, but the whiten- 
 ing soon sets in. 
 
190 
 
 PHOTOGRAPHIC 
 
 MANIPULATIONS. 
 
 CHAPTER YI. 
 
 PORTKAITURE. 
 
 § 1. — General Arrangement. 
 
 Having placed the sitter in an easy and natural attitude, and 
 with due attention to the management of light, as described in the 
 next section, it will not be sufficient to simply set up the camera 
 before him and take a picture. Care as to the point from which 
 the picture is taken is of the very highest importance. 
 
 If, for example, the camera is set as high as the head of a 
 standing figure, and is directed at him horizontally, the head will 
 occupy the centre of the plate, the body one-half of the plate 
 only. If we move the camera down so as to be opposite his 
 middle, we shall get the whole figure it is true, but we get the 
 figure as seen by an eye placed no higher than the camera. The 
 shape of the nose is altered and injured, the neck is shortened, 
 and the whole character of the face altered. 
 
 From these difficulties we are relieved by the contrivances 
 already explained in a previous chapter, the swing-back and the 
 sliding front. We raise the .camera at least as high as the 
 shoulders. The first effect of this is to throw the head nearly 
 into the centre of the plate and to cut off the feet. This may 
 be remedied — 
 
 1st. By inclining the camera downwards. This tends to dis- 
 tort the vertical lines, and here the swing-back comes into play 
 and straightens them, or, 
 
 2d. By lowering the sliding front. As the front is lowered, 
 the image moves down the plate, and takes its proper position. 
 
 This last arrangement has this notable advantage over the first, 
 that the best definition, which in the portrait lens correctly 
 focussed is that of the central pencils, is got for the head, pre- 
 cisely as if the bust only were taken. In the first arrangement 
 the middle of the body is formed by the central pencils and 
 receives the best definition. On the other hand, the lowering of 
 the sliding front has this disadvantage, that the feet and lower 
 part of the picture are then formed by pencils more excentric 
 
PORTRAITURE. 
 
 191 
 
 than enter into any part of the picture in the other case. Each 
 method has its advantages and evils, and in some cases the one, 
 in some the other, will be proper. 
 
 The swing-back is so valuable an adjunct to portraiture that 
 no one who has learned how to use it will ever willingly work 
 without it. It is especially useful in sitting figures ; without it, 
 for example, the feet will always be exaggerated in size, and 
 clumsy looking. It gives, in fact, a new power to the operator; 
 the plan of revolving the lens does not, as so often affirmed, answer 
 equally well. 
 
 A repeating back enables the operator to make the image of a 
 lens fall in succession on different parts of the sensitive film, thus 
 with two lenses and a repeating back, four or more card portraits 
 are taken on one plate. 
 
 Distance of Position. — As a large lens will produce a small 
 head by increasing its distance from the sitter, and conversely, a 
 small lens will give a large one by diminishing it, the question 
 naturally arises as to what are the best conditions under which 
 to obtain satisfactory results. 
 
 The impression of relief and rotundity is greatest with very 
 short focus lenses," and gradually diminishes as the size of the 
 lens increases, until with lenses of 30 or 40 inches focal length, 
 relief almost disappears (also the size of the stop has much to do 
 with it, a large stop giving much more relief with the same lens). 
 
 But, on the other hand, this excessive effect of rotundity and 
 relief is anything but pleasant in itself, and, still worse, it is 
 connected with an effect of " violent" perspective which draws 
 the middle of the face outwards, and in a full-face portrait, swells 
 up the nose and lips most objectionably. The effect is detestable 
 in those faces in which the size of the lips and nose is as large as 
 the rest of the face will bear, the enlargement of them introduces 
 a disproportion most annoying and vexatious to the sitter and 
 friends, whereas in another face with thin lips and small nose, no 
 bad result has attracted attention, simply because other circum- 
 stances rendered it less obvious. 
 
 It will be well, therefore, never to place the camera nearer 
 than twelve feet from the sitter as a minimum, and rather to ex- 
 ceed this by using a larger lens to make up for increased distance. 
 In fact, there is but little danger of getting too far from the 
 sitter in any ordinary glass room ; the danger is the other way. 
 
 Arrangement of Accessories. — The curvature of the field of lenses 
 
192 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 renders it desirable that objects around the central figure should 
 also be arranged into a counteracting curve, and be brought 
 nearer to the camera in proportion as they are farther from the 
 centre of the field of view. This enables them to be brought 
 into focus simultaneously with main figure. 
 
 Groups are naturally governed by the same rules. Of course 
 a sti^y circular arrangement is to be avoided, but it will be 
 always advisable to arrange that in a group the most distant 
 head shall be central, and those that are farthest from the centre 
 shall be nearest to the lens. A tasteful arrangement of inter- 
 mediate heads and figures will bring the whole into harmonious 
 combination. 
 
 With groups the swing-back will be always very valuable, 
 especially in avoiding sameness. For with a swing on a vertical 
 pivot, the figures on one side of the central object may be set as 
 far back as the central figure, and yet be brought into good focus, 
 provided that those on the other side are brought considerably 
 nearer. The advantages of the swing-back will thus continually 
 make themselves apparent, and multiply as the photographer in- 
 creases in familiarity with its applications. 
 
 Relative Size of the Figure. — It is highly important to propor- 
 tion the size of the figure to the size of the whole print, and it 
 may be said that the size of the figure is almost always made too 
 small. For one error in the opposite direction, ten are made in 
 "this, and the result is always to render the figure insignificant 
 and unsatisfactory. This remark applies to all sorts of photo- 
 graphs, from vignetted busts to full lengths. And the smaller 
 the figure the more conspicuous any accessories that may be 
 present, until, in some portraits, they fairly eclipse the figure 
 itself, so that the idea is conveyed that the sitter is taking care of 
 the large but suspiciously unreal-looking vases, tables, and carved 
 furniture, which, rather than the person, seem to be the actual 
 subjects of the picture. 
 
 It is surprising that so little criticism has been directed to this 
 almost universal fault. An examination of portraits by great 
 masters will show a very different system. The figure takes up 
 a very large portion of the whole surface, the accessories are 
 absolutely subordinate, and not noticed unless attention is expressly 
 directed to them. 
 
 No error produces worse results than this of making the figure 
 too small. The sitter feels the unsatisfactory and insignificant 
 
PORTRAITURE. 
 
 193 
 
 effect of the portrait offered to "him, without understanding why 
 it is so, and though he may be unable to say where the fault lies, 
 its existence is perfectly plain to him. The photographer is, 
 therefore, recommended to avoid this mistake most carefully. 
 
 2 2. — Management of Light.' 
 
 The play of light upon the sitter must be regulated partly upon 
 certain general principles of illumination, and partly according 
 to the needs of the particular case. 
 
 The general principles are — 
 
 That there shall be no cross light ; never shadows visibly cast in 
 more than one direction. 
 
 That the light on the side away from the glazing shall be main- 
 tained as subsidiary. 
 
 That there shall be no false light, especially no false reflection 
 from the eyes. 
 
 That there shall be no excess of illumination in some one or more 
 parts of the picture, otherwise the eye will be led away from 
 the face instead of led to it, as takes place in a judicious 
 distribution of light and shade. 
 
 That the shadows, wherever they may be, shall invariably receive 
 a sufiicient illumination that their details may impress them- 
 selves with strength enough to show agreeably in the print. 
 There must be no dark patches destitute of detail. 
 
 That the highest lights shall not be so illuminated but what they 
 shall be fall of detail. A bald head, for example, must not 
 run into a light background, as is occasionally seen. White 
 hair must preserve all its details. The play of light and 
 shade over white garments must be thoroughly well pre- 
 served, and all white patchiness rigorously excluded. 
 
 Conjointly with the above, two different systems of illumination 
 may be used. There is that almost universally adopted, in which 
 the effect of the picture is made as nearly as possible to imitate 
 what we commonly see around us. The part of the room, for 
 example, in which the model sits, is made, in its play of light 
 and shade, to resemble ordinary rooms. 
 
 There is another and very effective system occasionally used 
 
 1 See also chapter on the "Glass Room," and that on "Light and Shadow." 
 
194 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 in whicTi some of the effects generally produced by distinguished 
 portrait painters in their work, are imitated. The object of this 
 system is to allow no light, except that which stands in some 
 definite relation to the face. It was the dictum of a celebrated 
 painter that a portrait ought to be two-thirds dark. 
 
 To obtain this effect in photographic portraits, a dark back- 
 ground and dark hangings are used. Dark clothing is worn, 
 especially dark velvets, whose play of light is always exceed- 
 ingly effective in photography. Whatever of light is permitted 
 in the clothing must " lead up to the face," that is, so far as it is 
 permitted to catch the eye, the eye must pass directly from it to 
 the face. All this, of course, is more easily effected in women's 
 vestments than men's; still the application is not confined to the 
 former. The borders of the picture are all kept dark, and, in 
 fact, the shadows are accumulated in order that the light may 
 tell as effectively as possible. When well managed, this method 
 produces very striking and beautiful results, but it requires con- 
 siderable artistic knowledge and feeling on the part of the photog- 
 rapher. From the large use which Salomon, of Paris, has made 
 of this style, it is often called after him. The " Berlin Portraits''' 
 are made by taking a piece of glass, coarsely ground upon one 
 side, and making the negative upon the other. In this way a 
 certain softness is got, somewhat resembling, but inferior to, that 
 which is obtained by retouching. " Crayon Portraits''' are pro- 
 duced by printing a thin positive on glass, and laying this, film 
 side down, upon a lithographed sheet, shaded in imitation of 
 crayon work. When well done, the effect is good. The glass 
 positives for this purpose are often enlargements from card nega- 
 tives — the enlargements are made in the camera. Others raodif}'' 
 the effects and soften their paper points by interposing a sheet of 
 glass, of gelatin, of mica, or of tissue paper between the negative 
 and the paper ; in this way are made the so-called " Mezzotint 
 Prints^ This method, brought prominently forward by Mein- 
 erth, gives often very pleasing pictures. 
 
 So-called Bemhrandt Effects represent the head against a dead 
 black surface, with a peculiar and bright illumination round the 
 profile, brightest on the side away from the spectator. The effect 
 is produced as follows: The lighting is as usual; the sitter is 
 placed in the usual position. The camera is moved partly round 
 so that it somewhat faces the light, and thus the portrait shows 
 principally the side of the face that is farthest from the side light, 
 
PORTRAITURE. 
 
 195 
 
 what shows of the other side of the face, viz., the eyebrow and 
 cheek, is more brightly lighted than the near side, the former 
 being nearest to the light. The background must send no light 
 back, and is best made of black velvet, which should be rendered 
 by clear glass. As the camera is turned partly towards the light 
 it will need to be carefully shaded, otherwise the brilliancy of 
 effect, and entire blackness of the background may be impaired. 
 
 Finally, it is to be observed that the photographer must not 
 transfer any system of lighting from a given lens to another of 
 very different focal length. If accustomed to work with a lens 
 of a certain focal length, he finds occasion to change, it will be 
 necessary to study a proper arrangement for the new lens. A 
 lens of long focus will bear a bolder lighting than one of short 
 focus, and for want of it may seem tame and flat. 
 
 § 3. — Exposure. 
 
 A correct knowledge of the time of pose comes only with long 
 practice and through many failures. Not only does the light of 
 the glass room vary continually in strength, but different com- 
 plexions and different clothing will alter the needful time. More- 
 over, the photographer's task may be greatly increased in diflS- 
 culty if a style of clothing, unsuited to the character of the sitter, 
 chance to be worn by him or her. It would, in fact, be very 
 advantageous if the photographer could always direct in advance, 
 after personal observation, what description of clothes should be 
 worn during the pose, for it by no means follows that clothes 
 most becoming to the wearer under ordinary circumstances will 
 be most appropriate before the lens. The element of coZor, which 
 enters so largely into consideration, as to suitableness and effect, 
 here disappears, and the only question is as to the rendition of 
 light and shade on the film. A photographically suitable clothing 
 is, therefore, not at all one in which the colors harmonize with 
 the character of the wearer, but one in which the photographic 
 effect of the color harmonizes with the photographic character 
 of the face and hair. To get a clear insight into this matter it 
 will be necessary to begin by considering the relation between 
 the skin, eyes, and hair. 
 
 A clear white skin will, of course, impress its image rapidly 
 on the film. If the hair be fair, all will go on well and harmo- 
 niously. But if a white skin be combined with dark hair, the 
 
196 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 exposure will have to be more accurately timed, it must be con- 
 tinued until tlie details of the hair are fully out, and yet must be 
 stopped before the face is overdone. Conversely, where light or 
 white hair accompanies a red or dark complexion there is danger 
 of the hair being overdone and the details lost in it before the 
 face is duly taken. These are faults that are constantly seen in 
 card portraits, and constitute difficulties to be understood and 
 conquered. 
 
 Dress. — The clothes worn may evidently add a further com- 
 plication to such of these difficulties as exist, or may produce 
 them where they did not. Let us suppose that a lady with dark 
 hair and complexion presents herself to be photographed, attired 
 in white, or light blue or purple. It will follow that by the time 
 that justice has been done to the face, the fine gradations of shade 
 in the dress may be lost, or, if preserved, it can only be by skill 
 and care. 
 
 The difficulties occasioned by contrast are, however, now far 
 less unmanageable than they formerly were when iodide of silver 
 alone was used, and we see less tendency than formerly to black 
 spaces destitute of detail, and white ones perfectly flat : these 
 blemishes are now comparatively exceptional, and such work is 
 always destroyed by the intelligent photographer who prizes bis 
 reputation. 
 
 Some photographers keep two kinds of collodion on hand. 
 One sort for regular use, the other containing more bromide, to 
 be employed where too much contrast is apprehended, especially 
 where masses of white drapery are to be taken, in which case 
 the proportion of bromide may rise to one-half. For regular use 
 such collodions are liable to the objection that they yield thinner 
 pictures and require more redevelopment. 
 
 Nothing is commoner than for persons to present themselves 
 so attired as greatly to increase the photographer's difficulties. 
 Harsh contrasts, the effects of which are sufficiently bad on the 
 persons, become almost intolerable in a picture. Add to which 
 the various actinic powers of the different tints often tend yet 
 farther to exaggerate those contrasts which were before suflfi- 
 ciently annoying to the eye. A portrait in which the dress is 
 cut up into checkers of light and dark, or divided into parallel 
 stripes with striking contrasts, must always be unsatisfactory in 
 its character. 
 
 Attempts not wanting in ingenuity have been made to exhibit 
 
PORTRAITURE. 
 
 197 
 
 in photographic specimens the actinic value of different pigments. 
 But these can never be of much help, and the reason is obvious. 
 Taking any color, let us say Prussian blue, let a thin shade of it 
 be lightly washed over white paper, and then a very deep shade. 
 Photographing these, the first will act almost like pure white; 
 the second almost like black, indeed, if made thick enough, as, 
 for example, the cake of paint itself, it will be perfectly black. 
 If, then, one color is capable of impressing itself of all shades 
 from white to black, the assigning to it of any particular shade 
 of half tint, must be purely arbitrary and altogether deceptive. 
 So, if we attempt to compare two colors, let us say green verditer 
 and raw umber. If the first be put on lightly, and the second 
 thickly, the first will appear to be the more actinic color, and 
 by reversing the proportion we shall reach an opposite conclu- 
 sion. Precisely the same result will accompany the various 
 shades of material used in dress. Experience, and intelligent 
 observation of what takes place in the case of every portrait 
 taken, will soon give a pretty exact idea of what effect any 
 given costume will produce in the negative. 
 
 Velvet Drapery. — Salomon, the French portraitist, whose name 
 is always necessarily cited in speaking of photographic aesthetics, 
 avoids these difficulties by making appointments, and indicating 
 to ladies what colors will be most effective for them. He also 
 provides velvet drapery, with which he frequently covers and 
 conceals the whole of the dress worn. The velvet which he uses 
 is neither silk, nor is it black, but a dark purple cotton velvet, 
 and its effects are often magnificent. 
 
 Posing the Sitter. — When a whole sitting figure is represented 
 in profile, the point at which the back legs of the chair reach the 
 ground will invariably and absolutely need to be supported. N"o 
 rule is so commonly violated as this, and none with worse results, 
 for the figure will always appear to be slipping out of the chair, 
 because its lines want their due support. This it will not be 
 always easy to give ; the position is, therefore, especially for a 
 male figure, an objectionable one. If for any reason it is espe- 
 cially desired, the photographer must introduce some object, such 
 as a stool, best with drapery, or characteristic objects over or on 
 it. With the female figure the difficulty is less, for its own dra- 
 pery may be so disposed as to give the support required. 
 
 The position of the head of a standing figure with respect to 
 the top of the card, produces a very curious influence on the 
 
1 
 
 198 PHOTOGRAPHIC MANIPULATIONS. 
 
 apparent height. If the print is so cut as to bring the head very 
 near the top edge, a great impression of height is produced ; if, 
 on the other hand, the card extends far above the head, the figure 
 is dwarfed. This effect is independent of the position of the 
 figure with respect to other objects in the picture, and depends 
 chiefly on the cutting of the card after it is printed. Therefore 
 this principle may be used to improve the appearance of dwarfish 
 or very stout figures, providing it be not carried to excess. 
 
 Want of attending to this effect produces in card portraits the 
 most unintentionally ludicrous results. A man of average stature 
 may be made to look seven feet or more high. 
 
 Mr. Petsch makes some excellent suggestions with regard to 
 the overcoming of difficulties. Badly formed features he subdues 
 by the arrangement of the head : a crooked nose is always most 
 striking when seen from directly in front, therefore the head 
 should be so turned that the side with the smaller surface is next 
 the camera, and the larger surface is somewhat foreshortened. 
 An irregular mouth, the line of which is not parallel to that of 
 the eyes, should be similarly managed, the straighter end of the 
 mouth is turned towards the camera, and the drooping end is 
 seen less conspicuously, and is foreshortened. Those who squint 
 are taken in profile. Yery stout men are to be taken in three- 
 quarter lengths. 
 
 Arranging the clothes has likewise much influence. Buttoning 
 the coat adds breadth to the figure, opening it gives relief. Dark 
 clothes diminish the size ; light, and especially white ones, increase 
 it. Defects in the head and face may be exaggerated by inap- 
 propriate ways of wearing the hair. To arrange the hair with 
 ribbons, etc., at the sides, makes a broad face broader, but relieves 
 the thinness of a long narrow one. A high head-dress exagge- 
 rates the length of a long neck, but relieves a broad face if kept 
 front, otherwise if set far back. In profiles the hair should not 
 be too flat on the top of the head, or a flat expression is pro- 
 duced. 
 
 § 4. — Development in its Relation to Portraiture. 
 
 Some assistance can always be had in difficult cases by regu- 
 lating the development. The writer has attempted, in papers 
 written upon the subject of negative development, to demonstrate 
 the true character and the rules by which it is governed, and as 
 
POKTRAITURE. 
 
 199 
 
 a correct understanding of this is of much importance to the por- 
 traitist, a few words may advantageously be said on the matter 
 here. 
 
 The stronger the developer, that is, the more sulphate of iron 
 it contains, and the less restraining acid, gelatine, or sugar, the 
 more rapid will be the precipitation of the metallic silver that 
 forms the picture. Just in proportion as the silver falls ■more slowly 
 it is more subject to the attraction of the most strongly impressed parts 
 of the silver. In a slow precipitation the most strongly impressed 
 parts of the film will get a larger proportion of the deposit than 
 in a rapid precipitation. This fact, which has been thoroughly 
 established both by theory and practice, is of the highest import- 
 ance, and is the key to all the peculiarities of iron development 
 in the wet way. 
 
 If, then, danger of a flat picture is feared, either by reason 
 of— 
 
 1. An absence of contrast in the subject ; 
 
 2. Too uniform an illumination ; 
 
 3. A long exposure; 
 
 We should apply a iveak developer^ in order to increase the contrast. 
 
 On the other hand, if we have reason to dread a harsh picture 
 from — 
 
 1. Excess of contrast in the subject itself; 
 
 2. Insufficient light ; 
 
 3. Light badly controlled, so that it is excessive in places 
 
 and insufiicient in others ; 
 
 4. Too short an exposure ; 
 
 We should apply a strong developer to diminish the contrast by favor- 
 ing a more equal deposit of silver. 
 
 The application of these principles to special cases is suffi- 
 ciently obvious. If it is evident that the main difficulty of the 
 work to be done will lie, for example, in getting relief and form 
 into a quantity of white drapery, we shall need a slow develop- 
 ment, in order that the faint shadows which are to give life and 
 form to the white mass, shall not be overwhelmed by a rapid 
 deposit of silver. 
 
 But if, on the contrary, it is specially desired to obtain detail 
 in deep shadows, a strong developer will force the depositing 
 silver to find all the faint impressions in these shadows and 
 bring them out on the sensitive film. 
 
200 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 A comparison of this section and the former will lead directly 
 to the sufficiently obvious conclusion that exposure and develop- 
 ment stand to each other in opposite relations. 
 
 And the general rule will be : If all the parts of the subject 
 are actinic and well lighted, give a moderate exposure, and use 
 developer No. 1, p. 162. 
 
 So, if all the parts tend to be non-actinic, or if the light is poor, 
 give a long exposure, and use the same developer. 
 
 But if there is considerable contrast (and this is the more com- 
 mon case) so that some parts seem to demand a long and others 
 a short exposure, and there is danger of too much contrast, then 
 give a full exposure and use developer No. 2, p. 162. 
 
 It is not sufficient, however, to endeavor to overcome these 
 difficulties, the difficulties themselves must to some extent be re- 
 moved. Light must be so controlled that the illumination on the 
 actinic surfaces must be restrained, and that on the shadows and 
 non-actinic portion must be increased until the two can suffi- 
 ciently be combined in one development. 
 
 § 5. — Causes of Unsatisfactory Results in Portraiture. 
 
 1. Too much Front Light. 
 
 Excess of front light produces jiatness. Light is too equally 
 distributed over the projections and depressions of the face, so 
 that these lose their character, and the face assumes an unmean- 
 ing expression, sometimes even a stupid or silly one. Such a 
 light also throws, as Schrank has well remarked, too much illu- 
 mination on the centre of the forehead, the ridge of the nose, 
 the chin, and the cheek bones. What is worse still, it produces 
 a bright reflection in the centre of the eye, precisely where the 
 dark pupil properly appears, thus reversing the natural aspect, 
 and at times giving almost the effect of blindness. Of all defects 
 of lighting, excess of front light produces the most inartistic 
 effects, and the most thoroughly displeasing pictures. 
 
 2. Too much Side Light. 
 
 Excess of side light produces a too unequal illumination of the 
 two sides of the face, gives an excessive projection to the nose, 
 and a hatchet shape to the face. The effect upon the eyes is 
 sometimes very curious, causing them to look utterly unlike each 
 other in consequence of the difference in the amount of light that 
 
PORTRATTURE. 
 
 201 
 
 they receive. Still, the effects of an excess of such light are not 
 so bad as those of excess of top or of front light. The best 
 effects require a difference of illumination on the two sides, which 
 may in skilful hands be carried to a very considerable extent. 
 Nevertheless, it is easily overdone, and such attempts demand 
 good management. 
 
 8. Excess of Top Light. 
 
 This error produces effects precisely the reverse of those of 
 excess of front light ; all the features become hard and project- 
 ing ; a heavy frown settles on the brow ; the eyes appear deep 
 set and cavernous ; the nose is enlarged, and any hollows about 
 the mouth are greatly and unnaturally increased. A black 
 shadow is produced directly under the chin, sometimes almost 
 producing the effect of a beard. 
 
 4. Too even Illumination. 
 
 It is easy to fall into an error the reverse of all the foregoing 
 by diffusing the illumination too generally. This is most apt to 
 occur in operating under a flat, low glass roof, where the light 
 comes in around the sitter from a variety of angles and direc- 
 tions. The result is a soft, characterless picture, which finds 
 little favor, and deservedly so, whilst at the same time those 
 unacquainted with the subject cannot tell why the picture is so 
 unpleasing, for it is undoubtedly like the original, and there is 
 no prominent objection to seize upon. At the same time there 
 is the greatest of all objections, viz., that the portrait is totally 
 devoid of merit, and gives the face with its least interesting and 
 acceptable expression. The fault here spoken of is one that has 
 received too little attention, some photographers refusing even 
 to recognize it, and thinking, when they produce these pictures, 
 that they are doing creditable work ; they do not, however, find 
 the sitter or the sitter's friends to agree very cordially with them. 
 
 5, Insufficient Illumination helow. 
 
 When the illumination is at the same time chiefly horizontal, 
 and yet is not carried low enough on the side, it may result that 
 whilst the upper part of a sitter is well illuminated, the lower 
 part is not. There results from this a want of detail in the 
 shadows of all the lower part of the figure, a defect which can 
 only be remedied by an alteration in the system of lighting. 
 14 
 
202 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 6. Insvfficient Light. 
 
 As it must always be tbe object of the operator to work well 
 with a short exposure, a deficiency of light is one of the most 
 serious evils to which he can be exposed. I may, for example, 
 cite the case of a photographer in this city, who, after putting up 
 a complete gallery, found his light so deficient that he was led to 
 adopt the after-intensification of his negatives with mercury as a 
 regular system — a bad and dangerous one every way, worse by 
 far than even an expensive alteration in his defective glass room. 
 His case was by no means a solitary one. It is far better, in 
 constructing a glass room, to err by having too much light, the 
 excess of which is so easily shut out, than to make the opposite 
 mistake. When the mistake has been made, it is better for the 
 professional photographer to recognize it at once, and remedy it 
 radically by introducing more glass at any cost. In doing so, 
 however, he should work neither at random nor in a hurry. He 
 should first carefully ascertain by study in which description of 
 light his glass house is most wanting, and proceed with a view to 
 remedying that deficiency in the introduction of the additional 
 glass. If his glass room has abundant top light, it would be folly 
 for him to introduce his additional glass on the roof, and so on. 
 The explanations already given will enable him to detect in what 
 direction his glass room tends to err, and in arranging to admit 
 more light he will be in a position to get exactly the kind of 
 light which he most wants. Thus, in remedying a fault, he may, 
 if he takes care and study, succeed in making his room better 
 than if that fault had not been committed, for he may succeed in 
 distributing his light more scientifically than if he had at first 
 arranged to admit enough. It is in this, as in so many other cases 
 in photography, the man who thinks carefully first over what he 
 wants, and chooses, after reflection, that which is best fitted to 
 afford the desired result, will always in the end succeed. One 
 who can only learn through continual failures, will be weary 
 before he can reach success. Every failure met with should be 
 required to yield its fruit in the way of useful experience ; and 
 this should be made a fixed rule by every photographer. 
 
PORTRAITURE. 
 
 208 
 
 § 6. — Backgrounds and Accessories. 
 
 The subject of backgrounds is one of no small importance to 
 the portraitist, and one often of no small diflSiculty. Without 
 care, tact, and ingenuity, his productions are apt to be exposed to 
 the imputation of sameness. Every one has become thoroughly 
 tired of the column and the balustrade, which might as well now 
 be banished once for all. The heavy curtain has also been a 
 good deal employed, but it is too useful to be definitely dispensed 
 with. 
 
 The end of the gallery should be colored of a soft bluish gray, 
 and will form a useful background for taking groups of several 
 persons. Special backgrounds usually consist, when plain, of 
 colored cloth sold by the dealers, and which is usually stretched 
 on a large frame furnished with feet, rolling on castors. These 
 are of various shades, according to the effect desired. The photog- 
 rapher will need at least three — dark, light, and medium. Views 
 are sometimes sketched on canvas stretched on similar frames. 
 Considerable tact and skill are necessary for the production of 
 really good pictorial backgrounds. 
 
 Sometimes a very beautiful effect is produced by having the 
 upper part of the plain background lighter than the lower. This 
 is especially useful in the case of three-quarter figures, or those 
 which include from the head to the knees; the light part is made 
 to correspond with the head, gradually softened opposite the 
 shoulders into the dark shade of the rest. This calls attention 
 to the head and throws it out, with an effect which, when well 
 managed, is excellent. 
 
 Another useful effect which has attracted considerable attention 
 of late years is that of inclining the background so that either 
 side, right or left, shall be nearer than the other, taking care that 
 the screen is towards the light, not against it. This method of 
 proceeding has been very effectively employed by the celebrated 
 Salomon, of Paris, and his mode of managing it will be seen by 
 inspecting the adjoining sketch of his glass room. The sitter is 
 turned somewhat towards the light, and the camera stands in 
 the direction indicated by the arrow. The portion of the back- 
 ground nearest to the glazing receives the strongest light, which 
 diminishes gradually towards the other end, producing an agree- 
 able effect, which may be greatly varied by altering the position 
 of the background and screens. 
 
204 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 Fix. 104. 
 
 Fiff. 105. 
 
 Large backgrounds should move on heavy castors made ex- 
 pressly for the purpose, and running on wheels of five or six 
 inches in diameter. 
 
 Canopy Backgrounds. — The same photographer has for some 
 years past employed a peculiar arrangement enabling him to 
 obtain a great variety of effects, and dispensing with the necessity 
 
 of employing blinds and curtains. 
 As Salomon's work has never been 
 surpassed, his modes of proceeding 
 excite great interest ; the writer 
 annexes a figure copied from one 
 published in the London Photogra- 
 phic JVewSj after a drawing commu- 
 nicated by M. Salomon himself. 
 
 J. is a semicircular background 
 about 8 feet high, 10 wide, and 5 
 deep, from front to back. J3 B are 
 folding wings, about 4 feet wide 
 each, hinged to the background. 
 C is a corresponding canopy, 10 
 feet long and 4 wide, hinged to the 
 top. Another canopy, D covers 
 the background itself: it is in two 
 parts, hinged at the middle. The post E at the back carries a 
 pulley at the top, over which pass cords connected with the differ- 
 
PORTRAITURE. 
 
 205 
 
 ent canopies, and fastened at the back so as to be easily raised or 
 lowered. 
 
 The semicircular background A is covered with wall-paper of 
 a salmon color ; it has three feet, not represented in the cut. which 
 carry large castors. All the other parts, the wings and canopies, 
 are light frames covered with thin transparent white muslin, al- 
 lowing a good deal of light to pass, but softening any direct sun- 
 light. At the corners, between the wings and the canopy 0^ the 
 muslin of the upper canopy is continued out, so as to fill up the 
 corner ; this is not represented in the figure. 
 
 The sitter is placed in the centre of the curved part, and. just 
 under the front canopy, by raising or lowering which any desired 
 amount of soft and difi'used top light is obtained. So, too, the 
 side light is regulated by opening or closing the wings. The 
 illumination is farther controlled or altered by turning the whole 
 contrivance on its castors, and thus exposing the open portion 
 more directly to the light, or, on the other hand, turning it away. 
 The curvature of the background affords gradation, and its form 
 and depth tend to give relief to the figure, and even this may be 
 very much modified by raising or lowering the upper canopies, 
 D D, by which monotony and repetition of identical effects are 
 avoided, and every grade of effect, from the lightest to the dark- 
 est, is easily obtained. 
 
 When a full-length figure is to be taken, the curve line of the 
 background shows unpleasingly. A movable surbase or wash- 
 board placed behind the sitter cuts off the curve and removes the 
 difficulty. 
 
 The advantages of this system may be briefly summed up. 
 Effectiveness, as it gives every variety of light. Adaptability: 
 it may be either used in an ordinary glass room, or in a common 
 room, as in the latter case it takes the place of blinds, curtains, 
 and other machinery. Economy : that in use by M. Salomon 
 cost him fifteen dollars only. To construct it two curved pieces 
 of wood, for the top and bottom, are connected by thin upright 
 boards, tongued and grooved into each other, whilst the wings 
 and canopies are formed of light framework, covered as already 
 described. 
 
 Conical Backgrounds, about which a good deal has been said, 
 have scarcely answered the expectations that have been raised. 
 The plan, also, of a front screen, coated white, and interposed 
 
206 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Fiff. 106. 
 
 between the sitter and the camera, with an opening cut into it, 
 has also proved unsatisfactory, in consequence of its tendency to 
 produce flatness of effect. 
 
 Rotating Background. — Canvas is stretched over a flat wheel, 
 which, for lightness, consists simply of a round rim, connected, 
 
 by wooden bars or spokes, with the 
 axle at the centre. This canvas is 
 colored of a warm gray or fawn 
 color, shaded from one side to the 
 other (see Fig. 106), so that there 
 is a distinct but moderate difference 
 of tint. 
 
 This background can be put to 
 several uses. It may be set with 
 the lightest portion uppermost, and 
 used as a graduated background, the 
 advantage of which has been already 
 explained, or it may represent a 
 lighter shade on one side of the sitter 
 than the other. Or, finally, it may be made to rotate during the 
 whole sitting, and thus produce a perfectly even background, 
 with a perfection of evenness obtainable in no other way. 
 
 The invention is ingenious and useful, but the writer considers 
 it susceptible of a great improvement. If a triangular sector be 
 cut out of white paper and attached in front of the circle, with 
 its point at the centre, and widening towards the circumference, 
 then, if the background be made to rotate, it is evident that the 
 general effects will be lightened, and that in proportion to the 
 width of the sector. Similarly, by using black paper the effect 
 will be darkened. It is evident that, by having a supply of these 
 black and white sectors, a single wheel may be made to produce 
 an endless variety of shades of backgrounds, and always exhibit- 
 ing a perfectly pure and even tint. All photographers know 
 how difficult it is to obtain a plain background to their portraits 
 that is absolutely free from blemish. 
 
 Distance of Background lehind the Sitter. — Four or five feet is 
 a common distance, but the practice varies much. Salomon 
 makes his recede much more than most, and commonly places it 
 eight or ten feet back. 
 
 It is common in photography to act on the principle that with 
 a plain and indefinite background no furniture shall be intro- 
 
PORTRAITURE. 
 
 207 
 
 duced ; and that, on the other hand, if any furniture be visible, 
 the background shall correspond and complete the room. This 
 is, however, not so absolutely necessary as some suppose. For 
 example, if a three-quarter figure be represented standing at the 
 side of a small table and occupied in any way, as with papers, 
 letters, flowers, work, etc., the picture may be finished with a 
 plain, or, better, a simple shaded background, such as just de- 
 scribed, and thus the photographer is relieved from the incessant 
 use of a limited stock of combinations. 
 
 It is a most serious mistake to crowd quantities of objects, such 
 as vases, urns, bouquets, etc., into the picture. This only results 
 in distracting and confusing the attention. Certain points, where 
 lines of direction reach the floor, or a table, or other object, often 
 need imperatively to be supported by some object ; this part of 
 the subject will be treated of more particularly hereafter. A fore- 
 ground is often relieved by characteristic objects, grouped, not 
 scattered. But then they require to be handled with taste and 
 according to rule, and must never be strewn about or huddled 
 together promiscuously. Particular care should be taken to 
 avoid brilliant reflections of light from accessories, and for this 
 reason such objects should have dead, and not reflecting surfaces. 
 Anything, in fact, that tends to make them conspicuous, distracts 
 the attention from the figure itself. 
 
 In some photographs the figure itself is quite a subordinate 
 affair, being completely subdued by dazzling furniture and by 
 crowds of vases, bouquets, and other objects, placed in the most 
 unnatural and improper positions. Sometimes the very first 
 thing that catches the eye is the pattern of the carpet, composed 
 of ill-assorted figures and inharmonious lines. Such mistakes as 
 this last are doubly unfortunate, as they tend to repeat themselves 
 through a large part of the photographer's work. Generally 
 speaking, any object that must appear in many pictures should 
 be extremely inconspicuous, and this holds with nothing more 
 than with the carpet, if there is one. 
 
 A vignetted bust undoubtedly possesses advantages over any 
 other description of photographic portraiture : it is that form in 
 which the shortcomings of our methods are best overcome. It 
 may, therefore, be doubted whether, in the introduction of the 
 cabinet size, it has been wise to endeavor to exclude the vignette. 
 The whole plate vignette heads which were formerly made, and 
 
^08 
 
 PHOTOGRAPHIC MANIPULATIONS, 
 
 are now so rarely seen, were far more effective than the little 
 card heads that have taken their place. 
 
 When pictorial backgrounds are employed, it is necessary that 
 the lens should be directed at the point of sight, that is, at the 
 point to which, in the drawing of the background, the spectator's 
 eye was supposed to be directed, namely, the point at which the 
 line of vision cuts the horizon. If, as may happen, this point is 
 not very easily distinguishable, the lens should at least be di- 
 rected at the horizon line of the picture. Or, what is still better, 
 the horizon line should be completely concealed by a skilfully 
 arranged design. If neither of these precautions be adopted, there 
 will be no illusion whatever, and this is why the effect of fanciful 
 backgrounds is so rarely good. 
 
 Good efiects may be obtained by using a background of brown 
 paper, shading it off with white crayon in a light and sketchy 
 way. If it be desired that the print shall show parallel strokes 
 of shading over the shoulders and round the head, in imitation 
 of crayon drawing, it is evident that this result can be attained 
 by marking on the background a central spot for the head, and 
 sketching large, coarse shading around it. In this case black 
 crayon or charcoal should be used on a light buff ground. Such 
 backgrounds will need to be in sliding frames, balanced with 
 weights, that they may be raised or lowered to bring the centre 
 into exact correspondence with the head. 
 
 The appearance of the grain of drawing-paper is sometimes 
 given to the finished and mounted photograph by passing it, 
 before quite dry, through a press, together with a piece of coarsely 
 grained paper laid on the surface of the print. 
 
 CHAPTER VII. 
 LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 
 
 § 1. — General Remarks. 
 
 Landscape photography is a very fascinating pursuit; and 
 when once undertaken in good earnest, and pursued to successful 
 and satisfactory results, is not often or easily abandoned. 
 
 The first need will be to possess a good camera and good lenses. 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 
 
 209 
 
 The subject of lenses having been already discussed, the writer 
 will here simply repeat his conviction that for views which do 
 not include architectural subjects, the view lens is not easily 
 excelled, at least when its too small angle of view is remedied 
 as in Dallmeyer's wide-angle view lenses. Used with equal 
 .stops, these lenses have greater depth of focus than any others 
 that the writer has tried. The Steinheil aplanatic gives very 
 harmonious landscapes and renders architectural lines correctly. 
 
 It is important to repeat here that the best effects will never 
 be obtained with lenses of too small focus. Under their influence, 
 landscapes become so altered as to be unrecognizable. Buildings, 
 in place of seeming to stand upon a firm foundation, seem to totter 
 forwards. Eectangular corners are made to assume the appear- 
 ance of sharp angles, so that the building no longer appears 
 square, but lozenge-shaped. The upper corners of the roof look 
 high and peaked, and the real character of the edifice is lost. 
 
 Levelling the Camera. — When architectural subjects constitute 
 the picture or are included in it, the camera must always be 
 levelled, or the lines of the building will not be straight in the 
 image. The level may be either rested on the camera, or, what 
 is better, it may be countersunk into the camera, and so remain 
 permanently attached to it. To make this arrangement, the 
 camera should be placed on a perfectly level surface, ascertained 
 to be such by careful levelling. The "universal level," which is 
 round, and about an inch or an inch and a quarter in diameter, 
 is then permanently fastened into its opening with shellac cement, 
 and so placed in it that the bubble shall be central. 
 
 Of course, where a building is so unfortunately situated that a 
 view cannot be obtained except with a very short focus lens, its 
 use will be excusable, but the result will never be satisfactory. 
 
 It sometimes happens, also, that buildings in narrow streets 
 cannot be photographed except from the second or third stories 
 of opposite houses. Such pictures are inferior to those obtained 
 from the ground, and always give the idea of being taken from 
 some unnatural point of view. It is unfortunate that buildings 
 in cities are generally so situated that no first-class photograph 
 can be obtained of them, owing to the narrowness of streets and 
 crowding of houses. 
 
 With landscapes this levelling is less necessary. To obtain a 
 perfectly truthful representation, it is essential, and therefore no 
 view can be accepted as giving an accurate delineation of scenery 
 
210 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 unless the camera was levelled when it was taken. But in taking 
 views simply as beautiful objects, more latitude may be allowed. 
 
 § 2. — Choice of Conditions. 
 
 As landscapes are always seen with disadvantage under a noon- 
 day sun, so photographs taken under similar circumstances are 
 mostly unpleasing ; and as photography tends to exaggerated 
 contrasts of light and shade, the result is all the worse. Many 
 experienced landscape photographers therefore avoid bright days, 
 and like best of all those times when the sky is covered with 
 white clouds through which the sun occasionally breaks. If a 
 glimpse of sun can be secured at the end of an exposure, the 
 best of all effects is got, and this may be compared to the effect 
 in nature of the softened sun late in the afternoon, and we all 
 know the magical influence of such light even upon the tamest 
 of scenery. It is therefore a good plan, if there is hope of a 
 burst of sun, to cover the lens a little before the proper exposure 
 has been given, and then, when the sun comes, to expose for a 
 moment, and so light up the picture without getting harsh con- 
 trasts. These last may, in extremely bright weather, give an effect 
 of snowiness in the high lights, which is in the highest degree 
 displeasing. 
 
 The time during which the lens may be covered to wait for 
 this sun will depend upon the weather. In moist or cool weather 
 much more time may be prudently allowed than in hot or dry. 
 Great care should be taken not to disturb the camera in opening 
 and closing. For this, the morocco lined with velvet caps, now 
 furnished with all the best lenses, are very recommendable, and 
 work better than the common brass caps. 
 
 As the sky is apt to be over-exposed, it may often be advan- 
 tageously shaded during part of the exposure. This may be done 
 by holding the hand or other object in front of the upper part 
 of the lens, and near to it, moving it continually. To accomplish 
 the same object, sky-shutters are often made to the lens or to 
 the camera, but it is difficult to use them without disturbing the 
 camera. In landscape taking, the photographer will avoid the 
 use of the two smaller stops. The object of the stop should be 
 clearly understood. In the case of the view lens, it is to obtain 
 depth of focus, to have the distant and the moderately near 
 objects simultaneously in focus. With the doublets and the 
 
LAN-DSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 211 
 
 view lens, diminishing the size of the stop improves the defini- 
 tion and crispness at the margin. When these objects have been 
 sufficiently attained, no further diminution of the stop is advisable, 
 as the image loses in character and boldness, in addition to which 
 the time of exposure is of course increased. 
 
 All the most experienced photographers are agreed that a view 
 should invariably be taken with the largest stop that the condi- 
 tions of the case will permit. As soon as a satisfactory definition 
 is obtained, further reduction of the stop should be avoided with 
 the utmost care. A small stop produces a flat picture, without 
 gradation of distance or atmosphere. A large one gives a bold, 
 clear view, with the objects in the respective planes of distance 
 well made out. Objects that with a small stop seem pressed 
 together, with a large one stand well out and show what they are. 
 The photographer cannot be too strongly enjoined not, in order to 
 obtain a microscopic sharpness, to sacrifice the general character 
 and expression of his view. Of course, good definition cannot be 
 dispensed with. But when the operator finds that he cannot get 
 this without a very small stop in using any of the ordinary forms 
 of lenses, he may be sure that he is straining the lens, making it 
 do work for which it is unsuited, and therefore that he cannot 
 expect the best results. 
 
 A photographer may visit scenes of great natural beauty, and 
 may be deeply impressed by them. He may labor very hard to 
 reproduce them in his negatives, and yet, after much effort, he 
 may obtain but unsatisfactory results. Some will, under these 
 circumstances, lay the blame on photography, and affirm that the 
 indifferent results spring from the incapacity of the method to 
 yield what is wanted. Others will not perceive the deficiencies of 
 their own pictures, and think they have all that can be expected; 
 whilst others, again, with a truer sense of the beautiful, will be 
 disheartened by the difference between what they have seen in 
 nature and what they have been able to carry away. Bat this 
 is in reality the first step towards ultimate success. A keen 
 appreciation of errors and imperfections gradually helps to avoid 
 them, but not without many failures and much persistent effort. 
 
 In viewing a landscape in nature, the eye is apt to seize and 
 rest upon the characteristic features, overlooking those that are 
 secondary. A lens cannot do this, and, singularly enough, the 
 eye will not do that with a picture which it will with real objects, 
 
212 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 but insists, as it were, that the picture should represent them as 
 they should be. This fact is so conspicuously true, that examples 
 are scarcely necessary. They will, however, continually present 
 themselves to the photographer. Perhaps the view lies in a wild 
 valley in the midst of hills, and the scene is not marred by the 
 presence of a rustic cottage. But perhaps beside -it are lines 
 hanging full of clothes drying. This the eye passes over and 
 excuses in the scene itself^ but the same feature introduced into 
 any picture, photographic or otherwise, provokes inextinguishable 
 laughter. 
 
 So with the hideous telegraph poles that line all our roads and 
 railroads, and intrude into almost all our scenery. The eye con- 
 sents reluctantly to forget them by an effort, and to consider the 
 scene without reference to them, and to some extent succeeds. 
 But in the photograph they come out straight, stiff", and promi- 
 nent. Even the wire is perfectly made out. It results that often 
 a scene cannot be taken from its best points by reason of these 
 detestable adjuncts, and that, because of their continued repe- 
 tition at short intervals, the effort to wholly exclude them be- 
 comes totally unavailing. Telegraphs are necessary things, but 
 there is no reason that they should be permitted to intrude 
 through scenery of recognized natural beauty. This is carrying 
 utilitarianism too far, and would be tolerated in no country less 
 corporation-ridden than ours. Six miles of the scenery of the 
 beautiful Wissahickon are in this way marred by the poles that 
 carry a wire apparently for individual convenience, which might 
 better dispense with it, or choose another route. 
 
 As the camera has not the painter's power of excluding or 
 subduing intrusive objects, all that the photographer can do is 
 to endeavor so to select his point of view as to avoid them. This 
 is a matter that deserves more pains to be taken than it mostly 
 receives. After the view has been taken, it will sometimes 
 be found that a change of position of even a few yards only 
 would have made a material improvement ; a discovery morti- 
 fying and annoying, and better avoided by a careful search be- 
 forehand. 
 
 A question will often present itself as to whether any particu- 
 lar view will give the best effect if taken on a plate with its 
 longest side vertical or horizontal. The writer has elsewhere 
 pointed out that this question is best answered by observing what 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 213 
 
 is the direction of tbe jJrmcipal object in the landscape, and making 
 the greatest dimension of the plate correspond with it. 
 
 Thus, a dam will for the most part look best in a wide picture, 
 whilst for a narrow and high waterfall the greatest length of the 
 plate should be up and down. So, too, where the chief object is 
 a tree or a group of trees ; whereas with a bridge the principal 
 dimensions should be right and left. But no such rules can be 
 an absolute guide, it will only aid in deciding, and if any doubt 
 is felt, an excellent plan is to try it both ways ; on inspecting 
 the prints no doubt will remain as to which was the best position, 
 and the comparison will aid in forming a correct judgment on 
 subsequent occasions. 
 
 In a landscape, the best effects are to be secured by contrast. In 
 photography, as we have no effects of color, our contrasts are 
 limited to those of line and those of light. 
 
 Contrasts of line or form are always relished by the eye. The 
 effect of the mountain is enhanced by the levelness of the plain 
 at its base. A picture that should represent a plain with no 
 elevation, or simply an elevation with no plain to contrast with 
 it, will always be deficient. Other and beautiful contrasts of 
 line are often seen in a rolling country, even where there is no 
 plain and no great elevation. 
 
 Contrasts of light and shade, technically called chiaroscuro, are 
 the life of all pictorial representations. They give us, in a great 
 measure, our ideas of the form and relative position of bodies. 
 Negatives taken in dull weather are necessarily deficient in this 
 quality, whilst those taken in clear sunshine often present con- 
 trasts too harsh. A weak sun often gives beautiful effects, and 
 as the sun is less powerful when low, this, as well as many other 
 advantages, is obtained by working at such times, 
 
 "Whilst contrast is all-important in photography, it is to be 
 carefully remembered that too much of it is even worse than too 
 little. 
 
 If a negative be taken with insufi&cient exposure, and then this 
 be attempted to be made up in the development, it will most 
 frequently happen that the silver, instead of being deposited so 
 as to keep the regular graduation of tone, falls too much upon 
 the lights. Thus the picture becomes hard., and if the fault has 
 been great, it becomes snowy. 
 
 In some classes of subjects, snowiness is not easily avoided. 
 
214 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 If a landscape be in part very brightly, and in others very badly, 
 lighted, the photographer finds himself in the dilemma that 
 either he exposes and develops too long for the one part, or too 
 briefly for the other. In printing his negative, he may find an 
 absence of detail, accordingly, either in the lights or shadows. 
 This difiiculty is inherent to the nature of the subject, and may 
 be too great to be overcome. The best advice that can be given 
 is to give a full exposure, compensating for this by using a rather 
 weak developer, and letting it lie quietly on the surface of the 
 plate, without sending it to and fro. The collodion should con- 
 tain a rather full proportion of bromides. This checks contrast, 
 so much, indeed, as to render such collodion unsuitable for views 
 in which the contrasts are less striking. Some careful operators 
 carry with them two sorts of collodion, using the most highly 
 bromided for mastering contrasts. Those who are not willing 
 to take this trouble, find themselves obliged to avoid such com- 
 binations, and to return to them in sunless weather. Where 
 much bromide is used, it should always be borne in mind that 
 the negatives will prove in printing more transparent than they 
 appear to the eye. 
 
 In taking views along streams with high banks, and in ravines, 
 the contrasts of light and shade will always be really greater 
 than they appear to be, and due allowance must always be made 
 for this. In such places the shadows are apt to be very dark, 
 because so much of the sky is cut off, and it is always the diffuse 
 light from the sky that lights up the shadows. In such places it 
 will be found difficult to combine darkly shaded foliage with 
 sunlight in the same picture; this result can only be obtained by 
 prolonged exposure, and slow and careful development ; gene- 
 rally it will be best not to attempt it, if it can be avoided. 
 
 The development must always be graduated not merely with 
 respect to the character of the scene, but to the amount of ex- 
 posure that has been given. In order to combine exposure and 
 development, and so to get the best possible results in difficult 
 cases, the following observations may be useful. 
 
 A view that is strongly illuminated all over, with few con- 
 trasts, will demand a moderately short exposure and a long de- 
 velopment with a weak developer, the object being to preserve 
 detail, and yet at the same time to retain contrast enough to give 
 life to the whole. 
 
LANDSCAPE AND A EC H ITE CT U R A L PHOTOGRAPHy, 
 
 215 
 
 When the illumination is uniform and not good, or where all 
 the objects are non-actinic, and the light not very good, we shall 
 want a very prolonged exposure to get them well impressed. 
 And then we shall need a long development with a weak de- 
 veloper, otherwise the result will be tame and flat. 
 
 In this country the character of the light varies between ex 
 tremely wide limits. In cloudy weather there is apt to be, of 
 course, everywhere, a deficiency of contrast. Such light, how- 
 ever, is often very favorable for taking near foliage. On the 
 other hand, when the sun shines, the light is apt to be very 
 powerful, and as the air with us in clear weather is apt to be very 
 transparent, it results that the shadows are dark and wanting in 
 detail. In clear, cloudless weather the shadows are very dark, 
 and in such weather it requires great experience and very good 
 management to get first-rate effects. Attention must be paid to 
 the influence both of the seasowsind of the time of day. 
 
 Seasons. — The landscape begins in this latitude to show suffi- 
 cient foliage to commence photographic work towards the first of 
 J une, though the forest trees are not well in leaf till a fortnight 
 later. At this time of year the light is exceedingly powerful, 
 and exposures must be shortened. 
 
 A slight excess of exposure, generally unimportant, will some- 
 times give rise to solarization. A good deal of care and circum- 
 spection will be required. Sometimes, when the sky is covered 
 with low white clouds with the sun just breaking through them, 
 the power of the light is truly amazing. 
 
 Throughout the spring and summer, the days when the leaves 
 are still are far from frequent. In September, and even towards 
 the end of August, the air is much quieter, and it is far less 
 difficult to find favorable days ; the light is also softer. On the 
 other hand, there is more dust, and streams are apt to be low, so 
 that waterfalls show but scanty streams, and mill-dams, often 
 very beautiful at other times, are frequently quite dry. 
 
 A serious trouble at all seasons, in our climate, is the want of 
 softened light. We have but a few of those partly overcast yet 
 luminous days which give such beautiful effects of illumination 
 and such soft foliage; our light is mostly too abundant and 
 piercing. 
 
 Snow Landscapes should receive a medium exposure and a 
 full development, for, to obtain clean, bright snow scenes, all the 
 
216 
 
 PHOTOGEAPHIC MANIPULATIONS. 
 
 most fully lighted snow must be developed to absolute opacit}^, 
 shading off, however, to give it relief. 
 
 Time of Day. — Two or three hours after sunrise the light is 
 very powerful ; it goes on to increase till about 11 o'clock, then 
 remains stationary till 12, after which it diminishes till sunset. 
 The afternoon light is always weaker than the corresponding 
 part of the morning. Thus, the light two hours (for example) 
 before sunset is not half as powerful as two hours after sunrise, 
 though the sun in both cases is equally high. This is said to be 
 caused by the greater quantity of moisture dissolved in the air, 
 though the explanation is doubtful. 
 
 Cloudless weather is always unfavorable. Clouds act as re- 
 flectors to light up the shadows. In cloudless weather the shadows 
 are always very dark, and are apt to want detail in the image. 
 In such weather, the middle of the day is, in the writer's opinion, 
 very unsatisfactory for work. In the early morning, and in the 
 afternoon, the evil of want of clouds is less felt. At these times, 
 also, the effects of scenery are more agreeable, the shadows are 
 longer and give more relief, the air is generally stiller. Longer 
 exposures are necessary, of course, but the results are better. In 
 overcast weather, the middle of the day is apt to be the best 
 time. 
 
 Cast Shadows are such as retain more or less of the form of the 
 object that casts them, as distinguished from the more indefinite 
 shadow that comes from some less distinct source. Such shadows 
 are often the source of exquisite beauty in landscapes. A level 
 foreground of grass is apt to be flat and unmeaning ; the shadow 
 of a tree cast across it, gives it at once life, character, relief. The 
 landscapist cannot pay too much attention to such effects of fore- 
 ground. 
 
 Generally, the more that shadow is diversified the finer its 
 effect. A large dark shadow of a tree is far less beautiful than 
 one in which the sun penetrates the leaves, and falls in irregular, 
 broken forms upon the ground. 
 
 When it is required that a house shall appear in the foreground, 
 a diversified shadow upon its walls has an extremely good effect. 
 In neither case, however, must the lights and shadows be too 
 much broken, or the effect will lack breadth. And the greatest 
 care must be taken to avoid spottiness of effect. As this is a 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 217 
 
 common and fatal fault, the writer will endeavor to point out its 
 source. 
 
 Shadows of branches and boughs through which the sun pene- 
 trates partly, and which retain indistinctly the forms of leaves 
 and sprays, are very beautiful, A level sun will often throw 
 shadows of such sprays upon the trunks of trees, with an exquisite 
 effect. So shadows of leaves and boughs on walls, houses, roads, 
 and grass, are often very beautiful. But it is an essential con- 
 dition that the shadows must he transparent^ and shall present only 
 a moderate degree of contrast with the lights. If, however, we place 
 the camera in a grove and take a picture, we shall probably get 
 black shadows on the ground, interspersed with white patches of 
 sunlight, and these effects, instead of being of a wholly subordi- 
 nate character, will strike the eye before anything else in the 
 view. Such an effect is indescribably bad, and to be avoided 
 with the utmost care. 
 
 Parallel patches of shadow are especially ugly. These are apt 
 to occur when trees present themselves in rows, with sunshine 
 penetrating between each two trees. 
 
 The tree, the great beauty of the landscape, offers peculiar 
 difficulties in photography, owing to the non-actinic color of its 
 leaves. For this reason it has been thought advisable to use 
 much bromide in collodion intended for landscape photography; 
 the true explanation of its utility has been already given. There 
 is a remarkable difference between leaves of different trees, which 
 it will be necessary to bear in mind. Some have a brilliant sur- 
 face, as if they had been varnished; such are the sour-gum, black- 
 oak, and others. From this we descend through every degree to 
 those leaves which scarcely return any light, such as the white- 
 oak, &c. The first sort, if in direct sunshine, are apt to produce 
 a particularly disagreeable effect; they send back so much light, 
 that they develop to full opacity by the time the rest of the 
 picture has come up to printing strength, and so print quite 
 white. This is unnatural and unpleasing, and, as far as pos- 
 sible, to be avoided. In cloudy weather such leaves photograph 
 exceedingly well. Ivy-leaves on buildings easily give a very 
 beautiful effect. They send back a good amount of light and not 
 too much, and, as they are apt to look all in the same direction, 
 each leaf is bordered by a shadow. Thus each leaf is well made 
 out, and the effect is particularly pleasing and exceedingly easy 
 to catch, more so, perhaps, than with any other sort of foliage. 
 15 
 
218 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 It has been often advised in photography to have the sun well 
 behind the camera. This, however, is a rule of very doubtful 
 validity. When the sun shines full upon a group of trees in the 
 middle distance, the forms of the individual trees are never well 
 made out, and the result is apt to be a mere mass of brilliantly 
 lighted foliage. Often the separate twigs and boughs may stand 
 out in consequence of dark shadows falling between the leaves, 
 but the beautiful rounded effect of each particular tree is only 
 well thrown out by a good side-light. This inferiority of effect 
 produced by having the sun directly or nearly behind the camera, 
 on trees in the middle distance, is very striking. Near foliage^ 
 however, bears having the sun behind the camera perfectly well. 
 But the exquisite beauty of the rounded forms of individual trees 
 in the middle distance is only well rendered by a side-light. 
 
 One reason why this light from behind has been extensively 
 used is that it is the least exposed to Uurring. "Whenever dark 
 masses stand out against a bright sky, the light has a tendency 
 to get round and intrude upon the shadow ; an effect that arises 
 from reflection from the back surface of the glass. The partial 
 opacity of the film scatters the light that passes through it in 
 every direction, so that portions reach the back at very oblique 
 angles, and may return to the face at considerable distances 
 from where they entered. To a large extent this may be avoided 
 by wet red blotting-paper on the backs of wet plates and glycerine 
 plates (a precaution which should never be neglected), and by 
 painting the backs of dry plates. 
 
 Near foliage should be represented invariably in half-tone, and 
 this effect is generally obtained more easily when the sun is not 
 too bright, especially in the case of the polished leaves already 
 spoken of. Distant foliage is far more easy to manage, and bears 
 the brightest sunshine perfectly. It is far better rendered when 
 the sun falls upon it from the side than when the sun is either 
 nearly before or nearly behind the spectator. A fine single tree 
 or grove of trees lighted from the side affords a beautiful play of 
 light and shade, which disappears when the sun is in the line of 
 view before or behind, or even approaches to that direction. 
 
 Natural clouds are a great beauty when they can be included 
 in a landscape. The difficulties here are twofold. It is not very 
 common (at least in our climate) that there are clouds such as it 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 219 
 
 is desirable to take. In our fine weatlier we have mostly a clear 
 or nearly clear sky. And when there are beautiful clouds, the 
 weather is apt to be too windy for photographic work. But the 
 greatest difficulty lies in the fact of the great luminosity of clouds. 
 When the sun is shining, the darkest part of a cloud is generally 
 more luminous than the whitest object in a landscape. The eye 
 scarcely realizes this in observing a landscape, but it is easily 
 recognized on the ground glass. The consequence is that although 
 the clouds appear in the commencement of development, yet they 
 are buried in a mass of deposit before the details of the landscape 
 are got. 
 
 There are several methods of obviating this to some extent, 
 though it must be confessed that they leave much to be desired. 
 
 The camera may be provided with a sky-shade^ a shutter in 
 front of the lens (Figs. 92 and 94), which may be slowly raised 
 during exposure, so as to diminish the light admitted from the sky. 
 
 Or the hand, the hat, or the shutter of the plate holder may be 
 used in the absence of a sky-shade. 
 
 In either of these cases a trial should be made of the move- 
 ments beforehand, and the effect watched upon the ground glass, 
 that the operator may see in what position of the shading object 
 the sky begins to be uncovered. 
 
 The inclined diaphragm (Fig. 40, p. 66), by reducing the light 
 from the sky, will aid in obtaining clouds. 
 
 To secure clouds, the opportunity also should be favorable. 
 The landscape should be wide and well lighted, in order that a 
 brief exposure may suf&ce for the terrestrial objects. 
 
 According to Mr. H. T. Anthony, a developer of double sul- 
 phate of iron and ammonia 30 grains to the ounce, sulphate of 
 copper 5 grains, and acetic acid as needed, is very favorable to 
 the obtaining of clouds. 
 
 An agreeable diversification of the foreground is a capital 
 point in a landscape. It has been already remarked how much 
 this is aided by shadows. Almost any characteristic and promi- 
 nent objects will have a good effect; logs, stones, and, still more, 
 rocks, bushes — anything that breaks the level and changes the 
 lines, also attracts and pleases the eye, not in itself, but in the 
 general character that it imparts. It may generally be afi&rmed 
 that scarcely anything can so much detract from the effect of a 
 landscape as an unbroken foreground, level in form, and uniform 
 
220 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 in light. Such a foreground will mar, if not destroy, the effect of 
 the finest objects. The artistic photographer will always change 
 his position to avoid such a foreground; or, if he is tied down to 
 a particular spot from some imperative cause, he will, if possible, 
 have some object, such as a log, a large stone, or a trunk of a 
 tree, thrown where it will support his lines, as explained more 
 fully beyond. High banks are very picturesque objects, and 
 often aid to make beautiful foregrounds. 
 
 Bringing Out the Foreground. Acceleration of Exposure. — Often 
 the foreground, especially if consisting, as it so commonly does, 
 chiefly of foliage, lags behind in development ; and when some 
 other parts of the picture have reached a full intensity, so that 
 the development must perforce be stopped, the foreground will 
 often be still thin and poor. This is a great injury to a picture, 
 which is helped by nothing more than by a properly exposed 
 and developed foreground. 
 
 The writer has succeeded in obviating this difficulty to a con- 
 siderable extent as follows: He takes a piece of white pasteboard, 
 shaped as in Fig. 107, and of such a size that 
 Fig. 107. whilst the top lies flat against the inside top 
 
 of the camera, the tapering sides rest upon 
 the bottom, and act like legs to support the 
 top in its place. The inside is colored rose- 
 red with carmine (lump carmine, a grain or 
 two dissolved in half an ounce of water, 
 with a drop or two of liquid ammonia, is better than the paint). 
 The red light diffused and reflected by the surface of this paper 
 considerably increases the force of the adjoining portions of the 
 image, without in the least tending to produce fog. The sides 
 should taper very much, as - it is not desirable that any part of 
 the red paper should be alongside of any part of the sky. 
 
 There is in this device a real and solid utility, and the writer 
 never now goes out to take views without this adjunct. A piece 
 of pasteboard blackened with ink, and of such a size as to fit 
 against one of the sides of the camera, and so cover one of the 
 legs of the red pasteboard in case there is much sky on that side, 
 is convenient to have. 
 
LANDSCAPE AND ARCHITECTLTEAL PHOTOGRAPHY. 221 
 
 § 3.— Materials. 
 
 Camera. — The most convenient form of camera for ordinary- 
 use is that represented in Fig. 94, p. 149, except that, especially 
 if the camera be large, the writer prefers the wooden brace shown 
 in Fig. 92. When it is intended to pack the camera, to carry to a 
 distance, it is convenient to have the bottom jointed and hinged, 
 tbough this system weakens the whole construction. 
 
 Slides. — If the dry process is worked, the photographer can 
 use Changing Boxes, contrived to carry a number of plates, and 
 transfer them, one by one, to a peculiarly made slide ; or he can 
 use separate slides, which may be made to carry two plates each, 
 and are then called Double Backs. This is the plan preferred by 
 the writer. 
 
 Tripods. — A light folding tripod is essential for field work; and 
 as much of the photographer's comfort will depend upon having 
 a good tripod, the writer has 
 made drawings of tbe parts of 
 the form which, he prefers. 
 
 Fig. 108 shows the top table. 
 It is made of three thin pieces 
 of wood glued firmly together, 
 and having the form of a round- 
 ed triangle. At each corner a 
 block is fastened underneath, 
 carrying stout pins, J., J5, which 
 slip into holes in the legs, the 
 tops of which are shown in the 
 figure. 
 
 At the centre is a circular opening in the top thickness, in the 
 middle of which circle is set the screw S. There is no screw- 
 thread in the table, the screw merely passes through it and screws 
 into the camera. A pin passed through the stem of the screw, 
 just above where it passes through the table, prevents it from 
 dropping out; this is a great convenience, often neglected by the 
 makers, thus subjecting the photographer to the chance of over- 
 looking the screw in going out, and so losing his day. 
 
 The legs, one of which is shown in Fig. 109, fold over in the 
 middle, to save room. The cross-piece near the upper end moves 
 on a hinge, and permits of shutting the whole up flat. In Fig. 
 110 the writer has drawn the joint on a larger scale. When the 
 
222 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 leg is straightened out, a small brass cross-piece, attached by two 
 screws, confines the lower piece in its position, and a strong thumb- 
 
 screw at the side, when tightly turned, makes the whole perfectly 
 rigid. It is surprising how light a tripod, thus made, will hold 
 a heavy camera quite steady. 
 
 For additional information on materials, see Chapter XY. 
 
 If the wet process is the one selected, the photographer will 
 either use a developing box, a tent, or a dark room on wheels. One 
 of the simplest tent contrivances is a thick black cloth stretched 
 over the camera tripod, and kept in place by stones. In the de- 
 veloping box, the hands and arms only are inserted into sleeves, 
 whilst the operations are watched through yellow glass. 
 
 All the troubles, and there are many, that accompany these 
 methods of operating, are avoided by the use of dry plates. And 
 it is certain that the most improved methods of dry plate work 
 give results fully equal to those of the wet process. 
 
 Whichever method be adopted, an observance of the following 
 rules will save a great deal of vexation and the loss of many 
 negatives, occasionally perhaps of a whole day's work. 
 
 At the commencement of a day's work, see, once for all — 
 
 1. That the camera is light-tight, and that there are no cracks 
 in the front or holes in the bellows body. Cap the lens, cover in 
 
 Fig. 109. 
 
 Fig. 110. 
 
 § 4. — Manipulations in the Field. 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 223 
 
 the head well, and look into the camera with the ground glass let 
 down, racking back pretty well, to open the folds of the bellows.' 
 
 2. See that the lens 
 Is free from dust. 
 Has no dew on it. 
 
 That the parts of the lens and of the mount are properly 
 
 put together. 
 For each exposure make sure. 
 
 3. That the camera and tripod are perfectly steady. 
 
 4. Invariably use the largest aperture to compose the picture. 
 Make sure that no near objects out of focus are showing in the 
 foreground, which may easily happen with shrubs, weeds, and 
 the like. Also that no overhanging foliage is intruding upon 
 the upper corners of the plate, to appear, to the dismay of the 
 photographer, when he develops, as large, formless objects, ruin- 
 ing probably his picture. 
 
 5. Adjust the swing-back. Eemember that if the screws which 
 fasten it are not turned perfectly tight, they will probably move 
 when the plate holder is pressed up to attach it. 
 
 6. If working with dry plates, make perfectly sure that you 
 are not exposing a plate that has been already exposed before. 
 If habitually using dark slides or double backs, have each 
 painted conspicuously with a number on the shutter, and expose 
 in regular rotation. If using a changing box, adopt a regular 
 system of changing the plate immediately after, or immediately 
 before, exposing ; always the same. 
 
 7. If the sliding front has been moved up or down or side- 
 ways, for a previous exposure, make sure that it has been re- 
 placed. If the camera has been carried a distance, the front 
 may have jolted down, and if not attended to, some of the cor- 
 ners may be defective in the image. 
 
 8. After arranging and composing the picture with the largest 
 stop (in order that you may see exactly what the picture will be 
 like), turn the screw of the tripod under the camera, hard, so that 
 there shall not be the slightest change of position during the 
 subsequent manipulations. 
 
 9. Now put in the diaphragm which you intend to use, and 
 focus with it (never with the large one by which the picture was 
 composed, and for two reasons: 1st. It will not give a good 
 focus, being too large. 2d. If it did, its focus would not be the 
 same, the smaller the stop the longer the focus). 
 
224 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 The loose diaphragms that slide into slits in the tube (Water- 
 house diaphragms) are apt to drop out. To avoid this, hend the 
 shank a little. 
 
 10. Uncap the lens gently, pausing at the moment, to insure 
 perfect rest. 
 
 11. Watch the foliage intently during exposure, and at the 
 slightest sign of movement, replace the cap until the movement 
 wholly subsides, and repeat this as often as necessary — a dozen 
 times if needful. 
 
 The same objects will appear so differently in different lights, 
 that the painstaking photographer will not hesitate to wait or 
 to return when he finds the illumination to be unsuitable for his 
 purposes. There is a story told of a distinguished landscapist 
 that he once waited three weeks to get good weather and a par- 
 ticular effect of light upon a scene that he had come to photo- 
 graph. There is some contrast between this and the rapid worker 
 who points his camera at everything that catches his eye, and 
 exposes his dozen of dry plates in an hour or two. It should be 
 laid down as an axiom by every worker, that a good negative is 
 very valuable, a tolerable negative worth absolutely nothing. It 
 is at least as troublesome to print a tolerable negative as a good 
 one, and the prints from the tolerable one are not worth the pains 
 they have cost in printing. Twenty copies from a good negative 
 are valuable for exchanging against prints from good negatives 
 belonging to others; but twenty prints, each from a tolerable and 
 different negative, are nearly worthless. No multiplication of 
 indifferent results will give good ones, and the experimenter will 
 derive more satisfaction from a single thoroughly good negative 
 than from a score or a hundred of indifferent or tolerable ones. 
 Good results will come only with care, thought, close observa- 
 tion, and a resolution to have things right at any cost of time 
 and trouble. Care-taking soon becomes a matter of course, and 
 the habit once acquired, is invaluable. 
 
 Adapting Flanges. — The inconvenience arising from flanges of 
 different sizes has been already pointed out (p. 96). The writer 
 finds this annoyance materially lessened by having adapting 
 flanges made for lenses, so that several lenses may screw into 
 one and the same flange. Such adapters can readily be made 
 by any optician at a trifling cost. 
 
 Focussing. — A black cloth which will perfectly exclude the 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 225 
 
 light is essential. Black waterproof is suitable, and a piece a 
 yard and a half square will be a convenient size. 
 
 Photographers differ very much in their ideas of how a focus 
 should be taken. In the first edition of this manual it was 
 recommended to focus at a point in the foreground half-way 
 between the centre and a corner, racking back as far as prac- 
 ticable, and then putting on a small enough stop to obtain the 
 definition needed. 
 
 Now, however, the writer has gradually adopted the following 
 plan : There will be with any lens a stop which one habitually 
 uses when the objects are not very different in their distances 
 from the camera, and another, the next smaller, used when the 
 differences are greater. Therefore, selecting for the view about 
 to be taken the stop deemed appropriate, proceed to focus on the 
 distance, and then rack back the focussing screen just as long as 
 the distance will bear it, without its definition suffering too much. 
 This ought to bring the foreground into focus ; if it does not, a 
 smaller stop must be substituted, or else the position changed so 
 as to exclude the near objects that cannot be got into focus along 
 with the distance. 
 
 Either of these alternatives is unsatisfactory, because it may 
 be very desirable to include that particular part of the fore- 
 ground, and a small stop is always bad. 
 
 But if the camera have the valuable aid of the swing-hack, the 
 question is greatly simplified. The photographer will be enabled 
 to get an equally good general focus with a larger stop, and con- 
 sequently with better detail in the shadows, and better spacing 
 out of the distances. A swing-back should always be double, 
 that is, have both a horizontal and a vertical motion. 
 
 .The vertical pivot is to be used when, as so often happens, the 
 objects at one side of the view are nearer than those on the other. 
 The side on which the nearer objects fall is drawn a little away 
 from the lens. 
 
 The horizontal pivot is useful in getting the foreground into 
 focus at the same time with the distance. To this end, focus on 
 the distance, rack out the focussing screen as long as the distance 
 will bear it. Then draw the top of the screen away from the 
 lens, until the foreground is perfect. Both this and the vertical 
 action may be combined (see also p. 148). 
 
 The usefulness and convenience of the swing-back for bringing 
 the foreground into focus is exceedingly great, and when once 
 
226 
 
 PHOTOGRAPHIC MANIPUL ATIONSv 
 
 used habitually, this contrivance is felt to be indispensable. 
 There is one case, however, in which particular caution is needed 
 in its application. 
 
 If both the upper corners of the picture be occupied by near 
 foliage, then any drawing out of the upper side of the swing- 
 back to regulate the foreground will be apt to throw the corner 
 foliage out of focus, and deform it. In such cases it will be 
 needful to move the tripod farther back in order to lessen the 
 difficulties of the position. 
 
 If one upper corner only be covered by foliage, and if the 
 extreme distance of the view lie towards the other end, we may 
 then draw out the foreground without danger, because the foliage 
 in the upper corner can be got into focus again by regulating 
 the vertical pivot, and thus at the same time the distance at the 
 farther side will be also harmonized in focus. 
 
 Some persons are as anxious for sharpness in the distance as 
 in the foreground, and will exhibit a print with the boast that 
 the extreme distance will bear a microscope. As the eye cannot 
 see natural objects in this fashion, it can scarcely be right to 
 depict them so. And when we examine the works of the great 
 masters of landscape painting, we find that, with the power to 
 draw their distances precisely as they pleased, they did not think 
 right to make them sharply cut. 
 
 We find that, as distance softens down outlines to the eye, so 
 when outlines are softened down, the eye infers distance. 
 
 Not that this principle is to be carried to excess, and made an 
 excuse for blundering work. It is only that the same sharpness 
 is not to be exacted in the distance as in the foreground; espe- 
 cially as this can only be attained by the use of a very small 
 stop, which greatly mars the boldness and life of the image. 
 
 § 5.— The Wind. 
 
 In all landscapes the chief beauty lies in the foliage, and it is 
 necessary that this should be absolutely still, to be satisfactorily 
 represented. Every one who attempts landscape photography 
 has had severe experience of this sort, and fully understands the 
 ruinous effect produced upon a picture by blurred masses of 
 leaves. 
 
 It would be difficult to exaggerate the annoyance caused to the 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 227 
 
 photographer by this unending source of trouble. It is impos- 
 sible to foretell what the prospect of wind is, therefore a long 
 excursion may be taken uselessly, or may be abandoned only to 
 see, when too late, the wind entirely subside. 
 
 The following represents what aid can be given in this direc- 
 tion : — 
 
 Time of Day. — The very early morning is apt to be calm, and, 
 still more so, the afternoon for an hour or two before sunset. 
 Both of these are excellent times for photographic work. The 
 exposures in the late afternoon are necessarily prolonged, but the 
 quietness of the air generally makes this easy. 
 
 Between eight and ten o'clock A. M. the wind is apt to rise, 
 sometimes earlier, sometimes later. It may subside towards 
 midday, but quite as often not. Gradually towards three or four 
 o'clock in autumn, four or five in spring and summer, a sub- 
 sidence may be hoped for, and then no time should be lost in 
 improving it. It is one advantage of dry plates that they can 
 follow each other without losing valuable time in sensitizing and 
 developing ; the collodio-bromide dry plates hereafter to be de- 
 scribed are, by reason of their sensitiveness, excellent for after- 
 noon exposures. 
 
 Seasons. — The spring with us is apt to be windy, with, how- 
 ever, occasional calm days, which become rather more numerous 
 in June and July. August and September have mostly more 
 quiet days than any other months. October has beautiful quiet 
 days occasionally, with fine, soft illumination. By the first of 
 November the foliage is pretty well gone. Then, in place of the 
 soft lights and shadows of the woods, we get masses of parallel, 
 gray trunks, which produce the very worst effects. A single 
 tree, especially an oak tree, devoid of leaves, is a beautiful object, 
 its branches give gracefully opposing lines, that support each 
 other ; but there is nothing of this sort in a wood. 
 
 When the wind blows steadily it is a mere waste of time and 
 material to go out to photograph, however tempting the light 
 may be; except, indeed, we go expecting only to make use of 
 the late afternoon. On not very windy days we are almost sure 
 to have an hour or two of calm before sunset. 
 
 Often the wind blows in puffs. In this case we closely watch 
 the foliage and re-cap the lens the instant the first movement 
 shows itself. With care, quickness, and gentleness, it is wonder- 
 ful how much may be accomplished in this way. It should be 
 
228 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 remembered, however, that if the puffs of wind between the quiet 
 times are violent, it does not follow that the leaves, after this 
 violent agitation, will settle down, each leaf to the exact previous 
 position. 
 
 For the most part, however, it is a waste of time to attempt to 
 photograph landscapes in windy weather. The evil effects of 
 very slight winds may be materially diminished by observing 
 one or two precautions. 
 
 When light branches are projected against a bright sky or 
 clouds, the least motion of the leaves allows the bright light of 
 the sky to pass in behind them. The result is that the leaves 
 appear shrunk away and blurred, ^ an effect very often seen and 
 most displeasing. If the sky is very dense, and prints perfectly 
 white, such branches should always be painted out. A similar 
 result follows when branches are projected against the reflection 
 of the sky on water, or against any other bright object. 
 
 Again, where boughs with glossy foliage, well illuminated, 
 stand out against deep shadow, and are moved by wind, they 
 carry their bright reflection with them, and their image is ex- 
 tended, in place of being shrunk away as in the previous c£,se. 
 Each leaf, instead of being small and sharp cut, as we would wish 
 to have it, is large, blurred, and undefined. 
 
 Therefore, if the air be somewhat in motion, the landscapist 
 will do well to avoid foliage in either of these two positions, 
 which are those that produce the worst effects. For when foliage 
 standing before other foliage, and nearly equally illuminated, is 
 moved, the result, though anything but pleasing, is not so very 
 injurious as in the other cases. 
 
 On those priceless days, when the light is neither too strong 
 nor too weak, and the foliage perfectly still, the photographer 
 will do well to turn hig attention especially to those landscapes 
 in which the chief beauty lies in the foreground. Foliage should 
 be introduced quite near to the camera, provided it c^in be kept 
 in good focus together with more distant objects. Projecting 
 boughs seen against the reflection of sky in water, so objection- 
 able in the former case, may now be made to produce the most 
 charming results, especially when accompanied by their reflected 
 images. 
 
 ' When no paper is placed behind the plate (or color on the back of dry 
 plates), the same result may be expected by reflection from the back of the 
 plate, quite independently of any movement of the leaves. 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 229 
 
 When it is intended to photograph immovable objects in a 
 heavy gale, it is very desirable to find, if possible, some suitable 
 support, such as a wall, a rock, or the stump of a tree, on which 
 to place the camera, which is then steadied by placing on it a 
 heavy stone. Perfect steadiness may in this way be obtained. 
 In the absence of these resources, a cord may be fastened to the 
 screw under the table of the tripod, and a heavy stone be tied to 
 the other end, and let to hang down. Or it has been proposed 
 to tie a loop in the cord, reaching just short of the ground, and 
 to put the foot into the loop, and thus hold steady the camera. 
 
 It remains to say a word respecting the wind, in its relation to 
 long and short exposures. 
 
 It has been said that the wind does not act more injuriously 
 upon a long exposure than upon a short one, the effect having the 
 same average in each case, in proportion to the exposure. This 
 view is, I am persuaded, erroneous. The wind rarely blows 
 steadily (such weather is to be particularly avoided), but gene- 
 rally in puffs. And these puffs are apt to come at intervals, such 
 that, by watching, a short exposure can be caught between them, 
 when a long one cannot possibly. 
 
 Indications of Weather. — As the photographer's success in out- 
 door work is always dependent upon the weather, all means of 
 judging beforehand of what weather may be expected, acquire 
 no small importance. These signs differ materially in different 
 countries ; thus the writer, after a careful observation of the indi- 
 cations furnished by the English Admiralty for the guidance of 
 shipmasters, believes that, here at least, they are quite unreliable. 
 The following are what, from long experience and personal ob- 
 servation, have appeared to him useful. 
 
 And, first, as to wind. The direction of the wind has much to 
 do with its probable force. A westerly Vind may be expected 
 to blow moderately; a northwesterly wind strongly, and often vio- 
 lently; a north and northeast wind strongly; an east wind (if not 
 inclining northwards) is in clear summer weather not often strong. 
 But it is from southeasterly and southerly winds that the best pho- 
 tographic weather is apt to come, provided they do not bring rain. 
 Often with them the air is perfectly calm. When the direction 
 gets round to southwest, we have light breezes, often in puff's, a 
 state of weather ver}'- favorable. Thus we are most apt to have good 
 photographic opportunities with a southwesterly wind, but the 
 
230 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 best weather we have comes with a southeast or southerly wind, 
 though such a wind is less sure to bring it. 
 
 The clouds give many useful indications. Thus, if in the early 
 morning we see the clouds moving rapidly, then, although the 
 air below may be quite still, we are almost sure to have it rise in 
 an hour or two, and blast the fairest expectations. Much may 
 be inferred from the forms of clouds. Feathery clouds almost 
 always bring wind ; mottled, irregular clouds like flocks of sheep 
 may or may not. The most favorable indication for calm air is 
 when the clouds form in long, smooth, thin forms, imperceptibly 
 blending into each other and into the sky; this appearance gene- 
 rally portends a still air and a soft light. Abrupt contrasts in 
 clouds are more likely to bring wind. 
 
 The previous condition of the weather often affords a means of 
 judging. The first day after a storm is apt to be windy, each 
 succeeding day is more likely to be calm, and the calmest weather 
 is apt to be that which comes immediately before the next storm. 
 
 The above indications relate to stillness. As to clearness^ the 
 following will be found useful : — 
 
 A mackerel-back sky indicates a change of weather. This name 
 is given to collections of little clouds, three, four, or more times 
 as long as they are wide, and arranged in parallel groups. This 
 indication rarely fails to be followed by bad weather within 
 twenty-four hours. 
 
 A red sunset generally precedes a fine day, a gray sunset a rainy, 
 or, at least, an overcast day. 
 
 Although it is said that with the sunrise these indications hold 
 but with opposite meanings, yet for such an opinion the writer has 
 never been able to find any support, but has constantly seen good 
 days and bad days follow both red and gray sunrises. 
 
 After two or three white frosts, rain may be expected. This 
 fact, and also that when ditches or drains smell more than usually, 
 rain follows,- has long been familiar to all persons living in the 
 country. On the other hand, all indications drawn from changes 
 in the moon's quarters, position of the crescent moon, etc., in the 
 sky, certainly amount to nothing. 
 
 Changes in the barometer have not the significance in this hemi- 
 sphere which they have in the other, and little reliance can be 
 placed on them. 
 
 Finally, it should be observed that although the foregoing in- 
 dications as to stillness and as to clearness are generally reliable, 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 231 
 
 it cannot be affirmed that they are invariably so ; they can be 
 depended upon as showing the probable course of the weather, 
 but not as being infallible. 
 
 Before terminating these observations on landscape photogra- 
 phy, another remark needs to be made. In the very highest 
 class of landscape prints there is sometimes seen a combination 
 of great brilliancy and perfect softness, that surprises as well as 
 charms, and leads directly to the question, how is this difficult 
 combination of excellences obtained ? Not by any secret process, 
 that we know, for those who succeed best have always given 
 their formulae freely ; it is, therefore, not the materials used, but 
 the mode of using them, that is the essential point. 
 
 It is certain that — 
 Softness is promoted by length of exposure and rapidity of de- 
 velopment. 
 
 Brilliancy is heightened by shortness of exposure and slowness 
 of development. 
 
 The difficulty, of course, is that what promotes the one object 
 interferes with the other, and this is why so few fully attain both. 
 There is only one way in which it can be done, and this is to seek 
 for softness by length of exposure, and then to combine this with 
 brilliancy by a slow development. 
 
 In practice : Give a full exposure (using a fair dose of bromide), 
 such that with an ordinary developer the picture would flash up 
 instantly. So developed, the picture would be full of half-tone, 
 but flat and tame. Therefore add water and acetic acid to the de- 
 veloper until, notwithstanding the full exposure, the image comes 
 out gradually, avoiding, however, all exaggeration, both of ex- 
 posure and development, and combining the two so that each 
 shall correct the other's faults. 
 
 The best results, however, are always to be obtained .by the 
 use of a specimen of cotton that has had exactly the salting thai 
 suits it. To buy pyroxyline at random, even from the best 
 makers, and then select a formula for salting at random, even if 
 it be a formula of the highest authority, and then use a develop- 
 ment recommended either in a treatise or by a friend, but having 
 no definite relation to the cotton and salting, is to put the chances 
 against a full success. In England few even of the oldest and 
 most skilful landscape photographers make their own collodion ; 
 they buy ready made some particular sort which experience has 
 
232 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 shown tbem to suit their particular way of working, often 
 habitually and systematically mixing the collodion of two 
 different makers in certain proportions. The collodion maker 
 manufactures his own cotton, which he keeps as uniform 
 in character as possible. Very long experience has taught him 
 the very best salting for it, and he thus delivers a collodion 
 of very high quality. The photographer thus gets a great advan- 
 tage; in our system, where the photographer makes his own 
 collodion, he for the most part gets an inferior article, even with 
 the best cotton, unless by careful experiment (see p. 132) he finds 
 out just what treatment some particular cotton requires, and 
 manages it accordingly. This troublesome investigation he must 
 either make for himself, or else pursue his work under telling 
 disadvantages. The great excellence of English landscape work 
 is partly due to this system of buying collodion instead of cotton, 
 and partly to the character of the light in that country, generally 
 soft and broken, with little of the burning brilliancy of ours. 
 
 The brightness of the print will also largely depend upon the 
 albumenized paper. First-class prints will always need first-class 
 paper: solid, full-bodied paper, well albumenized with sound, 
 fresh albumen, and paper that has been carefully kept, and not 
 too long. 
 
 § 6. — Toning of Landscape Prints. 
 
 Although remarks on this point belong technically rather to 
 the head of printing, yet they are so closely connected with the 
 general subject of Landscape Photography, that I have preferred 
 to give them a place here. 
 
 A landscape print is subject to none of the conventional rules 
 of color that hold to a large extent with portraits, and even to 
 some extent with architectural views. Every pleasing tone is 
 appropriate — light brown, deep brown, warm brown, dark purple, 
 purple black, steel gray, and pure black. All of these do well. 
 Blue black is unpleasing, and is presumably never got intention- 
 ally, but results from accidental over-toning. 
 
 All the warm shades up to black do well, as has just been said, 
 and a wide range of them gives a most agreeable diversification 
 to a collection of views. It will be found, however, that every 
 negative has some particular tone that gives its best effects. This is a 
 fact that every photographer of refined artistic taste will perceive 
 and feel: it becomes, therefore, in the highest degree desirable 
 
LANDSCAPE AND ARCHITECTURAL PHOTOGRAPHY. 233 
 
 to be able to say approximately of any negative in advance, or 
 on seeing the first proof taken, what toning will best suit it. The 
 following remarks may afford some clue to this knowledge. 
 
 Some negatives that have been taken with a highly favorable 
 illumination, and have been developed exactly right, will exhibit 
 so exquisite a combination of contrast and harmony of light and 
 shade, that they will look well with any toning. They have no 
 defects to soften, and can hardly be spoiled in the printing. For 
 this higher class of negatives, a rich warm purple black, best 
 obtained by the acetate of soda or by the benzoate toning bath, 
 will be the most suitable. 
 
 Starting from a supposed perfect negative, we gradually pass 
 down to less excellent efi'ects. In all, we shall suppose that 
 both the denser and thinner parts are full of detail (for if either 
 lacks it the negative will not be worth printing), but that these 
 parts, though each full of detail, do not work well together. If 
 the printing be stopped when the thinneij parts are right, the 
 denser have not produced their best effects ; if it be carried on 
 until the latter are right, the former are too heavy and dark. 
 
 Now, this is a fault which may exist in every variety of degree. 
 If it exists to a large degree, the negative is worthless; if only to 
 a slight one, the intention here is to point out what course of 
 action will render such a fault the least conspicuous. 
 
 The lighter and the warmer the color, the less this bad effect 
 will be noticeable, a fact, I believe, which has never been pointed 
 out before, though possibly some may have acted on it. A print 
 must be exposed until the detail is out in the high lights, other- 
 wise it is a complete failure. The effect, therefore, of the dis- 
 cordance here spoken of, is always to produce heavy black 
 shadows, without detail, and the lighter and warmer the toning, 
 the less offensive will be these dark masses, and the more of de- 
 tail will be left in them. An observation of this rule will go far 
 towards getting a fair print from a somewhat hxxlty negative. But 
 it must be understood in the clearest way, that beyond a certain 
 point the want of harmony is an irretrievable one. 
 
 Conversely, it is evident that if a negative lack contrast, either 
 from the subject having been too monotonously lighted, or from 
 an over-exposure, a pure black toning, without too much over- 
 printing, will do what can be done towards affording a good 
 result. 
 
 16 
 
234 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 If these precautions be neglected, and if, for instance, a nega- 
 tive in which the contrast is already too great, be toned up to 
 full black, the result will be that its faults, instead of being 
 softened, will be aggravated. And if the photographer is un- 
 aware of, or does not appreciate, the principle here laid down, he 
 may never obtain more than a passable result from a negative 
 which, properly handled, might give a really good, though not a 
 first-rate, print. Generally an acetate toning bath will be found 
 the best for landscape prints. 
 
 CHAPTER YIII. 
 COMPOSITION. 
 
 § 1. — Landscapes. 
 
 Of late years there has been a continually increasing realiza- 
 tion of the defects and incompleteness of landscape photographs 
 taken with entire ignorance of the principles of composition, and 
 it is becoming well understood that mere technical skill cannot 
 compensate for want of this knowledge, which, even in a very 
 elementary form, is found to be invaluable. So that, if two 
 persons, the one having some knowledge of artistic composition, 
 and the other ignorant of it, undertake to photograph the same 
 view, the former will always be enabled to make the best choice 
 of the point at which to plant his tripod. 
 
 Cultivated taste has learned that the representation of a land- 
 scape gives a completely satisfying effect to the mind most easily 
 by complying with certain general conditions which have been 
 reduced to fixed rules. Too slavish a compliance with these 
 leads directly to mannerism and sameness, but some acquaint- 
 ance with them cannot but be of the highest use to every intelli- 
 gent photographer. 
 
 Line of Direction — Balance. — In examining any picture, we 
 may discern certain lines of direction. These lines may be of 
 one prominent object, or may depend upon the directions of the 
 principal portions of a succession of objects. 
 
 It is a rule that these lines of direction should support each other, 
 as in Fig. Ill, where the longer line is supported by the shorter. 
 
COMPOSITION. 
 
 285 
 
 The longer line may, for example, be that of a distant range of 
 mountains, and the shorter that of a conspicuous bough of a tree, 
 or of any other prominent object in the foreground; or both 
 lines may depend partly upon distant and partly upon near 
 objects — it is immaterial. The essential point is only that the 
 characteristic lines of the picture shall balance each other. But 
 
 if the lines be all in one direction, as in Fig. 112, or even if not 
 quite parallel, there is a want of balance, and the idea of weak- 
 ness and of falling is given. Moreover, the effect of the repeti- 
 tion of direction is generally unpleasing, though it is occasionally 
 used to convey the idea of receding distance. In any case, how- 
 ever, it is necessary that these lines should be balanced. 
 
 A succession of perpendicular (see Fig. 113) or of horizontal 
 (Fig. 114) lines is, for the most part, unpleasing. As an example 
 
 Fiff. 113. 
 
 Fig. 114. 
 
 of the former, we may take a row of straight-stemmed trees, the 
 effect of which is infinitely less pleasing than if their directions 
 are diversified. Parallel horizontal lines are rarely allowable; 
 sometimes, however, they are employed by artists in " parallel 
 perspective" — that is, where buildings are represented in full 
 front view. 
 
 As pictures are commonly bounded by four right lines, any 
 arrangement of the important objects in a picture that brings 
 them side by side, and at equal distances from the base line, pro- 
 duces to some extent the parallelism of Fig. 114. Similarly, if 
 
236 
 
 PHOTOGEAPHIC MANIPULATIONS, 
 
 tbey are directly over one another, they form parallels with the 
 side, as in Fig. 113. The same principle applies also to the in- 
 troduction of a tree with a straight, perpendicular shaft, near to 
 the edge of a picture. It falls into an objectionable parallelism 
 with the side line. These faults are to be borne in mind and 
 avoided. 
 
 The Diagonal Line. — According to the direction into which the 
 principal lines of the picture fall, the composition is distinguished 
 
 into angular and circular. The diago- 
 rig. 115. nal line, the simplest form of angu- 
 
 "\~ lar composition, is exceedingly well 
 
 ^\ ' adapted for representation of perspec- 
 
 tive, especially when, to get a better 
 \. range of effect, the distance is placed 
 ^\ towards one side of the picture. 
 It is by no means necessary that the 
 
 principal line of direction should pro- 
 ceed directly from one angle to the other. This angular line 
 of direction should always be supported — that is, the eye carried 
 along it should not be dropped vaguely, but fall upon some 
 object, which, though it must be distinct, need not be large. 
 This object is termed the " ruling points An inspection of land- 
 scapes and groups executed by artists will show how far inge- 
 nuity has often been taxed to hit upon some object of this sort 
 in which to terminate a line of principal direction. In country 
 scenes, a dog, or a fowl, or any other small object in keeping 
 with the general subject, will be introduced into the foreground. 
 A little examination will show that its exact position has been 
 determined by a line of principal direction, and that the object 
 has been placed at its exact intersection with the ground. The 
 universality of this practice seems to indicate that it is correct ; 
 the principle is evidently that, after the eye has been carried 
 from one to another of the striking features of a picture, it 
 should not finally fall blankly upon nothing, but that there must 
 be some sufficient object upon which to rest. In most cases the 
 resting point or ruling point is made dark on a lighter ground, 
 though in some cases a lighter object than those that surround it 
 is used. 
 
 A beautiful and familiar instance of the balance of opposing 
 lines of direction is seen in mountains, the opposite sides of which 
 
COMPOSITION. 
 
 237 
 
 rest against each other thus: A- So a gap between two moun- 
 tains gives lines that balance each other in the form V- 
 
 Circular Composition. — Curved lines of direction are often intro- 
 duced with very fine effect. Views of lakes, or of curved reaches 
 of rivers, will be apt to fall into this form, and it is seen in many 
 other compositions of rural scenery. 
 
 The Foreground. 
 
 The foreground is the portion generally most under the photo- 
 grapher's control, and those who desire to obtain the greatest 
 success will spare no pains in the selection of this part of their 
 picture. 
 
 The foreground should be diversified. A level, unbroken fore- 
 ground of grass or meadow cannot be expected to give a good 
 effect. It weakens the effect of the distance, and deprives the 
 picture of much of the character that it ought to possess. 
 
 A portion of the foreground should be occupied by some dark 
 object, whose effect will be materially enhanced if brought into 
 immediate contrast with some of the highest lights of the picture. 
 The best effect is for the most part attained by placing the dark 
 object in the foreground under the farthest distance. This gives 
 great tenderness and softness to the distance, causes it to recede 
 from the foreground, and at the same time supports it by lending 
 firmness and foundation to it. Too much attention to this point 
 cannot be given by the landscapist, who will, however, often have 
 his patience and ingenuity taxed to the uttermost to find anything 
 like a satisfactory foreground to his pictures. 
 
 There is a great beauty in very trifling objects, which many 
 habitually overlook. Bushes and vines, rocks, stones, logs, often 
 have elements of attraction that reveal themselves only by ob- 
 servation and cultivation. A tasteful arrangement of such objects 
 in the foreground of a photograph lends to it an inexpressible 
 charm. 
 
 The writer cannot, perhaps, find a more striking illustration 
 than in a clump of brambles. To many, such a thing would 
 seem to be so essentially ugly that it should be excluded, is pos- 
 sible, whereas, on the contrary, it is, both in nature and in repre- 
 sentations of scenery, almost always a very beautiful object. The 
 stems present often a beautiful combination of right lines and 
 graceful curves, the leaves have a surface that sends back light 
 
238 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 enough to give brightness to the lights, and, by contrast, depth 
 to the shadows. Often the more succulent shoots will hang over 
 in festoons of singular gracefulness. Late in the autumn, banks 
 of brambles retain their leaves long after the trees are stripped, 
 and then, if they can be introduced into a picture, they are most 
 valuable. 
 
 When the foreground is so level and unbroken that no diver- 
 sification can be introduced, a shadow, as of a large tree, falling 
 across it, at once relieves the tameness, and produces a beautiful 
 effect. 
 
 The Distance. 
 
 The distance should never find its place exactly in the middle 
 of the picture, which by such a disposition becomes divided, as 
 it were, into two equal halves, to the complete destruction of its 
 artistic character. In fact, no important object should be placed 
 exactly at the centre of the picture, which is by artists considered 
 to be a "weak point." Nor should any important object be 
 placed exactly upon the middle line which divides a picture from 
 top to bottom or from side to side. Its effect will be always 
 better if it is distinctly removed from either of these lines. 
 
 A peculiar pleasure is given when the eye is conducted from 
 the foreground to the distance by lines of direction. These lines 
 may be one or both banks of a river or stream, a picturesque 
 road, or other object. The leading should be rather by broken 
 and diversified lines than by straight ones. 
 
 A certain pleasure is communicated when objects in the middle 
 distance are repeated in the farther distance. Such a repetition 
 is not to be by the same object, but rather by some other object 
 in strict keeping. This rule is closely allied to one in painting. 
 It is laid down in painting, that if a particular color be introduced 
 in one place only, it has the effect of a spot or blot ; the color 
 must be carried through the picture, or at least part of it, by 
 recurring here and there. As in colors, so in objects. If trees 
 are seen in the foreground or middle distance, the eye is gratified 
 by seeing them reappear in the distance. If a cottage or other 
 building be a conspicuous object in the foreground, the eye likes 
 to see something similar in the distance. 
 
 The effect of a high light in the extreme distance is greatly 
 enhanced by placing a dark object in the foreground, somewhat 
 under it, but not perpendicularly. This acts partly by throwing 
 
COMPOSITION. 
 
 239 
 
 the distance farther back, and thus powerfully aiding the impres- 
 sion of distance, and partly because the light becomes lighter and 
 the darkness darker through contrast. 
 
 If the different planes of distance are not well made out in a 
 photograph, that is, if they do not appear to occupy the same 
 relative position in the photograph which belongs to them in 
 nature, the fault may arise from the use of too small a stop, 
 which tends to produce a sort of map-like effect, or from the use 
 of a lens of too short or too long a focus. In the first case the 
 middle distance is transferred to the extreme distance, and con- 
 founded with it. In the latter case the middle distance is forced 
 forward into the foreground. (See chapter on Perspective.) 
 
 The Skies. 
 
 A blank white sky always disfigures a photograph, and must 
 be avoided if possible. Several alternatives present themselves, 
 one or other of which should be adopted whenever possible. 
 
 If large slow-moving clouds are present, they may sometimes 
 be caught, especially if the illumination of the landscape be good, 
 and so that it comes out rapidly, and without a prolonged devel- 
 opment, which, in wet plates, always thickens up the skies. 
 Large stops are always favorable for getting clouds with. 
 
 If clouds cannot be taken with the landscape, they may be 
 taken separately and printed in, for which directions are given 
 elsewhere. 
 
 But it is an excellent plan to cover as much as possible the sky 
 with foliage or other objects. Large trees in the foreground will 
 aid in this. In hilly countries the elevations will be a great aid. 
 In level districts it will often be useful to raise the horizon line. 
 Fortunately this line is, in landscapes, very much under control. 
 In architectural subjects, as the camera must always be hori- 
 zontal, we can only effect this by raising the camera front, or 
 bringing in the use of the swing-back. But in landscapes with 
 no buildings a good deal of tilting may be done without evil 
 effects. The horizon line is thus raised, and the proportion of 
 sky diminished. 
 
 In dry plate work we may often keep the sky thin, and thus 
 avoid the unpleasant whiteness. This is a very great advantage, 
 and is especially to be obtained with coUodio-bromide plates, a 
 most important feature of that process. 
 
240 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Some experienced landscape pliotograpliers, who know the 
 value of even a little shading to the sky, adopt regularly the fol- 
 lowing plan : When the printing is done, they open one-half the 
 back, and bend the sky end of the print in a curve backwards, 
 and so hold it to the light ; it thus becomes somewhat darkened, 
 and by doing this skilfully, the shading is regular. The amount 
 of trouble is almost nothing, and the gain decided. The writer 
 believes, from an inspection of prints by Bedford, Sowlier, and 
 other masters of the art, that they constantly avail themselves of 
 this method. 
 
 Position. 
 
 The whole picture is generally composed with reference to 
 some one important object, to which all the rest stand in some 
 more or less definite relation. 
 
 Care must be taken that this object (or indeed any object to 
 which it is intended to give prominence) shall not occupy the 
 centre of the picture, which is always the weakest point in the 
 whole. Such an object may be thrown to the right or the left, 
 above or below; it is unimportant, provided it be kept out of 
 the centre. If the conspicuous object improperly placed there 
 be small, it will look like a spot or blot ; if long, as, for example, 
 a tree, it will divide the picture into equal right and left halves. 
 
 It is apt to be a blemish if an object be represented as partly 
 in the picture, and cut off by its edges : it is true that to some 
 extent this is unavoidable, but it is objectionable, especially 
 when the subject so cut off is important. 
 
 Thus, if in a landscape a river is seen to run into one side, and 
 out of the other, a peculiarly unsatisfying impression is left upon 
 the eye, which is removed if the ends of the river are concealed 
 by trees in the foreground, rising ground, buildings, etc. Trees 
 themselves are often unavoidably cut off by the sides and top of 
 the view. This is supported by the eye ; but if a building of at 
 all a conspicuous character appears in the picture, and is partly 
 cut off by the edge, the effect is most unpleasing. With the 
 human figure this is still worse. 
 
 It has been held by some that no figure should be introduced 
 with the eyes directed at objects not themselves included in the 
 picture, and it cannot be doubted that the unity of effect is broken 
 by the spectator's attention being thus drawn away from the ob- 
 jects represented. 
 
COMPOSITION". 
 
 241 
 
 It is still worse when the figures are represented looking at 
 the camera itself. This is the commonest of mistakes. At the 
 moment of taking the picture the camera is of course the central 
 point of interest to all present, and, unless expressly cautioned 
 by the photographer, any person who is in sight will inevitably 
 be found to rest his eyes on that instrument. In a great many 
 cases the figure will give a better effect if the back or side is 
 turned to the camera. Let us suppose that we are looking over 
 the brow of a hill, upon a lake or river below. A figure in the 
 foreground, resting against a tree, and apparently contemplating 
 the scene, will have an infinitely better effect than one apparently 
 watching those operations which it is the special object of the 
 photographer to avoid recalling. In the one case the figure 
 draws attention to, in the other from, the subject of the picture. 
 
 The figure itself should be thoroughly in keeping with the 
 scene. Just as a neat trim villa is a particularly uninteresting 
 subject for a picture, so a carefully dressed person looks com- 
 pletely out of place in any rural scene that is worth planting the 
 camera before. A laborer, a pedestrian carelessly dressed, country 
 children, these are figures in keeping with the subject. If a river 
 or a lake form part of the picture, a man fishing or wading will 
 add to the life of the scene, but his appearance must correspond 
 with surrounding objects. 
 
 Generally speaking, whatever is neat, trim, and elegant, is dis- 
 pleasing in any view of natural scenery. A handsome carriage 
 introduced into the picture will look absurd — a farmer's cart 
 will probably be in place and a great help. It is not so much 
 the object itself, as its condition. A new market wagon, for in- 
 stance, with a glazed top, would spoil any picture. An ele- 
 gantly shaped and prettily painted skiff may look absurd, an 
 old barge or canal-boat will be appropriate and pleasing. A 
 gentleman in a dress coat, with a cane, a lady with flowers and a 
 parasol, introduced into any country scene, will spoil all our satis- 
 faction in observing it, whilst appropriate figures will be always 
 useful ; the rule that such figures must not look towards the 
 camera is never to be forgotten. 
 
 Nor should the figures be placed in too close juxtaposition 
 with the objects of principal interest, from the effectiveness of 
 which they would tend to detract, whereas in weak points of the 
 picture they will prove a positive benefit. They should always 
 assume easy attitudes, and such as will not be ungraceful or ridi- 
 
242 
 
 PHOTOGEAPHIC MANIPULATIONS. 
 
 culous. The writer has seen an otherwise very pretty photo- 
 graph, in which was a male figure reclining on the ground. As 
 the face was towards the camera, the body was foreshortened, and 
 the one conspicuous object about him was the soles of his boots, 
 which exactly faced the spectator, and which, by reason of the 
 violent perspective of a short-focus lens, appeared greatly in- 
 creased in proportionate size. Such errors need only to be under- 
 stood to be shunned. 
 
 The Horizon. 
 
 It is always in the power of the photographer to place the 
 horizon where he will. If there be no subjects presenting per- 
 pendicular lines, the camera may be tilted at will ; if there be, 
 the sliding front may be raised or lowered, or inclination of the 
 lines resulting from tilting may be cured by the use of the swing- 
 back. 
 
 Eaising the horizon line will often increase the beauty of the 
 picture, but, it must be confessed, somewhat at the expense of 
 truth. If a perfectly correct delineation of any scene be desired, 
 the camera must be levelled. Eaising or depressing the camera, 
 entirely alters the relative inclinations of natural objects. Thus, 
 if a road descends a hill, it will equally descend in the picture if 
 the camera be levelled, but the writer has seen such a road repre- 
 sented in a negative as perfectly level, the whole descending effect 
 having been obliterated by inclining the camera downwards. 
 This raises the horizon line, and with it all the objects beyond 
 the foreground. 
 
 Where the object of the photograph is simply to produce a 
 beautiful picture, it is perfectly allowable to modify and improve 
 the scene in any way that we can. But where a truthful repre- 
 sentation is desired, the greatest care will be needed. There 
 exists a mistaken idea that photographs, being taken by mechani- 
 cal means, are necessarily correct representations of natural ob- 
 jects, and they are consequently offered and received as absolute 
 proof in courts of law, whereas nothing is easier than to create 
 false impressions with the aid of photography. No delineation 
 of natural objects is correct unless made with a lens of not less than 
 ten nor more than twenty inches in focal length, with a levelled 
 camera, and with a centrally stopped lens. And before any photo- 
 graph is received in evidence, the photographer ought to be re- 
 quired to testify as to these points ; at least this is true when the 
 
COMPOSITIOlSr. 
 
 243 
 
 question depends upon relative size or position. Of course, if tlie 
 question is simply as to the existence or non-existence of some 
 particular object, the objections here stated do not exist. 
 
 It is an axiom with artists that the horizon lines should never 
 come across the middle of the picture and divide it into two equal 
 halves, but always above or below it. From what has been 
 already said it will be evident that in photographs the horizon 
 line will be more frequently above than below the middle. 
 
 Contrast. 
 
 Some of the highest pleasures which the eye is capable of en- 
 joying depend upon contrast. Contrast is of various kinds. Of 
 lights where the artist throws his deepest darkness against his 
 highest light, thus strengthening both. Of size^ as, for example, 
 where the greatness of the majestic oak is made more apparent 
 by the shrubs or bushes at its base. Of /om, as where the grand 
 elevation of the mountain is further ennobled by the level lake 
 or plain at its foot. Of character^ as when the graceful lines of 
 pine-trees are contrasted with rugged roughness, as in Alpine 
 hills, or where slight and tender vines, with delicate tracery, are 
 seen clinging to strong trees or to the rocky sides of hills, or are 
 contrasted with the rigid lines of architecture. Of season^ as 
 when winter snows look down from the mountain upon summer 
 verdure in the valleys beneath. Of mass, as when light clouds, 
 the lightest of all visible objects, rest upon mountains, which, of 
 all natural objects, give the most striking effect of weight. In a 
 word, the beauty of contrast is that which most completely per- 
 vades all nature. All our ideas are formed by comparison, and 
 contrast is comparison in its most vigorous form. 
 
 The brightest objects in a picture should not be too far from 
 the centre. If placed close to an edge, the effect is very objec- 
 tionable. The tendency of a picture should be to converge atten- 
 tion to the centre, not to scatter it towards the edges. 
 
 Repetition. 
 
 The repetition of lines of direction, as has been already said, 
 is for the most part unpleasing, and this holds with both groups 
 and landscapes. 
 
 But the repetition of objects themselves is often very pleasing 
 The echoing of a near object by a distant one has been already 
 
24:4 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 spoken of, but perhaps the greatest beauty of repetition is where 
 we see objects mirrored in calm water. Few persons are so utterly 
 destitute of the sense of the beautiful as not to appreciate, how- 
 ever imperfectly, the charm of this exquisite reflection. The 
 commonest object may in this way be rendered beautiful and 
 attractive. A log, a branch, a boat, insignificant in themselves, 
 immediately acquire a charm by being repeated in the water. 
 Often the inversion that accompanies reflection materially adds 
 to the charm by the variety which it affords, or by forming, as a 
 reflection often does when looked on in connection with the 
 object itself, a charming symmetrical figure. 
 
 Atmospheric Effect. 
 
 When a scene in nature, embracing objects at various distances 
 from the spectator, is depicted upon a flat surface, we are enabled 
 to distinguish between objects near and distant, in two different 
 ways. 
 
 One of these is Linear Perspective, treated of elsewhere. By 
 virtue of it, distant objects are diminished in size and brought 
 closer together, thus giving to the eye the information that they 
 are proportionately remote. 
 
 But the effect of linear perspective is greatly enhanced by 
 another agency, to which the name of aerial perspective, or, 
 better, atmospheric effect, has been given. 
 
 The atmosphere in its usual conditions is not wholly transpa- 
 rent, but interposes an exceedingly delicate veil, imperceptible 
 ijideed as respects neighboring objects, but becoming more 
 evidently distinguishable as the distance increases. The eye is 
 thus greatly aided in judging distances, which it unconsciously 
 computes by the extent to which the softening effect of the 
 atmosphere reaches. 
 
 If this softening effect of the atmosphere be studied, it will be 
 found to act as follows : — 
 
 1. diminishes contrasts. Dark shadows lose something of 
 their darkness, high lights of their brightness. This opposite 
 effect of the atmosphere on light and on shade needs some ex- 
 planation. Lights lose part of their brightness by reason of the 
 slight opacity of the atmosphere through which they pass. But 
 the darkness of the shadows is lessened by the light which falls, 
 not on them, but on the atmosphere through which they are vievjed. 
 
COMPOSITION. 
 
 245 
 
 We have a familiar example of this in the sky itself, which is 
 only the deep shadow of the outer darkness of space viewed 
 through a not perfectly transparent medium, which medium is 
 itself lighted up by the sun, and, under a well-known physical 
 law, diffuses the more refrangible or violet rays, and transmits 
 the rays belonging to the less refrangible end of the spectrum. 
 In clear weather the sky is deepest in color, because there is less 
 opacity in the atmosphere to receive and reflect the sun's light. 
 On a high mountain the sky is darker still, and at very great 
 elevations appears almost black. 
 
 2. It obliterates details. Smaller objects and parts of objects 
 easily distinguishable when near by, cease to be so in proportion 
 to the distance to which the object is removed, and of this the 
 eye takes due note and recognizes the cause. 
 
 8. It softens outlines. The dead limb of a tree near by, for ex- 
 ample, cuts boldly and sharply on the sky, but the outline of a 
 trunk upon a hill in the middle distance is already somewhat 
 softened, and the outlines of distant mountains are still more so. 
 
 Consequently, atmospheric effect tends to give soft grays and 
 middle tints to distant objects, and to efface all sharp contrasts of 
 light and darkness. Lines also cut each other less sharply. In 
 nature we find a very wide range of variety as to this influence. 
 When the air is very free from moisture, as on some of the arid 
 plains at the base of the Eocky Mountains, atmospheric effect 
 almost disappears, and distant objects appear unnaturally and de- 
 ceptively near. It is not too much to say that the capacity of the 
 Qye for judging correctly of distances is actually destroyed. From 
 this extreme we may pass through every degree to the other, 
 when the air is so laden with mist that near objects seem farther, 
 and distant objects disappear altogether. 
 
 It is a curious fact, and one of the highest importance for the 
 photographer to understand, that both the process which he uses 
 and his lenses themselves may have a great influence on the 
 amount of atmospheric influence which will appear in his pictures. 
 
 The tendency of the ordinary wet process is to give a mode- 
 rate amount of atmospheric effect. The dry processes differ 
 extremely in this respect, according to the preservative used. 
 Thus tannin, cloves, coffee, gallic acid, and similar preservatives 
 tend to diminish atmospheric effect, whilst gum has the very 
 valuable property of enhancing it in quite a remarkable way, and 
 
246 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 thus becomes a most valuable adjunct to other preservatives, 
 though, when well managed, it is capable of acting well alone. 
 
 The lens has likewise something to do with this rendering, 
 though its action has been by some writers a good deal exagge- 
 rated ; it is the size of the diaphragm used that has more to do 
 with the atmospheric effect than the lens itself. 
 
 A large diaphragm will always tend to increase, a small one to 
 diminish, aerial perspective. This is caused in two distinct ways, 
 co-operating to the same result. For a small diaphragm will 
 always greatly increase the depth of focus, so that when the focus 
 has been taken, as it always must be, on near objects, a small 
 diaphragm will cause the distance to be in sharp focus also. This 
 will increase the detail of the distance, and, as it has been already 
 shown that one way in which atmospheric effect shows itself is in 
 tending to obliterate detail, the greater depth of focus necessarily 
 tends to counteract the effect of the atmosphere. Again, a small 
 diaphragm always tends to harshness of contrast, and it has been 
 also shown that aerial perspective especially shows itself by 
 diminishing contrast. Clearly, therefore, aerial perspective will 
 be produced in direct proportion to the size of the diaphragm. 
 This explanation tends to throw additional light upon the fact 
 stated in a previous chapter, that a large stop materially aids the 
 effect of distance by placing objects in their proper planes of 
 distance from the eye. 
 
 It is, however, suf&ciently apparent, from what has been pre- 
 viously said, that lenses will differ somewhat amongst themselves, 
 independently of the diaphragm, as to the rendering of atmos- 
 pheric effect, inasmuch as some have greater depth of focus than 
 others. 
 
 Those photographers who are accustomed to plant their cameras 
 in front of any conspicuous object, satisfied if it covers enough of 
 their plate, and if they can get a clean negative of it, will natu- 
 rally, in the same spirit, endeavor to get the same sharpness in 
 the distance (so far as practicable) as in the foreground. Such 
 will be found working with small diaphragms, and acid baths, 
 and getting technically perfect negatives, which will yield prints 
 that no one cares to look at a second time, prints in which the 
 foreground lies flat upon the middle distance, and both on the 
 extreme distance, which, instead of striking the eye at once with 
 a unity of effect, have to be looked at attentively before the rela- 
 
COMPOSITION. 
 
 247 
 
 tions of tlie different parts explain themselves — in a word, prints 
 whicli are a reproach to photography. 
 
 It must at the same time be very clearly understood that the 
 writer is as far as possible from wishing to say that a photo- 
 graphic landscape should show a clean cut foreground, and a 
 hazy, woolly-looking distance. Ko rules must be carried to 
 excess, or the truth and beauty that result from them are de- 
 stroyed by exaggeration. That objects several miles away should 
 be as distinct and sharply cut as those near at hand, is unnatural, 
 or at least occurs in certain regions and in peculiar states of the 
 atmosphere only, with which we have not here to do. It cannot 
 be right, therefore, and it certainly is not pleasing to an educated 
 eye, that they should be so represented in a photograph or in any 
 other form of delineation. As already said, the landscape painter, 
 with this matter under his absolute control, always softens the 
 distance. 
 
 § 2. — Portraiture. 
 
 What has been said in the foregoing section finds its natural 
 application also to portraiture. Lines must be balanced and sup- 
 ported ; light must be brought out by opposing it to shade, in 
 portraiture as in landscape work. 
 
 To give an agreeable and graceful effect to a single standing 
 male figure, has always been a difficulty which has taxed the 
 genius of artists to evade. When a man clothed in our modern 
 habiliments stands erect, the lines of his arms and legs fall into 
 parallelism with his body, and the objectionable effect of parallel 
 perpendicular lines has been already pointed out (Fig. 113). There 
 is perhaps no effectual way by which, in our ordinary portrait, 
 this difficulty can be disposed of, unless some characteristic occu- 
 pation or position can be adopted. A soldier, for example, may 
 rest upon his musket, a fisherman may have his rod so disposed 
 as to afford a supporting line, and so on; but as the great mass of 
 those who present themselves to be represented by the camera *ak) 
 not care to figure in connection with any particular vocation, it 
 follows that for the most part the best that can be done is to adopt 
 a sitting posture, not in profile unless the back legs of the chair 
 can be supported, and try to relieve this by surrounding objects. 
 Good effects are often obtained by representing the sitter as either 
 engaged in some occupation, reading, playing on some instru- 
 
248 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 ment, examining some object, or, often better, as having just 
 turned from having so done. 
 
 When several male figures are introduced together, their lines 
 may be made to support each other ; but here, again, a photo- 
 graphic difficulty is introduced — the necessity of keeping the 
 heads to a certain extent in the same plane of distance. 
 
 The ingenuity of the photographer will often be here taxed 
 to a severe extent. He may be aided by the following obser- 
 vations : — 
 
 Where two or three heads are present, they should rarely be 
 placed, as so very often seen, on the same level, but should form 
 a pyramidal arrangement, or else fall into the diagonal line. Or 
 the middle head may be the lowest. If a fourth head be intro- 
 duced, it may either fall into one of the lines of the above forms, 
 or the lozenge-shaped composition may be adopted. If more 
 than these are present, they may either have a place in the 
 principal arrangement, or a secondary group may be formed. It 
 is always to be remembered that, in obedience to the exactions 
 of the lens, the farthest figure must be also the most central. 
 
 A group of three persons will generally be the most manage- 
 able. Somewhat less so with two or four. When the number 
 increases, difficulties are multiplied ; when it diminishes to one, 
 the difficulties of getting a satisfactory attitude are, as already 
 said, most serious. A standing portrait of a man gives almost 
 invariably the effect of a person placed for the express purpose 
 oT having his picture taken, and this is apt to be made worse by 
 the conscious look generally assumed by the person. 
 
 The same remarks apply, though to a somewhat less extent, to 
 female portraits. The form of the dress considerably relieves 
 the difficulty, as it represents two opposing inclined lines which 
 tend to support each other. Nevertheless, single portraits of 
 standing female figures are apt to bear a stiff appearance, unless 
 in the hands of very artistic photographers. When sitting, 
 however, this is wholly changed. The drapery can be very much 
 •^ried, and a great support can be got by regulating the folds of 
 the dress so that these shall run in directions which shall relieve 
 and support the other lines of the picture — that is, that some of 
 the lines of drapery shall oppose and support the lines produced 
 by the direction of the body, the position of the arms, &c. The 
 position of the arms can often be regulated in sitting figures, 
 both of men and women, to greatly aid in balancing the lines of 
 
COMPOSITIOISr. 
 
 249 
 
 the body ; and here a thousand expedients come in to give occu- 
 pation to the arms and explain their position. 
 
 In groups of female figures, or of men and women together, 
 the same remarks as those made respecting the positions of the 
 heads for men of course apply. 
 
 Two useful observations remain to be made before we close 
 this very brief section on an important subject. 
 
 The lines which connect the heads of a group, form always the 
 principal lines of the picture. Such lines should never be per- 
 mitted to simply run out and end in nothing, but when carried by 
 the eye to the bottom of the picture, should fall on some object, 
 precisely as already explained in landscape composition. Thus, 
 if a line of direction, when extended by the eye, reaches a table, 
 for example, at the point of intersection there should be placed 
 some small but very distinct object, dark on a light ground, or 
 light on a dark ground. A book, an open letter, or, still better, 
 some object characteristic of the taste or occupations of one or 
 more of the sitters, will be suitable. If a line of direction reach 
 the floor or a wall, the same principle of course holds good. 
 
 Again, a line in some parts of the picture, whose direction 
 crosses that of the main line of the picture, will give an excellent 
 effect by supporting it. This line- may be anything, a cane or 
 staff, any object whatever, even the line of an arm. need not 
 cross the line of direction, only so that its direction does so. 
 
 Thus, let A, B, C, be the heads of any group. A B will be the 
 most important line, opposed and balanced by A C. But, also, 
 
 Fig. 116. 
 
 A 
 
 some other line, D if introduced, will greatly support the line 
 A B and balance the picture. And where the line A B, if con- 
 tinued, would terminate at F, on the ground or elsewhere, there 
 should be some object for it to rest upon, as explained above. 
 17 
 
260 
 
 PHOTOGKAPHIC MANIPULATIONS. 
 
 § 3. — Influence of Light/ 
 
 Our perception of the inequalities of surface, of relative distance, 
 and in fact of the shape and position of bodies generally, de- 
 pends almost wholly upon light and shadow. 
 
 Take, for example, an outline drawing of a building. The 
 eye, chiefly by habit and education, understands that a solid 
 body, and not a flat surface, is intended to be depicted. I say, 
 the eye understands^ for it seems more like a deduction than a 
 perception. 
 
 If now the artist washes in even only a single shade of neutral 
 gray behind each projection, how these projections suddenly start 
 out and strike the eye! As if by magic, the whole building has 
 assumed a visible solidity, and if the work has been correctly 
 performed and the shades duly graduated, the eye instantly recog- 
 nizes the length, breadth, and height of the edifice, and is able 
 to derive whatever pleasure its justness of form is fitted to afibrd. 
 
 Any photographer who frequently passes a public building 
 with many projections, such as are especially to be found in 
 Gothic architecture, and who will stop and carefully study the 
 effects of different lights upon it, will be amply repaid, and will 
 learn more by a few minutes given twenty or thirty times, or still 
 oftener, than by a year's random photographing. 
 
 At times the light is so exceedingly uniform and so broken by 
 clouds, that every portion of a building will be almost equally 
 lighted. So far from this being an advantage, the structure will 
 be found on critical examination to look extremely flat and tame, 
 and if photographed in such a light, its photograph will also be 
 deficient in relief. This great uniformity of light may occur with 
 various amounts of illumination, and though more common in 
 dark weather, will sometimes be seen when the light is tolerably 
 good. 
 
 When the clouds are thinner, a considerable quantity of direct 
 light (without notable sunshine) may pass through them. In 
 this case projections cast faint shadows, and the relief is greatly 
 improved. 
 
 With still thinner clouds, /am^ sunshine passes through. The 
 inestimable value of a very faint sunshine every experienced pho- 
 tographer will fully recognize. Photographs of natural scenery, 
 
 ' See also ante, Remarks. on causes of unsatisfactory results in portraiture. 
 
ON" COPYING. 
 
 251 
 
 taken in the absence of sunlight, are apt to be tame and monoto- 
 nous. A faint sunlight gives an exquisite relief and life to the 
 whole, with beautifully illuminated shadows. 
 
 "When the sun is fully out, and especially towards the middle 
 of the day, the contrasts become excessive, and before the details 
 in the shadows impress themselves, the high lights suffer. 
 
 The case of a building has been chosen as an example, but 
 precisely the same holds good with portraiture. The shape of 
 features, the character and expression of th6 face, all these depend 
 upon light and shade and their due management, j 
 
 In examining the work of professed portraitists, we constantly 
 observe the faults here pointed out as being so easily seen and 
 judged in a building, which last, from its invariable position 
 and (so to speak) expression, enables us to compare the effects of 
 different lights so very advantageously. These faults lie, on the 
 one side, in too uniform a lighting, by which the features are 
 rendered fiat and the expression stupid, or at least less intelligent 
 than the original; and, on the other, in too great contrast of 
 lighting, whereby the character of the features is exaggerated, 
 and the expression rendered stern and hard. 
 
 These two generic faults represent the Scylla and Charybdis 
 of the portraitist, and, with the varying lights of the day, will 
 require his most intelligent efforts to avoid. 
 
 CHAPTBE IX. 
 ON COPYING. 
 
 Copying by photography falls into three classes : — 
 
 1. Copying oil paintings and drawings in color. 
 
 2. Copying mezzotints and lithographs, and drawings in 
 
 Indian ink and sepia, &c. 
 8. Copying line engravings, wood-cuts, pen and ink drawings, 
 and pencil drawings. 
 These three classes will require different treatment, but all the 
 varieties in one and the same class will require the same, or 
 nearly the same, management. 
 
 Old oil paintings, in which the backgrounds have become very 
 
252 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 dark and the colors have lost their brilliancy, are especially 
 difficult to copy; in fact, in many cases, it will be impossible to 
 obtain really satisfactory results. 
 
 The best instructions that can be given are, to use a pretty 
 wide stop, give a long exposure, and use a collodion containing 
 equal parts of bromides and iodides. (See also Chapter XV., 
 Eemarks on keeping plates.) 
 
 In the second class above enumerated, we included subjects 
 which, though in monochrome, present gradation of tint. These 
 will require to be treated, through all the stages, very much as 
 views, and with the same care to avoid harshness and excess of 
 contrast. 
 
 On the contrary, the third class will require a widely different 
 treatment. With these the object will be to get, not to avoid, 
 strong contrasts. The originals are composed of only white and 
 black, the half-tints depending upon the presence of more or 
 less of each of these constituents. A white and black negative 
 will therefore be wanted. 
 
 But it is an entire mistake to suppose, as was for a long time 
 believed, that this was best accomplished by the use of a collo- 
 dion containing little or no bromide. The author of this book 
 long since pointed out that copying was best done with ordinary 
 landscape collodion. Iodide of silver is more sensitive to a strong 
 light, bromide to a weak light. Now, as line engravings require 
 to be copied with a very small stop, the light is always weak, 
 consequently bromide is needed ; and this view is fully supported 
 both by direct experiment and by common experience. 
 
 To obtain a fine copy of a line engraving, in which the hair- 
 lines are to be faithfully and sharply reproduced, requires a good 
 lens, well managed. The stop must be very small, not exceeding 
 / 60, or one-sixtieth of the focal length. The lens should be a 
 large one. 
 
 Copying is the most delicate and difficult branch of photo- 
 graphy. The faint light admitted by the small stop cannot form 
 a brilliant image; the attraction to the developer is therefore 
 'weaker, and the tendency to the production of stains is greater, 
 whilst no department of photography requires so absolute an 
 absence of stains as this. Consequently, photographers generally 
 confine themselves to the central parts of the plate, or at least 
 leave a border of an inch or more around the image, as it is the 
 borders that are most exposed to these troubles. 
 
ON COPYING. 
 
 253 
 
 The bath must necessarily be in good order, giving clean, 
 blooming negatives. The developer must have a full, though 
 not excessive, dose of acetic acid. The development must not 
 be prolonged, but be rather a brief one, and if a very strong 
 negative be wanted, recourse must be had to after-intensification. 
 
 The best means of effecting this is to place the plate in a solu- 
 tion of corrosive sublimate until it becomes entirely white, and 
 then to flow it with a 1-grain solution of cyanide of potassium. 
 The cyanide instantly blackens the negative, whilst at the same 
 time it clears away all tendency to veiling, if any existed. 
 
 Another excellent method is to chlorize the paper, and then to 
 apply Schlippe's salt. (For details of both methods see p. 173.) 
 
 But, for the most part, an ordinary development, followed if 
 necessary by a re-development, after fixing, will be sufficient, re- 
 membering, however, that neither development nor re-develop- 
 ment should be pushed. The re-developing liquid should be 
 used no longer than it is quite colorless, instead of serving, as 
 in other work, as long as it is clear. Heavy deposits of silver, 
 if allowed, will evidently clog up the finer lines. 
 
 The lens to be used must be free from distortion, and have as 
 flat a field as possible. The old orthoscopic lens, now rarely 
 made, copied excellently. The view lens is unsuitable. Almost 
 any centrally stopped lens, except the portrait combination, may 
 be used with success, the Zentmayer, Steinheil aplanatic, Dall- 
 
 Fiff. 117. 
 
 meyer rapid rectilinear, Eoss's doublet, the triplet, from any of 
 these, if a good specimen of its class, good work may be expected. 
 As the focus is always longer in proportion as the size of the 
 
254 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 image is large compared with the object, it follows that for copy- 
 ing, the camera will often need to be lengthened out, and this is 
 done with an " extending cone." Fig. 117 represents a form 
 devised by the writer, in which the flap 0 is hinged on to the 
 cone, and serves to support and steady it. The cone at B ex- 
 tends beyond the tube of the lens, so as to form a sort of hood, 
 excluding extraneous light. Unless means are taken to prevent 
 extraneous light from falling on the lens, brilliant and clear 
 copies cannot be obtained. 
 
 Generally speaking, it is best to place a line engraving in 
 full sunshine, which should fall on it in a direct line, and not 
 obliquely. The more slanting the direction of the sun's rays, 
 the more conspicuously will the grain of the paper, and also 
 other irregularities, be rendered in the negative. By using direct 
 sunshine, it becomes possible to work with the smallest stop fur- 
 nished with lens, thereby reducing the astigmation (p. 61) to a 
 minimum, and so to obtain the hairlines in the high lights of the 
 engraving, accurately reproduced. 
 
 For copying Daguerreotypes, sunlight reflected by a mirror 
 gives excellent results. Photographs may be copied in the same 
 way, or by a good strong out-door diffuse light. They do not 
 need so very small a stop as line engravings do, and consequently 
 not so brilliant a light. 
 
 Mechanical Appliances. — When an old picture is to be copied, 
 it will be well cleaned and then hung up in the sunshine. (It 
 seems probable that an application of glycerine would give a 
 clearness and brightness that would materially aid in copying. 
 Afterwards the glycerine could be easily removed with a wet 
 sponge.) Fix the camera so that each corner of the picture shall 
 be equally distant from the centre of the front lens, and take 
 care that all parts of the picture shall be equally illuminated, 
 also that the direction of the sunlight shall be such that no re- 
 flections shall reach the lens. 
 
 The copying of engravings and smaller pictures may be done 
 in the same way. But it is more convenient to make a special 
 arrangement as follows : — 
 
 A square piece of wood of convenient size is placed upright 
 upon a long narrow table, giving the piece of wood the same 
 breadth as the table. At the sides of the board (see Fig. 118) 
 strips two or three inches wide are fastened, coming some inches 
 
THE STEREOSCOPE. 255 
 
 below the table top, and fitting close np to it. These act as guides, 
 so that when the square piece of wood is pushed backwards or 
 
 Fig. 118. 
 
 forwards, it always retains a position at right angles to the long 
 side of the table. Behind another narrow strip is fastened, to 
 act as a base and keep the board vertical. Diagonal lines are 
 drawn from the corners, fixing the centre. The camera is raised 
 on blocks until the middle of the lens is opposite the intersection 
 of the diagonals. 
 
 If now we place any object to be copied on the centre of the 
 board, which the diagonals easily enable us to do, we have 
 simply to move the board backwards and forwards until the size 
 and the focus are obtained. The general arrangement secures 
 what is always essential in copying, viz., that the object to he copied 
 shall he exactly parallel with the focussing screen. In the arrange- 
 ment here described, the camera is always kept with its sides 
 exactly parallel to the table, then the board being at right angles 
 with the side of the table, the necessary parallelism is insured. 
 
 Plans may be well copied by simply laying them on sensitized 
 paper and exposing. This gives a paper negative, which is to be 
 laid on other sensitized paper and exposed— if the resulting posi- 
 tive is not strong enough, it is brought up by development. 
 Plans of several feet square, made for the Treasury Department 
 at Washington, are thus beautifully multiplied by Mr. Walker, 
 the photographer of the department. 
 
256 
 
 PHOTOGRAPHIC 
 
 MANIPULATIONS. 
 
 CHAPTEE X. 
 
 THE STEREOSCOPE. 
 
 This ingenious invention of Prof. Wheatstone depends upon 
 the fact that the two eyes see the same objects differently in con- 
 sequence of their difference of position. If we view a collection 
 of objects, as, for instance, trees in a grove, and then moving 
 our position by a few yards, we view them again, their relative 
 positions will seem changed. A smaller change produces this 
 in a lesser degree, and even the space between the eyes cor- 
 responds to a change of aspect, which, small as it is, aids greatly 
 in fixing relative positions. This will be better exemplified as 
 follows : — 
 
 Let the polygonal figure (Fig. 119) be viewed by the eyes B 
 and E'. Its distance from them and its size may easily be 
 imagined such that the eye E will see the five 
 sides, 1, 2, 3, 4, 5 ; whilst E' will see the five sides, 
 2, 3, 4, 5, 6. The eye has, by long experience, 
 learned unconsciously to combine these two por- 
 tions of the polygon, and to understand thereby 
 that it is a solid body, and not a mere projection 
 on a flat plane. 
 
 If we suppose, instead of the polygon at Fig. 
 119, that we look at a pillar, of a portion of which 
 that polygon is a section, the mind realizes that 
 it is a solid body by its consciousness that the one 
 eye sees partly round it on the one side, and the 
 other upon the other side. 
 
 If then, whilst viewing any scene, we close 
 first the one eye and then the other, it is evident 
 that we shall see slightly different scenes with the respective eyes, 
 the combination of which two scenes gives us a distincter sense 
 of distances and positions, than what would result from observa- 
 tion by either eye separately. 
 
 Now, if we place two lenses in positions of distance corre- 
 sponding with that of the two eyes, each will be capable of pro- 
 
MICROSCOPIC PHOTOGRAPHY. 
 
 257 
 
 ducing an image corresponding with those seen by the separate 
 eyes. And if these pictures be placed side by side before the 
 eyes, and each be looked at by one eye separately, these two 
 images may be combined by the brain, precisely as the two views 
 seen by the eyes in observing a landscape. Such pictures are 
 made in the stereoscopic camera^ in which, however, the lenses are 
 placed somewhat farther apart than the distance which separates 
 the human eyes, it having been found by experiment that the 
 efiect so obtained is more striking than if the actual distance 
 between the eyes were maintained with the lenses, which also it 
 would not be easy to carry out in practice. 
 
 All the operations with the stereoscopic camera are precisely 
 the same as with the ordinary, except the mounting of the prints 
 when finished. These should be cut with care to a convenient 
 size, keeping the centres of the cut prints to correspond as nearly 
 as possible with the point directly opposite the centre of the lens. 
 
 In pasting, they must be reversed, that is, the print which is 
 on the right hand side as printed, must be mounted left. It has, 
 •however, been shown that this may be avoided by cutting the 
 sensitized paper to twice the length of the negative, and folding 
 its ends till they meet at the centre. 
 
 The figure represents the paper loosely folded. B and G are 
 pressed down till the edges EE' meet. The sensitive side of the 
 paper is outermost. Apply the side 
 B Gto the negative ; a print is taken. ^^S- 120. 
 
 The sheet is then turned round and 
 the other side printed. Cutting 
 through at A, and opening out, B 
 and the piece behind it give one 
 print, and G and that behind it, 
 
 another, each with the sides cor- 
 rectly placed for mounting, and not needing to be reversed, 
 
 A pair of stereoscopic views may be obtained with a single 
 lens. The two views are taken separately, and the camera moved 
 a little laterally for the second view. 
 
 The stereoscope, which for some time enjoyed an almost un- 
 bounded popularity, has latterly been much less prized. Larger 
 views, from half size to 10 x 12, are capable of so much more 
 artistic effect, that they are taking the place, and deservedly, of 
 the stereoscopic slides, and will, no doubt, increasingly in future. 
 
258 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 CHAPTEE XL 
 
 MICEOPHOTOGRAPHY AND MICROSCOPIC PHOTOGRAPHY. 
 
 The first of these processes has for its object the production of 
 extremely small images of objects intended to be viewed by the 
 microscope. The second is the impression upon a collodion film 
 of the image seen in the microscope, 
 
 § 1. — Microphotography. 
 
 If a negative be placed in a suitable apparatus, and its image,' 
 extremely reduced in size, be thrown by a very short focus lens 
 upon a sensitized albumen plate, that image may readily be de- 
 veloped by appropriate means, and a sharp fine positive image 
 be got, which, when viewed by a sufficient magnifying power, 
 may exhibit satisfactory detail if all the manipulations have been 
 well performed. The process evidently involves no real difficulty, 
 except that the image is so exceedingly small that its develop- 
 ment requires to be followed by the microscope. 
 
 The form in which this description of work first attracted public 
 attention was in the reproduction of objects which, by magnify- 
 ing, were made to exhibit striking details, lettering, for example. 
 A monumental tablet, for instance, reduced until much smaller 
 than a pin's head, when placed under the compound microscope, 
 showed many lines of lettering, all perfectly distinct. 
 
 Surbsequently, however, M. Dagron gave a new impetus to the 
 matter by substituting for the microscope a modified Stanhope 
 lens, having one end a plane surface, to which the microscopic 
 print was attached permanently by Canada balsam. These lenses 
 were manufactured out of glass rods at an infinitesimal price, and 
 enormous quantities have been sold in Paris. In this country 
 they have attracted but little attention. 
 
 In the late war between Germany and France, immense use 
 was made of microscopic photographs, by sending them on coUo- 
 dium plates with the aid of carrier pigeons, into Paris. 
 
MICROSCOPIC PHOTOGRAPHY. 
 
 259 
 
 § 2.— Microscopic Photography. 
 
 In microscopic photography the images are enlarged greatly 
 above the natural size. The operation differs from ordinary en- 
 larging, both in its object and method. 
 
 In ordinary enlarging, the object is usually to reproduce from 
 a small negative a large paper picture, though we also may 
 obtain enlarged negatives on glass. But in microscopic photo- 
 graphy the object is to get negatives, large or small, of micro- 
 scopic objects, often enormously enlarged. 
 
 Dr. Woodward, of the U. S. Army, has far exceeded all other 
 experimenters in this direction, whose results have come under 
 the writer's notice. Amongst other interesting specimens re- 
 ceived from him are images of test plates made with different 
 kinds of light. The effects obtained with sunlight are altogether 
 inferior to those yielded by the artificial lights, and of these the 
 magnesium light and the electric light obtained with carbon 
 points gave better results than the calcium light ; even the latter, 
 however, proved itself far superior to sunlight, the inferiority of 
 which last could hardly have been anticipated in the absence of 
 decisive tests. 
 
 A powerful beam of light, from any of these sources, is thrown 
 through a compound microscope, and the image is received upon 
 a sensitized collodion film. An ordinary nitrate bath was used 
 by Dr. Woodward, with the author's collo-developer (see p. 164) 
 and an after-intensification with Schlippe's salt, or with mercury. 
 
 By these methods Dr. Woodward has been "enabled to pro- 
 duce pictures of the utmost sharpness, and perfectly satisfactory 
 in every other respect, with powers up to two thousand and five 
 hundred diameters, and these pictures bear a further enlargement 
 of from six to eight diameters in a copying camera. We have 
 thus obtained excellent pictures up to ten thousand diameters." 
 
 Ordinary collodions were found to work very well. For great 
 enlargements, where the light was weak, a collodion containing 
 two grains of bromide of magnesium and five of iodide of magne- 
 sium was found useful, the deliquescent action of the nitrate of 
 magnesium formed preventing the drying of the film. 
 
 With the very highest powers, such as Powell & Lealand's 
 one-fiftieth objective, the correction of the objective to suit the 
 violet light was found to be so small as to be practically unim- 
 portant. But with one-eighth, for example, it was found to be 
 
260 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 essential. As a general thing, images taken with the one-eighth 
 and enlarged, gave results as good as those obtained directly with 
 the one-fiftieth. 
 
 Drs. Woodward and Curtis have obtained many valuable mi- 
 croscopic photographs by this process, which is exceedingly well 
 adapted to increase our knowledge of the structures of animal 
 and vegetable tissues. The writer has received from them beau- 
 tiful enlargements of minute bloodvessels and blood-corpuscles, 
 etc. One of their most successful amplifications has been that 
 of the Pleurosigma angulatum, of which they have obtained good 
 photographic prints on paper, magnified up to nineteen thousand 
 diameters. 
 
 CHAPTER XIL 
 
 DEVELOPMENT ON PAPEE. 
 
 § 1. — Positive Development on Chloride of Silver. 
 
 Development on paper requires to be differently managed 
 according as we wish to obtain positives or negatives. These 
 operations will be considered under difi'erent heads, commencing 
 with positives. 
 
 Positives may be developed on paper with the aid of either 
 iodide, bromide, or chloride of silver, or with a mixture of these 
 substances. From his own trials, the writer long since decided 
 on chloride as being the best, and the process published by him 
 several years ago has been largely adopted with or without con- 
 siderable variations. 
 
 If paper be impregnated with chloride, bromide, or iodide of 
 silver, be exposed for a short time under a negative, and then be 
 thrown into a saturated solution of gallic acid, a picture will 
 soon be developed, which will go on increasing in strength, and, 
 when satisfactory, may be taken out, washed, and fixed. Such 
 was the original idea of development, which we owe to the late 
 Eev. J. B. Reade, though it was shortly after taken up and per- 
 fected by Mr. Fox Talbot, to whom, by many, it has been as- 
 cribed. Both these experimenters operated with iodide of silver, 
 and turned their attention rather to negative development than 
 positive. Some years later, Blanquart Evrard took the process 
 up, used a mixture of bromide and iodide of silver, fumed with 
 hydrochloric acid, and toned his pictures with hyposulphite and 
 
DEVELOPMENT ON PAPER. 
 
 261 
 
 gold. His results were magnificent, and for a while it was as- 
 serted that none of his pictures had ever been known to fade. 
 With increasing lapse of time, however, this has ceased to be 
 true, and his pictures have in some cases faded. 
 
 The process which the writer brought forward was based upon 
 the use of lead in connection with gallic acid. It had been known 
 before that the addition of acetate of lead to gallic acid greatly 
 increased its powers of action, but as a precipitate was formed, 
 rendering the liquid muddy, this objection interfered with the 
 use of the lead salt, and the fact remained without application. 
 
 Having ascertained that gallate of lead, the precipitate formed 
 when acetate of lead was added to gallic acid, was soluble in 
 acetic acid, the writer applied this observation to development 
 both positive and negative, and with excellent results, especially 
 in the former case. The economy of gallic acid was enormous, 
 the rapidity of development was heightened, and, what was of 
 far more consequence, the clearness of the development was 
 greatly enhanced, so that of all kinds of development, this was 
 the safest and least liable to accident. The course was so regu- 
 lar and uniform that many prints could be developed at once, and 
 the bath kept in working order for a longer time and with a 
 greater number of prints. This was probably because the large 
 quantity of acetic acid used restrained the precipitation of the 
 silver, whilst the action of the lead expedited the development. 
 
 The following are the details of this process. 
 
 For a twenty-four ounce developing bath, dissolve four grains 
 of gallic acid in a few ounces of water, and add about half an 
 ounce of a solution of acetate of lead, thirty grains to the ounce, 
 of which a stock may be conveniently kept on hand. A thick 
 white precipitate falls. Next add acetic acid till this precipitate 
 redissolves — a little excess of acetic acid does no harm, but is 
 rather beneficial. Filter this and dilute to twenty ounces. To 
 four ounces of water add a few drops of solution of nitrate of 
 silver from the positive printing bath, and mix with the rest. 
 
 These various operations should be performed a short time 
 only before the bath is wanted, as naturally it will not keep. 
 
 The development may be effected either on plain or on albu- 
 menized paper. It is commonly believed, universally it might 
 be said, that development on albumenized paper is impossible, 
 but this is a mistake. The treatment of the paper must be dif- 
 ferent, but either sort will develop in the foregoing bath. 
 
 To develop on plain paper, float it for one minute upon a five- 
 
262 
 
 PHOTOGRAPHIC MANIPULATION'S. 
 
 grain solution of sal-ammoniac. Sensitize on a nitrate bath acidu- 
 lated witli tartaric acid, as follows : — 
 
 Nitrate of silver 1 ounce. 
 
 Tartaric acid 26 grains. 
 
 Water 13 ounces. 
 
 Grood results can be obtained with half this strength, but for 
 general use it is not advisable to economize the silver so much. 
 It is almost superfluous to say that this sensitizing, and the 
 placing in and taking out of frames, will be performed in a room 
 by yellow light, and not as in the preparation of ordinary posi- 
 tive paper. The same care in excluding white light as in the 
 wet collodion process must be exercised. 
 
 The paper, when dry, is placed under a negative and exposed 
 to light, direct sunlight is best, for from fifteen to sixty seconds, 
 according to the light, the season, and the negative. The writer 
 advises to continue the exposure until the image reaches a pale 
 chocolate color. Some stop at the pale violet. Good results are 
 got either way, but the former seems preferable. Of course the 
 frame must not be opened for examination. 
 
 It is a mistake to. assert, as some have done, that no details are 
 got in the development that were not visible faintly in the print 
 when taken from the frame. On the contrary, much that is not 
 any way visible, comes out distinctly in the development. 
 
 In fact, the writer has proved this capacity of chloride to yield 
 details in development, which were originally invisible, in rather 
 a striking manner. A piece of paper sensitized with a chloride 
 only, was taken and placed behind a negative, and a single mag- 
 nesian spiral was burned at a little distance. On removing the 
 paper nothing was visible, but the careful application of a de- 
 veloper brought out the image with all the details, in a surprising 
 manner. The details were as full as if iodide of silver had been 
 used, but the picture was very flat. 
 
 When, then, the print is judged to have been sufl&ciently ex- 
 posed, it is removed from the printing frame, and plunged evenly 
 and quickly into the developing bath. With the bath- above 
 described, the development requires about five minutes to com- 
 plete it. The prints should generally be stronger than they are 
 intended to be when finished, for they lose in the fixing. 
 
 As soon as the print is judged to be sufficiently developed, it 
 is thrown into water to stop the action, and is then toned with 
 gold precisely in the same way as with any other positive on 
 paper. If not toned, it will have an unpleasant coppery color, 
 
DEVELOPMENT ON PAPER. 
 
 263 
 
 which seems almost unavoidable in developed prints. The writer 
 has, however, obtained a pleasant purple tone by using serum of 
 milk (whey, see foot of p. 264) in the salting of the paper. 
 
 It will be seen that the above bath, though containing only 
 one-sixth of a grain of gallic acid to the ounce, acts much like 
 an ordinary developing bath, made twenty times stronger. This 
 shows how remarkable is the agency of lead in increasing the 
 activity of gallic development. 
 
 For albumenized paper a larger dose of tartaric acid is ad- 
 visable. Take — 
 
 Nitrate of silver 1 ounce. 
 
 Tartaric acid 36 grains. 
 
 Water 13 ounces. 
 
 Float on this ordinary albumenized paper for two to three 
 minutes, and then proceed otherwise as before. 
 
 Paper prepared in this way, although albumenized, bears de- 
 velopment very well, and gives good results. Not so good, how- 
 ever, either on albumenized or plain, as with sun-printing, though 
 sometimes not far behind. Still, it must be said that when the 
 sun's light is left to do its perfect work, that work is better and 
 more completely done than when we break it off just commenced, 
 and force our solutions to complete it. It would seem that it 
 could not be otherwise. There is less depth in the shadows and 
 less brilliancy. The developed print is apt to be softer than the 
 direct sun print, and shows less contrast ; it is also more sunk in, 
 and shows the grain of the paper more. And, although the de- 
 velopment can be efiected on albumenized paper, it is more diffi- 
 cult and less certain than on plain. 
 
 This last described paper has good keeping properties. If 
 placed in a tight tin case, thoroughly protected from light, it 
 shows but little tendency to spontaneous decomposition, and I 
 have succeeded in developing a perfectly clean picture, after an 
 interval of at least ten days aftei* sensitizing. 
 
 § 3. — Negative Development on Paper.' 
 
 Calotype Process. — Float paper on a 20-grain plain solution of 
 nitrate of silver, and then, after drying, upon a 25-grain solution 
 
 ' An interesting negative process on paper, by Mr. H. J. Newton, will be 
 found in the Philadelphia Photo gra-pher, vol. iv. page 187. The writer regrets 
 that space will not allow him to extract it in full. 
 
264 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 of iodide of potassium ; on the first solution for one minute, on 
 the second, ten minutes. Dip in water to wash off the excess of 
 iodide and dry. In this condition the paper keeps well, if pro- 
 tected from light. 
 
 Make now 6 ounces of cold saturated solution of gallic acid, 
 dissolve 300 grains nitrate of silver in 6 ounces of water, mix the 
 two and add an ounce of strong acetic acid. No more of this 
 sensitizer should be made than is needed, as it will not keep more 
 than a few hours. Therefore, in sensitizing a few sheets it is 
 better to make much less and brush over the paper instead of 
 floating. Whether dipped or floated, the solution is left on but 
 a minute; the sheet is dipped into water, the excess of moisture 
 blotted off with bibulous paper, and the sheet is ready for use. 
 A very brief exposure is sufficient to form an image which will 
 go on strengthening in the dark, or may be hastened by washing 
 over with the sensitizing mixture, just above described, and 
 holding to the fire. 
 
 This process gave excellent results, and was long a great 
 favorite, until the collodion process superseded it. The negative 
 so obtained may be paraffined as follows. 
 
 Paraffining. — Take a fine translucent paraffine candle — not the 
 paraffine that resembles spermaceti, but the very translucent 
 sort — and scrape it down to shreds with a knife or piece of broken 
 glass. Strew some of these on a piece of filtering paper, lay the 
 negative upon them, put more shreds on the negative, then another 
 piece of filtering paper, and iron with a right warm, but not hot, 
 flat-iron. If on looking at the negative it is not found to be 
 moist all over, put more shreds on the dry part, and repeat. 
 
 Wax Paper Process. — Legray showed that paper might be first 
 waxed, and that, even after this, it would take up sufficient iodide 
 of potassium if immersed in the solution, to admit of sensitizing 
 on solution of nitrate of silver and exposing in the camera. Serum 
 of milk, or whey, was found useful in this process, and the writer 
 has used it with good effect in developing positives. After wax- 
 ing good photographic paper with fine bleached wax, soak it for 
 an hour in — 
 
 Serum of milk ....... 25 ounces. 
 
 Milk sugar • h ounce. 
 
 Bromide of potassium 48 grains. 
 
 Iodide of " 180 " 
 
 To obtain whey, heat the milk to boiling, add a very few drops 
 of acetic acid till it turns, then the white of an egg to clear, and 
 
DEVELOPMENT ON PAPER. 
 
 265 
 
 filter through paper. Milk sugar can be had of the druggist. 
 Dry and put away between folds of paper. Sensitize, when 
 wanted, on a thirty-five grain solution of nitrate of silver to 
 which glacial acetic acid has been added in the proportion of one 
 ounce of acid to fourteen of bath. Immerse in two waters suc- 
 cessively, dry between folds of blotting-paper. Expose in the 
 camera either between two pieces of plate glass, or else paste the 
 edges of the paper over the edges of a piece of glass. Develop 
 with a saturated solution of gallic acid, to which nitrate of silver 
 has been added in the proportion of one grain to two ounces of 
 gallic acid solution and a little acetic acid. Probably the lead 
 developer, already described, would be every way better. (See 
 section 1 of this chapter.) 
 
 § 3. — Paper Enlargements. 
 
 Life-sized portraits may evidently be obtained in the same way 
 as ordinary portraits, provided we proportionately increase the 
 size of the lens. But unfortunately the defects of lenses increase 
 with their size, and this is especially true with respect to depth 
 of focus. The larger the lens, therefore, the more difficult it will 
 be to get different parts of the subject simultaneously in focus, 
 and consequently, while it is by no means impossible to take life- 
 sized portraits direct, it is much more common to effect this object 
 by enlarging, with the aid of a solar camera, from a small nega- 
 tive, generally made expressly for this purpose (see p. 177). 
 
 Enlargements^ printed by the solar camera, may be finished in 
 the camera, that is, the whole work may be done by sun-printing, 
 precisely like printing in a frame. But the method of develop- 
 ment is also practicable, and this may be done in the manner 
 already described, by chloride development, or, at the option of 
 the operator, the negative process on bromo-iodized paper may 
 be used, of course without taking means to render the paper 
 transparent. But as the negative process is specially intended 
 for those cases where the illumination is very weak, as in the 
 camera obscura, and as the light of the solar camera is always 
 abundant for chloride development, that process will give the 
 most satisfaction, provided, as before said, that the operator de- 
 sires to develop, and not to finish in the usual way. Also when 
 the picture has been supposed to be finished, and has been found 
 to be too weak, development may be resorted to to bring it up. 
 18 
 
266 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 4. — The Solar Camera. 
 
 The apparatus for enlarging from a small negative may be 
 arranged in several different methods; these instruments are 
 known as solar cameras. 
 
 Woodward's Camera. — In this instrument the solar rays are 
 received upon a mirror of silvered (not quicksilvered) glass, 
 whose ofi&ce it is to reflect them horizontally. They then pass 
 through a plain convex flint glass condenser of eight inches in 
 diameter. 
 
 Fig. 121. 
 
 R B parallel rays from the sun falling upon the mirror 
 which reflects them horizontally through the opening in the wall 
 W W of an apartment. Inside is the condenser G C, which con- 
 verges them to a focus where a photographic objective is 
 placed. A negative N being interposed between the condenser 
 and the objective, its magnified image is formed on the screen. 
 In Woodward's apparatus the lens at F is an ordinary portrait 
 objective. 
 
 The mirror if is mounted with racks and pinions, and requires 
 to be moved every few seconds to keep the rays horizontal. 
 
 Van Monckhoveri's Camera. — The objection made to Woodward's 
 apparatus has been that the condenser was not large (eight inches 
 diameter), and consequently the working was slow. The size 
 could not be increased without introducing much spherical aber- 
 ration and injuring the sharpness of the image. 
 
 To avoid this evil. Van Monckhoven introduced a negative lens 
 behind the condenser, a thin meniscus, and also replaced the ob- 
 jective by one of a construction devised by himself. 
 
 Light is thrown upon the apparatus in the same way as with 
 Woodward's. Or a heliostat may be-very advantageously applied 
 to any solar camera. In this instrument the mirror is regulated 
 
DEVELOPMENT ON PAPEK. 
 
 267 
 
 by clock-work, so that it moves witk the sun and takes always 
 such an angle that the rays reflected by it fall horizontally upon 
 the condenser. 
 
 Very good work has been executed with Yan Monckhoven's 
 camera. 
 
 Other Solar Cameras. — The same optical principle which was 
 adopted by Woodward, has been made the basis of a number of 
 different arrangements, by Shive, Eoettger, Fontayne, Gales, Car- 
 butt, and others. In Shive's, Eoettger's, Fontayne's, and Carbutt's 
 the direct rays of the sun are used without a reflector. The dif- 
 ference in these instruments depends upon the mechanical con- 
 trivances applied to carry out the optical arrangement. In all a 
 plano-convex lens is placed with its convex side to the light. 
 Between its posterior surface and its focal point the negative is 
 introduced. At its focal point the photographic objective is 
 placed, and the image is thrown upon a screen in the back of the 
 camera. Eoettger claims for his, to which he gives the name of 
 "parallactic," a greater facility for following the sun's path. 
 The most recent modification is Carbutt's, which is itself a modi- 
 fication of Stuart's; in it the whole tripod moves. The base of 
 the tripod is a triangle, moving upon a hinge at one corner. 
 The corner falls directly under the condensing lens ; this gives 
 a facility for making a great angular movement in a very little 
 space. The apparatus is mounted permanently in a room at the 
 top of the house. A section is removed from the south end of 
 the roof, to admit the direct sunshine. 
 
 It will be seen that the only modification of the optical prin- 
 ciples of Woodward's camera which has been made is that of V. 
 Monckhoven, who introduced the negative meniscus into it, to 
 correct the spherical aberration, and thereby enable him to use 
 a larger condenser. The size of the condenser is of material im- 
 portance, for on it depends the intensity of the image. Wood- 
 ward's condenser was eight inches in diameter, while Y. Monck- 
 hoven was enabled to raise his to twenty. The time required 
 for printing an enlargement of a given size with the two would 
 be approximately inversely as the squares of the diameters, 
 namely, as 400 to 64, or as 6 to 1, or thereabouts. 
 
268 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 5. — Printing by the Solar Camera. 
 
 Little special need be said on this head. Albumenized paper 
 is attached to the screen, and the image gradually appears, re- 
 quiring a time which may extend from half an hour to many 
 hours to reach full strength. 
 
 This slow printing, requiring, as it does, incessant attention to 
 keep the apparatus duly placed as respects the sun, unless the 
 operator possesses a heliostat, is very objectionable and annoying, 
 and therefore leads to the extensive use of development in order 
 to shorten the time. This part of the subject has been already 
 explained. 
 
 Efforts have been made to shorten the time required for sun- 
 printing. That of M. Yan Monckboven, founded upon the use 
 of nitroglucose, has been well spoken of, but does not seem to have 
 passed into general use. The nitroglucose process may be used 
 either for direct printing or for enlargement. 
 
 Nitroglucose is prepared by adding one part of pulverized 
 sugar to one of sulphuric acid previously mixed with one of 
 monohydrated nitric acid. After an action of about five minutes, 
 the mass is to be removed from the acid and washed with cold 
 water. This crude nitroglucose is to be purified by dissolving 
 in alcohol and precipitating by adding water, in which it is in- 
 soluble. 
 
 This nitroglucose, according to Dr. V. Monckhoven, does not 
 precipitate nitrate of silver, but acquires that property if its alco- 
 holic solution is kept for eight or ten days at a temperatue of 
 110° F. Its application is as follows : the paper is passed through 
 an alcoholic solution ten grains to the ounce, is hung up to dry, 
 and is then immersed for two hours in an ordinary salting solu- 
 tion. Next, sensitized on a twenty-five grain plain solution of 
 nitrate of silver, and hung up to dry. So prepared, it keeps for 
 many months. 
 
 In use, the paper is exposed in the solar camera for about a 
 minute, and is then developed with gallic acid five grains, water 
 ten ounces, glacial acetic acid fifty minims. The author of the 
 process claims for it that a gallic development causes albumenized 
 prints to turn yellow in the whites, whereas with the nitroglucose 
 process the whites remain perfect. Now, when the development 
 on albumenized paper is carefully conducted on the principles 
 laid down in this manual, the whites do not tuila yellow. More- 
 
SILVER PRINTING. 
 
 269 
 
 over, V. Monckhoven observes that the operation for making nitro- 
 glucose is so delicate that the method would be useless were it not 
 for a modification discovered by him, and as yet unpublished. 
 
 The writer has himself prepared nitroglucose, and found no 
 difficulty whatever in it. He has found it advantageous to sub- 
 stitute fuming sulphuric acid for one-half of the ordinary acid. 
 The mixed nitric and sulphuric acids must be allowed to cool 
 thoroughly in a covered vessel after mixing, powdered white 
 sugar is then stirred in, enough to make a thin paste. Soon a 
 kind of grayish dough makes its appearance, which is at once 
 removed with a spatula and thrown into water. This is con- 
 tinued till the dough ceases to form, when a little more sugar 
 may be added, though its yield will be much less in proportion 
 than that of the first. 
 
 The nitroglucose must at once be kneaded up with water to 
 get out the excess of acid with which it is saturated, and which 
 by remaining in it might cause its decomposition. For completer 
 purification, the nitroglucose is dissolved in alcohol and precipi- 
 tated by water. The alcoholic solution should be poured into 
 water (not the reverse), with constant stirring. The nitroglucose 
 separates a thin dough, which is to be washed by agitating with 
 several waters, and then should be kept under water. 
 
 CHAPTER XIII. 
 
 SILVER PRINTING. 
 
 Elementary directions will be found in the Introduction. 
 Here will be given some special remarks on the various branches 
 into which the subject divides itself, including the description of 
 a new and hitherto unpublished method of sensitizing paper for 
 positive printing, recently devised by the author, and which has 
 for its object the preparation of paper which can be kept for a 
 long time after silvering, without deterioration, and ready for use 
 at any moment. (See sec. 6.) 
 
 § 1. — Selection of Paper. 
 
 The paper preferred in this country almost universally is the 
 Saxe paper, of which the genuine is manufactured by Steinbach, 
 
270 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 and of which there are many imitations. Some of Marion's paper 
 is also sold here, often as "Saxe paper," even as the writer has 
 seen done, with Marion's name water-marked on the edge. "Eive" 
 paper is little known here, nor Canson. Whatman's paper, much 
 liked in England, especially for negative work, scarcely finds its 
 way to this country. 
 
 The qualities required in paper are — to be made of good stock 
 — that is, fine clean rags ; to have had the chlorine used for 
 bleaching thoroughly removed, as also the antichlor (generally 
 hyposulphite of sodium). Chlorine left in the paper tends to in- 
 jure the fibre, but is otherwise of little importance, but even the 
 slightest traces of hyposulphite make ineffaceable stains and dis- 
 colorations. A print thrown by mistake into hyposulphite wash- 
 ings, turns black all over, the hyposulphite being decomposed, 
 and sulphide of silver formed ; of course a similar reaction takes 
 place when hyposulphite is left in the paper — faint traces make 
 brownish spots, visible in the sensitized paper before printing. 
 
 Again, the paper must be free from all kinds of metallic grains, 
 which, without care, are liable to drop into the pulp. Metallic 
 dust, abraded from the machinery, forms imperceptible specks, 
 which, however, reduce the silver from the nitrate bath, and 
 make spots in the print. 
 
 In this country, prints are almost universally made upon white 
 paper, but rose, purple, and other tinted papers are being intro- 
 duced, and serve to give an agreeable variety. 
 
 §2. — Albumenizing Paper. 
 
 Few operators take the trouble to albumenize their own paper. 
 But as original experimenters require to understand every por- 
 tion of the process of photography, and as it may happen that 
 photographers may desire to print where albumenized paper 
 cannot be got, the writer gives the formula which he has used 
 with good results. 
 
 Take the whites of perfectly fresh eggs and add thereto liquid 
 ammonia in the proportion of five drops for each egg. Measure 
 the quantity, and take six grains of sal ammoniac for each ounce 
 of albumen. This may be dissolved in an ounce of water for 
 each five eggs, or if very high albumenizing is desired, it may 
 be dissolved in the smallest possible quantity of water. 
 
 Add the sal ammoniac solution, and let the whole be beaten up 
 
SILVER PRINTINa. 
 
 271 
 
 to a froth, so that no liquid portion be left. Set away for twelve 
 hours or more (a cool damp place is best), and pour off the liquid 
 portions which have settled out of the froth. These are per- 
 fectly clear and free from foreign matter. 
 
 The albumen thus prepared is placed in a flat pan and the 
 papers rested on it for three or four minutes, and then lifted off 
 and bung up to dry. The faster the drying the higher the gloss, 
 and therefore these papers, when prepared commercially, are 
 often dried in rooms kept at a suffocating heat. 
 
 In small experiments, the albumen may with a little dexterity 
 be applied with a broad (two-inch or more) camel's-hair brush. 
 With care, streaks may be avoided. 
 
 Some have recommended the use of glacial acetic acid (three 
 drops to each egg) instead of the ammonia. Lyte remarks that 
 this tends to yellowness in the whites of the prints, and the 
 author's experience has been the same. 
 
 In salting, considerable latitude is allowable. Eight or ten 
 grains of sal ammoniac is about an average quantity, which is 
 sometimes reduced to six, sometimes increased to twelve. An 
 absurd secrecy is practised by many makers of albumenized 
 paper as to their salting, and this introduces some uncertainty as 
 to the proper treatment : strong salting requires a stronger bath, 
 and with paper of which the salting is not known, some trials 
 may be requisite to determine the appropriate bath. 
 
 The weaker the salting the less is the exhaustion of the posi- 
 tive printing bath, but it is not quite sure that the pictures so 
 produced are quite as permanent. 
 
 In the preservation of albumenized paper, two things are to be 
 borne carefully in mind. First, that if the paper be kept in a 
 moist atmosphere, it will not give brilliant prints. This, is be- 
 cause the salt used becomes to some extent dissolved in the 
 hygroscopic moisture absorbed by the paper, and is drawn by 
 capillary attraction into the body of the paper ; thus the silvered 
 surface is less perfect. This is more the case with common salt, 
 chloride of sodium, and less with chloride of barium, than witb 
 chloride of ammonium. Common salt is the most deliquescent, 
 chloride of barium the least soluble of the three. 
 
 On the other hand, excessive dryness is to be avoided, the coat 
 of albumen becomes too horny and not suflaciently permeable. 
 Many adopt the plan of keeping the stock of albumenized paper 
 in a thoroughly dry place, but take out what will be wanted for 
 
272 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 one day's printing, and leave it twenty-four hours in a damp 
 cellar, in order that it may take the nitrate bath more evenly. 
 
 Generally speaking, the fresher the paper the better, and the 
 less chance of defects. To be sure of obtaining the quality of 
 paper desired, it is best to purchase directly from the maker or 
 his authorized agent. 
 
 Decomposed albumen is always hurtful. If it be kept so long 
 before applying to the paper as to acquire a bad smell, it must 
 be rejected. And if the paper be kept in a very moist place, the 
 albumen may putrefy on the surface of the paper. 
 
 I 3. — Salting" Plain Paper. 
 
 In salting ordinary paper, the most various proportions of salt 
 have been recommended. Two, three, or four grains to the ounce 
 are about a recommendable proportion, and give good results. 
 A little gelatine may be advantageously introduced; the latter 
 should not exceed two grains to the ounce, and may be less. It 
 will need the aid of heat to get it into solution. If not over 
 one grain be used, the liquid will scarcely gelatinize in cooling. 
 
 The following may be taken : — 
 
 Chloride of ammonium 50 grains. 
 
 Gelatine . . . . . . , _ . 16 " 
 
 Water 10 ounces. 
 
 By some, chloride of barium is preferred. The greater equiva- 
 lent weight of this substance requires that it should be used in 
 larger proportion. As follows : — 
 
 Chloride of barium 200 grains. 
 
 Gelatine 45 " 
 
 Water 30 ounces. 
 
 A difference of opinion exists as to the proper mode of prepa- 
 ration. High authorities recommend that the paper be drawn 
 through the solution. But as it is the invariable object to keep 
 the materials on the surface, it is perhaps better to float the paper 
 for a few moments in the bath. In any case, it is desirable that 
 it should be rapidly dried, before the solution soaks too much in. 
 
 Arrowroot paper may be purchased ready salted. The effect 
 of the arrowroot is to keep the picture more on the surface, and 
 so avoid a sunk-in, mealy effect. If warm tones are wanted, use 
 the benzoate or acetate toning ; if black, the lime. These papers 
 
SILVER PRIN-TING. 
 
 273 
 
 need vigorous printing, and should not (according to Liesegang) 
 be toned in a fresh toning bath, but only after some albumen 
 prints have been toned in it. 
 
 Good results may be obtained by floating albumen paper Avith 
 the albumen side up. This gives the print a good deal the effect 
 of being made on plain paper very highly finished. There is 
 not the transparency of shadow which makes the peculiar beauty 
 of the albumen print, but there is also less gloss and glitter. 
 
 § 4. — Sensitizing. 
 
 Since the first edition of this book was published, fuming with 
 ammonia in one shape or other has come into general use, and 
 with this change the practice of making the " ammonio-nitrate 
 bath" has comparatively passed out of use, 
 
 "When paper is to be fumed, it is not very important whether 
 the sensitizing bath is acid or alkaline, because the fuming 
 always renders the paper alkaline, either beforehand, as when 
 the fuming box is used, or during the exposure, or when fumed 
 pads are employed. The usual strength of the bath is now 50 
 to 60 grains of nitrate of silver to the ounce. A satisfactory 
 bath will be : — 
 
 Positive Bath. 
 
 Nitrate of silver 3 ounces. 
 
 Water 24 " 
 
 Tlie usual practice is to make this bath faintly acid with nitric 
 acid, though some excellent operators make it slightly alkaline 
 with ammonia. 
 
 On this bath the albumenized paper is to be floated about a 
 minute — a little less in hot weather, a little more in cold. 
 
 After the sheet has floated for a proper time, it is to be pinned 
 or otherwise fastened up to dry. Buff shades to the room, if 
 wide enough to cover the window jambs, will be a sufficient pro- 
 tection; if too much white light be admitted, the high lights of 
 the prints cannot be expected to be satisfactory. In some 
 establishments a table is provided with a back or screen towards 
 the left, seven or eight feet square. This protection, and keeping 
 the sensitized paper and prints in drawers, is found sufficient, 
 provided that the table is near a wall, so that but little diffuse 
 light can pass round the screen. 
 
274 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Consumption of Nitrate of Silver. — Different photographers have 
 calculated the amount of nitrate of silver consumed in sensitizing 
 an albumenized sheet of 18 x 22, and have varied between wide 
 limits, some fixing it as low as 60 grains, others as high as 110 
 or over. Seventj-five to eighty grains is probably about the 
 true quantity that is abstracted from the silver bath, part of 
 which is subsequently recovered from the washings. 
 
 Alum in the Printing Bath. — Mr. H. T. Anthony recommends 
 the addition of alum to the bath ; about 2 grains to the ounce of 
 bath seems to be the right proportion, and to tend to keep the 
 bath clean and free from discoloration. By this means, he states, 
 he gets as good results from a 35-grain bath, as on the old plan 
 with a 50-grain. He advises, after the printing is done, to soak 
 the prints in water acidulated with acetic acid, before toning 
 them. 
 
 Blotting Sensitized Paper. — Some very successful workers Hot 
 all their paper, to obtain equal action and avoid drops of bath 
 solution collecting on the surface in drying. Thick blotting pads 
 are provided, rather larger than the sheets. On one the sensi- 
 tized sheet is laid face down and pressed, then another pad and 
 another sheet, and so on. The pads may be used many times 
 over before they become too much charged with solution — finally 
 they are burned to recover the silver. The abstraction of the 
 silver solution does not reduce the vigor of the prints, which are 
 obtained very uniform in character and free from stains. 
 
 If the paper is allowed to dry between the pads, it will be apt 
 to turn yellow. It is, therefore, best, as quickly as the liquid is 
 completely absorbed, to remove the sheets, pin them up, and let 
 them dry. 
 
 Management of Bath. — The positive bath by use soon turns 
 yellow and loses strength. The first trouble is to be remedied 
 by shaking up with half an ounce to an ounce of kaolin, accord- 
 ing to the size of the bath. The strength must be kept steadily 
 up to the mark originally fixed, and this is either done by watch- 
 ing carefully the character of the prints, and adding silver liber- 
 ally as soon as they show any signs of deterioration, or by means 
 of the argentometer, a sort of hydrometer expressly made for the 
 photographer, and which, by sinking more and more deeply into 
 the bath, indicates the exhaustion of the nitrate of silver. "With 
 the age of the bath, however, its indications become less reliable. 
 
SILVER PRINTING. 
 
 275 
 
 in consequence of the accumulation of other nitrates in the 
 bath. 
 
 These, however, appear to some small extent to take the place 
 of nitrate of silver. At least, Meicke's experiments showed that 
 the quantity of silver abstracted from an old bath was less than 
 from a new one, sometimes by as much as 15 or 20 grains to the 
 sheet, and it seems not unreasonable to suppose that the alkaline 
 nitrates gradually accumulating in the bath had something to do 
 with this. A sharp controversy was carried on in England for 
 some space of time over the question of the utility of alkaline 
 nitrates in the bath. Generally, nitrate of soda was tried. The 
 bulk of the rather conflicting evidence seems to have been in 
 favor of the advantage of the addition, a result undoubtedly 
 confirmed by Meicke's experiments above mentioned. 
 
 § 5. — Washed Sensitive Paper. 
 
 One of the serious annoyances connected with photographic 
 printing lies in the rapid deterioration of the paper, which quickly 
 turns yellow, thus destroying the brilliancy of the white. It is 
 rarely safe to keep the paper from one day to another, especially 
 in hot weather. Two bad results follow: that if the weather 
 changes from fair to dark, a portion of the paper prepared for 
 the day's use is apt to be spoiled; whilst, on the other hand, it 
 the day changes from dark to bright, there is no paper ready to 
 profit by it. 
 
 The preparation of a paper with good keeping qualities has 
 consequently been felt to be an object of the greatest importance. 
 Such paper has been prepared commercially in France; its mode 
 of manufacture, however, has been kept absolutely secret. So 
 far the only published method of obtaining a paper that can be 
 kept is the Washed Paper Process, here to be explained. This 
 process, however, involves a considerable amount of additional 
 manipulation in the washing of the paper after sensitizing it. 
 The writer has lately taken up and finished some investigations 
 commenced some years ago, and has succeeded in finding a method 
 free from this objection, and requiring no more labor to prepare 
 than the ordinary silvered paper, yet sufiiciently permanent to 
 be kept for a considerable length of time without deterioration. 
 This method will be described in the next section following. 
 
276 
 
 PHOTOGKAPHIC MANIPULATIONS. 
 
 In the Washed Paper Process, the paper, as soon as it is 
 removed from the printing bath, is thrown into water, to remove 
 the excess of nitrate of silver. As to the amount of washing that 
 the paper will bear, different operators have reached very differ- 
 ent conclusions, and the practice has not been so generally 
 adopted as to have led to the accurate fixing of these conditions. 
 Some succeed best by simply drawing the paper through one 
 water; in this condition it approximates more nearly to ordinary 
 silvered paper. Others draw it through two, three, or even four 
 waters, so that the last water shall show no clouding by reason 
 of chlorides present in it, thus indicating that the whole of the 
 nitrate is washed out. When thus treated, the salting must not 
 be too low, and the silver bath must be kept well up to the mark, 
 strengthening, from time to time, with fresh nitrate, according to 
 the number of sheets sensitized. The amount of silver abstracted 
 will depend upon the salting, but for average paper it will be 
 fair to estimate from five to six drachms for each four sheets of 
 paper of 18 x 22. After what number of sheets the strengthening 
 will be required will, of course, depend much upon the quantity 
 of bath used, but it is best always to be on the safe side ; a rule 
 used by some experienced operators is to strengthen after each 
 five sheets. After each strengthening, try the bath with test- 
 paper, to make sure that it is alkaline, but not too much so. If 
 too alkaline, the albumen will be dissolved off the surface of the 
 paper. If the strengthening of the bath be neglected, the prints 
 will want vigor. 
 
 Paper thoroughly washed has been kept, according to M. 
 Baden, from March till October, without deteriorating. When 
 it is intended to keep the paper for a long time, much more 
 care with regard to light must be exercised through the opera- 
 tions of sensitizing, washing, and drying, and in keeping it in a 
 dark and dry place. The prints themselves cannot be kept with 
 the same safety as the paper, because of the fuming before 
 printing, but they may lie over for some days or even longer. 
 
 An advantage in using several waters is that the first pan can 
 be used many times, until its contents become very rich in silver, 
 and fit to evaporate down and recover the silver fit for use. 
 Then the second pan receives the first, and so on, fresh water 
 taking the place of that which was previously the last. 
 
 The washing of the paper after sensitizing does not take the 
 
SILVER PRINTING. 
 
 277 
 
 place of the subsequent washing, but the prints, after they come 
 from the printing frame, must be again washed before toning. 
 
 Care is also necessary with the fuming, which may easily be 
 carried too far. Pad fuming (see p. 279) is said to answer best. 
 If the prints are fumed in a box, and are left in too long, they 
 will tone to a cold blue. It is said, however, that this over- 
 fumed paper, by keeping for a day or two, will lose some of its 
 excess of ammonia, and give better tones. Five minutes is about 
 the right time to leave this paper in the fuming box. 
 
 The high salting of the paper above spoken of, appears to be 
 essential. This introduces a difficulty, inasmuch as the photo- 
 grapher rarelj'- prepares or knows how much salting is contained 
 in the paper that he habitually uses. 
 
 It will be easily understood, from the foregoing, that there is 
 more or less uncertainty connected with this method. Some 
 have obtained very satisfactory results with it, whilst others 
 have been disappointed and have rejected it. This uncertainty, 
 and the considerable additional manipulation required, appear to 
 render the method much less advantageous than the following. 
 
 § 6. — New Method of Sensitizing Paper. 
 
 Some years ago the writer, whilst investigating the subject of 
 Paper Development, ascertained that by the addition of tartaric 
 acid to the sensitizing bath the paper could be kept for ten days. 
 As paper for development is still more liable to deterioration 
 than that prepared for positive printing, it appeared to him likely 
 that this property of tartaric (probably also of citric) acid might 
 be made the foundation of a new printing process of great utility. 
 Other occupation, however, interfered with the prosecution of 
 the matter till recently, when the experiment was tri-ed, and with 
 complete success. At the time when this sheet goes to press, the 
 writer has kept this new paper about seven weeks, at the expiration 
 of which time it was still in excellent condition, giving brilliant 
 prints with whites just as perfect as when freshly made, and 
 toning with the utmost ease. 
 
 Formula. 
 
 Crystallized nitrate of silver 2 ounces. 
 
 Tartaric acid 40 grains. 
 
 Water .16 ounces. 
 
278 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 The nitrate and the tartaric acid are not to be thrown into the 
 water together, but dissolved in separate portions, mixed, let to 
 stand some hours, and then filtered. This bath is then used and 
 treated precisely like an ordinary printing bath, except that it is 
 best to keep it out of the light. The albumenized paper is floated 
 for the usual time and hung up to dry. More care should be 
 taken in excluding the light than in the case of ordinary silvered 
 paper intended to be used at once, and when the paper is dry it 
 is to be put aside in a close-fitting box and kept in a dark, dry 
 place until wanted for use. 
 
 Sometimes the author adds — 
 
 Gelatine 4 grains, 
 
 Glycerine 3 drops, 
 
 to each ounce of the bath. The gelatine should be set to swell 
 in a part of the water, and then be dissolved by warming, add 
 the glycerine and tartaric acid to this, and pour it into the rest 
 of the water in which the silver-nitrate has been dissolved. 
 Although the bath now contains four grains of gelatine to the 
 ounce, the tartaric acid prevents any gelatinizing, even if one 
 employs, as the writer has sometimes done, a much larger pro- 
 portion of gelatine. It also filters easily. When gelatine is used, 
 the prints as taken from the frame have a bright brown color ; 
 they tone to any shade desired as easily as the others. The 
 use of gelatine would seem to tend to kegp the print more on the 
 surface, but whether there is any real benefit in it is scarcely 
 certain. Perfectly satisfactory prints are obtained without it. 
 The object of the glycerine is to remove the stiffness which the 
 gelatine tends to give the paper. 
 
 The fuming is done shortly before using, and requires no par- 
 ticular care, and the print is washed and toned in any of the ordi- 
 nary methods. The writer uses the acetate toning bath. What is 
 rather curious is that while the albumen side of the paper remains 
 white, the back often acquires by keeping a brownish coloration, 
 which, however, disappears entirely in the toning or fixing, and no 
 one, in examining either the face or the back of the print, could 
 distinguish it from one made on paper just dry after the printing 
 bath. It seems possible that the quantity of silver in the bath 
 might be reduced, but in these examinations it was thought 
 better to adhere to the proportion of silver actually employed by 
 the most successful workers with the ordinary bath. 
 
SILVER PRINTING. 
 
 279 
 
 It will be seen from the foregoing description that paper with 
 excellent keeping properties is as easy to prepare as paper that 
 spoils immediately. It is only adding a few grains of tartaric 
 acid and proceeding otherwise precisely as usual. The advan- 
 tages are very great and the trouble nothing. The method will, 
 the author trusts, be found a valuable alleviation to the troubles 
 of printing. 
 
 § 7. — Fuming. 
 
 A convenient and close-fitting wooden or tin box is provided 
 with a door, and either pieces of cork are attached to the sides 
 near the top inside, or else cords are stretched across. To these 
 the dry sensitized paper is attached for fuming. This operation 
 lasts for ten minutes, and is best performed only a few minutes 
 before printing. If the fuming be too much prolonged, the print 
 may be. expected to be flat and mealy, and to be severely reduced 
 in the fixing bath. On the other hand, an irregular spotty effect 
 indicates insufficient fuming. 
 
 In a saucer at the bottom of the box is poured some strong 
 liquid ammonia. The quantity is not very important ; for a 
 small box and a dozen or twenty quarter sheets of paper, an 
 ounce and a half to two ounces will be sufficient. For a large 
 box and twenty or thirty whole sheets, two dishes with two or 
 three ounces in each will be sufficient, if the ammonia be good. 
 (The liquid ammonia of commerce is very variable in strength.) 
 Carbonate of ammonium has been recommended by Dr. Liesegang 
 as an advantageous substitute for the liquid ; the mode of ope- 
 rating is precisely the same, except that a larger quantity is 
 employed, and may be used many times. 
 
 It is best that the fumed paper should be exposed to the air for 
 ten or fifteen minutes, to allow the adhering ammoniacal fumes to 
 pass ofi", before laying upon the negative. 
 
 The effect of fuming is to give rich, brilliant prints with ease 
 and certainty. This method, now in very general use, was first 
 pi'oposed by Mr. H. T. Anthony. 
 
 Pad Fuming. — Another plan, which has lately been a good 
 deal used, is to fume j^ac^s instead of the sensitized paper. 
 These pads are left for some hours, or over night, in the fuming 
 box, and are placed behind the silvered paper whilst it is in the 
 printing frame. In this way the ammonia acts upon the silvered 
 
280 
 
 PHOTOGEAPHIC MANIPULATIONS. 
 
 surface during tlie operation of printing. The influence of this 
 fuming can be heightened by putting pieces of oiled silk directly 
 behind the fumed pads, in order to prevent all escape of ammonia. 
 Another plan has been recommended, that of simply rubbing the 
 pad with a lump of carbonate of ammonia, taking care, of course, 
 to leave no grains or dust on the pad. 
 
 Fuming with a pad is less likely to injure valuable negatives 
 than fuming the paper itself. 
 
 § 8.— Printing. 
 
 Before placing the paper in the frame, it is necessary to be 
 certain that it is perfectly dry, otherwise the negative may be 
 injured; a careful examination should be made of every part of 
 the sheet before it is cut to pieces, bearing in mind that a single 
 moist spot may cost a valuable negative. The paper, especially 
 if albumenized paper be in use, must be set in the frame neither 
 roughly nor carelessly. For it is to be always borne in mind 
 that a negative is a delicate thing. Even the best varnish is 
 no protection against rough handling, and a slight scratch may 
 easily occur in some place where touching out may be either 
 impossible or nearly so. The paper should never be drawn over 
 the plate, especially when pressed close to it. It must be laid 
 flat down in its proper position, and the pads laid easily and 
 squarely down upon it and secured by the back. 
 
 Printing may be done either in the direct rays of the sun or in 
 diffuse light ; the choice between the two will depend upon the 
 nature of the negative, and the preparation of the paper must be 
 regulated accordingly. 
 
 The characteristic of printing in the sun is softness, of printing 
 in the shade, strength and contrast. Nevertheless, prints made 
 in sunshine are mostly the stronger, simply because strong, hard 
 negatives require sun-printing. And so, soft prints will often be 
 found to have been executed in the shade, because taken from 
 very thin negatives which could not be made to yield a good 
 print in any other way. For want of understanding this, very 
 contradictory and erroneous statements have often been published 
 on the subject of sun and 'shade printing. 
 
 A photographer will, for example, start out with the intention 
 of printing in the shade, and will make all his negatives very 
 thin with that intention. If these negatives were printed in the 
 
SILVER PRINTING. 
 
 281 
 
 sun, the prints would be utterly worthless. By the time that the 
 shadows were deep enough to stand toning and fixing, the lights 
 would be discolored and the prints spoiled. To examine his 
 prints and observe his mode of printing might lead to the conclu- 
 sion that shade-printing gave soft prints, whereas the fact would 
 be that the thin negative gave soft prints in spite of the mode of 
 printing. • 
 
 Another will prefer bold, vigorous negatives, and will develop 
 and redevelop till he gets them. These, if printed in the shade 
 until details were got in the high lights, would lose all transpa- 
 rency of shadow, which would be converted into black patches. 
 The exposures would be tedious and the prints bad. But exposed 
 to a bright sun, the intense rays pierce through the dense parts 
 of the negative, and give us the details in the lights before the 
 shadows are overdone. 
 
 Under the head of Salting, it has already been remarked that 
 both the salting and the nitrate bath mast be regulated so as to 
 act as a counterpoise to the printing. With a thin negative the 
 bath must be a rich one, or the picture will tend to flatness. A 
 bold negative will print well upon a less highly sensitized paper. 
 In this lies the explanation of the much discussion over strong 
 and weak printing baths, some succeeding with what fails with 
 others, all depending upon the nature of the negative. Again, 
 when, by accident, a very hard negative is taken, which gives a 
 harsh black and white picture, its prints may be improved by 
 using an extremely weak sensitizing bath (prolonging the floating 
 of the sheet upon it proportionally). Extremely hard negatives, 
 so hard as to be unserviceable in any other way, are made to 
 yield good prints by washing the paper after sensitizing it, so as 
 to remove all free nitrate, then drying and exposing. 
 
 Very thin negatives, that only give flat prints under the ordi- 
 nary treatment, may often be made to yield excellent prints (pro- 
 vided they are not actually deficient in detail in the shadows, so 
 that they are wanting in density only, not in graduation ; the 
 distinction is important) by printing under one or more folds of 
 tissue-paper. 
 
 It will easily be understood that where negatives are printed 
 in large quantities for sale, they are likely to give better results, 
 because the treatment for any particular negative, in respect to 
 salting, sensitizing, and exposing, can be well made out. 
 
 The proper degree of salting will always depend upon the 
 19 
 
282 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Strength of the sensitizing bath, and correspond with it. A rich 
 nitrate bath should follow high salting, and the reverse. Where 
 it is wanted to get a soft print from a very hard negative, the 
 salting may be reduced to one or two grains per ounce of water 
 or albumen, to be followed' by a weak printing bath of twenty to 
 thirty grains nitrate of silver. 
 
 Another remark of importance is this, that the image produced 
 by a strong light stands the subsequent operations better than 
 that produced by weaker light. A print made in direct sunshine 
 is less reduced in toning and fixing than one made in the shade. 
 Consequently, a shade-print requires more over-printing in the 
 frame than a sun-print. The sun-print is undoubtedly the stronger 
 picture of the two, and the writer holds that, other things being 
 equal, its chance of permanence is greater than that of the shade- 
 print. * 
 
 The time required for printing will of course vary extremely; 
 in extreme cases, from a minute or two to many hours. The 
 prints are to be examined by carrying the frame to a dark corner, 
 loosening one end of the back, opening it and observing the con- 
 dition of the print. Particular care is necessary to avoid injuring 
 the negative with the nail in lifting back the print. The usual 
 test of sufficient printing is when the shadows begin to bronze. 
 At this time the highest lights should be either still quite clear 
 or only just commencing to darken, so little that it will be re- 
 moved in the subsequent operations and the white left pure. If 
 in sun-printing the whites begin to darken before the shadows 
 are sufficiently printed, it is a sign that the negative is thin and 
 will require shade-printing. If in shade-printing the shadows 
 are fully printed before the details in the high lights are got, it 
 is an indication that sun-printing is needed; and if this defect 
 appears in sun-printing, it is a hint that the negative in use will 
 require paper less highly silvered. 
 
 Friniing on Carhonaie of Silver has been introduced in France, 
 and has acquired considerable popularity. The paper is first sen- 
 sitized with an alkaline carbonate, and then silvered on a plain 
 silver solution (not ammonio-nitrate). Such paper keeps long 
 after sensitizing, but requires thorough fuming before use, and 
 to have oiled paper or oiled silk behind the back of the paper 
 whilst printing, to retain the ammonia. It is asserted that the 
 prints can be kept a month, if desired, before toning and fixing. 
 
SILVER PRINTING. 
 
 283 
 
 Printing under Ground Glass. — The effect produced upon the 
 printing of a negative by interposing a plate of ground glass 
 between the light and the negative is undoubtedly very curious. 
 A great softening is produced ; negatives which, printed in the 
 ordinary way, give harsh and blocky prints, will sometimes, by 
 this treatment, yield excellent results. The writer has seen soft, 
 beautiful, and delicate prints got from negatives that must have 
 been rejected, had they not been rendered useful by the applica- 
 tion of this ingenious contrivance. 
 
 It is, of course, chiefly in portraiture that this device is useful. 
 The writer, without ever having used it himself in landscape 
 printing, has seen fine prints made by its help from hard nega- 
 tives. 
 
 Printing under ground glass has somewhat the same effect as 
 printing under tissue-paper in softening the image. To what has 
 already been said under the head of Berlin Portraits''^ (p. 194), 
 it may be here added that some vary the effect by coating the 
 ground side of the glass. This communicates a part of the grain 
 of the glass to the print, producing somewhat the effect of an 
 engraving. 
 
 Mezzotint Effects. — The method of obtaining^ these is explained 
 at p. 194. It remains to mention here that the printing should 
 be done in direct sunshine, and that it is found that the best re- 
 sults are got when the sun shines perpendicularly on the negative. 
 M. de Constant suggests driving a nail perpendicularly into the 
 face of the printing frame ; when this nail casts no shadow., it is a 
 proof that the frame is perpendicular to the sun's rays. 
 
 Portraits softened in these ways lose the harshness so con- 
 spicuous in some photographic work. They show less definition 
 and boldness, but more harmony and softness. The improve- 
 ment obtained in this way can never equal that resulting from 
 retouching the negative; but, where this is not practised, it may 
 often be useful. 
 
 § 9.— The Pressure Frame. 
 
 The construction of the frame is of too great an importance not 
 to receive a word of comment here. Two very serious troubles 
 arise from bad pressure frames, breakage of negatives, and blurred 
 prints. Pressure frames generally distribute the pressure very 
 badly. 
 
284 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Take an ordinary piece of glass, the size of the frame, lay it in, 
 put in the pads you commonly employ ; take hold of the frame 
 in both hands, the fingers on the back, the two thumbs resting 
 on the glass near the centre. Press forcibly with the thumbs, 
 until the glass moves back a little, and observe the amount of 
 resistance. Next bring the thumbs up to one end, and press 
 there ; you will probably be surprised to find how much less the 
 resistance is there, and, consequently, how unequal the pressure. 
 
 This inequality is a principal cause of the breakage of nega- 
 tives in the frames, and is also a disadvantage to the print; for 
 wherever the contact is not good, the sharpness of the print will 
 be impaired, and this more so with shade-printing than printing 
 in direct sunlight. The writer has already expressed his prefer- 
 ence for the bar-frame, Fig. 12, p. 45. 
 
 Many operators are extremely careless as to what padding they 
 use between the back of the frame and the print, considering that 
 anything is good enough — mill-boards, old newspapers, etc. This 
 is quite wrong ; such inelastic substances cannot give good con- 
 tact, and always endanger the negatives. Moreover, as the mate- 
 rial for this purpose lasts indefinitely, it is worth while to provide 
 it right, once for all. 
 
 The one thing that is better than anything else is piano-cloth. 
 This is a soft, thick, green felt-cloth; when really good, it is about 
 a quarter of an inch thick. It is expensive, but as a yard will 
 make pads for twenty whole plate frames, the cost is not worthy 
 of consideration when the safety given to the negatives is coht 
 sidered. A single thickness is sufficient, and a fine, elastic, 
 equable pressure is obtained, which is invaluable. If by long 
 use the felt has become flattened down, all that is necessary is to 
 slightly wet it and let it dry. 
 
 The next best substance to this is probably a good thick flannel 
 — woollen or cotton; the former is the more elastic. Whatever 
 substance is used, should of course be of some non-actinic color. 
 
 The Registering Pressure Frame^ for combination printing, has 
 already been described. See Figs. 102 and 103, p. 183. 
 
 To accomplish the printing of as many frames as possible at 
 once, a platform is set up outside of the windows and on the level 
 of their sills. On this are placed slanting blocks, so that, when 
 the frames rest upon them in rows, each frame will be inclined 
 so as to face the sunlight as much as possible. At different 
 times of day the frames are differently placed ; when the sun is 
 
SILVER PRINTING. 
 
 285 
 
 low, they are kept more nearly perpendicular, and as the sun 
 rises, they are placed more level. Much time is saved by having 
 the frames kept well facing the sun. 
 
 A southeast exposure is the most desirable, though it is con- 
 venient to have at least one window with a westerly exposure 
 for shade-printing. Some negatives will do best when not only 
 printed in the shade, but also by having tissue-paper interposed. 
 It is therefore convenient to have some frames kept permanently 
 with tissue-paper stretched across the borders. 
 
 § 10.— Vignetting. 
 
 When the print softens into a white border, it is called a vignette, 
 and this mode of printing offers a beautiful variety. The nega- 
 tive is usually taken in precisely the same way as for ordinary 
 printing, and the difference is made in the printing, though the 
 effect can be very well produced once for all in the negative, if 
 desifed, as will be presently explained. 
 
 It should always be borne in mind that a vignette requires a 
 light background. A sketchy effect (see section on Backgrounds) 
 is very pleasing in vignettes. 
 
 Vignetting with a Frame. — This is the most usual way. The 
 negative is placed in a frame on the face of which are springs 
 which confine blocks of wood; in these blocks oval holes are 
 cut, widening on the under side which is next the negative. On 
 the upper side, farthest from the negative, tissue-paper is pasted 
 to soften the light. 
 
 Vignetting frames are also made expressly. These commonly . 
 have pieces of tin set in front, provided with wire rings, over 
 which the tissue-paper is to be pasted. For large negatives a 
 convenient vignetting frame may be made by tacking a piece of 
 stiff pasteboard upon the front of the frame. In this a hole is 
 cut of the size desired, and this hole is covered with tissue-paper. 
 
 Vignetting glasses are sold in which a deep orange enamel is 
 applied to the border, leaving an oval space in the middle, of 
 clear glass; of course the color is shaded off at the edges of the 
 oval. This glass is to be placed in the frame between the nega- 
 tive and the light. 
 
 Any one accustomed to photographic manipulations may pre- 
 pare such glasses for himself, by photography. Cut a small piece 
 
286 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 of oval hard wood, smaller than the part of the negative that is 
 to be printed. Prepare a collodio-chloride or albumen plate for 
 positive printing, lay the little block on it, and expose to diffuse 
 light, turning the plate now and then. It is evident that the part 
 of the plate that is covered by the block will be completely 
 protected, and the portions round it will be shaded off. Or, by 
 reversing the operation, and using a hole in a shield instead of a 
 block, a reverse vignetting plate may be got, that is, a shaded 
 centre in a transparent border. This may be used as a negative 
 from which any number of vignetting plates may be prepared, 
 either by contact printing or by development. The writer can- 
 not recommend this as being a very easy method, but it is per- 
 fectly practicable, as he knows from having devised it and used 
 it several years since. More lately, it has been proposed and 
 advocated by others in print. 
 
 Vignetting with Cotton. — A piece of stiff m'ill-board is tacked to 
 the front of the frame, in which an opening is cut considerably 
 larger than the size of the portion of the negative which it is 
 intended to print. White cotton-wool is pressed under the mill- 
 board, and allowed to project beyond it until only that part of 
 the negative is exposed which it is intended to print. 
 
 Vignetting with Paper. — In this case and in that immediately 
 foregoing, the part of the negative that is to be printed is exposed 
 uncovered. A piece of thin tissue-paper is cut with an opening 
 
 the size of the part of the nega- 
 tive that is to be fully printed ; 
 then another piece with the. 
 opening a little larger, and so 
 on for a considerable number. 
 These are pasted together and 
 form a graduated shield, acting 
 somewhat like the vignetting 
 glass already described. By 
 fastening this paper shield on 
 the glass side of the negative 
 and printing in the shade, the 
 lines of the successive layers of 
 paper can be concealed. 
 
 The sketch in the margin is 
 taken from Mr. Blanohard, as 
 showing a set of elegant and ap- 
 
 Fiff. 122. 
 
SILVER PRINTING. 
 
 287 
 
 propriate curves suitable for card size (the size of the cut is 
 necessarily smaller than that of a card portrait, but the curves 
 are preserved of full size). Models of each of the diminishing 
 openings are to be cut into card -board or thin tin ; these once 
 provided, any number of tissue vignettes may be made from 
 them by using them to guide the point of the penknife in cutting 
 the tissue-paper. The same photographer recommends, for other 
 and more irregular shapes of vignettes, to attach to the back of 
 the negative a piece of tracing paper, to run round lightly with 
 the pencil the portion that is to print full tint, and again outside 
 that, the portion to be quite white. This last is rendered opaque 
 with any red or black color, and the space between the two lines 
 where the softening is to be is graduated by rubbing in color 
 with a common artists' stump. 
 
 Vignetting with a Lens. — This ingenious method is practised by 
 some professional photographers to the exclusion of all others, 
 and has the advantage of great rapidity. A burning-glass of some 
 size (four to six inches in diameter) is set in a wide frame, or a 
 piece of thin board. The negative Is placed with silvered paper 
 behind it in an ordinary frame, and the concentrated sunlight 
 through the lens is allowed to fall upon the face. The lens is 
 kept moving with a little circular motion, confining the light to 
 the parts intended to be printed. In from ten seconds to half a 
 minute the printing is finished. As the heat as well as the light 
 is concentrated by the lens, it is necessary to have a thin piece of 
 plate glass in the frame between the negative and sunlight, to 
 prevent injury to the negative. 
 
 All these methods give excellent results. The last is evidently 
 applicable chiefly to small heads, but the writer has seen beau- 
 tiful vignetted cards made by it. 
 
 We next come to vignetting on the negative. 
 
 Vignetting hy Development. — When the dark slide comes from 
 the camera, the back is opened and an opaque shaded object of 
 the shape and size of the vignette desired is laid on the back of 
 the plate, which then, and without removing from the slide, is 
 exposed for a few seconds to weak diffuse light. When the 
 image is developed, of course all parts of the plate not protected 
 by the opaque screen just described are developed black, in con- 
 sequence of the second exposure. As the image is invisible at 
 the time the opaque screen is applied, this last mdst of course 
 
288 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 have been arranged in such a way bj the image, as seen in the 
 camera, as to make sure of the screen being correctly applied. 
 
 Vignetting ly a Screen. — Another method has been proposed. 
 A large white screen is to be prepared with an oval opening. 
 This screen is to be placed between the camera and the sitter, who 
 is thus seen through the oval opening. The screen being white, 
 reproduces itself by opacity on the negative, and being so much 
 nearer to the lens than the sitter as to be completely out of focus, 
 it of course has an indistinct shaded border. There seems an 
 objection to this plan, that it tends to throw so much white light 
 into the lens. It has also been proposed, instead of a large stand- 
 ing screen, as just explained, to have a small one, only a few 
 inches from the lens, and attached to the camera itself, capable 
 also of being regulated in distance and position. 
 
 These last methods are rather exceptional ; the use of the 
 tissue-paper fastened over openings in wooden blocks or on 
 metal rings, as above described, is almost universal. 
 
 § 11.— Toning. 
 
 After the prints are removed from the frame, they may either 
 be thrown directly into water or may first be trimmed ; the latter 
 method is found preferable by those who operate on a large scale. 
 
 The prints are washed by placing them one by one in a pan 
 of water, where they all lie for a short time. This water is to be 
 repeatedly changed, and of course is to be saved, at least the two 
 or three first washings. It is rich in silver, which is to be thrown 
 down as chloride by common salt. A neglect to wash the prints 
 sufficiently is liable to produce two evils, a yellowing of the 
 whites in the toning bath and a difficulty in toning; these 
 troubles may come separately or together. This is the case 
 especially with the toning baths now commonly in use. Those 
 toning baths into the composition of which sulphocyanide of 
 ammonium or hyposulphite of sodium enters, do not present 
 this difficulty, and although it is best to wash the prints before 
 toning in them, it is not absolutely necessary, nor need it be so 
 carefully done. 
 
 The principle of toning is the substitution of gold for silver in 
 the print. If a washed print be simply thrown into a dilute solu- 
 tion of chlorWe of gold, it will tone, but the acidity of the solu- 
 tion will lead to a great reduction in the strength of the picture. 
 
SILVER PRINTING. 
 
 289 
 
 It is, therefore, needful in some way to neutralize the acidity, 
 which may be done with carbonate of sodium, carbonate of cal- 
 cium, or certain salts that have an alkaline reaction, such as 
 phosphate of sodium, acetate of sodium, or borate of sodium, 
 each of which substances forms the foundation of various toning 
 formulae. The explanation of their action is this : part of the 
 alkali present becomes converted into chloride, which enters 
 into combination with the chloride of gold, forming, for ex- 
 ample, in the case of soda, chloraurate of sodium. The acid pre- 
 viously in combination with the alkali is set free, but being in 
 all the above cases a weak acid (carbonic, phosphoric, acetic, 
 boracic), is without injurious influence on the bath. In fact, other 
 combinations of alkali with weak acids may be substituted. The 
 writer has obtained excellent results with benzoate of potassium, 
 which he some time since proposed for making the toning bath 
 with, and which has been very favorably reported on by others. 
 Tungstate of sodium has also been used with good effect. Certain 
 acids have a reducing effect upon salts of gold ; oxalates and 
 formiates cannot be used for this reason. Citrate of sodium has 
 been used and was highly recommended some years back, but is 
 now little employed. 
 
 VAEIOUS TONING FOEMUL^E. 
 
 Alkaline Carbonate Toning Bath. — To make this very popular 
 bath, the gold solution is simply rendered alkaline with bicar- 
 bonate of sodium ; the following proportions may be used : — 
 
 Water 32 ounces. 
 
 Chloride of gold 1 to 3 grains. 
 
 Bicarbonate of sodium 5 grains. 
 
 Mix twenty -four hours before using. 
 
 The gold gradually tends to precipitate from this bath, whereby 
 it becomes inactive. Some operators, after using, add just enough 
 hydrochloric acid to make it turn litmus-paper red, and then, 
 before using again, add enough bicarbonate of sodium to cause it 
 to turn red litmus-paper blue. In this way it keeps indefinitely. 
 
 Calcio-chloride Toning Bath. — A solution of chloride of gold is 
 made, one grain to each ounce of water, and a couple of grains 
 of precipitated chalk to each ounce are added and shaken ; next 
 day it is ready for use, diluting each ounce with ten to twenty of 
 water. 
 
290 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 This bath tones mucTi like the preceding ; gives brown, purple, 
 black, or black tones, and, bj overtoning, blue. Succeeds best 
 with paper sensitized on neutral baths. 
 
 Acetate of Sodium Toning Baths. 
 
 Chloride of gold 10 grains. 
 
 Water 80 ounces. 
 
 Acetate of sodium 1 ounce. 
 
 This bath differs considerably -from the foregoing. It will not 
 give black tones, no matter how prolonged its action, but gives 
 splendid warm purple shades that cannot be excelled and cannot 
 be equalled by the common carbonate of sodium bath. If wanted 
 for use in the shortest time, it should be mixed with warm water 
 and let to stand. 
 
 Benzoate Toning Bath. 
 
 Bicarbonate of sodium 5 grains. 
 
 Benzoic acid ....... 10 " 
 
 Chloride of gold 1 grain. 
 
 Water 10 ounces. 
 
 G-ives warm tones similar to the preceding. This bath, origi- 
 nally proposed by myself, works satisfactorily and keeps very 
 well. It acts, perhaps, a little more uniformly than the preceding. 
 Instead of the benzoic acid and bicarb, sodium, an alkaline ben- 
 zoate may be employed. 
 
 Although any of these, or of the following, can be used for 
 almost any purpose, yet certain baths will always have uses for 
 which they are specially adapted. Landscapes should be toned 
 only with the acetate or the benzoate bath. Small heads, as, for 
 example, card portraits, are best toned with the carbonate bath. 
 Eeproductions of engravings, needing a pure black, may be toned 
 with the carbonate, but still better with the chloride of lime bath, 
 to be presently described. 
 
 The following special formulae have been adopted and published 
 by experienced and successful photographers : — 
 
 Mr. Notman's Formula. 
 
 Water . . . . 
 Acetate of sodium 
 Bicarbonate of sodium 
 Nitrate of uranium 
 Chloride of gold . 
 
 210 ounces. 
 1 ounce. 
 
 3 U 
 4 
 
 16 grains. 
 13 " 
 
SILVER PRINTING. 
 
 291 
 
 Keep twenty-four hours before using. When about to use, 
 add eight grains more gold, and continue to add according to the 
 quantity of prints toned,^ 
 
 Dr. Shepard^s Formula. 
 
 Chloride of gold 4 grains. 
 
 Water 1 ounce. 
 
 Keutralize with powdered chalk. 
 
 Chloride of lime . 4 grains. 
 
 ■ Let stand a few hours ; pour the whole, including sediment, 
 into twenty ounces water ; shake well ; let stand over night, and 
 pour off the clear part. 
 
 After use, return to bottle, shake up, add gold in proportion 
 to prints toned, and a grain of chloride of lime for every grain 
 of chloride of gold, or thereabouts, keeping the bath smelling 
 faintly but distinctly of chlorine.^ 
 
 This bath gives a variety of good shades, up to full black. In 
 fact, a pure black seems to be obtained more easily with a chlo- 
 ride of lime bath like this, than with the other formulae. The 
 bath keeps in order for many months, always ready for use. 
 
 Dr. Liesegang^s Formula. 
 
 A. Water 50 ounces. 
 
 Fused acetate of sodium 1 ounce. 
 
 Phosphate of sodium 45 grains. 
 
 Chloride of lime . . . . . . . 15 " 
 
 B. Water 50 ounces. 
 
 Chloride of gold and potassium .... 15 grains. 
 
 These two solutions are to be kept separate and mixed in equal 
 bulks as wanted, immediately before use. 
 
 It seems useless to farther multiply formulae, but it may be 
 remarked here that, as the function of the substance added to the 
 gold solution is to neutralize it, and prevent the corrosive action 
 of the chloride of gold in its primitive state, it follows that alka- 
 lies combined ivith almost any weak acid are likely to give good 
 toning baths, of which an almost endless variety may be com- 
 posed, differing considerably in the tones which they impart. 
 In addition to the baths given here, alkaline tungstates and borates 
 are occasionally used and liked by operators. Those who desire 
 to experiment can take the second formula and substitute for the 
 acetate of sodium such other salts as they may like to test. 
 
 Philada. Phot., III. 253. 
 
 s Ibid., II. 109. 
 
292 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Slow toning gives the richest and finest effects. The work 
 may be expedited by heating or by using stronger baths, but the 
 results are not so fine. When a bath refuses to tone, a little 
 more chloride of gold may be added to start the action. 
 
 § 12. — Toning and Fixing Baths. 
 
 It remains to speak of certain baths which effect at once the 
 toning and fixing. These are made either with hyposulphite of 
 sodium or sulphocyanide of ammonium. 
 
 Hyposulphite Fixing and Toning Bath. — If two ounces of hypo- 
 sulphite of sodium be dissolved in eight ounces of hot water, a 
 grain of chloride of gold previously neutralized with carbonate of 
 sodium (ammonia or phosphate of sodium will not answer) be added 
 after the hyposulphite has dissolved and heen stirred up, we obtain 
 a mixture which, after half an hour's standing, is in condition to 
 fix a print, at the same time toning it to a rich purple black. 
 
 Great fault has been found with this mode of toning, and it 
 is certainly less safe than the foregoing. If used a few hours 
 after mixing, and if a very moderate number of prints be fixed in 
 it, they are as permanent as those treated separately. But, after 
 standing, or if more than a very moderate number of prints be 
 fixed in it, these are sulphur-toned, and speedily fade and turn 
 yellow. 
 
 Good tones are more easily got by separate toning than by this 
 bath, which often gives coppery tones when it is diflScult to find 
 a reason why. 
 
 Sulphocyanide Toning and Fixing Bath. — The writer believes 
 that he was the first to show that a toning and fixing bath could 
 be made with a sulphocyanide and chloride of gold. His experi- 
 ments were made in 1865, and are referred to in the British 
 Journal for 1866, p. 460 and p. 508. A solution of sulphocyanide 
 of ammonium mixed with chloride of gold is quite free from the 
 objection of fading. But the prints must be left some time in a 
 second and fresh bath of sulphocyanide, otherwise a silver com- 
 pound remains in the paper, and eventually darkens. 
 
 To prepare this bath, chloride of gold is to be precipitated with 
 a very few drops of ammonia, and redissolved with sulphocyanide 
 of ammonium. This rose-colored solution, if used fresh, stains 
 the lights rose-color. But if kept twenty-four hours, it becomes 
 colorless, and then no longer stains the lights. Dr. Liesegang 
 
SILVER PRINTING. 
 
 293 
 
 finds the addition of a little sal ammoniac very advantageous for 
 preserving the whites clear. 
 
 When toning baths lose their toning properties, there frequently 
 remains gold in them which has passed to an inactive state. 
 This can be thrown down by making the bath acid with a little 
 hydrochloric acid, and then adding a few drops of solution of 
 sulphate of iron. The gold falls immediately as a brown powder, 
 which may be collected on a filter and preserved. 
 
 After the toning is finished, the print is passed through clean 
 (but not necessarily distilled) water, and is thrown into the fixing 
 bath. 
 
 Using it a little stronger in winter than in summer. A print 
 ought to be completely freed in ten to twenty minutes. Too long 
 a time in the fixing bath will diminish its beauty. 
 
 Until lately, the substance exclusively used for fixing positives 
 on paper has been hyposulphite of sodium. Within a year or 
 two sulphocyanide of ammonium has been proposed as a substi- 
 tute, on the ground that the prints were thereby secured from the 
 injurious action of partly used hyposulphite, which causes fading. 
 
 When either chloride or nitrate of silver is added to a solu- 
 tion of hyposulphite of sodium, decomposition takes place, with 
 formation of tetrathionate of sodium,^ an unstable substance 
 which readily undergoes farther decomposition. Tetrathionate 
 of sodium will itself tone a print very beautifully, entirely with- 
 out the aid of gold ; its toning action seems to depend upon the 
 formation of sulphide of silver, an intensely black substance, so 
 that this process may be likened to some extent to the blackening 
 of a collodion picture with alkaline sulphide, with this difierence, 
 that the action of alkaline sulphide is far more powerful and 
 extends to chloride and iodide of silver, which it blackens readily 
 and intensely. Tetrathionate of sodium, or rather the hyposul- 
 phite bath containing this substance, will not do this, nor will it 
 
 § 13.— Fixing the Prints. 
 
 Hyposulphite of sodium 
 Water .... 
 
 1 pound. 
 4 to 5 quarts. 
 
 > Tetrathionic acid (S^O^) differs from hyposulpliurous acid (SjOj) in having 
 one-fifth less oxygen. 
 
294 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 attack the albuminate of silver wbich remains to some extent all 
 through the substance of the picture. A sulphur toning bath 
 spares, therefore, the whites of the albumen print, which a solu- 
 tion of alkaline sulphide would turn brown. 
 
 The tendency to fade seems to be distinct from this production 
 of sulphide, although it mostly accompanies it. The mere pro- 
 duction of sulphide of silver could not cause fading, for sulphide 
 of silver is a very permanent substance. This we see abundantly 
 proved in the case of negatives which have been treated first with 
 solution of iodine and then with a bath of sulphide of potassium, 
 and which have no disposition to fade, even by long keeping. 
 The addition of three or four grains of bicarbonate of sodium to 
 the ounce of fixing bath, is useful as checking somewhat the 
 tendency to produce unstable prints. 
 
 Generally speaking, the print tends to gain in permanence by 
 a prolongation of the action ; some which the writer left for over 
 an hour in a joint toning and fixing bath exhibited remarkable 
 resistance to the destructive agencies of various tests which he 
 applied to them. But the loss of brightness by long immersion 
 indisposes photographers to permit it. 
 
 No more important ddvice can be given to the photographer 
 than Do not spare the hyposulphite. Even a fresh bath should not 
 be used for too many prints, and a bath which has stood over 
 night after using, should be unhesitatingly rejected, because the 
 decomposition goes steadily on, and such a bath is in much worse 
 condition the next day than it was at the end of the day of use. 
 
 It is always difiicult to induce photographers to act upon cor- 
 rect principle as respects the toning bath, not merely on account 
 of the expense of the gold solution (it requires a better toned 
 print to withstand the action of the fixing bath when the latter 
 is fresh and in right condition for the permanency of the print), 
 but because it is easier to work with a decomposed fixing bath ; 
 so much so, that ten years ago it was even recommended to start 
 decomposition in the bath by substances purposely added. But 
 the photographer who really desires to do justice to his work 
 will not allow himself to be swayed by such considerations, and 
 may be assured that with a little care he will obtain admirable 
 tones that will resist the fresh hyposulphite and give prints that 
 will not disgrace him by turning yellow and fading out. 
 
SILVER PRINTING. 
 
 295 
 
 § 14. — Washing. 
 
 The subject of washing is one that demands the greatest care 
 on the part of the photographer, and there is an almost positive 
 certainty that unless it be done systematically and thoroughly, 
 the prints, however carefully managed in other respects, will 
 rapidly fade. To work thoroughly, the water must be used 
 abundantly, and must be continually changed. 
 
 If prints be thrown into a tank, and a stream of running water 
 be made to flow into it for several hours, a few prints may be 
 satisfactorily washed. But if the number be large, they will 
 interfere with each other, and the washing will be more or less 
 imperfect. 
 
 The simplest contrivance for obviating this difficulty is to have 
 a plug in the bottom of the tank which can be removed from 
 time to time and the tank emptied. Both the time of washing 
 and the quantity of water necessary are in this way very much 
 diminished, but care is necessary that the prints be not drawn 
 into the orifice. 
 
 To obviate the necessity of attending to the washing and re- 
 moving and replacing the plug, a siphon may be adapted to the 
 tank, which will come into ope- 
 ration as soon as the water Fig. 123. 
 reaches a given height (see Fig. 
 123). The siphon pipe passes 
 under and through the bottom. 
 The opening in the bottom which 
 communicates with this pipe is 
 to be covered with a strainer. 
 Or, what is much better still, is 
 a plan adopted by the writer : 
 a ledge is made all round the 
 sides at a height about an inch 
 above the bottom, and on this 
 rests a sheet of metal pierced 
 with a great many holes about 
 a quarter of an inch in diameter. The prints, as the water drains 
 away, rest on this plate and get a very thorough draining away 
 of the wash-water. There is an additional advantage in this 
 arrangement, that it is impossible for prints to lie over and block 
 
296 
 
 PHOTOGEAPHIC MANIPULATIONS. 
 
 up the exit pipe. The sheet should be made of sheet tin, var- 
 nished, and not of zinc. 
 
 Considerable care must be taken in the arrangement of the 
 siphon to make it do its work regularly. To empty the tank, the 
 water must of course run out faster than it is supplied ; the dia- 
 meter of the siphon must therefore be larger than that of the 
 supply pipe, especially as the water comes from the street mains 
 under a stronger pressure than it runs off, and therefore it is sup- 
 plied faster than the mere proportion between the pipes. This 
 larger size of the siphon introduces this difficulty, that the water 
 tends simply to drain off through it, instead of starting the action 
 of the siphon and so emptying the tank. This difficulty the 
 writer finds may be lessened by lengthening the lower limb of 
 the siphon, and contracting it a little at the opening of the lower 
 end. 
 
 The stream of water should, in all cases, be thrown obliquely 
 against the side of the tank ; this gives a rotary motion to the 
 whole body of water and keeps the prints constantly moving, a 
 most important consideration, and which should never be neg- 
 lected. The flow of water through the siphon will be regulated 
 as to rapidity by the difference between the length of its legs. 
 The greater length given to the long leg the more rapid the flow 
 of the water, and the less danger of draining off without starting 
 the siphon. 
 
 Other and more complicated plans for supplying the water 
 have been proposed, such as carrying a pipe round the inside 
 top edge, and piercing it with holes, so as to sprinkle the surface 
 of the water with small jets. But unless these are so contrived 
 as to send slanting streams, and so keep up a rotary motion, a 
 great advantage is lost. 
 
 An ingenious arrangement consists in dividing the tank into 
 two parts by a compartment, underneath which, and under the 
 bottom of the box, is placed a fulcrum on which the tank balances 
 backward and forward with a see-saw motion. The compartment 
 that is uppermost receives the stream of water till it reaches a 
 certain height ; it then rocks over, and the other side receives 
 the water. Meantime the first side is emptying out, and, when 
 empty, rises again and again fills. In a narrow compartment or 
 drawer under the tank, and attached to it, a quantity of bullets 
 are placed loose. These roll from end to end, and by their 
 weight prevent the end that is lowest from rising too soon. 
 
SILVER PRINTING. 
 
 297 
 
 In whatever way the photographer elects to wash his prints, 
 he must satisfy himself that the work is done effectually. The 
 mortification which must be experienced by those who have dis- 
 tributed handsome-looking prints, at finding them turn yellow 
 and fade, cannot be otherwise than very great, and nothing has 
 acted upon photography so unfavorably as the universally recog- 
 nized uncertainty as to the durability of its most attractive pro- 
 ductions. 
 
 There are several ways of testing whether hyposulphite is com- 
 pletely washed out. Two simple but not very accurate methods 
 are the following : — 
 
 1. Touch the white of the print with a little weak solution of 
 nitrate of silver. If a brownish mark is made, it is certain that 
 the print is very imperfectly washed. 
 
 2. Touch the white of the print with a little very dilute solution 
 of iodine in alcohol. A blue mark indicates that the print is 
 pretty nearly free from hyposulphite. Before using this test, it 
 should be ascertained that the particular paper used is sized with, 
 starch, or at least has some starch in the sizing, which strikes a 
 blue tint with iodine when no hyposulphite is present. To fix 
 this point, touch a piece of the paper that has not been sensitized 
 with a little very weak solution of iodine in alcohol, on the back. 
 If no blue stain is produced there is no starch in the sizing, and 
 this test cannot be used. 
 
 3. By far the best test is the following: Take a clean beaker, 
 or even a two-ounce vial, provide a small piece of white blotting- 
 paper, on which make some irregular marks with a glass rod 
 dipped in weak solution of acetate of lead. 
 
 Fill the beaker or vial nearly full of water, add a few drops 
 of sulphuric acid, and mix. Then put in a part of the print to 
 be tested, several square inches at least, and drop in ten or twenty 
 grains of granulated zinc, and immediately cover the mouth with 
 the blotting-paper marked with acetate of lead, which must be 
 still moist. Leave the whole for ten or twenty minutes. If the 
 markings turn brown, it is a proof of insufficient washing. Prints 
 that will stand this test may be considered as thoroughly washed, 
 which cannot be said of (1) and (2), which are less exact. 
 
 It is necessary to be sure of the purity of the sulphuric acid and 
 zinc employed, and the best way to accomplish this is to try the 
 experiment d hlanc, that is, go through it without the print to be 
 tested. If then the markings become brown, it is a proof that 
 20 
 
298 
 
 PHOTOGRAPHIC MANIPULATIONS 
 
 the materials are impure. This preliminary trial entails very 
 little trouble, as one may immediately afterwards proceed to test 
 the print, adding it to the other materials, and, if necessary, a 
 few drops more acid to keep up a very gentle escape of gas, 
 
 "Where sulphocyanide of ammonium is used as a fixing agent, it 
 is probable that a materially less amount of washing is sufficient. 
 But care must be taken that the fixing has been effectual. This 
 may be ascertained by covering one-half of a print and exposing 
 the other half to a bright sunlight for three or four hours, or, 
 better, a day. If any difference in the purity of the whites is 
 perceptible in the two halves, the fixing has been insufficient, 
 
 § 15. — Finishing the Print. 
 
 The fixed and washed print will next require to be trimmed 
 and mounted. 
 
 When very large quantities of prints are trimmed, machines 
 are made that cut them out of the required shape at a single 
 blow. This method is peculiarly suited to portraits, especially 
 card portraits. Landscape prints require more attention, and the 
 trimming can often be so regulated as to improve the general 
 effect. 
 
 An extremely convenient arrangement is to procure a thick 
 plate of glass with its sides exactly at right angles to each other, 
 and to rule on it with a diamond a number of 
 Fig. 124. lines parallel to the sides. Then resting the 
 I [ j I plate on the print, some one of these lines is 
 '. kept parallel with a vertical or horizontal line 
 
 of a building, or with the line of the horizon 
 itself. Then a sharp blade is run round the 
 edges. 
 
 I It is convenient to have one end of the plate 
 
 dome-shaped. The edges should bevel a little, 
 
 I I i I I receding as they rise from the print ; the ruling 
 
 should be on the under side.^ 
 Some operators use brass frames. These are very objection- 
 able, as fine fragments are chopped off and ground into the paper, 
 
 1 These plates are made and for sale in London, but, apparently, not here. 
 Mr. B. Shoemaker, of this city, has made one for the author, of 8x10, a larger 
 size than is kept in London. Probably when they are better known here, they 
 will be kept by dealers. 
 
SILVER PRINTING. 
 
 299 
 
 eventually making stains. Steel edges to glass plates are excel- 
 lent, but brass edges to glass plates are to be condemned. 
 
 The trimmed print is next to be attached to the mount with 
 some adhesive substance. Glue is undoubtedly the best, but not 
 the least troublesome, and is therefore less used than paste and 
 gum. 
 
 "Whatever is used should be applied freely, and a few minutes 
 given to swell, otherwise the print cannot be applied smoothly 
 and evenly to the mount. Whatever adhesive material is used, 
 should be freshly made. Sour paste is very objectionable. 
 
 Many amateurs like to paste their prints into scrap-books 
 instead of mounting on cards, attaching them to the leaf by the 
 four corners only. A good deal of annoyance is often caused by 
 the cockling up either of the print, the leaf, or both. The writer 
 finds that this trouble can be perfectly avoided as follows : — 
 
 Place some powdered gum-arabic in a wide-mouthed vial with 
 a long thick cork. Moisten the bottom of the cork with the 
 tongue, place it in the bottle, reverse it, and some powder will 
 adhere ; moisten again slightly, and gently rub the under corners 
 of the print with the cork, transferring thus a very thick muci- 
 lage, which dries almost instantly, and without cockling, No 
 one who uses this method will ever use any other. It has, beside 
 its freedom from cockling, the advantage of being always ready, 
 and yet always affording a perfectly fresh material, free from 
 danger of sourness, and certain not to black the corners of the 
 print. 
 
 Too little attention is paid to the quality of the pasteboard 
 used for mounting. If this contain hyposulphite of sodium, used 
 as " antichlor" by many papermakers, the eventual destruction 
 of the print is almost certain, as in damp weather enough moisture 
 penetrates to transfer the hyposulphite to the print. It has been 
 affirmed that three-fourths of all the mounts in the market give 
 indications of hyposulphite when tested carefully. 
 
 It is therefore no small protection to the print to have a litho- 
 graphic " tint" printed on the board for mounting, and extend- 
 ing a short distance beyond the print all round. In this way 
 the transfer of soluble ingredients from the mount to the print 
 is rendered well-nigh impossible. As various adhesive prepara- 
 tions adhere much less well to thick " photographic tints" than 
 to ordinary paper, it is generally necessary to use good glue, 
 otherwise the prints readily peel off. 
 
300 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 In damp weather tbe drying of the adhesive application between 
 the two hard surfaces proceeds slowly, and care must be taken 
 not to pile up the prints too soon, or the evaporation may be checked, 
 and the paste or other material may mould, and immediately 
 stain the prints. Hundreds are sometimes lost in this way before 
 the danger is perceived. 
 
 Boiling. — Prints, after mounting, are always rolled, usually in 
 powerful presses between steel surfaces. This forces together 
 the fibres of the paper, gives a hard, fine surface, darkens the 
 print a little, and improves its appearance materially. It is best 
 done just before the print is dry after mounting. The steel sur- 
 faces must be kept bright, which is often troublesome. Nickel 
 plating greatly diminishes the trouble of preserving a high sur- 
 face. 
 
 Encaustic paste is prepared by dissolving white wax in essential 
 oil of lavender, or any other volatile solvent, to a pasty consist- 
 ency. This mixture, well rubbed into a print with a tuft of 
 flannel, adds considerably to the transparency of the shadows, 
 and, in many cases, decidedly improves the picture. It has also 
 a favorable influence upon the durability of the print. Salomon, 
 whose prints are remarkably fine, gives the following formula : — 
 
 Pure virgin wax 5 ounces. 
 
 Gum elemi .44 grains. 
 
 Benzole 2 ounces. 
 
 Essence of lavender 3 " 
 
 Oil of spike 66 drops. 
 
 Griine boils equal parts of white wax and castile soap in an 
 earthen vessel with a little water, enough to make a soft paste. 
 
 § 16. — Permanence of Silver Prints. 
 
 Great discredit has been thrown upon photography by the 
 fading of silver prints, an effect which the author believes to 
 have resulted from negligence in washing. A well washed and 
 toned print is, according to his experience, very durable. Of 
 gold-toned prints made by the writer of this manual not a single 
 one has faded or altered in any respect. 
 
 The writer believes that in very many cases of fading, espe- 
 cially of views made for sale, there has been no gold toning at 
 all, but simply a sulphur toning. With albumenized paper this 
 toning is sure in the long run to decolorize very much, though 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 
 
 801 
 
 some specimens on plain paper, executed by him many years ago, 
 are still as good and as pure black as the day they were finished. 
 The different modes of gold toning seem all to yield results 
 equal in respect of permanence. Developed prints, although 
 gold-toned with equal care, are less permanent, according to 
 careful and extended experiments made by the writer, than sun- 
 prints. Of these last, the strongest seem to be those that have 
 been over-printed enough to bear a very full time (twenty minutes 
 or thereabouts) in a strong fresh hyposulphite bath. 
 
 CHAPTER XIV. 
 
 FAILURES IN PHOTOGRAPHIC OPERATIONS. 
 
 The beginner in photography will be very apt to find that, 
 after proceeding reasonably well for a time, his success suddenly 
 terminates for some reason quite undiscoverable to him. He 
 appears to be proceeding exactly as before, yet he cannot get the 
 same results. A very simple and useful course will be to change 
 each of his materials in succession, collodion, bath, and developer, 
 and so endeavor to detect the proximate source of the trouble. 
 This plan does not always, however, succeed, for the new mate- 
 rial substituted may have precisely the same fault as the old ; it 
 may not be in any respect bad or impure, but may be simply 
 unsuitable to the other materials with which it is employed. 
 
 Not only the beginner, but even the experienced photographer, 
 will occasionally find that things go wrong ; no one can claim 
 entire immunity from photographic troubles. For these reasons 
 the writer has endeavored to make this chapter a very complete 
 one, believing that it will be very frequently referred to, and 
 with advantage. He has collected the information here given 
 partly from personal experience, but also very largely from other 
 sources in various languages. For convenience of reference, it 
 has been carefully classified under different heads : — 
 
802 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 I. Failures Common to Negatives, Ambrotypes, and Fer- 
 rotypes. 
 
 Sec. 1. Fogging and Veiling. See page 802. 
 " 2. Thinness of Film. Page 310. 
 
 " 8, Irregularity of Film, Crapy and Structural Lines, Gran- 
 ularity, Warty Lumps, etc. Page 810. 
 " 4. Transparent Mottling at Corners. Page 312. 
 " 5. Defects in the Image. Page 318. 
 " 6. Splitting and Slipping of the Film. Page 316. 
 " 7. "Want of Sharpness. Page 317. 
 " 8. Streaks. Page 818. 
 
 " 9. Transparent Spots and Pinholes. Page 321. 
 " 10. Opaque Spots, Comets, etc. Page 324. 
 " 11. Lines. Page 326. 
 
 " 12. Stains and Surface Markings. Page 827. 
 
 " 18. Feathery Markings : Imperfect Fixing. Page SBO. 
 
 " 14. Faults in Varnishing. Page 830. 
 
 " 15. Miscellaneous. Page 338. 
 
 II. Failures belonging especially to Negatives. Page 
 334. 
 
 III. Failures belonging especially to Ambrotypes and 
 Ferrotypes. Page 835. 
 
 IV. Failures belonging especially to Paper Develop- 
 ment. Page 836. 
 
 V. Silver Printing. 
 
 1. Failures Common to Glass and Paper Worh. Page 336. 
 
 2. Failures Peculiar to Silver Printing on Paper. Page 838. 
 8. Failures Peculiar to Gollodio- Chloride Printing. Page 342. 
 
 I. Failures Common to Negatives, Ambrotypes, and 
 Ferrotypes. 
 
 § 1.— Fogging. 
 
 Fogging is a trouble that affects different operators very vari- 
 ously : some are very frequently, others almost never affected 
 by it. The learner may expect to be frequently troubled ; the 
 experienced operator will have learned how to avoid it, except, 
 
FAILURES IN" PHOTOGRAPHIC OPERATIONS. 
 
 803 
 
 perhaps, when he works under unusual conditions, or with chemi- 
 cals different from those which he habitually employs. 
 
 Before proceeding to the particular sources of fogging, some 
 observations of a general nature may advantageously be made. 
 
 General Remarhs. — When a case of fogging presents itself, a 
 careful study of the appearance of the plate will often afford a 
 clue to the source of the trouble. 
 
 A fogged plate may present a uniform sheet of blank fog all 
 over, without a trace of a picture. Or an image may come out 
 with more or less strength, but, after showing itself, may pre- 
 sently become covered with a dense deposit of silver. Or, finally, 
 the fogging may be very slight, leaving all details of the image 
 perfectly visible, but ruining it by veiling the deep shadows 
 sufficiently tg prevent them printing to a full rich black. 
 
 The above various cases are alike in this, that the action of the 
 fogging is uniform all over the plate. We, therefore, presume 
 that the trouble lies either in the chemicals, the light, or the 
 atmosphere of the dark room, and, if we cannot get rid of the 
 evil by the addition of a little iodine to the collodion, we must 
 commence a series of systematic trials (see p. 306), to detect the 
 source of the trouble. We do not, however, in the above case, 
 suspect the camera. For, if the camera leaks light, the effect of 
 that light is invariably partial and irregular. The unequal con- 
 traction and expansion of the wood round the flange, into which 
 the lenses are screwed, will often produce a crack; this will give 
 a mass of fog somewhat denser in the middle, and shading off 
 towards the ends of the plate. A hole in the bellows body will 
 produce an irregular mass of fog on some part of the plate on 
 which the light falls. If the dark slide does not fit tight, the 
 fogging will mostly be at one end of the plate. A crack in the 
 shutter will produce a bar of fog lengthwise of the plate, and 
 shading off on both its sides. Cracks in the woodwork will send 
 in fan-like masses of light, and so on. These appearances will 
 aid at once in the detection of the cause of the troubles (see also, 
 beyond, "White Light," p. 806). 
 
 Another very valuable distinction is drawn as follows : — 
 
 A superficial fogging^ one that rests on the film and not in it, 
 and can be rubbed off with the finger, is always attributable to 
 the chemicals, never to exposure to white light, which last always 
 produces an action in the interior of the film. 
 
 Therefore, if the fogging be internal and not superficial, it is 
 
PHOTOGRAPHIC MANIPULATIONS. 
 
 most probably owing to intrusion of light; this cannot be affirmed 
 with entire positiveness, but is the most likely cau^e, for faults in 
 the bath, collodion, etc., most generally give rise to superficial 
 fogging. That is, fog from chemicals is generally superficial; 
 superficial fog is always from chemicals. 
 
 1, Chemicals in Fault. — Generally speaking, when fog shows 
 itself, and when the presence of white light is not suspected, the 
 first thing done is to treat the bath. 
 
 But, in all such cases, the first step should be invariably to try 
 another collodion, or to add a little tincture of iodine to that in 
 use. Iodine tends to make the bath slightly acid. Therefore, the 
 addition of acid to the bath, or iodine to the collodion, is, in each 
 case, a step in a somewhat similar direction. And it would at 
 first seem more correct to add the acid to the bath, as that brings 
 the bath at once to the requisite point of acidity, and stops there, 
 whereas, by adding iodine to the collodion, every plate tends to 
 render the bath more acid. 
 
 But, in practice, it is found that the results of the two treat- 
 ments are very different. Sometimes a very little iodine will 
 effect a cure when acid seems to have no effect. For example, 
 the writer has seen a bath made of fused nitrate of silver abso- 
 lutely refuse to give a clean picture, even when acidified beyond 
 what is proper, and yet work excellently by adding a very little 
 iodine to the collodion — a collodion which was not new, but had 
 worked perfectly a month before, in cooler weather, with a nearly 
 neutral bath. 
 
 When a neutral nitrate has been used, acidulation should not 
 be carried beyond one drop of nitric acid or twenty -five drops of 
 No. 8 acetic acid to every fifteen or twenty ounces of bath, and 
 this much is only allowable when the nitrate of silver was free 
 from acid. When the acidifying has reached this point, if the 
 picture is not clean, the remedy is most certainly needed in the 
 collodion. And it must never be forgotten that these treatments 
 with acid or with iodine are but necessary evils, and that the 
 more nearly neutral the bath and collodion the more rapid will 
 be the work. There appears to be no doubt that excess of nitric 
 acid in the bath may cause fogging. 
 
 The bath, however, may have been alkaline, and may therefore 
 need neutralizing and acidifying. This will be ascertained by 
 introducing a piece of red litmus-paper. Alkalinity may arise 
 from having introduced an alkali intentionally, especially if am- 
 
FAILURES IN PH OT O G R A-PH I C OPERATIONS. 305 
 
 monk have been Jiclded, previoas to sunning. Bicarbonate of 
 sodium renders a bath rather neutral than alkaline, and is the 
 only substance that should ever be employed for removing an 
 excess of acidity. Or alkali may have been carelessly introduced, 
 when glasses cleaned with caustic soda or other alkali have been 
 insufficiently washed before coUodionizing. 
 
 The use of fused nitrate of silver, that has been kept too long 
 in a state of fusion, or heated to too high a temperature, may tend 
 to produce fog. Remedy : add very dilute nitric acid very cau- 
 tiously, or try an older collodion. 
 
 An old bath, highly charged with impurities, may lead to 
 fogging. As a palliative, add bicarbonate of sodium till a per< 
 manent precipitate falls, and then expose for several days to the 
 sun. Filter, and acidify if necessary. 
 
 Sometimes an old bath will lead to fogging, not by reason of 
 impurities, but simply by having become too weak by mere 
 exhaustion of the silver. This will be more apt to happen with 
 baths whose evaporation is checked by being kept covered. 
 Remedy : add crystals or fused nitrate of silver. 
 
 Or the collodion may be in fault. A very new collodion, espe- 
 cially one containing little or no alkaline salt, but chiefly cad- 
 mium salt, particularly if used with a nearly neutral bath, will 
 sometimes refuse to give clean, bright pictures. (See also p. 136.) 
 
 In this case, especially if the collodion be very pale, it is well 
 to add to it a little tincture of iodine, and so apply the remedy to 
 it rather than to the bath. Or the admixture of a little old (but 
 not too old) and more highly colored collodion will be found 
 useful. 
 
 The developer may be in fault. If, when thrown upon the 
 plate, it becomes almost immediately muddy, more acetic acid is 
 wanted. Or, a developer that has hitherto worked well, may 
 cease to do so in consequence of a change of weather and tem- 
 perature. 
 
 It has been af&rmed that excess of acetic acid may produce 
 fogging. 
 
 If copper be used in the developer (sulphate of copper, blue 
 vitriol), and the plate have been left in the bath for a time insuf- 
 ficient to convert all the soluble iodides into iodide of silver, 
 brown fog may be produced by the formation of iodide of copper 
 in the film. 
 
 Old specimens of pyrogallic acid used in developing or rede- 
 veloping, have been known to produce blue fogging. 
 
306 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 2. The vessels may he in fault. India-rubber or vulcanite bath, 
 or even dippers, may lead to fogging, and are more likely to 
 when new than old. In work in the house, they should never 
 be used. Even for work in the field, the writer advises a glass 
 bath with a case and screw cover. But if weight is very im- 
 portant, and a rubber bath is to be used, it should, if new, be put 
 aside for twenty-four hours with a strong solution of caustic alkali. 
 The "concentrated lye," sold in sheet-iron boxes, is very good 
 for this purpose, and may be dissolved in eight or ten times its 
 weight of water. In the case of an old bath, it should be scrubbed 
 out with a sponge tied to a stick between each using. 
 
 3. The luater may be in fault. It is said that cases of fogging 
 have been traced to this source, but the writer has never expe- 
 rienced it. The sorts of water said to cause it are — water con- 
 taining iron; water containing much lime; rain-water collected 
 off of dirty roofs, or water from wells into which any decaying 
 matter penetrates, or any foul drainage. 
 
 4. White light will, of course, cause fogging. As already said, 
 a careful examination of the appearance of the plate will gene- 
 rally indicate whether light has been admitted into the dark room, 
 or has made its way into the camera, because, in the first case, 
 its action extends uniformly over the whole plate, in the other it 
 does not, but mostly appears in bars, fans, brushes, or long slant- 
 ing rays, the positions of which will always aid in tracing out 
 the cause, remembering that the more indistinct the boundary 
 of the fog the farther is probably the opening or leak from the 
 plate. 
 
 A few systematic trials will always force out the source of the 
 fault. 
 
 Develop a plate without exposure and without removing it 
 from the dark room. If no tendency to fog appears, the fault 
 was clearly in the camera or the dark slide. Then sensitize a 
 plate and carry it into the glass room in its dark slide. Leave it 
 a few minutes and develop it again without having exposed it or 
 withdrawn the shutter. If it then fogs, the leak is in the dark 
 slide; if not, then it must be in the camera. 
 
 Let us, on the other hand, suppose that the plate fogged, when 
 developed, without having been removed at all from the dark 
 room. Then the fault is, either that white light gets into the 
 dark room, or the chemicals are in fault. 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 307 
 
 A simple way of deciding this is to try a plate at night. Use 
 only a candle or lamp, well protected with yellow or green glass. 
 Sensitize a plate, lay it on a dark object, put a worthless negative 
 over it, and carry it into another room, in which is a gaslight, 
 turned on. Hold the plate a foot from the burner for fifteen 
 seconds, taking care that the back is perfectly protected. Then 
 carry and develop, by the light of a lamp or candle, behind yel- 
 low glass. If a clean picture comes out, it is a proof that white 
 light gets into the dark room in daytime. If it fogs still, when 
 tried thus, the chemicals are wrong, and must be changed, one 
 after another, until the wrong one is detected. 
 
 This simple but systematic and exhaustive search will invari- 
 ably lead the operator straight to the source of his trouble. 
 
 If the foregoing examination shows the fault to be with the 
 camera, it must be carefully overhauled. Carelessly made cameras 
 are quite worthless, and a great many such are exposed for sale. 
 The writer dislikes walnut, although this wood is so great a 
 favorite, because it cracks so much, and prefers mahogany, and 
 next to it, cherry. Look, therefore, carefully for cracks. Exa- 
 mine if the shutter works close in the dark slide. Notice if a 
 hole has been worn into the bellows body. But the commonest 
 place to crack is the camera front, which often splits at the screws 
 that fasten the flange in. When a crack once appears, do not 
 trust to filling it up, but get a new front. A crack slowly widens, 
 and so leaves a space between the edges and the filling. A crack 
 may, however, be neatly mended by a good workman. The front 
 is cut half-way through at the crack, for half an inch each side, 
 and a piece set in. Then if the crack widens, it can do no harm, 
 and another crack is not likely ever to form, as the tension that 
 caused it has been relieved. 
 
 When a camera is used in the open air, it must invariably be 
 covered with a thick cloth. Strong light, especially direct sun- 
 light, will make its way through almost any camera, unless so 
 protected. 
 
 5. Sunlight falling directly upon the lens may cause fogging, 
 though this result does not necessarily follow. 
 
 6. Atmospheric Causes. — The sources of fogging may depend 
 upon impurities in the air. These may be of several sorts. 
 
 A. Ghemical. — Fumes of various sorts may cause fogging. 
 Ammonia is especially to be avoided. See that the ammonia 
 
308 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 bottle hae a well-fitting glass stopper — not a cork. Sulphuretted 
 hydrogen, arising from exposure of solutions of sulphide of potas- 
 sium, or of Schlippe's salt, is even worse. 
 
 B. Certain organic suhstances have a tendency to cause fogging. 
 The vapor of turpentine and of fresh paint. The smell of kero- 
 sene lamps in the dark room does not seem to be hurtful, as might 
 be supposed. 
 
 C. Foulness in the air is liable to cause fogging. Emanations 
 from drains, cesspools, and the like, or any putrefying or decay- 
 ing organic matter. Emanations from stables are always ammo- 
 niacal, and tend to fogging. It should be borne in mind that 
 immunity from these sources at one time, is no proof that they 
 may not be acting at another. Dampness acts very remarkably 
 as a vehicle for odors, and emanations may rise in wet weather so 
 as to cause fogging, when they would not at other times. Inde- 
 pendently of this, the state of the barometer controls currents and 
 movements of air remarkably. When the barometer is rising, a 
 room will be supplied with air from channels quite different from 
 those that act when the barometer is falling. Drafts of chimneys 
 are always worse with a rising barometer. Whether carbonic 
 oxide, the gas which flues are intended to carry away from fires, 
 will cause fogging, the writer cannot state, but no one is justified 
 in permitting this most dangerous gas to escape into apartments 
 by defective flues. Its danger is not greatest when it asphyxiates, 
 for then the evil is noticed in time, and remedies are applied. 
 But if inhaled continually in small quantities, it causes diseases 
 of the brain and spine. Leakage of illuminating gas may cause 
 fogging. 
 
 7. Errors of Manipulation. — Under this head the following are 
 to be classed : — • 
 
 a. Plate left too long in the bath. This, especially in warm weather, 
 is a fruitful cause of foggy plates. When the plate is perfectly 
 free from oiliness, it is ready for removal. The sensitiveness in- 
 creases by leaving in for a full time ; the brightness and cleanness 
 are greatest when the plate is taken out as soon as the oily lines 
 are gone. In the latter case, undecomposed bromide remains in 
 the film, diminishes sensibility, but checks veiling and fogging. 
 
 b. Too long -a development^ rendered necessary by too short an 
 exposure. 
 
 c. Neglect to add acid to the developer or the redeveloper. 
 
 d. Insufficient wasliing off of the developer, so that enough 
 remains to act. 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 
 
 309 
 
 e. Considerable over-exposure with a large stop will produce fog- 
 ging, or rather an appearance closely resembling the effect of fog. 
 
 f. Re-dipping the plate into the negative hath before development 
 is very apt to cause stains and fog, especially with a bath not in 
 first-rate order. 
 
 g. Too strong a developer, or using in summer a developer suit- 
 able for winter. 
 
 h. Keeping on the developer after spangles of silver show in it. 
 
 i. Developer turns muddy at once. Developing vessel not duly 
 cleaned. Use the bichromate solution. Bad condition of the 
 nitrate bath. Keeping and using pyrogallic acid dissolved in 
 water instead of alcohol. 
 
 In the case of glass positives, fogging, when superficial, may 
 be wiped off carefully with soft cotton-wool. 
 
 7. Temperature of the Dark Room. — Either extreme of tempera- 
 ture may cause fogging. In very hot weather, use less iron and 
 more acetic acid. Some operators find it advantageous to place 
 the bath in a vessel of cold water, to keep down the temperature. 
 
 In very cold weather, if the dark room be nof artificially heated, 
 the chemicals will not act well. Great perplexity is sometimes 
 caused to inexperienced operators in this way, who will perhaps 
 suddenly find that they pass from success to failure without any 
 assignable reason, and only learn by the most painful experience 
 the real source of their trouble. A temperature of about 65° is 
 always the best, though considerable variation may occur before 
 evil results. 
 
 Veiled (that is, very slightly fogged) negatives often print as 
 well as brighter looking ones. If the veiling reaches the extent 
 of slight fogging, a clearing process may be resorted to in either 
 of several ways. A very weak solution of sesquichloride of iron 
 may be washed over the plate. Or it may be washed a little 
 with weak Lugol's solution, and then thrown into the fixing 
 bath. Or the plate may be chlorized (see article on After-inten- 
 sification) to a very moderate extent, and then passed through 
 the fixing bath. Whichever plan is adopted, experience should 
 be first gained on worthless negatives. 
 
 8. Dew Collecting on the Lerts. — In hot damp weather dew may, 
 at any time, collect upon the lens almost in a moment. This is 
 especially apt to happen in passing from a cool, shaded spot to a 
 warm, damp one. Watchfulness for this cause of trouble will be 
 particularly needed in warm, damp, steamy weather. 
 
310 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 9. In portraiture, an excess of diffused irregularly reflected 
 light may veil the plate. 
 
 § 2.— Thinness of the Film. 
 
 A thin gray film, so appearing when removed from the sensi- 
 tizing bath, may be caused by too strong a bath, which at first 
 acts rapidly upon the film, but gradually diminishes its density. 
 This is the case with ordinary collodion. With a collodion con- 
 taining bromide only, intended for the dry process, thinness of 
 the film results from too weak a bath. 
 
 A thin bluish film, with wet plates, indicates insufficient salting 
 of the collodion, or insufficient time in the bath. With collodio- 
 bromide plates, it indicates that the collodion has not stood long 
 enough after sensitizing. 
 
 Very old collodion will sometimes give very thin, transparent 
 films, as will also a foul nitrate bath. 
 
 § 3.— Irregularity of the Film, Crapy and Structural Line, Warty 
 Lumps, Granularity, &c. 
 
 Crapy Lines. — 1. Too watery alcohol or ether. (Fig. 125, 
 lower corner.) 
 
 It does not necessarily follow that the materials are in fault as 
 purchased, for the water may have been in- 
 Fig. 125. advertently introduced by the photographer 
 
 himself. After cleaning a bottle, in which 
 collodion is to be made, proceed as follows : 
 Drain it well, pour in an ounce or two of al- 
 cohol, shake well so that the alcohol wets 
 every part, pour it out, and repeat the opera- 
 tion. The quantity of water that may be in- 
 troduced by a wet bottle is more than would 
 be supposed. 
 
 2. Neglect to rock the plate from side to 
 side, after collodionizing, especially when using a rather thick 
 collodion. If this is the case, thin with equal parts alcohol and 
 ether. Before deciding, however, that the collodion requires 
 thinning, the operator, if not experienced, should endeavor to 
 satisfy himself that the fault is not in his manipulation: thinning 
 should not be unnecessarily resorted to. 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 
 
 311 
 
 The larger the plate the thinner must be the collodion. A 
 small plate can be managed with a collodion which will inevita- 
 bly give crapy lines when used for a large one. 
 
 Excessive cold may produce crapy lines. 
 
 Ridges. — 1. Too much pyroxyline in collodion. 2. Too much 
 alcohol and too little ether. (Both these defects are cured by 
 adding a little ether.) 3. Excess of ether may, however, produce 
 a similar effect. 4. Bad cotton, tending to gelatinize; or the col- 
 lodion may have become too thick by the agency of bromide of 
 cadmium. The action of this substance upon collodion is very 
 remarkable, and varies extremely at different times. 
 
 Mottling may arise from irregularity in the porosity of the film, 
 so that the developer penetrates irregularly. It usually results 
 from using too thick a collodion; sometimes from not plunging the 
 plate into the bath soon enough after coating. Mixing witli 
 ether and immersing as soon as set will usually remove this 
 trouble, which is most apt to show itself in the flat tints, espe- 
 cially in semi-opaque skies. Or it may arise from a bad quality 
 of cotton. Cottons vary extremely in this respect ; some have 
 much tendency to mottling, others none at all. Or the alcohol 
 may be too watery. 
 
 Collodion that has thickened through the agency of bromide of 
 cadmium, may be made to work by mixing with very fluid collo- 
 dion. Much circumspection is, however, needed. The mixture 
 should stand for several days, with occasional shaking, and then 
 be carefully filtered. 
 
 Blistering is not a common fault, but arises from using a too 
 old and rotten collodion. 
 
 Warty Lumps. — As the collodion film dries after coating, any 
 solid particles present collect around them a 
 portion of the collodion, making little raised 
 prominences. Most commonly, these are 
 caused by fine filaments, either of wool, from 
 the dust caused by wear of clothes and car- 
 pets, or of undissolved fibres of pyroxyline. 
 These little warty places, examined with a 
 microscope, present the appearance seen at 
 Fig. 126. When motes are visible as the film 
 flows over the plates, they can often be floated 
 off by pouring on an abundant quantity, and 
 managing to make the collodion, as it flows off, carry away the 
 
 Fig. 126. 
 
 A warty lump magui- 
 fied, showing a filament 
 nucleus. 
 
312 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 mote. Careful filtering of the collodion, and thorough brushing 
 off of the plate immediately before coating^ are the best preventives. 
 In field work it is often best to take several small bottles of col- 
 lodion rather than one larger one. 
 
 Want of homogeneity in the collodion must result in irregu- 
 larity of density and streakiness. If different collodions be 
 mixed without sufficient shaking ; collodion that drains off from 
 the plate is always denser, and sinks to the bottom if drained off 
 into other collodion. By standing a long time, the mixed collo- 
 dion may become homogeneous by diffusion, but it is unsafe to 
 trust to this. 
 
 Again, suppose the drainings from the plates have been re- 
 ceived, as they always should be, into a separate bottle, and that 
 a quantity of such be filtered in a collodion filter, of which the 
 bottom part is already partly filled with collodion, each drop 
 will sink to the bottom, and the two collodions will remain quite 
 separate. If poured out, and handled carelessly, there will be 
 formed an irregular mixture which cannot diffuse itself with 
 perfect regularity over glass plates. 
 
 Therefore, collodions either should be kept thoroughly separate, 
 or, if mixed, should be mixed thoroughly by shaking, and then 
 be either filtered in separate lots, or allowed to settle separately. 
 Those curious to observe the action of collodions in mixing, can 
 tinge one portion with a little rosaniline, by which means it can 
 be distinguished in its movements. 
 
 Granularity. — After a certain time of action, the iron developer 
 will always become muddy ; and if allowed to remain on the plate 
 in this condition, it may fog ; or, if it does not, it will probably 
 form a gray, granular deposit, destructive to the fineness of the 
 negative. A negative, to give a rich, velvety print, should be 
 made up of an extremely fine silver deposit. Too much bromide 
 in the collodion will also cause granularity in the image. 
 
 § 4.— Transparent Mottling at one Corner of the Plate. 
 
 This is owing to the heat of the fingers. It will be found that 
 these marks always, come at the corner by which the plate was 
 held whilst being collodionized. (See Fig. 125, upper corner.) 
 Often, if the plate be held up to the light before putting into the 
 dark slide, these irregularities will be perfectly visible. 
 
 What is remarkable is that, in the great majority of instances. 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 
 
 313 
 
 the plate can be held without this result following. It appears 
 to come only with certain temperatures and conditions of the 
 atmosphere, and principally in cool weather. The remedy is to 
 fold up a piece of paper, and keep it between the finger-ends and 
 the bottom of the plate. In fact, this sort of marking is so great 
 an annoyance where it comes, and so irregular in its coming, that 
 it is a good plan always to use the paper ; it is little trouble, and 
 the cure is perfect. 
 
 In making dry plates, this precaution should never be neglected. 
 
 This sort of mottling can always be distinguished from that 
 which arises from bad cotton or bad alcohol (see last section) by the 
 marks corresponding with the shape and position of the fingers. 
 
 § 5. — Defects in the Image. 
 
 Image strong but coarse. Too much pyroxyline. 
 
 Image fine but weak. Too little pyroxyline. 
 
 Too much Contrast. — 1. Under exposure followed by over-de- 
 velopment is by far the most common cause. 2. Too little py- 
 roxyline in the collodion. 3. Bromide either wanting entirely 
 or too little of it. 4. The introduction of a great deal too much 
 bromide will produce the same effect. That is, a little too much 
 bromide will make the image too flat, whilst a still greater excess 
 will render it harsh. 5. Acidity of collodion. (See also §13, Insen- 
 sitiveness.) 6. Use of old, red collodion. 7. It has been said 
 that alkalinity of collodion may also produce this defect. 8. 
 Insufficient salting of collodion. 9. Old and foul nitrate bath. 
 Although by good management a negative bath can be kept in 
 working order for a very long time, still the best rendering of 
 strong contrasts will always be made by a nearly new and pure 
 bath. Shaded foliage in well-lighted scenes and instantaneous 
 effects will be better rendered by plates made under these con- 
 ditions. If the bath wants sunning, it may be expected to give 
 harsh pictures. 10. Too intense a pyroxyline. 11. Working in 
 too cold temperatures. 
 
 Too Little Contrast. — 1. Over-exposure, 2. Too much bromide. 
 3, Alkaline collodion. 
 
 Too Much Vigor. — Powerful, slow-printing negatives, requiring 
 sunshine and long exposure to print, come with a thick, highly 
 salted collodion and rich nitrate bath. Such will need to be 
 printed with a weak positive bath and sunlight. 
 21 
 
314 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Too Little Vigor. — Good negatives, except that they are thin, 
 yet very delicate and full of detail, are got with fluid collodion, 
 lightly salted and sensitized in weak baths. Such will need a 
 rich positive batk and printing in the shade. 
 
 This fault may arise from under or over exposure, the effects 
 of which are, however, different. In the under-exposed image, 
 the least defective parts will be the high lights of the object, 
 which will in general be good, and the worse lighted parts will 
 be defective. Where the picture is over-exposed, the reverse 
 will be the case. Generally speaking, in an under-exposed pic- 
 ture, especially after redevelopment, the contrasts will be too 
 great. An over-exposed picture will be gray and feeble, and 
 deficient in contrast. 
 
 It may easily happen that a negative may be condemned as 
 thin and flat, when in reality it may need nothing else than 
 printing on paper sensitized with a materially richer positive 
 bath. 
 
 Weakness may also arise from exhaustion of the negative bath, 
 in which case it must receive more nitrate of silver. Now that 
 more bromide is used in the collodion, a thirty-grain bath is no 
 longer sufficient, but forty to forty-five grains give a better result. 
 The employment of these strong nitrate baths has become much 
 more general than at the time when the first edition of this 
 manual was published. A strong negative bath tends to keep 
 the iodide and bromide of silver (and consequently the image) 
 within the film. A weak bath tends to give a superficial image. 
 
 Thin White or Gray Image difficult to Intensify. — This is gene- 
 rally the result of having too much nitric acid in the bath. Add 
 a very little bicarbonate of sodium. If, at the same time, the 
 bath gives pinholes, dilute it, render it alkaline with bicarbonate 
 of sodium, sun it, filter, and then faintly acidulate. 
 
 The following causes are assigned by Hardwich as leading to 
 weak and slaty-blue images : Negative bath newly made with 
 impure crystals of nitrate of silver. Too much free iodine in the 
 collodion. Camera image very weak, as in copying old manu- 
 scripts, etc., full size. Use of a negative collodion made from 
 weak pyroxyline. Sulphuric acid left in the collodion from im- 
 perfect washing. Coating large plates too leisurely in hot 
 weather : the film dries, and there is no penetration of the de- 
 veloper. Over-exposure. 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 315 
 
 Half Tone.— The greatest beauty of result will always depend 
 upon the presence of plenty of varied half-tone, relieved and 
 supported by a certain quantity of deep shadows and high lights. 
 A negative that consists chiefly of dark shadows and bright lights 
 with but little half-tone, will always be greatly inferior in effect. 
 Nothing can compensate for the absence of these broad soft half- 
 shades, which are abundantly present in all good work. No 
 royal road to this result can be indicated: it comes by a full 
 but not excessive, exposure; collodion well, but not excessively,' 
 bromized; careful arrangement of light; and judicious develop- 
 ment. Those who find great difficulty in subduing contrast may 
 find it a valuable hint to increase their exposures, and dilute their 
 developer proportionately, as otherwise the prolonged exposure 
 might lead to flatness. 
 
 Two Images at Once.— Imperfect cleaning. Eemedy : Use the 
 bichromate mixture. 
 
 Blurring or Halation. — Several difierent sorts of blurring pre- 
 sent themselves. 
 
 1. Internal reflection, i. e., from the back surface of the glass. 
 This vexatious evil occurs in proportion to the transparency of 
 the film, except that, in the wet process, there is apparently left a 
 portion of iodide and bromide unconverted, at the bottom of the 
 film, which tends to check it. Therefore this difficulty exists 
 less in. wet than in dry plates. Nevertheless, wet plates are far 
 from being free from it. In taking views of interiors, the win- 
 dows are apt to be blurred. Generally speaking, blurring shows 
 itself most where a brilliant light comes next to a deep shadow. 
 Especially where a dark portion is surrounded by high lights, 
 as in the case where dark objects are projected against the sky,' 
 or, still more, against bright clouds. In this way, roofs of houses,' 
 instead of being bordered by a well-defined line, will shade of!; 
 as it were, into the sky. Small objects projected against the sky,' 
 as, for example, a lightning-rod, may be obliterated almost en- 
 tirely. With wet plates the remedy is to apply a piece of wet 
 red blotting-paper ; with dry plates, to paint' the back with a 
 mixture of annatto, glycerine, and water, as directed under the 
 head of dry plate work. 
 
 2. Where a high light meets a dark shadow, if the portion of 
 the light next the shadow is too light, the result is that the dark 
 object is surrounded by a light band. This is only seen in wet 
 
316 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 plate work. In the shadow, the development consumes but little 
 of the nitrate of silver, so that the adjoining part of the high 
 light is developed in the presence of a solution richer in silver 
 than the rest of it. 
 
 3. The image seems to slide off into the portion next belo\v. 
 This only happens with wet plates, and in cases of difficult de- 
 velopment, owing to a cold temperature, a weak image, etc. 
 
 4. Objects moved by the wind are also blurred. If a bough 
 be projected against the sky, and moves during exposure, the 
 white light from the sky may almost obliterate the image of the 
 bough. Any blurring by the wind produces a most disagree- 
 able effect upon the picture. 
 
 Part of the Image weaker than the Best, with a distinct Boundary. 
 
 This is occasioned by not carrying the developer over the 
 
 whole plate with a single sweep. 
 
 Irregular Refractions. — When a piece of smooth ground inter- 
 venes between the camera and the objects, a strong sun falling 
 upon the ground may give rise to irregular movements of rarefied 
 air, which are capable of destroying the sharpness of that part of 
 the image that is just over the line of the ground. 
 
 § 6.— Splitting and Slipping of the Film. 
 
 \.- Splitting in Sensitizing Bath. — 1. Immersing too soon in the 
 bath, before the film is properly set. 2. Ill-cleaned, greasy, or 
 damp glass. 3. Omitting to roughen the edges. 4. Too much 
 alcohol in the collodion. 5. Too much salting. 6. Alcohol too 
 watery. 7. Immersing the plate too roughly. 8. Pyroxyline 
 made in too strong acids. 
 
 2. Splitting in Washing. — Bad quality of pyroxyline ; also, the 
 faults above enumerated may exert their influence in the washing 
 as well as in the sensitizing. 
 
 3. Sj)litting in Drying. — This may also be the fault of the 
 pyroxyline, but it is apt to result from the treatment which the 
 film has received. Much redevelopment with pyrogallic acid 
 and silver is very apt to cause the film to split. Treatment with 
 mercury for forcing (which see) also makes the film very tender. 
 Eemedy : coat the rest of the plates (when warned by one split- 
 ting) that are in danger, with a solution of gum in water, about 
 thirty grains to the ounce, or with one of gelatine, about half as 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 
 
 317 
 
 Strong. This will not take the place of varnishing, which must 
 be done as usual, unless but few copies are wanted, and little 
 value is attached to the plate. 
 
 Splitting in drying may also arise from an insufficient quantity 
 of pyroxyline in the collodion, or from too large a proportion of 
 ether. Too alkaline a collodion gives a weak film. 
 
 In the case of dry plates, a tendency to split at the edges will 
 occur with some sorts of cotton that otherwise are all that can 
 be desired. In such cases edge with solution of rubber in ben- 
 zole, not only before coating as usual, but a second time before 
 developing. 
 
 Slipping off of the Film. — Omitting to roughen the edges. Bad 
 or imperfect cleaning. Old and acid negative bath. Immersing 
 too quickly. Pyroxyline of bad quality, or too old. 
 
 § 7. — Want of Sharpness. 
 
 1. The necessity for having the sensitive film occupy the pre- 
 cise position of the ground glass, has been before dwelt on. 
 Without the nicest attention to the perfect adjustment of the 
 camera in this respect, perfect sharpness is impossible. Careless 
 focussing may also have been done. And some lenses have no 
 focus at all, but mav be racked in and out for half an inch, 
 without great variation, being really sharp nowhere. Such are, 
 of course, worthless, and with a bad lens nothing can be accom- 
 plished. It will sometimes happen that, after a lens has been 
 taken to pieces to clean, the parts will be put together wrongly, 
 either through simple inadvertence or from want of knowledge. 
 When bad results are got, they seem inexplicable, and perhaps 
 the optician is blamed for sending out a bad lens. The figures 
 in the earlier portion of this book will show the proper arrange- 
 ment of the parts of the various combinations. 
 
 2. Camera Moving During the Exposure. — This may arise from 
 carelessness or from the wind. A simple mode of avoiding the 
 latter consists in fastening a string to the under part of the tripod 
 head which hangs down and ends with a loop reaching nearly to 
 the ground. The foot placed in this loop and pressed forcibly 
 down, holds the camera securely in its position, supposing always 
 that the legs rest on a hard surface. On a yielding surface, the 
 legs might sink during the exposure, enough, at least, to destroy 
 the sharpness. 
 
 3. Want of coincidence between the chemical and visual foci. 
 
318 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 8.— Streaks. 
 
 There are several causes that are fruitful in streaks which may 
 utterly ruin the negative. 
 
 1. Immersing the Plate too Rapidly. — The mixed alcohol and 
 ether, with which the film is saturated, gives it a repellent action 
 to the bath solution, and if the plate be rapidly lowered into it, 
 parallel streaks may follow. As some collodions are more repel- 
 lant than others, a degree of rapidity may produce this result 
 with one that does not with another. 
 
 2. Removing too soon from the Negative Bath. — When this has 
 been done, oily-looking branching lines may be seen at once, if 
 the reflection of a light be caught on the surface (for this reason 
 the light ought to be arranged with special reference to observing 
 the surface of the plate as it is removed from the bath). These 
 streaks will appear in the development. 
 
 3. Repellent Action of the Film on the Developer. — The developer 
 for an old bath must always contain a certain amount of alcohol 
 to keep up its relation with the bath solution. When the nega- 
 tive bath is charged with alcohol and ether, the developer may 
 cease to mix quickly and evenly with the bath solution on the 
 plate, and may collect on it in ridges ; under these ridges the 
 plate develops faster, and consequently they are represented by 
 dark streaks in the image. (See B, Fig. 127.) One point is es- 
 pecially worthy of attention. Often the developer on the film is 
 in a condition that it just barely holds together in an even film 
 so long as the plate is level, ready to break into ridges the 
 moment the plate is tilted up to look through, for the purpose of 
 judging whether it is sufficiently developed. The moment this 
 breaking up takes place, the development becomes unequal, and 
 streaks are formed. Numbers of otherwise successful plates are 
 spoiled in the development in this way, and the danger must 
 constantly be borne in mind. Generally it may be said that 
 (unless the operator is quite sure that his materials have no ten- 
 dency to this defect) it is a safer way to let the iron development 
 go as far as is judged safe, then first wash it off, and then hold 
 up to the light and examine. Unless the picture flashes up very 
 suddenly and quickly, it is safe to let the iron development do 
 all it can, before washing. Then wash off ; if the negative is 
 found, on looking through it, to be of the right density, all is 
 right. If not, redevelop with pyrogallic acid, citric acid, and 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 319 
 
 nitrate of silver, taking care not to pour on the solution till 
 every atom of the pyrogallic acid is dissolved, or else to keep 
 the pyrogallic acid in solution. 
 
 When, in examining a negative, it is found that along the edge 
 which was farthest from the operator during development there 
 are streaks, especially branching streaks, the operator may be 
 pretty sure that the fault arises from the cause here described. 
 And if he doubts it, let him watch the plate from the first appli- 
 cation of the developer to its complete washing off, making sure 
 that the film was unbroken, and even for every second of time. 
 On that negative the streaks will be absent, always supposing it 
 was not removed too soon from the negative bath. (See 2.) 
 
 Where a great tendency exists in the negative bath to form 
 these streaks, it is well to agitate the plate, during immersion, 
 from side to side, as well as up and down. In fact, this last is a 
 very good practice for habitual adoption. A repellent action in 
 the film may arise from the use of too strong alcohol and of too 
 much ether in the collodion. Such films dry rapidly, do not 
 take the nitrate bath well, and repel the developer. 
 
 Blanchard has remarked that the keeping qualities of plates 
 may be greatly increased by using a good proportion of bromide, 
 two to two and a half grains to the ounce, and removing from the, 
 bath as soon as the oily lines disappear — further, hastening that 
 time by keeping the plate constantly in motion from its first 
 entrance into the bath. In this way some of the bromide may 
 remain undecomposed by the silver bath, and, decomposition 
 continuing after the removal from the bath, the concentration of 
 the nitrate of silver and its consequent evils are prevented. He 
 afiirms that in this way he has been able to keep a plate for three 
 hours. Such plates must be developed without sulphate of copper 
 in the developer, or brown fogging may result. 
 
 4. Omitting to wipe the hack, or to drain sufficiently. 
 
 5. If the table is allowed to be sloppy, it will follow that the 
 bottoms of the developing vessels will become wet. When they 
 are turned over in throwing the developer on the plate, there 
 will be a tendency in any liquid adhering to the bottom to run 
 along the side and mix with the liquid poured out from the vessel 
 upon the plate. Such a result can hardly fail to produce ugly stains. 
 
 6. Inequalities of Temperature. — It has been affirmed that when 
 a material difference in the temperature of the bath and developer 
 exists, this may be the cause of streaks. 
 
320 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 7. Streaks Descending more or less Perpendicidarly from the TJ'pfer 
 Part of the Plate. — During exposure the bath solution drains 
 down to the edge of the plate, and tends to flow thence upon the 
 edge of the dark frame. When collected there in a drop, it easily 
 rises again by capillary attraction as the film becomes drier by 
 standing, and mounts up the film again, so giving rise to a streak. 
 Eemedies : 1. Wipe out the dark slide. 2, Attach a piece of 
 blotting board to the edge of the plate. 8. Drain better after 
 removing from the bath and before placing in the dark slide. 
 
 Another source is changing the position of the plate after it 
 has drained after removal from the sensitive bath. If the plate 
 after draining be turned so that what was the bottom becomes a 
 side, the change in the direction of the currents will produce 
 streaks that infallibly ruin the negative. 
 
 Neglect to keep the dark slide always in one position till the 
 plate is out of it will evidently produce the same result. 
 
 In a word, the plate, after it has once begun to drain, must re- 
 main with the same side down till, by the completion of the 
 development, danger is ended. 
 
 8. Streaks in the Direction of the Dip may be caused by the 
 projection of the dipper that holds the plate; this may cause 
 irregular currents over the plate as the dipper descends. Where 
 this tendency exists, it may be checked by lowering the plate 
 very gently and slowly into the bath. The ether in the collodion 
 mixes only very slowly with the bath solution, and by rising in 
 currents along the surface of the plate may cause streaks. 
 Kemedy : move the plate from side to side as well as up and 
 down. In fact, this lateral motion is well to practise as a habit, 
 together with the regular up and down movement. Scum on the 
 surface of the bath may also cause this defect ; a piece of blot- 
 ting-paper drawn lightly over the surface will remove the scum. 
 
 9. Streaks along the Border, or working in from the Borders. — 1. If 
 the film becomes loose at any part of the edge, hyposulphite may 
 remain under it and escape complete removal by a short washing. 
 If then the plate be reinforced with pyro and silver, brown streaks 
 may result. 2. Eedeveloper getting under the film. 
 
 10. Parallel Sets of Smeary Streaks or Lines. — Cleaning marks. 
 Every sort of cleaning and rubbing upon the plate leaves invisi- 
 ble traces, which may subsequently come out. Whether or not 
 they will do so depends upon various influences: If the develop- 
 ment is much pushed; if the bath or other chemicals are in a 
 
 / 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 321 
 
 condition tending sliglitly to fogginess, the tendency to abnormal 
 deposit will be apt to show itself by first depositing on the clean- 
 ing marks. Much also will depend upon the cleaning, as, if the 
 .plate was well cleaned first in the bath; if the chemicals used in 
 cleaning were removed or not ; if the paper or rags used in rub- 
 bing were clean and fresh, or old and soiled; if rubbing were too 
 hard. 
 
 Or the operations immediately preceding coating may have 
 been in fault, as if the broad soft brush used for removing dust 
 were soiled or damp ; or if there were any deposit of dampness 
 from the atmosphere on the plate when brushed, which dampness 
 would by the brushing be drawn into streaks, and, moreover, 
 soil the brush and spoil also the next following plate. Kemedy, 
 or, rather, prevention : keep the plates between sheets of clean 
 blotting-paper in a tin box, and the brush with them, removing 
 each plate as wanted only. Avoid removing the plates from a 
 cold to a warmer room shortly before using. 
 
 § 9.— Transparent Spots and Pinholes. 
 
 Pinholes.— Ei^Qn to experienced photographers pinholes are a 
 source of no small trouble. They consist of small transparent 
 dots in the negative, and are generally occasioned by the pre- 
 sence of opaque matter adhering to the plate and interposing 
 between the light and the plate. During the subsequent opera- 
 tions these are removed, and the portion of iodide beneath having 
 been sheltered from the light, dissolves out in the hyposulphite. 
 These pinholes have been traced to the following sources :— 
 
 1. Dust in the bath— remedy, filtration. 
 
 2. Crystals of iodo-nitrate of silver floating in the bath. 
 Iodide of silver is capable of dissolving in nitrate of silver, 
 
 and certain conditions of the bath appear greatly to favor this 
 solution. A new bath may be pretty thoroughly saturated with 
 iodide of silver and yet give no pinholes, whereas an old bath 
 can at times scarcely be kept free from them, and, even if removed 
 by appropriate treatment, they quickly return. The treatment 
 
 is as follows : — 
 
 a. Add a few drops of solution of sal ammoniac, and filter. 
 This is a palliative ; the pinholes mostly soon return. 
 
 &. Take one-half the bath, and pour it slowly into a quantity of 
 water about its own bulk (do not reverse this), that is, if you have 
 
322 
 
 PHOTOGRAPHIC MANIPULATION'S. 
 
 a thirty-ounce bath, pour fifteen ounces of it into fifteen ounces 
 of water, and filter. Add the rest of the bath, without filtration, 
 and then add forty grains of nitrate of silver for each ounce of 
 water added, unless the bath was at the time impoverished, in 
 which case, of course, the addition must be larger. Sun it, and 
 filter. 
 
 In some states of the bath this treatment will give effectual 
 relief for a considerable time. But an old bath seems to acquire 
 an increasing tendency to dissolve out the iodide of silver from 
 the plate and precipitate it in these irritating crystals. When it 
 is found that this tendency to recur is obstinate, it is better to— 
 
 c. Evaporate the bath to dryness in a porcelain basin ; and if, 
 after going down to thorough dryness, the heat be raised gradually 
 till the saline mass fuses, it will be so much the better. But 
 even evaporation to dryness, without fusing, will be a valuable 
 help. For the presence of alcohol in the bath, introduced by the 
 collodion on the plates, seems greatly to facilitate the solution of 
 the iodide and the formation of iodo-nitrate ; the dry mass when 
 dissolved in water gives a milky liquid, by reason of the iodide 
 now become insoluble, and which is got rid of by filtration. If 
 the heat have been raised to the fusing point, the riddance of the 
 iodide seems to be still more complete ; the fused nitrate may be 
 used as new, remembering, however, that it contains alkaline 
 nitrate, and is not all silver-nitrate, more, therefore (if weighed), 
 will be needed than of unmixed nitrate of silver. Probably the 
 bath will not require acidulating, and acid should not be added 
 till it is found that a trial plate is fogged without. 
 
 3. Another source has lately been brought forward as causing 
 pinholes, viz., the presence of sulphuric acid, or sulphates, in 
 the water. Trouble from this source is, however, rare. 
 
 4. Some hold that acidulating with acetic acid gradually leads 
 to pinholes by reason of formation of acetate of silver. 
 
 5. If the salting in the collodion is not thoroughly dissolved, 
 it may remain as a fine powder in suspension, and every grain of 
 it may be expected to cause an insensitive spot, which may be much 
 larger than the grain itself, as its influence will extend around. 
 The bromides are less soluble in alcohol and ether than the 
 iodides, especially the bromide of potassium ; and this substance, 
 even if not introduced as such into the collodion, will always be 
 formed if iodide of potassium is used in connection with any 
 
FAILUEES IN PHOTOGRAPHIC OPERATIONS. 
 
 323 
 
 bromide. The stronger and better the alcohol and ether the 
 more liable they will be to this trouble. 
 
 Therefore, if it be considered essential to introduce a potassium 
 salt, it will be necessary to select a cotton which will work well 
 with alcohol not too high. In this respect cottons differ very 
 widely, some requiring the strongest solvents, and some working 
 with quite watery ones. Cotton having this last quality will be 
 appropriate for ambrotypes and ferrotypes, as it is for such that 
 potassium is commonly introduced into the collodion. 
 
 As a remedy, introduce a few drops of water, shake thoroughly,^ 
 set in not too cool a place, and at the end of twenty-four hours 
 filter through a close filter. 
 
 Or dilute the collodion with a little plain collodion, thus in- 
 creasing its solvent powers. According to V. Blanchard, this is 
 very effective, when, after working for some time well, one is 
 suddenly troubled with pinholes. The explanation of the remedy 
 is evident. 
 
 Continual moving of the plate whilst in the nitrate bath, with- 
 out ceasing till it is withdrawn, is also recommended by the same 
 photographer. ^ 
 
 Large Clear or Hazy Spots. — 1. When the developer is not swept 
 along the upper edge as here recommended, but poured over the 
 plate in the same manner as the collodion (as is practised by some 
 operators), a transparent spot, half an inch or more in diameter, 
 is very apt to be formed unless the operator rapidly moves the 
 hand which pours on the developer. This spot is caused by the 
 washing away of the bath solution, so that when development 
 sets in, that part of the film is deficient in free nitrate of silver, 
 and is proportionally weaker in effect. 2. Collodion poured too 
 suddenly back into the vial, making an irregular film. 3. Bad 
 cotton, which does not thoroughly dissolve in the fluid, and which 
 has not been properly filtered. 4. Bad collodion, too thick, or 
 with alcohol and ether badly proportioned (^'. e., alcohol should be 
 J to I, ether | to f). 5. A new bath, not saturated with iodide 
 of silver, will corrode the first plates. 6. An over-strong bath 
 may produce the like effect. 7. Keeping too long before develop- 
 ing may produce roundish hazy spots, especially when the bath 
 is acidulated with nitric acid. Apparently, this happens most 
 easily in hot weather, when the evaporation is most rapid. The 
 bath solution becomes concentrated and dissolves out portions of 
 the film. It does not act equally, because as it evaporates it has 
 
324 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 a tendency to collect in drops on the surface. 8. Fragments of 
 collodion (generally from the back of the plate) in the bath. 
 
 As mentioned elsewhere, small transparent spots in a negative 
 should always be touched out with opaque color. This causes 
 them to print white spots in the print, which are easily retouched 
 and brought up to the surrounding shade. But a transparent 
 spot prints dead black, and this is much more difficult to manage 
 and the blemish is never so well concealed. 
 
 Rings. — If the collodion bottle be held too high above the plate in 
 collodionizing, rings may appear in the development. 
 
 10. — Comets and other Opaque Spots. 
 
 Fig. 127. 
 
 A, A', Comets. 
 
 B, Development stains. 
 
 The name comet (A, A', Fig. 127) very aptly designates those 
 larger or smaller spots with tails, opaque in the negative and 
 showing more or less white if printed, so 
 that unless but a few prints are wanted, 
 ^ and the photographer is willing to touch 
 
 Mout the comet's mark, the negative may 
 generally be considered as worthless. 
 
 The heads of these comets mostly are 
 towards the direction from which the de- 
 veloper came, and the tails pointing to 
 the side on which it ran off. They may 
 be caused by anything that forms reduc- 
 tion at some chance point. A fragment of undissolved pyrogallic 
 acid, unnltered solutions of sulphate of iron, organic dust on the 
 plate, or in the sensitizing bath, or floating on its surface, any of 
 these causes may produce comets. Their appearance may be 
 taken as a plain indication that one or more of the solutions 
 worked with wants filtering. 
 
 Or, suppose that hyposulphite is spilt about the room. The 
 grating of the feet on the floor or carpet grinds off dust which is 
 charged with hyposulphite. If the glass be rubbed immediately 
 before coating, it becomes electrical, and every floating mote near 
 it is drawn to it. These are imbedded in the collodion, and on 
 plunging the plate in the bath, they become centres of reduction. 
 Sometimes these are even observable as dark spots on removing 
 the plate from the bath. But if the proportion of hyposulphite 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 325 
 
 is infinitesimal, yet they may escape attention on withdrawing 
 the plate, and cause comets. 
 
 If this dust is about the room, it can scarcely but get into the 
 dark slide, and then in moving, especially if roughly moved, it 
 may be transferred to the plate, and lead to comets. 
 
 Metallic hinges to the dark slide will sometimes grind off par- 
 ticles of metal which may be transferred to the plate. Each be- 
 comes a centre of reduction, and must lead to the formation of 
 a spot of some sort, probably a comet. 
 
 Imperfectly filtered collodion may give rise to opaque spots. 
 Also, neglect to wipe thoroughly the lip of the vessel from which 
 the collodion is poured. 
 
 Where any cause of comets is present, a strong developer tends 
 naturally to aggravate the evil. A rather acid developer is the 
 easiest worked with, but does not give as fine results, viz., as 
 much transparency of shadow. At the same time, it diminishes 
 the tendency somewhat to stains, and helps detail in high lights, 
 such as white dresses in portraiture, or a strongly illuminated 
 distance in landscapes ; also fine lines in copying line engravings 
 (not mezzotints, photographs, lithographs, or India-ink drawings), 
 for all of which a well balanced, i. e., moderately acidified, deve- 
 loper is needed. Finally, the developer, if not kept in continual 
 motion over the plate, may allow particles of metallic silver to 
 fall, which presently become nuclei of development. 
 
 Opaciue spots may be caused by a lumpiness of the film, arising 
 from some insoluble substance in the collodion. Often minute 
 fragments of dried collodion are carried over from the neck of 
 the poorer, by neglect to wipe after every pouring. The least 
 dust in the collodion will cause these spots ; after it is examined 
 with a lens they will be found to be caused by a minute fibre of 
 wool : it is surprising how much thickening a single fibre may 
 cause in this way. These fibres may get into open vessels of 
 collodion, or may have settled into vials or pourers before they 
 were filled with collodion. Or (as this is the commonest case) 
 they have settled on the _?9/a<e itself, either from neglect to brush 
 it off, or from doing so too long before coating, so that dust set- 
 tles on it between times. Dust is a foe to many photographic 
 operators, and most of all to albumemzed plates, and every care 
 should be taken to exclude it. 
 
826 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 11. — Lines. 
 
 Fig. 128. 
 
 
 
 
 B 
 
 
 1. A pause, however momentary, in the immersion of the plate, 
 produces a line, generally as thin as a hair, at the place where 
 
 the pause took place. With a vertical bath, 
 such a line is necessarily a straight, or nearly 
 straight, one (see A, Fig. 128). With a hori- 
 zontal bath the most curious curves and sinu- 
 ous lines are seen (B B, same figure). If the 
 horizontal bath has not been deep enough to 
 cover the plate with a single wave, but pauses 
 for a fraction of a second, the mark of that 
 pause will inevitably appear in the develop- 
 ment, and the negative is of course ruined- 
 Eemedy : with a vertical bath, immerse the plate with perfect 
 regularity. With a horizontal bath, have plenty of solution, 
 raise the bath at one end, place the plate in at that end, raised so 
 high that the solution leaves it, and then, at the same time, lower 
 that end and let the other end of the plate fall gently in. 
 
 2. Wavy Lines at Edges. — Developer too small in quantity, or 
 too slowly applied, especially where the plate has been kept 
 some time after leaving the bath. 
 
 3. Fine Parallel Vertical Lines in Direction of Dip. — The writer 
 has seen this result from sulphate of iron in the silver bath, 
 thousands of such lines being thus produced. 
 
 4:. Sinuous Lines over the Plate. — If the film be of a very repel- 
 lent nature, the bath solution may, instead of remaining as an even 
 film, gradually collect in oily lines, or the plate may by inatten- 
 tion have been removed from the bath with these lines actually 
 upon it. This repellent character (see p. 818) may come from 
 
 various sources: 1. Bad quality of 
 cotton. 2. Alcohol and ether too high ; 
 add a very little water. 3. A horny 
 and contractile collodion. 
 
 5. Parallel Lines, darker than the Ad- 
 joining Par^5.— When a plate which has 
 not been very well cleaned is subjected 
 to a long and severe development, 
 traces of the lines of the cleaning will 
 be forced out in the development. (See Fig. 129.) Sometimes 
 these are simply parallel lines as at A, sometimes they show 
 
 Fig. 129. 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 327 
 
 angles as at B. These angles are where the direction of the 
 hand was changed in the cleaning. Eemedy: Clean better and 
 rub longer. 
 
 § 12. — Stains and Surface Markings. 
 
 Fig. 130. 
 
 "Marbled" or "oyster- 
 shell" surface stains. 
 
 Marhled Stains. — " Oyster-shell" stains of reduced silver (also 
 called " matt silver stains"), with a gray metallic surface and in 
 curious curved and arabesque patterns, occasionally make their 
 appearance. They are exceedingly peculiar and unlike any other 
 stains, and have occasioned much speculation and discussion. 
 They come from too long an interval between collodionizing and 
 plunging into nitrate bath, too strong a de- 
 veloper, or too long a development, espe- 
 cially with sulphate of iron. 
 
 The longer a plate is required to wait be- 
 tween sensitizing and development the worse 
 will be these stains. Plates which when de- 
 veloped within five or ten minutes after 
 withdrawal from the nitrate bath are per- 
 fectly clean, will sometimes, if kept for 
 half an hour, show abundance of these 
 stains. Some operators find them come on 
 large plates when they do not on small. 
 
 Or they may be caused by neglect to wipe the back of the 
 plate, or to let it drain a sufficient time before putting it into the 
 dark slide. In these ways bath solution may run down to the 
 bottom of the back, and work round to the collodion film. They 
 may also arise from scum on the surface of the bath, which is 
 taken up by the plate, and is subsequently developed by the 
 action of the developer. According to some reliable photo- 
 graphers, iodide of ammonium in the collodion tends strongly to 
 the formation of this species of stains. They usually, however, 
 indicate too long an interval between collodionizing and de- 
 velopment. Remedy: Let the operations follow each other more 
 rapidly. If this cannot be, use more bromide, agitate the plate 
 the whole time that it is in the bath, and remove it from the 
 bath the moment the oily lines disappear. 
 
 In very hot weather these stains will show themselves npon 
 plates otherwise every way perfect, even with a bath quite suffi- 
 ciently acidulated, and with a collodion containing iodine. The 
 
S28 
 
 PHOTOGRAPHIC MANIPULATION'S. 
 
 longer the interval between the operations the larger and more 
 numerous they are. They appear to depend upon the drying of 
 the collodion film on the surface, and upon a partial return by 
 capillary action of silver solution which has drained down to 
 the corner. Silver solution which has once touched the holder 
 becomes sufficiently changed to throw down its metal much more 
 rapidly under the developer. 
 
 The writer has devised and used the following remedy with 
 great advantage. A piece of thick blotting pad is cut to the 
 length of the lower edge of the plate, and made about an inch 
 and a half wide. A very narrow portion, say an eighth of an 
 inch or less in width, is bent over to a right angle for the whole 
 length, and after the plate is put into the holder it is raised up a 
 little, and this bent edge is pushed in between the plate and the 
 corners. Thus the edge (not the face) of the glass and of the 
 collodion film touch this blotting-paper over the whole length, 
 and whatever solution drains down is absorbed by the blotting 
 pad, and is drawn round by it to the back. This remedy was 
 found very valuable. 
 
 Or it is advisable, when such a tendency appears : 1. To care- 
 fully wipe out the dark slide with a wet cloth, in order super- 
 ficially to wet the surface. 2. To place a piece of thick blotting- 
 paper on the back, as just explained. 3. To diminish the inter- 
 vals before the development as much as possible. 4. If neces- 
 sary, to roll the dark slide in a damp cloth. The first remedy is, 
 however, by far the best. (See also p. 344.) 
 
 It has been stated that these oyster-shell markings may arise 
 from something in the acetic acid used in the developer, and that 
 they have instantly disappeared by changing the specimen of 
 acid used. Others, again, have attributed them to the greater 
 thickness of the film at the corner where poured off, so that this 
 portion, drying more slowly, is exposed to become loose in the 
 nitrate bath, and to retain some bath solution beneath it. 
 
 Stains of this sort are very superficial, and, by dexterous 
 manipulation, may often be entirely removed. The surface of the 
 collodion is to be thoroughly wetted, best with alcohol, and a piece 
 of very soft paper is well moistened, and a point of it carefully and 
 repeatedly drawn over the stain. Unless the pressure is exceed- 
 ingly gentle, the film gives way, but when care is taken, the stains 
 disappear wonderfully. The writer has seen a third of the surface 
 of a negative covered with these stains, and yet has succeeded in 
 
FAILURES PHOTOGRAPHIC OPERATIONS. 329 
 
 getting rid of them witli care and patience. A kind of very thin 
 brown paper, made of jute, is that which has been found to 
 answer best. It becomes exceedingly tender when wet. The 
 operation is best performed after fixing. 
 
 Brown Stains. — If it is desired to reinforce after fixing with 
 hyposulphite, careful washing is necessary before the pyro and 
 silver are applied; if traces of hypo remain in or under the 
 film, a brown stain of sulphide of silver makes its appearance 
 the instant the redeveloping solution is put on the plate. 
 
 These stains are also said to arise from using pyrogallic acid 
 with too little acetic acid, when the water is hard (limestone 
 water), and sometimes from white light admitted to the dark 
 room. Eedeveloper getting under the film will stain brown. 
 
 If the collodion be alkaline it will be highly sensitive, and 
 tend to give flat images, and at the same time to stain with the 
 slightest cause. The least impurity on the glass, the least mis- 
 management of development, may be expected to spoil the plate. 
 
 Neglect to keep the plate-holder clean will give rise to very 
 troublesome markings. The all but universal use of glass corners 
 in the slides has largely diminished the injuries from dirty plate- 
 holders, nevertheless it is still advisable to be on the safe side. 
 Paraf&ning the slide, or, what is easier, rubbing it well with lard, 
 prevents the soaking in of droppings and drainings, and renders 
 the slides more easy to keep clean. 
 
 It seems scarcely necessary to say that any solution left upon 
 the glass corners for want of wiping is transferred to the next 
 plate, and may show itself in the production of different sorts of 
 stains according to the condition of the chemicals. 
 
 Irregular Markings are said, in some cases, to arise from the 
 use of too strong alcohol and ether in the collodion. Mr. Terry 
 mentions a case as occurring in a gallery in which not a perfect 
 negative had been made in a week, and where the trouble was at 
 once removed by adding a few drops of water to the collodion. 
 It had been made by the photographer himself; absolute alcohol 
 was used instead of 95 per cent.^ 
 
 ' Really absolute alcohol is rarely to be met with in commerce. The differ- 
 ence between 95 per cent, alcohol and absolute is over 25 drops of water to the 
 fluidounce, rather more than 5 drops to each hundred. It will thus appear 
 how important it is to understand the exact strength of the materials used 
 
 22 
 
330 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 13. — Faults in Fixing. 
 
 Feathery Markings over the Plate. — Yellowish feathery markings 
 are owing to insufficient fixing. These may appear at any part 
 of the plate, most frequently, however, at 
 Fig. 131. the corner at which the collodion was 
 
 poured off. At times a yellow shade is left 
 over the whole plate ; this indicates a still 
 more imperfect fixing. 
 ■ When this fault is not noticed until the 
 plate has been washed and dried, particular 
 care is necessary ; for plates thrown into 
 hyposulphite a second time are almost cer- 
 tain to loosen in the film, or to split in some 
 part of the operation, either in the fixing, or 
 washing, or the drying ; therefore, the best 
 precaution is to take a grain solution of 
 India-rubber in benzole, to pour out an ounce or two of it into a 
 pan, and tilt the pan upward at one side, so that the solution may 
 lie in the angle opposite. We thus have a pool the length of the 
 pan, and about one-fourth of an inch deep in the middle. The 
 four edges of the plate are to be plunged in this successively, 
 giving each a full minute to allow the varnish to soak in, and 
 also to allow the previous side to drain and dry before it becomes 
 the top. The plate thus cemented fast at the edges, will stand 
 the necessary treatment without difficulty. After refixing and 
 washing, coat with gum-water or dilute albumen, dry and 
 varnish. 
 
 Image Weakens too much in Fixing— ^hQ fixing bath may be 
 too strong and need weakening. The result may also come from 
 too weak a negative lath, used too long without strengthening up. 
 The iodide of silver is then formed too much on the surface of, 
 instead of within, the film. Or the development may have not 
 been continued sufficiently long. It should be borne in mind 
 that the portions of the image formed by redevelopment are less 
 easily attacked by the fixing bath than those formed in the first 
 development. 
 
 § 14.— Faults in Varnishing. 
 
 Drying Dead. — This may result from one or more of three dis- 
 tinct causes. 
 
FAILURES IN" PHOTOGRAPHIC OPERATION'S. 331 
 
 1. Want of dryness of the film. As water curdles varnish by 
 precipitating the resin, so any dampness in the film will produce 
 a similar effect. Surface drying is insufficient. The film must 
 be dry clear through to the glass. By standing for a day, the 
 film dries sufficiently in dry weather, but a damp atmosphere, 
 even in sunny weather, will dampen films to that extent (even if 
 they were previously dry) that the varnishing may be affected. 
 As a general thing, it is best to varnish in dry weather only ; but 
 if it is to be done in damp weather, artificial heat must be used. 
 Merely warming the plate will not dry it ; it must be kept warm 
 for some little time. 
 
 2. Insufficient penetration. Yarnishes penetrate rather more 
 slowly, than many persons imagine, and if poured off before pene- 
 tration has taken place, the varnish continues to soak in, and 
 thus the upper portion has not enough left to give it a glossy 
 surface. After the plate has been completely covered, the writer 
 advises to count ten or twelve seconds before beginning to pour off. 
 
 3. Insufficient heat. Some varnishes require more heat than 
 others, and if enough is not applied they dry dead. Most var- 
 nishes require heat both before and after applying. 
 
 Remedy for Deadness. — Flow with alcohol (see below). 
 
 Ridges. — If the pool of varnish be allowed to stop too long in 
 any position, it dries at the edge and makes a ridge, and the 
 tendency will always be greater in proportion as the plate is 
 hotter. If, while varnishing, the photographer sees that he has 
 made a ridge, he can, if it is not a bad one, get rid of it by 
 pouring an abundant supply of varnish on, and letting it remaia 
 longer on the plate than usual. 
 
 Different varnishes work differently, and sometimes the mere 
 change from one that the photographer is accustomed to, to an- 
 other equally good, but different, will cause him to make ridges. 
 
 When, after drying a negative by heat, the varnish is found to 
 have made a ridge across the film likely to show in the printing, 
 or has dried sufficiently dead to unfavorably affect the print, it 
 is not necessary to remove the whole of the varnish. The writer 
 simply flows the negative over with 95 per cent, alcohol, letting 
 it stand on the film for two or three seconds, and pours off"; then 
 warms the plate and applies another coat of varnish. For this 
 last varnishing it is best to use a thinner varnish, lest the coat 
 become too thick. Therefore dilute the varnish (if a spirit var- 
 
332 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 nish, and the writer advises to use none other) with an equal bulk 
 of alcohol. The same remedy applies for drying dead. 
 
 Scaling Off after a Lapse of Time. — This arises from leaving the 
 varnish on too short a time before pouring off. Those places 
 where it has not soaked through to the glass will always be liable 
 to scale off. Or if the plate has been badly washed and hypo- 
 sulphite crystallizes under the film. Exposure of the negative to 
 damp atmosphere. Great changes of atmosphere, as if the room 
 is allowed to frequently become very cold and then is strongly 
 heated. Bad varnish, containing no essential oil (oil of lavender, 
 etc.). Coating with gum-water before varnishing, in order to 
 prevent splitting in drying. . 
 
 Any varnish which tends in the least degree to show this 
 defect should be rejected without hesitation. Under the head of 
 varnishes, will be given further on several formulas for varnishes 
 which will resist the action of moisture so completely that nega- 
 tives varnished with them may lie under water for many weeks 
 without injury of any sort. 
 
 Dissolving of the Image in Varnishing. — The cotton too soluble 
 in alcohol alone without ether. Alcohol in the varnish too 
 strong. Eemedy : add a little water ; shake well, and if not quite 
 bright, filter through paper ; or use a benzole varnish. This 
 trouble comes chiefly with pyroxyline made at a low temperature 
 with weak acids ; and as, of late years, the tendency has been to 
 strengthen the acids, and counterbalance this by raising the tem- 
 perature, the tendency to dissolve in varnishing occurs less fre- 
 quently than formerly. 
 
 Honeycomb Cracks. — The varnish after a time rises in ridges, 
 and finally parts. Cause : insufficient removal of hyposulphite in 
 washing. If attended to in time, this may be remedied. Alcohol 
 is put into a pan, and the plate put over it, face down, until the 
 varnish softens and returns to its position ; or the plate is simply 
 flowed over with hot alcohol. The ridges sink down sufficiently 
 not to afi'ect the printing. 
 
 Parallel Lines running diagonally down the Plate. — Certain var- 
 nishes, and especially thick ones, require to be rocked whilst 
 draining and drying, for want of which this trouble may arise. 
 
 Scratching in Handling. — Too thin a varnish will not afibrd an 
 adequate protection to the film, which may thus be unable to 
 stand ordinary wear. A habit of thinning the varnish with 
 .alcohol may easily be carried to excess, and lead to this trouble. 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 333 
 
 Generally speaking, tlie solid gum should be in the proportion of 
 one ounce to seven fluidounces of alcohol, with some essential oil 
 to prevent cracking. 
 
 A more common source of this trouble lies in the use of var- 
 nishes made with too soft gums. Lac is liable to this objection. 
 The saudarac varnish, for which a formula will be given in the 
 chapter on varnishes, gives an extremely strong, hard coat. 
 
 Specks and Irregularities on the Surface. — Although the var- 
 nish have been perfectly clean and bright, and although the 
 negative may have been carefully brushed off immediately before 
 applying the varnish, it will often happen that there will be 
 specks and irregularities. Examined with a lens, these will 
 mostly show a filament of wool (from abrasion of clothes or 
 carpets) in the centre as the cause. The air is mostly much fuller 
 of dust than we imagine, and these filaments will settle on the 
 plate even in the few seconds between brushing and coating. 
 
 § 15. — Miscellaneous. 
 
 1. iVb Image at all. — In copying by a bad light, if too small a 
 diaphragm be used, and a much too short exposure be given, with 
 insensitive chemicals, the developer may fail to bring anything 
 out. A very exceptional case. In some states of the negative 
 both cadmium collodions will fail to give any image at all, when 
 the mere substitution of a collodion made chiefly with salts of 
 ammonium will lead to good results immediately (p. 136). 
 
 2. Insensitiveness arises either from too acid a condition of the 
 negative bath or from the use of too old acid, or dark collodion. 
 If from the latter cause, it will be at once removed by substi- 
 tuting a collodion in good condition. And if the old collodion 
 be not too defective, it may be used up by mixing with some 
 that has been very newly prepared of thoroughly neutral mate- 
 rials, preferably with cadmium salts only, and which by the 
 admixture of an older collodion will at once pass into good con- 
 dition. 
 
 It is usually collodions made with alkalies that become insen- 
 sitive. Cadmium collodions will keep in cool places for several 
 years. 
 
 As to the proportions in which to mix new and old collodions, 
 one part of old may be added to three, four, or five of new, ac- 
 
334 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 cording to circumstances. If the old collodion be quite dark, it 
 will hardly be safe to add in larger proportion than five. Over- 
 acidity of the bath is generally the result of tampering with it — 
 as a general rule, after your bath is once rightly made, ascribe 
 all troubles to anything else, and apply no remedies to it, until 
 it is certain that it is in fault. If too much acid has been 
 added, by mistake, in making it, bicarbonate of sodium may be 
 added very cautiously until a precipitate falls, then filter and 
 acidulate again. 
 
 An old bath, choked with organic matter, may cause insensi- 
 tiveness. 
 
 3. The Film^ after Fixing with Cyanide^ shows a Bluish Color. — • 
 InsuflScient washing ofi" after development, so that iron salt re- 
 mains on the plate. 
 
 4. Want of Adherence. — Too much cotton in collodion. Im- 
 mersing too quickly. Grreasiness of plate. Too much alcohol 
 in proportion to ether. 
 
 5. Iodide comes off in the Bath^ in Flakes. — Too little cotton in 
 collodion. 
 
 6. Developer Bepelled — fails to moisten, or to act upon the film 
 or parts of it. Collodion too gelatinous by reason of cadmium 
 salts. Too much ether for the alcohol. Alcohol and ether too 
 strong. Bad cotton. Waiting too long before immersion. Plate 
 kept too long after removing from negative bath, so that it be- 
 comes surface-dry in spots. 
 
 7. Bluish Deposit in Shadows. — Insufficient acid in negative 
 bath. (This appearance is not unfrequent in the glycerine and 
 honey process.) 
 
 8. Ghost or Flare. — Indistinct thicker spot on the plate opposite 
 centre of lens. Faulty lens needing to be rejected. 
 
 9. Transparent Insensitive Band around the Plate. — Too long 
 delay between coating and immersing the plate. 
 
 10. Plates have a Dusty, Powdery Look. — Excessive deposit of 
 iodide of silver. Filter after diluting, precisely as for pinholes. 
 Note, this is not to be confounded with Granularity , which see, 
 but the film is in this case more veiled. 
 
 II. Failures belonging especially to Negatives. 
 
 1. Too Little Density. — 1. Too weak a bath. 2. Too strong a 
 bath. 3. Over-exposure. 4. Too short a development. A be- 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 335 
 
 ginner is often so afraid of fogging, that he cuts short the develop- 
 ment when the negative has only reached the ambrotype stage. 
 5. Insufficient illumination. 
 
 2. Excessive Density. — 1. Over-development, especially with 
 under-exposure. 2. Too much salting. 
 
 3. Solarization, results from over-exposure. For a film ex- 
 posed to light for a gradually increasing time gains in strength 
 up to a maximum point, then remains stationary for an exceed- 
 ingly short time (in case of iodide of silver), and then loses again 
 in the over-exposed parts, showing little tendency to take a de- 
 posit under the developer. A great disposition to solarization 
 in a collodion indicates an insufficiency of bromides ; the ten- 
 dency of bromides is greatly to prolong the stationary point just 
 spoken of. 
 
 III. Failures belonging especially to Ambrotypes and 
 
 Ferrotypes. 
 
 1. Want of Detail in Shadows. — Under-exposure. Too little 
 bromide in collodion. ' Too old and red a collodion. Insufficient 
 development. Too acid a negative bath. Too thin a collodion. 
 
 2. Want of Detail in High Lights, which are at the same time 
 vigorous and dense. Too much development, so that the plate 
 tends to become a negative. 
 
 3. Grayishness or Want of Contrast. — Over-exposure: in this 
 case the shadows are good in respect of detail, but want depth. 
 Use of hyposulphite of sodium as a fixer instead of cyanide. 
 
 4. Veiling of the Shadoios. — Over-exposure. Too new a collo- 
 dion. Add a little tincture of iodine, or mix with some old red 
 collodion. 
 
 5. Excessive Contrast. — Too old a collodion ; too acid or foul a 
 bath. Too little bromide in collodion. Under-exposure. 
 
 6. Dark rounded Spots visible after backing. Pouring on the 
 developer like collodion instead of sweeping it from along one 
 edge. 
 
 7. Want of Transparency in the Film when Dry. — Bad cotton. 
 
 8. Too Slow a Development, may arise from too much acidifica- 
 tion of the bath. 
 
 9. Oreen or Blue Color in the Film, according to Hardwich, may 
 arise from too scanty a deposit of silver, depending upon either 
 
336 
 
 PHOTOG-RAPHIO MANIPULATIONS. 
 
 insufficient development or over-exposure, or from too thin a 
 collodion film. A bad cotton or a disordered bath may likewise 
 affect unfavorably the color of the image. 
 
 IV. Failures in Paper Development. 
 
 Much that has been already said applies itself necessarily to 
 working with paper, especially the remarks on fogging, and 
 effects of under and over-exposure. 
 
 Harshness.— Too much iodide. 
 
 Stains are often ascribable to handling with not perfectly clean 
 fingers. Indeed, so absorbent is paper, that almost any touch 
 will become visible to the developed print, even with very clean 
 fingers. The addition of bromide has a great tendency to check 
 the staining ; and in the case of positive printing by development, 
 where extreme brevity of exposure is not important, it will be 
 found best to develop on chloride of silver. 
 
 The use of very weak gallic acid in connection with a lead salt 
 and acetic acid, as proposed by the writer, and explained else- 
 ■where, exposes less to danger of stains than other modes of 
 development. 
 
 Sunh-in Appearance. — All development tends to this effect ; 
 developed" pictures are always less brilliant than sun-prints — the 
 picture does not so much lie upon the surface. Nor is it easy to 
 state the causes upon which a more or less sunk-in efJ'ect depends, 
 though the quality of the paper appears to have very much to 
 do with it. It is far more difl&cult to find a good paper for de- 
 veloping upon, than for ordinary silver printing. When the 
 photographer finds paper that will yield a bright print by deve- 
 lopment, such paper should be carefully placed aside for this use, 
 and an exact note should be made of the details of the method 
 which was found to give good results with it. 
 
 Y. Silver Printing. 
 
 § 1. — Failures common to Glass and Paper Prints. 
 
 1. Weak Oray Prints. — Use of negatives destitute of light and 
 shade, generally from over-exposure or bad manipulation. Also 
 may arise from bad paper or too weak or exhausted positive bath. 
 
 2. Harsh Black and White, or Snoivy Prints. — Over-developed 
 negatives. Strong negatives, which would give good prints with 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 337 
 
 sunlight, may produce this fault in printing by diffuse light, 
 especially if the light is weak, or the nitrate bath very rich. 
 
 8. Whites turn Yellow. — Throwing the prints into the toning 
 bath without thoroughly removing the nitrate of silver by wash- 
 ing, tends to yellowness of the whites. Also exposure of the 
 sensitive surface to light. Old hyposulphite causes the same 
 fault. Paper kept too long after sensitizing. Eemedy : Use the 
 author's method of printing described at page 277. 
 
 Some hold that the turning yellow depends upon the bath 
 solution having penetrated through the albumen to the paper 
 beneath, and that consequently the shortest practicable time that 
 the paper is left on the bath the better, especially in hot weather. 
 
 It is found that paper, after sensitizing, may be washed off with 
 pure water, and that in that condition it keeps many days. Be- 
 fore use, the sensitiveness is to be restored by strong priming. 
 Even without this it will print with very strong dense negatives. 
 Hyposulphite dust about the room. Eemedy : Tone in a separate 
 room. 
 
 4. Prints weakening in the Toning Bath. — Use of bath too soon 
 after making. Insufficient printing. Use of an acid toning bath. 
 Bemedy: Add bicarbonate of sodium, or better, acetate of sodium. 
 
 5. Prints refuse to Tone. — Toning bath badly made or acid 
 (see article on Toning Baths). Too acid or too weak a printing 
 bath. An acid printing bath often gives prints that will not tone 
 well. Eemedy: Drop in ammonia till the bath is alkaline to test 
 paper. Or fume adulterated chloride of gold, or exhausted bath. 
 Insufficient washing before immersion in the toning bath. Too 
 cold a temperature ; the bath generally works better at blood- 
 heat. Print kept too long after printing. Impurity introduced 
 into the toning bath, especially a trace of hyposulphite. Toning 
 bath too freshly mixed or too strong. Fuming for too long a 
 time with too much ammonia. 
 
 6. Prints lose too much Intensity in Fixing. — Insufficient print- 
 ing, but oftener too thin a negative; or may arise from too weak 
 a positive bath. Or they may have been fumed too long. 
 
 7. Toned and Fixed Print too Bed. — Insufficient toning. Con- 
 tinue the toning till the redness is gone when the print is held 
 up to the light and looked through, but avoid over-toning. 
 
 8. Fixed and Toned Print too Blue. — Over-toning. Poor tones, 
 or a want of richness of tone, may arise from conducting the 
 toning operation too rapidly. 
 
338 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 9. White Spots. — Air-bubbles. 
 
 10. Albumen dissolves in the Sensitizing Bath. — The bath is either 
 too weak, or alkaline; the remedy is obvious. 
 
 11. Over- Printing. —A yerj weak solution of cyanide of potas- 
 sium is the best means of reducing over-printed positives. It 
 must be applied carefully, both as respects the print and the 
 operator, and the fingers should not be immersed in it. Strength 
 proper will be about a half grain to ounce of water, or even less. 
 
 § 2.— Failures Peculiar to Silver Printing on Paper. 
 
 Albumenized Paper repels the Positive Bath. — Paper too dry. 
 Leave for twenty-four hours in damp place before sensitizing, or 
 blot off the paper immediately on taking it from the printing 
 bath, between folds of clean, white blotting-paper. 
 
 Stains in the Print as it comes from the Frame. — 1. Soiled fingers 
 handling the paper. Too much care can never be taken in hand- 
 ling photographic paper. The sources of stains by soiled or 
 moist fingers undoubtedly often precede the purchase ; in this the 
 professional photographer has a great advantage over the ama- 
 teur, that his paper is purchased in quantities, and so undergoes 
 far less fingering. Two corners of the sheet, whether whole or 
 cut up, should at once be folded down at the commencement of 
 operations, and no other part of the paper be touched from first 
 to last. 
 
 Care will not only be required as to the handling, but as to 
 everything that the paper comes into contact with. 
 
 2. A very common source of stains is the presence of very fine 
 metallic particles in the paper, produced by the grating of the 
 mill-machinery. These particles, however infinitesimal, become 
 causes of reduction, and inevitably make stains. 
 
 3. Imperfect removal of hyposulphite used in bleaching. 
 
 4. Foreign substances of almost any sort, constituting invisible 
 imperfections in the paper. These may act in several ways. They 
 may diminish the penetrability of the paper locally. Such por- 
 tions will take up less silver and print lighter than the rest. 
 Often these foreign matters can be detected by holding the paper 
 up to the light and observing its regularity. 
 
 5. Irregular^ distribution of resin or other sizing material 
 through the paper. Resin easily combines with silver, making a 
 
FAILURES IN PHOTOGRAPHIC OPERATIONS. 339 
 
 sensitive compound. If the resin is not equally distributed, the 
 quantity of silver compound will vary accordingly. 
 
 6. Eeflected light from bright objects near the printing frame. 
 
 7. Printing by sunlight through a window-frame, with irregu- 
 larities in the glass. 
 
 8. Paper not well floated on the bath, or left on it an insuffi- 
 cient time for the equal absorption of nitrate, causing irregular 
 marbled stains. 
 
 9. Impurities floating on the surface of the printing bath, taken 
 up by the paper. 
 
 Irregular or patchy effects in printing may be caused by fuming 
 for too short a time. 
 
 Spots appearing in the Toning. — Neglect to keep the prints 
 moving. Where one print rests upon another, the action of the 
 toning bath is slower, and a spot results. This is a very common 
 source of trouble, unless the necessity of care is borne steadily in 
 view ; or if the print floats on the bath, instead of being kept 
 under the surface. 
 
 Spots in the Fixing. — Adhesion of prints to each other in the 
 bath, by neglect to continually move them. 
 
 Want of Brilliancy. -~F]oa.tmg the paper too long on printing 
 bath. Half a minute to three-quarters is sufficient, and gives a 
 far better print than a longer time. 
 
 Prints have a Sunh-in or Mealy Appearance. — Insufficient albu- 
 menizing. Bad paper. Old and foul, or acid, printing bath. 
 Too much salting. Old albumenized paper that has not been 
 kept thoroughly dry, especially if chloride of sodium has been 
 used for salting. Dampness causes the chloride, which should 
 be wholly in the layer of albumen, to penetrate into the body ot 
 the paper. Printing bath too newly made, or paper floated too 
 long. Too much fuming with ammonia, or too strong fuming, 
 tends to produce a flat, mealy print. 
 
 Print refuses to Bronze in the Shadows while Printing. — This de- 
 pends upon the salting bath having been too strong for the print- 
 ing bath. Eemedy : Add more nitrate of silver to the positive 
 bath, or change the paper. Paper kept too long after sensitizing. 
 
 If the image does not bronze in the shadows by the aid of the 
 printing, a brilliant print cannot be expected. An opposite cause 
 may be expected to produce the opposite effect, viz., too deep 
 bronzing and too harsh a print. 
 
 Print takes a different tone at the two ends, as, one end black 
 
840 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 and the other blue, or one black and the other brown. Cause, 
 irregular albumenizing of the paper, so that the coat of albumen 
 is thicker at one part than another; where the albumen is thinnest 
 the toning proceeds most rapidly. For this reason it is especially 
 important, for large prints, to select the paper carefully. 
 
 BImcIc Dot with a White Tail. — If the pin to which the sheet 
 hung to dry was put through a wet place, a local reduction fol- 
 lows with this result. Pins left for some hours in an old cyanide 
 fixing bath become silvered, and are exempt from this trouble ; 
 silver may be dissolved in cyanide for the purpose. 
 
 Albumen dissolves off in the Silvering Bath. — Bath is either too 
 alkaline or too weak in silver. 
 
 Failures appearing only in the Toned and Fixed Print. — Troubled 
 appearances in the substance of the paper. 1. If the chloride of 
 silver has not been thoroughly, or rather has been very imper- 
 fectly removed, the print has a mottled look on holding up to the 
 light, and as this remaining chloride of course darkens by con- 
 tinued exposure to light, the mottled appearance becomes with 
 time more perceptible. This imperfect removal may arise from 
 not leaving long enough in the hyposulphite bath, or from the 
 exhaustion of the bath, or, possibly, by exposure to light before 
 fixing. The first are the most probable causes. Eemedy : Use 
 hyposulphite of sodium liberally ; one pound to twelve sheets is 
 none too much. Make no more than wanted, and begin each 
 day afresh, under no circumstances using a bath a second day, 
 even if but a single print was fixed in it the previous day. 
 
 2. Cases have been observed in which the prints were in per- 
 fect order when toned and fixed, and yet exhibited stains after 
 the final washing. This has been found to arise from the use of 
 zinc vessels, or a zinc bottom to the washing trough. The more 
 thoroughly the vessel is cleaned, the worse the spots. Eemedy : 
 Varnish thoroughly the whole surface of the zinc, or have a 
 wood bottom with a layer of white quartz pebbles (which may 
 be obtained from those who make a business of gravel-roofing). 
 These are easily kept clean. 
 
 Over-contrast. — If necessary to print from a negative too harsh, 
 the excess of contrast can be reduced by exposing the paper to 
 light for a few .seconds, or a minute, before placing it in the 
 printing frame. The print is thus somewhat improved, but will 
 never be first-rate. 
 
 Bard negatives will require light silvering. It often happens 
 
FAILUKES IN PHOTOGRAPHIC OPERATIONS. 341 
 
 that a negative is full of detail, and unobjectionable in every re- 
 spect except that of being so dense that the shadows of the print 
 are overdone before the detail in the lights come out. Such 
 negatives will need paper very lightly silvered. Often the paper 
 after going through the regular sensitizing may be floated for a 
 minute on water. The writer has seen most beautiful results got 
 in this way from negatives that would not give any good efiect 
 ■with ordinary silvered paper. 
 
 Blurred Spots. — A bad frame may not have brought the paper 
 home to the glass everywhere. Many printing frames are very 
 defective in this, that they throw all the strain into the middle of 
 the plate, thereby endangering the safety of the negative, and get- 
 ting bad definition at the edges, which is apt to be attributed to a 
 falling off in the power of the lens. Try the frames always with 
 a piece of plain glass, fastening down the springs and pressing up 
 the glass with the thumbs on various parts in succession, to find 
 how the pressure produced by the springs is distributed. The 
 old pattern, with bars at the back, is the best by far. 
 
 Blistering of the Albumen. — 1. Peculiarity of the albumen film 
 which will not bear the sudden change from the fixing bath to 
 pure water without endosmose. Kemedy : Let the prints lie for 
 a short time in a weak intermediate bath of hyposulphite, between 
 the regular fixing bath and the washing. 2. Acid washing after 
 toning in an alkaline gold bath containing alkaline carbonates. 
 3. Over-dryness of the albumenized paper. For this and other 
 reasons it is a good plan to leave the paper for a day before using 
 it in a damp place; not too damp, however, nor for too long a 
 time, as this would lead to the working inwards of the salting, 
 occasioning a loss of brilliancy to the print. 
 
 It has been said that the addition of a small quantity of ether 
 {\ ounce to 20 -ounce bath) to the fixing bath will prevent blister- 
 ing. 
 
 Fading of the Pn'n^s.— Insufficient washing. Old hyposulphite 
 fixing baths. A solution of hyposulphite of sodium in water 
 keeps perfectly. But if used, it should be rejected and not em- 
 ployed on any subsequent day to that on which it was first used. 
 Acid in the fixing bath. Use of a fixing and toning bath. 
 
 Black Specks showing first after Mounting.— Ap^ea.Ta,nGes of this 
 sort may almost invariably be traced to the agency of fine metal- 
 lic particles. These, by the aid of atmospheric moisture, gradu- 
 ally act upon the print and produce the specks. They come— 
 
342 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 1. By trimming the print upon a brass plate. The point of the 
 knife detaches fine particles of metal, these are by the pressure 
 forced into the print and soon make stains upon it. Glass or hard 
 wood should be used to cut on. 
 
 2. By using a brass form to trim by. Particles are abraded 
 and enter the print in the same way as before. Steel or glass 
 forms should be used exclusively. 
 
 3. By using Bristol board for mounting, on which borders or 
 designs have been printed in gold or bronze. The designs are 
 printed in varnish and the metallic powders are rubbed on; 
 grains adhere elsewhere than on the design, and are not entirely 
 removed in the subsequent brushing, but eventually destroy the 
 print. 
 
 Crystallizations in the printing bath or on the paper may occur 
 in consequence of the nitric acid used in preparing the ammonio- 
 nitrate bath containing sulphuric acid : sulphate of silver is but 
 very slightly soluble in water. A bath so contaminated may be 
 brought into order by adding nitrate of haryta in solution so long 
 as a precipitate forms. The same substance may be used to test 
 the purity of the nitric acid used, and also to purify it, if found 
 contaminated. When nitrate of baryta is added to a liquid con- 
 taining sulphuric acid, sulphate of haryta, a very insoluble salt, is 
 thrown down as a heavy white powder, easily separated either 
 by decantation or filtration. 
 
 Cracks or Buptures in the Albumen Coat are sometimes produced 
 by drying the print too rapidly. Dry slowly at ordinary tem- 
 peratures. 
 
 § 3.— Collodio-Chloride. 
 
 Fading is said to be owing to the use of albumen as an under- 
 stratum. 
 
 Bad Tones. — Citric acid in collodion. Substitute tartaric. 
 Slow Toning. — Eepellent collodion. Moisten the plate before 
 ^ immersing in the toning solution with equal parts of alcohol and 
 water. 
 
 Flat, weak Pictures. — Insufficient quantity of pyroxyline in 
 collodion. Omitting to fume when fuming is needed. 
 Sunk-in Prints. — The cotton may not be suitable. 
 Splitting of Film. — Neglect to edge the plate, 
 z^ois.— According to Mr. Simpson, the discoverer of the pro- 
 
FAILUEES IN PHOTOGRAPHIC OPERATIONS. 843 
 
 cess, spots are caused by — 1. Too much free nitrate of silver in 
 the collodio-chloride. 2. Keeping the plates too long after coat- 
 ing. Dry before a fire and expose at once. 
 
 CrystalUzaiions in the Film. — Excess of nitrate of silver in the 
 collodion. Add more salting. 
 
 Insensitiveness. — Insufficient quantity of nitrate of silver, more 
 will be needed. 
 
 Detaching of the Film (from paper in the collodio-chloride paper 
 process), want of sufficient sizing in the paper. Tew or no papers 
 have the necessary quantity, and a coat of gelatine is usually 
 necessary. 
 
 Rolling up of the Prints. — This is an annoying peculiarity of 
 the process, and difficult to avoid. It is said that plunging for an 
 instant into very hot water will destroy the tendency. 
 
 Blue Tones. — The toning is much more rapid than with albu- 
 menized paper, and unless care is taken, the print may be over- 
 toned before the operator is aware. 
 
 Final Observation. — In closing this chapter on Failures, which 
 the writer has endeavored to make as complete as possible, he 
 feels compelled to remark that whilst the sources of non-success 
 are almost innumerable, none do anything like so frequent and 
 fatal damage as want of care and of perfect cleanliness. The 
 commonest sources of trouble are — 
 
 1. Use of insufficiently cleaned vessels. 
 
 2. Immersing of fingers into solutions, which fingers have been 
 in other solutions without intermediate washing. 
 
 3. Tables slopped with solutions, which thus adhere to the bot- 
 toms of bottles, measuring glasses, beakers, &c., so that when 
 these are poured from, a fatal drop runs along the outside from 
 the bottom and mixes with the other materials. A drop of hypo- 
 sulphite solution will spoil almost any other chemical solution 
 with which the photographer works. All these sources of trouble 
 have this in common, that they introduce foreign matter into the 
 photographer's materials unknown to him, and this is the most 
 frequent of all causes of failure. 
 
344 
 
 PHOTOGKAPHIC MANIPULATIONS. 
 
 CHAPTEE XV. 
 
 OUT-DOOR PHOTOGRAPHY WITH WET AND PRESERVED 
 
 PLATES. 
 
 § 1.— Wet Plates. 
 
 In Chapter VII. most of the information necessary for view- 
 taking has been given, nevertheless some special details remain 
 to be noted. 
 
 When negatives are to be taken at a distance from the dark 
 room, we are obliged either to work with a tent, to use " pre- 
 served plates," or to resort to " dry plates," which last method 
 will be considered in subsequent chapters. 
 
 Although plates are apt to deteriorate pretty rapidly by keep- 
 ing after sensitizing, yet, with care and attention, remarkable 
 delays may be supported, especially in cold weather. Heat 
 hastens the destruction of the plate. Since the first edition of 
 this Manual went to press, the writer has paid particular atten- 
 tion to this subject, and has succeeded in keeping wet plates in a 
 very satisfactory way. His method will be found below. 
 
 The following are the troubles which will be apt to show them- 
 selves : — 
 
 1. Fog. 
 
 2. Marbled stains. (See also p. 327.) 
 
 3. Transparent or hazy spots of various sizes up to one-quarter 
 of an inch diameter, generally nearly round. 
 
 Fogging is not a very common trouble, and seems to depend on 
 newness of collodion, for which a riper must be substituted. 
 
 Marbled stains are very apt to come, especially in hot weather. 
 After a careful study of these sources of trouble, the writer ad- 
 vises as follows : — 
 
 1. Use a rather ripe collodion containing a liberal proportion 
 of bromides (from 2| to 3 grains of bromide to 4 of iodide), and 
 immerse the plate into the sensitizing bath as soon after coating 
 as possible. In hot weather just as soon as the drops cease to 
 fall. 
 
 2. Adopt the excellent system of having two negative baths, 
 
OUT-DOOR PHOTOGEAPHY WITH WET PLATES. 845 
 
 one to make tlie film, 35 or 40 grains to the ounce, and the other 
 20 to 25 grains to the ounce, exclusively reserved to pass the 
 plates into after the film is completely made to the first. Thus 
 the plate is always covered with a comparatively fresh, pure 
 bath solution. This is an excellent plan for general adoption ; 
 but when the plates are to be kept long, it is indispensable. 
 
 3. Withdraw the plate as soon as the oily marks are gone. 
 
 4. Apply thick wet blotting-paper on the back. This must 
 not be too wet, or it will make stains by running down the back 
 of the plate and getting round the bottom and irregularly diluting 
 the liquid on the film. 
 
 5. But the most important precaution of all lies in avoiding 
 accumulation of bath solution. For this purpose, the writer, 
 after draining the plate thoroughly on successive pieces of folded 
 blotting-paper, and wiping the back thoroughly, sets it in the 
 frame, of which the corners have been carefully and thoroughly 
 wiped out immediately before. A piece of the thickest blotting 
 pad has been provided, about an inch wide and as long as the 
 plate. On the long side of this a narrow edge, about an eighth 
 of an inch wide, is folded over at right angles. This strip is laid 
 along the bottom of the plate, but the chief peculiarity of the 
 arrangement is that the plate is lifted up to the narrow edge passed 
 under it. This edge is not to pass between the face of the plate 
 and the glass corners, but under the bottom edge of the plate. It 
 thus comes just into contact with the bottom edge of the collodion 
 film, which it keeps steadily drained during the whole delay. 
 This has a really wonderful influence in preventing marbled stains, 
 for which it is a perfect cure. 
 
 By operating in this way, the writer has been able to keep 
 plates with facility and certainty for an hour, and even much 
 longer. On one occasion a plate was carried twelve miles, and 
 developed at the end of nearly two hours (1 hour 55 minutes), 
 and gave an excellent negative. No preservative was applied, 
 and the success depended upon the foregoing precautions, of 
 which a second bath of weaker and purer solution, and the blot- 
 ting pad under the edge, were the most effective. Plates kept for 
 two and a half hours gave hazy spots, but were free from all other 
 faults. This mode of operating the writer strongly recommends. 
 
 The hazy spots are very annoying and troublesome when the 
 delay is very long ; difficult by their size to touch out, and ruin- 
 ing the picture if left in. They appear to arise from a concentra- 
 23 
 
346 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 tion of the bath solution reacting^upon the iodide of silver in the 
 film. The presence of acid, especially of nitric acid^ has seemed 
 to the writer to increase this tendency. For plates that are to be 
 kept, acetic acid is better than nitric. The addition of a few- 
 grains of acetate of potash or soda, with a little acetic acid, will 
 change a bath from a nitric to an acetic bath. The proportion is 
 roughly about a grain to five or six ounces of bath. Dissolve in 
 half an ounce of water and pour slowly into the bath, stirring. 
 The cloud of acetate of silver at first formed will speedily dis- 
 appear. 
 
 Tripods. — See Chap. YII., sec. 3. 
 
 Tents and Boxes. — When the distance of the object makes it 
 clearly impossible to carry a wet plate, we must either use a dry 
 one, or else take the means with us for preparing wet plates on 
 the spot. 
 
 In using a tmt^ the operator works inside. With a developing 
 hox, he passes his arms through sleeves provided with India-rubber 
 rings, and watches his operations through yellow glass let into 
 the front of the box. Of the two methods the former is the more 
 satisfactory. With the box there is more danger of spilling hypo- 
 sulphite, and so exposing the delicate operations of photography 
 to the effects of hyposulphite dust. 
 
 Of tents, probably Carbutt's is as convenient as any. A still 
 more convenient mode of operating is with a van, either altered 
 or built for the purpose. Mr. G. W. Wilson, the well-known 
 Scotch photographer, recommends a very light tripod covered 
 with two thicknesses of black calico and an inner one of yellow. 
 The calico is a foot longer than the tripod, on which extra foot- 
 stones are placed to steady the tent and exclude light. There is 
 probably nothing better than this simple and convenient plan. 
 The tripod may be very light, and of course folds up into a small 
 space, so that the whole weight, including that of the cover, is 
 trifling. An umbrella has been found an excellent support for a 
 tent ; it is secured to a stake driven in the ground, and an opaque 
 cloth thrown over it ; a piece of yellow muslin set in, lets in light 
 enough to work by, and water is introduced from a vessel outside 
 by a flexible tube. An exceedingly convenient arrangement has 
 been made by altering an old barouche, the front part being 
 arranged with an operating table and racks for bottles, the photo- 
 grapher sitting on the back seat to sensitize and develop. 
 
 Where the object is rather lightness than folding up into short 
 
OUT-DOOR PHOTOGRAPHY WITH WET PLATES. 347 
 
 lengths, three pieces, or four if preferred, of cane-angle may be 
 fastened together at one end and a cloth thrown over them. 
 
 Any of these plans seem preferable to the more elaborate sort, 
 which are heavier to carry, and require the loss of valuable time 
 to put them together and get the whole concern into working 
 order. It is to be remarked, both with this plan and that of the 
 tripod, that the wider the stride given to the legs the steadier the 
 whole arrangement. 
 
 Shortening the Out-door Work — Various plans have been found 
 useful to cut short the development and postpone the fixing (also 
 a redevelopment, if needed) until it can be conveniently finished 
 in the dark room at home. 
 
 The first plan used was to flow the plate with glycerine to 
 which a little water had been added, but this has given way to 
 the syrup treatment. A filtered mixture of clear syrup molasses 
 and water is provided, and as soon as the development is over, 
 the plate is carefully flowed with it, and in this condition may be 
 kept for a day or two. Mr. Gulliver makes a decoction of saffron 
 in water, to be used in the same way, and lines the top and bot- 
 tom of the plate box with wet felt. Some, in using syrup, add 
 alcohol, as follows :— ■ 
 
 Syrup molasses 10 ounces. 
 
 Water 10 " 
 
 Alcohol 6 drachms. 
 
 The plate is then slid into a groove in a light tight box of 
 wood or tin. It must be well washed before redeveloping. 
 
 ^ 2. — Instantaneous Photography. 
 
 When objects in motion are to be photographed, it becomes 
 necessary that the exposure should be so reduced that the move- 
 ment shall be inappreciable. To these exposures the name of 
 "instantaneous" has been applied, although they are in many 
 cases reduced to a small fraction of a second. Various contriv- 
 ances have been devised for effecting them. The most usual and 
 one of the best is to have a slide attached to the camera front, 
 capable of moving up and down in a groove. In its centre is a 
 circular opening of an inch or two in diameter. When the slide 
 is up or down it covers the lens, but in descending it uncovers it 
 for the space of time that the circular opening takes to pass the 
 front of the lens. 
 
348 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 For exposures which, though brief, are to be longer than those 
 attained as above described, the cap may be removed and instantly 
 replaced. This is best done by raising the lower part whilst the 
 upper part is held nearly still, almost like turning upon a hinge. 
 In this way the foreground gets a much longer exposure than 
 the distance and sky. Another method is to let the focussing 
 cloth hang over the uncapped lens ; the palm of the hand is placed 
 over the lens, and the corner of the cloth held between the thumb 
 and the lower part of the forefinger. The hand being then turned 
 upwards over its own back edge as an axis, uncovers the lens 
 for a moment and is instantly returned, in both cases carrying 
 the cloth with it. As in the former case, this exposes the fore- 
 ground longer than the sky. 
 
 The conditions under which instantaneous pictures are to be 
 taken differ extremely. Widely extended views throw back a 
 great volume of light and much facilitate the operation. Ships 
 at sea, with breaking waves, offer no very serious difficulty, if 
 the size of the plate is not too large, Eiver scenes, with sail 
 boats and steamboats, are similar in character. Instantaneous 
 views of these subjects will be best taken with the Steinheil 
 aplanatic or the Dallmeyer rapid rectilinear, remembering always 
 that the shorter the focal length the more powerful the image, 
 and that success is thereby very greatly facilitated. 
 
 On the other hand, objects in motion near by, sending back 
 comparatively little light, no matter how brightly they are illu- 
 minated, will be most easily managed with a portrait lens. But 
 as this lens has comparatively little depth of focus, care must be 
 taken to get the objects pretty nearly into the same plane; and 
 as the corners will be very apt to be out of focus, it may be 
 necessary to vignette the negative in printing. 
 
 The Chemicals. — The bath should be forty grains to the ounce, 
 new or nearly new, and nearly neutral. The collodion should be 
 just old enough to work, and, what is of special importance, must 
 be made of cotton of a very sensitive character. Cotton capable 
 of giving intense images that need no redevelopment, does not 
 possess the exalted sensibility necessary for instantaneous work ; 
 we need a cotton of a very impressible character, and this is 
 usually accompanied by a tendency to form images needing re- 
 development. Without a suitable cotton, it will be hopeless to 
 attempt the work. The developer must contain no restraining 
 acid, and be simply an eighty-grain solution of sulphate of iron. 
 
OUT-DOOR PHOTOGRAPHY WITH WET PLATES. 349 
 
 The development must be very brief, or sucb a developer will 
 produce fog. 
 
 The subject must not present dif&culties too great. The illu- 
 mination must be good everjT-where, and there must be no strong 
 contrasts. Objects in motion will be much more easily taken 
 when their line of movement is either towards or from the ope- 
 rator. An object passing rapidly, directly in front of the camera, 
 will be exceedingly difl&cult to catch successfully ; it is, however, 
 accomplished. 
 
 Instantaneous views are most easily obtained in the spring, at 
 which season the light is more active than at any other. There- 
 fore those who especially interest themselves in this branch of 
 work find it desirable to accomplish it in May and June. 
 
 It is a not uncommon mistake for those who desire to have a 
 " quick acting collodion," to seek for it in some special formula. 
 This is all a delusion. A highly sensitive collodion is one made 
 with a highly sensitive cotton. As for the formula of salting, a few 
 trials of dijfiferent proportions of bromide must determine what is 
 best suited to it. But what suits one specimen may not suit 
 another. One way is to make with the cotton a collodion con- 
 taining but little bromide (as, for example, by Eeutlinger's 
 formula, p. 142). If on trial it seems sensitive, make up another 
 portion by a formula rich in bromide, and compare these, and 
 one or two mixtures of each, in different proportions. 
 
 Mr. Chapman recommends after the iron development has done 
 all that it can, to wash it ofi" and to apply an alkaline develop- 
 ment with pyrogallic acid (see Chap. XYI.) ; when this ceases to 
 act, to finish with acid pyro and silver in the ordinary way. 
 
 The writer has found that a very material acceleration can be 
 obtained by lining the inside of the camera with pasteboard 
 which has been colored red with carmine dissolved in water with 
 the aid of a drop or two of ammonia. This pasteboard is not 
 to line the whole of the inside (see Fig. 107, p. 220), but only 
 those parts where the light is least strong — :opposite ground and 
 trees, but not sky. 
 
 The red rays of light have a continuing, but no exciting power. 
 They, therefore, exalt the action of the image upon the plate, 
 and, when rapidity is an object, this method will be found de- 
 cidedly advantageous. 
 
 Animals. — Yery beautiful photographs are obtained of horses, 
 dogs, cattle, &c. In order not to risk motion of the subject, it is 
 
850 PHOTOGRAPHIC MANIPULATIONS. 
 
 best to make very brief exposures, simply uncapping and in- 
 stantly replacing the lens. A quarter-size portrait lens is the 
 most suitable. If larger pictures are desired, it is best to take 
 the small size just mentioned and to enlarge afterwards. This is 
 the method adopted by Mr, Schreiber, of this city, who makes 
 this subject a specialty, and who has shown the author of this 
 manual some very fine enlargements, taken from quarter-plate 
 negatives. He prefers to take even small animals, such as dogs, 
 in the open air, with appropriate surroundings, rather than under 
 the skylight. 
 
 § 3. — Preserved Plates — The Glycerine Process. 
 
 The preserved plate stands intermediate between the wet and 
 the dry. Of various preservative processes, the glycerine and 
 honey, first brought prominently forward by Mr. W. H. Harrison, 
 is the best. A plate coated and sensitized as usual is plunged 
 without previous washing into a bath prepared as follows : — 
 
 Price's glycerine 2 ounces. 
 
 Pure honey 2 " 
 
 Ordinary bath solution 2 " 
 
 Water 2 " 
 
 Glacial acetic acid 8 drops. 
 
 These are well shaken up and set in the sun for a few hours, 
 or still better, a day, then half an ounce of kaolin is added, well 
 shaken up, and the whole, after standing for a day, is filtered into 
 a bottle. A large funnel with a filter in it is left permanently in 
 the neck of the bottle. When wanted for use, a sufficient quan- 
 tity is to be poured into a pan. After using it, it is poured back 
 into the funnel ; it is a saving of trouble to have the funnel large 
 enough to carry the whole at once ; the mixture is then always 
 through and ready for next day. The glycerine keeps the filter 
 moist and ready to filter well and rapidly. 
 
 The sensitive bath is a common acetic bath, a bath acidulated 
 with nitric acid does not work well. The usual formula for the 
 glycerine preservative does not include the acetic acid as above, 
 but the writer has found a marked advantage from adding it. 
 
 As above directed, the preservative bath contains about eight 
 grains of nitrate of silver to the ounce. By use it becomes con- 
 tinually richer in silver, and thereby deteriorated — from eight to 
 ten grains is its proper dose. Therefore we must add glycerine 
 
DRY PLATE PHOTOGRAPHY. 
 
 351 
 
 and honey, and if necessary a little water from time to time to 
 maintain a correct proportion. After such addition it must inva- 
 riably be sunned and shaken up with kaolin again. 
 
 The development of these plates takes place in the ordinary way 
 with an iron developer or with a pyrogallic one. In the former 
 case, an exposure about three times as long as for wet collodion 
 is proper. With a pyrogallic development a longer exposure is 
 needed; this mode is preferred by Mr. Harrison, as allowing of 
 more latitude in exposure. The writer's trials have worked best 
 with iron development; for this purpose he does not like the 
 plain iron developer so much as the sugar developer. (See p. 164.) 
 The development is generally best done in a pan. The edges 
 sometimes become a little dry, especially if the plate has been 
 kept six to twelve hours ; and then these do not take the de- 
 veloper evenly, and the edges may be defective even when all 
 the rest of the plate is good, unless developed in a pan. A red 
 transparent sky indicates over-exposure. 
 
 This method will, when well managed, give results about as 
 good as ordinary wet work, but scarcely up to the best wet work. 
 It has no great capacity for mastering contrasts, because over- 
 exposure causes a deep red solarization, obliterating every trace 
 of detail. It is, therefore, necessary to be extremely careful to 
 avoid over-exposure. It is probable that this process would 
 work well with a collodion containing bromides exclusively. 
 Filtration before each using is necessary. No under-stratum is 
 required. 
 
 It seems exceedingly probable that the introduction of glyce- 
 rine into the negative bath would enable us to obtain plates that 
 would keep for a long time, especially if the method of two baths 
 be adopted, the glycerine used in the second one. 
 
 ■ CHAPTBK XYI. 
 
 DKY PLATE PHOTOGEAPHY. 
 
 ♦ 
 
 Before describing specific processes, the writer proposes to 
 give such manipulations as belong to all dry work, and which 
 need not be repeated in connection with individual processes. 
 
 Formerly it was held that only second-class work could be 
 
352 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 done with dry plates. But it is now established that soft and 
 delicate negatives, full of half-tone, can be made on dry plates, 
 and that in place of the tedious and exaggerated exposures needed 
 by the older method, dry plates can be made as rapidly as wet. 
 
 ? 1.— Preparation of the Glass. 
 
 It will be desirable to clean the glass by the bichromate pro- 
 cess already described. Before receiving the coat of collodion, 
 they should have an edging of India-rubber dissolved in benzine. 
 
 Procure some fresh clean India-rubber, wet the blade of a 
 knife and pare off the outside and reject it. Cut the rest into 
 very thin strips, put about a quarter of an ounce of it into half a 
 pint of good benzine ; common benzine will not answer at all, 
 but a pure specimen is needed. Shake up well, and in a few 
 days solution will take place. This solution may be diluted by 
 adding twice its bulk of benzine; it is then ready for use. (It is 
 said that moistening the strips of India-rubber with chloroform 
 will aid the solution.) The writer has always succeeded in 
 making the preparation without this aid. 
 
 Tie a camel's-hair pencil to a glass rod of medium size a little 
 way from the end. Take a wide-mouthed four-ounce vial, and 
 into the cork make a hole that will just receive the 
 glass rod. Into the vial put the diluted rubber solu- 
 tion to the depth of half an inch. Push the glass 
 rod down so that when the cork is in, the rod will 
 touch the bottom. (See Fig. 132 ; the rod should 
 project about ten inches above the cork.) 
 
 When ready to begin, take a plate, hold the glass 
 rod against its edge so that the brush will press on 
 the face of the plate. Draw the rod round, and thus 
 make a neat border an eighth of an inch wide round 
 the plate. Edge half a dozen plates in this way, and 
 set them in a rack to dry (they dry immediately) 
 before beginning to coat. 
 
 Many sorts of dry plates Uister — that is, the solu- 
 tions penetrate the film and get between it and the 
 glass, raising the film into blisters. It is best, there- 
 fore, to leave the corners open, so that this may have 
 a fair chance to run out, or rather ; it is better to carry the coat- 
 ing along the longer sides, but leave a break at the ends of the 
 
DRY PLATE PHOTOGRAPHY. 
 
 353 
 
 shorter side. This allows the liquids to drain easily out of the 
 breaks in the edging. (See Fig. 133.) 
 
 "With plates larger than 6J X 8|, however, or when the films 
 show themselves tender, it is an excellent precaution to varnish 
 the edges just before developing, as well as 
 before coating. This double application gives 
 great steadiness to the film, without interfering 
 with the escape of any liquid which may have 
 worked through. The writer has often saved 
 plates in this way which would undoubtedly 
 have split without the second edging. 
 
 Some edge the plates after exposure, but the 
 protection afforded is inferior by very much, 
 and the trouble fully as great. Some use 
 albumen as an under-stratum for the whole plate; the method of 
 doing this has been described at page 155. Others use an under- 
 stratum of thin solution of India-rubber over the whole plate, 
 which plan the writer does not think well of. 
 
 The writer recommends always, when possible, to prepare dry 
 plates at nighty because at that time the windows can be kept 
 raised enough to thoroughly ventilate the room, and so diminish 
 the injurious effects of the fumes of collodion. 
 
 § 2.— Drying. 
 
 Thorough drying is necessary for dry plates, and may be effected 
 by spontaneous drying^ by heat, or with sulphuric acid. 
 
 Heat. — A 4-sided vessel is made of sheet-copper, in shape a 
 truncated pyramid. A ledge at bottom keeps the plate in its 
 place. The vessel is half filled with 
 water, and heat applied from below. If ^^S- 134. 
 
 the water is boiling, or nearly so, the / 
 
 plates will be safely dry in twenty-five / 8 
 
 to thirty minutes. They should always / 
 stand five or ten minutes to drain before / 
 the heat is applied. Irregular surface / 
 markings, which at one time caused the / 
 writer considerable annoyance, he suc- 
 ceeded in tracing to this cause, and they at once disappeared 
 wholly by taking the precaution of letting the plates stand and 
 
354 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 drain. The hotter the drying temperature the longer the plates 
 should wait. 
 
 Drijing hy Sulphuric Acid. — The writer believes that much of 
 the difficulty experienced in making good dry plates depends 
 upon the method of drying. The slow, even drying obtained by 
 placing the plates in a tight box with a pan of sulphuric acid, as 
 recommended by him many years ago, gives a remarkably even 
 and perfect plate, and he uses it exclusively. 
 
 Drying Box. — After planning and having made several sorts 
 of drying boxes, all of which proved unsatisfactory, the writer 
 has contrived that shown in the adjoining figure, and which, after 
 full trial, has seemed to him to leave nothing to desire. 
 
 The box (Fig. 135) has the front hung on strap-hinges so that 
 it turns entirely over and rests on the top, as shown in the figure. 
 
 When brought down, it closes upon a rebated edge, and is secured 
 by the turn buttons T T. About five inches from the bottom 
 are placed at each end the cleats A A, and at the same level, the 
 bridges B B. On these four pieces the rack (Fig. 186) slides in, 
 and when the front is brought down and secured, the rack is per- 
 fectly protected from light. A small door, D, permits the pan, 
 containing about a pound of sulphuric acid, to be slid in. This 
 door opens outwards, not inwards, as represented in the cut, by 
 an error of the engraver. 
 
 The rack (Fig. 186) is constructed as shown in the section (Fig. 
 137). B B are two long strips of light wood, into these are mor- 
 
DRY PLATE PHOTOGRAPHY. 
 
 355 
 
 tised cuttings of thick plate-glass Fig. 137, 
 
 about half an inch wide, over a quar- 
 ter thick, and about seven inches 
 
 long. These are laid with the flat 
 
 I 
 
 lull 
 
 In I 
 
 side against B and are mortised in, 
 but not fully, so that when the out- 
 side pieces, A A, are screwed against 
 B B, thej hold the glass firmly in e 
 its place, and leave spaces, E B. 
 
 Between each two glass uprights, these spaces, B B, extend all 
 the way to the top. On the pieces A A, strips of glass, C 0, are 
 cemented. 
 
 If the reader will carry the construction of this section over to 
 the full view (Fig. 136), he will see that every sensitive plate, when 
 set in, is supported in six places, and yet touches nowhere any- 
 thing but glass. It leans back on the two uprights behind it, at 
 the lower front edge it touches the two uprights in front of it, 
 and near its corners it touches the outside edges of the glass 
 strips, 0 C. It is consequently held very securely, and also the 
 drainings are conducted away at four different points from each 
 plate. As the back of the plate rests against two points only 
 (the tops of D D, Fig. 137), the backing can be applied as soon 
 as the plate is out of the sensitizing bath, and the back and front 
 thus dry together, saving much handling. 
 
 In Fig. 136 the rack contains, for simplicity, ten pairs of up- 
 rights, accommodating nine plates. In the box used by the 
 writer there are twenty-five pairs, accommodating two dozen 
 plates of any size, from half-plate up to 8 x 10. In fact, this 
 form of rack has the advantage that it will support any size of 
 plate, and if the box were of suitable dimensions, would contain 
 plates from half-size up to 10 x 12, or larger. 
 
 If the box is not kept in the dark room, it should have a thick 
 black cloth cover. The writer usually leaves his plates in the 
 box thirty -six hours before using them, in order to insure per- 
 fect drying in every part. 
 
 A simpler but less compact mode of making a drying box is 
 simply to take an empty box, set a pan of acid in the bottom and 
 a range of empty tumblers round the sides. In each tumbler set 
 the lower corner of a plate, and let the upper rest against the side 
 of tlie box. Cover up securely from light and from change of 
 atmosphere. 
 
356 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Drying spordaneously is effected in a dark cupboard, or even on 
 shelves in a dark room. Drain the plates for a minute or two, 
 not more, on blotting-paper, and then set them in the cupboard, 
 each with the lower end resting in an empty tumbler, its upper 
 corner against the wall. Some allow the plates to dry on blotting- 
 paper ; this has the disadvantage of keeping the lower end very 
 long in drying, and so risking unequal action in development. 
 
 § 3, — Backing the Plates. 
 
 Dry plates are almost always more transparent than wet ones, 
 so that the tendency to internal reflection is greater than with 
 wet plates. The result is blurring, otherwise called " halation," 
 and its effect is that the high lights work into the adjoining 
 shadows. Thus the foliage adjoining the sky is more opaque 
 than it should be. Eoofs of buildings shade off towards the sky. 
 Boughs of trees, when bare of leaves and projected against the 
 sky, are especially apt to become blurred, as the light works in 
 on both sides. These effects are ruinous to the work, so that it 
 becomes advisable always to coat the backs. 
 
 After much careful study, the writer has finally come back to 
 annatto as combining, on the whole, more advantages than any 
 other substance with which he is acquainted. It is, however, 
 essential to use glycerine with it, or the whole coating will 
 gradually become everywhere penetrated by fine cracks. Quite a 
 small proportion of good glycerine will wholly remove this diffi- 
 culty. The writer uses iwo fluidrachms of thick syrupy glycerine 
 to the quarter pound of annatto in lumps. A convenient way of 
 managing the mixture so as always to have it ready is the 
 following: — 
 
 Provide a half-pint porcelain bowl with cover and handle (to 
 be obtained from a dealer in chemical utensils). Put into it a 
 quarter pound of annatto with a little more water than necessary 
 to cover it, and set aside for several days. The annatto will 
 soften, and can now be easily worked into a smooth paste. Add 
 two fluidrachms of glycerine and work it well in. This mixture, 
 if kept closely covered, will keep good for weeks, 9,nd if too 
 thick can be thinned by stirring in water. As the quantity 
 diminishes, add more weighed annatto in lumps, taking care to 
 add also the proportionate quantity of glycerine. The additions 
 
DEY PLATE PHOTOGRAPHY. 
 
 357 
 
 of glycerine are always to be proportionate to the quantity of 
 annatto added, and not to the water. This last will, of course, 
 be added when needed ; the mixture should, however, form a 
 pretty thick paste, and is to be put on liberally. 
 
 The writer has examined many other mixtures. Oum may be 
 colored deeply by aniline brown or other suitable pigment. To 
 prevent cracking, sugar must be freely added, so that the quan- 
 tity of sugar will be nearly up to that of gum, say in the pro- 
 portion of three to four by weight. But the annatto is preferable, 
 and in practice does not cost more, as it goes much further. 
 
 A round bristle brush as thick as the thumb will be found 
 convenient for applying the paste. Bring it up to within a 
 quarter of an inch of the edge all around. It should be thick 
 enough not to run : annatto has much less tendency to run than 
 mixtures of gum, and this is no small advantage. 
 
 When plates are dried by sulphuric acid or spontaneously, the 
 backing may be put on as soon as they are out of the preserva- 
 tion bath. In drying by heat this cannot be so well done, at 
 least the heat has a tendency to liquefy the backing and make it 
 run down. 
 
 The character of the coat when dry should be carefully tested. 
 Not only should it show no tendency whatever to crack, but it 
 should resist perfectly when tried with the thumb-nail. Even, 
 however, if the coating appear perfect when examined from the 
 back, it may have separated in places from the glass suflEiciently 
 to be no longer in optical contact^ and from that moment it is per- 
 fectly useless. That it is then useless not only follows from 
 theoretical considerations, but is abundantly proved by expe- 
 rience, as the writer has seen in his own work. If a dry plate, 
 after thorough drying, be examined in the dark room, catching 
 the reflection upon the film side, it should have a perfectly even 
 coloration and a certain dark look all over. If it appears here 
 and there lighter in spots, then in these spots the backing is no 
 longer in optical contact, however perfect it may seem, and the 
 film at these spots is unprotected and liable to blur if any cause 
 of blurring be present. 
 
 Before developing, sponge off the back thoroughly with cold 
 water. 
 
358 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 4. — Acid or Silver Development. 
 
 This is conducted in precisely the same way as the pyrogallic 
 development of an ordinary wet plate, except that the silver is 
 added very cautiously, so as to avoid too rapid a deposit upon 
 the high lights. The acid development of dry plates has, how- 
 ever, almost wholly given way to the 
 
 § 5. — Alkaline Development. 
 
 This method shortens the exposure to one-half or one-third, 
 giving at the same time softer and more harmonious effects. 
 
 The first idea of using alkali for the development of dry plates 
 originated with Mr. Borda, of Philadelphia. The next steps in 
 it were made by Mr. H. T. Anthony, of New York. These 
 gentlemen were undoubtedly the discoverers of the principle of 
 alkaline development. Subsequently it was taken up in Eng- 
 land, and gradually brought into its present shape by Mr, Glover, 
 Mr. Leahy, and especially Major Eussell, who made the discovery 
 that the development might be controlled and restrained by add- 
 ing a few drops of solution of bromide of potassium to the alka- 
 line developing bath. This last discovery has given us the means 
 of managing the whole operation at pleasure, and producing every 
 variety of negative, from the most veiled to the most transparent. 
 
 Management. — Prepare the following solutions: Pour some 
 alcohol into an ounce vial of pyrogallic acid, and filter the solu- 
 tion into an eight-ounce vial, washing the filter with alcohol 
 until the vial is full. This gives a solution of nearly 60 grains 
 to the ounce. 
 
 Take 6 ounces of good clean flinty carbonate of ammonia, and 
 pour over it enough warm water (not hot, hot water decomposes 
 it) to cover it. After standing an hour or two,* filter into a quart 
 (32-ounce) bottle, add more water to the undissolved residue, and 
 so on until the whole is dissolved in the 82 ounces. This gives 
 a solution of about 80 grains to the ounce, which must be kept 
 well corked. 
 
 Dissolve bromide of potassium in water in the proportion of 
 60 grains to the ounce. 
 
 In commencing to develop a lot of plates, put into a small vial 
 half an ounce of the 60-grain bromide solution, and three- 
 
DRY PLATE PHOTOGRAPHY. 
 
 859 
 
 quarters of an ounce of 80-grain carbonate of ammonium, and 
 mix well by shaking. 
 
 Next, for a whole size (6| x 8 J) plate, take a 7 X 9 porcelain 
 pan, and put into it 4 ounces of water. Add J drachm of the 
 solution of pyrogallic acid, and immerse the plate so as to wet 
 it equally and avoid lines of unequal development when the 
 alkali is added. 
 
 Now remove the plate and add to the bath 15 to 20 minims of 
 the mixture of bromide and carbonate, mix, and return the plate. 
 The image should rapidly come out, and when its details are well 
 out, add, without waiting longer, half a drachm of the carbonate 
 of ammonium solution. Density rapidly comes, and when the 
 plate has reached printing strength, fix it as an ordinary wet 
 negative. Except that with plates made with a collodion con- 
 taining bromides only, the fixing bath must be very weak, one 
 part of hyposulphite to fifty of water. 
 
 Heat in Development. — The water used in making the develop- 
 ing bath should never be cold, but rather of the temperature of 
 70 to 80°. A higher temperature than this is very useful in 
 case of under-exposure. If in the development of a plate it is 
 evident that it has been considerably under-exposed, and there 
 are other plates that have had a like exposure, it will be well to 
 develop them in a bath at about blood-heat, or even a little 
 warmer. This will be found to aid materially in getting out the 
 image, and will often save plates that would otherwise be lost. 
 A little more bromide in the developer will be advisable when 
 it is used hot. 
 
 Acid Development to Finish the Alkaline. — In the writer's expe- 
 rience, it is always best, if possible, to finish the plate wholly by 
 the alkaline development. The results are softer and more har- 
 monious, and the shadows more luminous. Some, however, pre- 
 fer only to bring out a thin image, and then finish with pvro- 
 gallic acid and silver. The writer does this only when, from a 
 material under-exposure, it is impossible to get printing density 
 without it. It should, however, be very clearly understood that 
 in such cases it is better to resort to an acid development than to 
 push the alkaline under circumstances that lead to fogging. 
 
 If the alkaline development stops entirely (if it even goes on 
 very slowly, it is best to let it take its time), it can generally be 
 started again by adding a little more carbonate of ammonium. 
 But, after carrying this addition to a certain point, it is best to 
 
360 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 stop. The writer does not find any good effect, but rather mis- 
 chief, result from raising the proportion of carbonate over one 
 and a quarter, or at most one and a half, grain to the ounce. 
 
 If, then, the addition of carbonate has reached this point, and 
 the development has quite ceased, it will be well to redevelop 
 with acid. The first thing needed is to wash the plate under the 
 tap, to get the alkaline liquid out of it, which, in contact with 
 silver solution, would cause instantaneous fog. Meantime, sufii- 
 cient water is placed in a clean basin, and acetic acid (No. 8) is 
 added in proportion of about one-twelfth of the water and mixed 
 by agitating. Into this the plate is put, that the acid may remove 
 the last traces of alkali before the silver is applied (if the plate is 
 put into the acid solution without previous washing, bubbles of 
 carbonic acid gas may form under the film and detach it, as the 
 writer has seen happen). Pyrogallic acid and the usual solution 
 of silver (nitrate of silver 10 grains, citric acid 15 grains to the 
 ounce) are added in very moderate quantities to the bath. 
 
 § 6. — Failures in Dry Plate Operations common to Dry Plates 
 
 generally. 
 
 Dry plates are much more exposed to accidents than wet, partly 
 because the latter remain in the sensitive stage so short a time 
 and are used at once. There is also in dry-plate work a greater 
 need of strict cleanliness. Any operator, for example, who ever, 
 under any circumstances, places hyposulphite in any vessel used 
 in any of the operations other than fixing, actually invites failure. 
 The least trace of hyposulphite in the developing pan will cause 
 the development to fail. A pan that has been once used for fix- 
 ing must never be used in any of the other operations, neither as 
 a water pan for soaking the plates before the preservative nor for 
 any other use whatever. Each pan must have its special use, and 
 be reserved for it. 
 
 Again, dry plates must never be exposed to the air, especially 
 not the air of a work-room, which may have in it gases of various 
 sorts. The plates, both before and after fixing, must remain in 
 tight boxes, perfectly excluding air and dampness, for all damp- 
 ness is destructive to dry plates. And as to gases, the vapor of 
 acetic acid, which is often in the air of the dark room, tends to 
 destroy the latent image. Sulphur vapors of any sort tend to fog. 
 
 Another source of trouble lies in wet tables. The bottles or 
 
DRY PLATE PHOTOGRAPHY. 
 
 361 
 
 other vessels resting on tlie wet take up some, and when turned 
 over to pour from, a drop or two from the bottom may run along 
 the outside, and fall unnoticed along with the contents. 
 
 Keeping. — Although many sorts of dry plates show good keep- 
 ing qualities, yet their sensibility in most cases slowly diminishes, 
 so that plates a month old should have full one-half more to 
 double the exposure of fresh ones. Also, the image, after ex- 
 posure, tends to fade in the delicate details; it is, therefore, com- 
 monly said that the golden rule of dry-plate work is to develop 
 as soon as possible after exposure. The same evening is the best 
 time of all, but generally two or three days' delay will not be 
 very important. For longer delays a longer exposure should be 
 given. But it is to be carefully borne in mind that, quite apart 
 from fading, the longer a plate is kept after exposure the more 
 it is exposed to adverse influences of all sorts. 
 
 Errors as to Length of Exposure. — This is a serious source of 
 difficulty with dry plates. With wet, the first plate tried gives 
 a clear idea of the character of the day's light, and the rest are 
 measured thereby. But with dry plates, all on any one excur- 
 sion must be exposed on a venturCj and there is no criterion from 
 the first to the rest. Fortunately, there is a good deal more lati- 
 tude with dry plates than wet, and in exposing, it is best to err 
 on the side of too much rather than too little. Certain points 
 are of consequence to remember. 
 
 1. After midday the light soon falls off, and about three hours 
 before sunset, at some irregular time, the diminution begins to 
 be very considerable. 
 
 2. In the beginning of September the light is already materially 
 weaker, and a great allowance must be made for its failing. 
 October, compared with May or June, will need about a triple 
 exposure. 
 
 3. Cloudy days, excellent for soft effects, are often deceptive as 
 to strength of light. With very thin clouds, the light is some- 
 times extremely powerful. With a grayish color in the clouds, 
 the light is much weaker. 
 
 4. Sheltered places, partly under trees, receive a great deal 
 less light than open ones ; the difference is so much greater than 
 appears, that such views are extremely apt to be under-exposed. 
 
 The Ratio of Exposure^ compared with wet plates, varies with 
 different sorts of dry plates, but it must never be forgotten that 
 the proportion of exposure increases always as the light is fainter. 
 24 
 
362 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Thus, a dry plate whicli in a good light needs a threefold expo- 
 sure, will in a poor light need four or five times the exposure of 
 a wet plate in the same light, and in very dull, rainy weather 
 will scarcely receive any impression at all. 
 
 Non-actinism of the Film varies greatly with different processes, 
 so that in changing one's process, one is apt to be deceived. 
 Two plates by different processes, looking equally dense, will 
 probably differ very much in the printing. 
 
 Irregularity of Surface before Developing. — This peculiarity the 
 writer has been able to trace to the use of too strong preservative 
 solutions. Some films will hold in them much more solid matter 
 than others, and what they will not retain in them of the solids 
 dissolved in the preservative bath solution must come up to 
 their surface in drying. Merely thinning a collodion with alco- 
 hol or ether may cause it to give a thinner film, so that the 
 preservative in use can no longer be held wholly in the film. 
 Use more pyroxyline or weaker preservative, and wash such 
 plates before developing them. 
 
 Image, after advancing awhile, goes back. — Too much carbonate 
 of ammonium, which never should exceed one and a quarter grain 
 to the ounce of developing bath. 
 
 Fogging. — Same cause. Also, too much pyrogallic acid. Ex- 
 posure of plates to deleterious gases. Pushing too far the deve- 
 lopment of under-exposed plates. Using pans that have had 
 hyposulphite in them. 
 
 Want of Detail in /Shadows. — Under-exposure. Too much bro- 
 mide used in the development. Insufficient development. 
 
 Surface Stains. — Drying by heat without allowing to drain five 
 or ten minutes before applying the heat. 
 
 These stains, like the irregularity explained above, may depend 
 upon the preservative. If the preservative solution be pretty 
 strong, and collodion not a full-bodied one, the film, as it contracts 
 in drying, may not be able to hold all the dry preservative, and 
 thus this will be forced up to the surface in places as it dries, 
 and dry in superficial stains. The coffee process is subject to 
 this difficulty. Eemedy : Change the collodion or dilute the pre- 
 servative. 
 
 Want of Intensity. — Bad pyroxyline. Under-exposure. Over- 
 exposure may produce same result. In the latter case the whole 
 picture flashes up — in the former the high lights come easily, and 
 the rest very slowly. 
 
DRY PLATE PHOTOGRAPHY. 
 
 363 
 
 Stains. — Insufficient cleaning. Handling with dirty hands, or 
 touching the plate at all. 
 
 Dampness. — Exposure, even temporary, to dampness, gives rise 
 to more or less decomposition of the sensitive film, resulting in 
 insensitiveness and other troubles. The 'writer invariably, in all 
 weathers, wraps his slides in waterproof black cloth, using a 
 piece sufficiently large to cover them with several folds. Another 
 piece, about four and one-half feet square, is again wrapped over 
 this; the latter serves as a focussing cloth also. Slides, even 
 when so wrapped, should never be laid on the ground or on damp 
 stones. In a word, every precaution must be taken to insure 
 dryness before and after exposure. 
 
 Transparent Dots and Filamentous Marks. — Dust in the pre- 
 servative solutions, or falling on the plates in the slides or in the 
 camera. 
 
 Blistering. — This annoying trouble depends upon the pyroxy- 
 line. Often the sorts otherwise the best, blister badly. Leaving 
 open places in the edging, that the water may wash out, is the 
 best remedy. (See Fig. 133, p. 353.) 
 
 Mistakes in Exposing. — Nothing is more vexatious than to ex- 
 pose by mistake a second time a plate that has been already used. 
 Every dark slide should have a number plainly painted on it, 
 and the slides should be exposed in the order of their numbers. 
 Those who find a tendency to mistakes of this kind may render 
 them impossible by pasting a strip of paper, one end to the slide 
 and the other to the shutter. The exposure cannot be made 
 without breaking or cutting the strip previous to withdrawing 
 the slide, and thus the condition of the strip indicates at once 
 whether the slide has been exposed or not. 
 
 Accidental Uncovering. — If the slides are carried far, and much 
 jarred or bolted, the shutters will sometimes slip aside and un- 
 cover one end of the plate. 
 
 With single dark slides the writer always has a small flat hook 
 attached to the slide and fastening to the shutter handle. With 
 double slides this cannot so well be done, and the best way is to 
 tie twine round them. 
 
 Noxious Fumes. — Any reducing vapor or gas must destroy 
 plates. Sulphuretted hydrogen, or any foul emanation from 
 drains or water-closets, chemical vapors of many sorts, probably 
 also carbonic oxide, the so-called " gas" that comes from badly 
 drawing stoves. Sulphurous acid would also destroy plates. 
 
864 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Resinous wood used for drying-boxes or for plate-boxes, or 
 freshlj^-varnished wood surfaces would be very suspicious. 
 
 It will be observed that all of these sources of trouble point 
 amongst other things to the necessity of the complete exclusion 
 of external influences. ' And this can, perhaps, in no way be 
 better effected when plates are to be carried to any distance, and 
 preserved for any time, than by inclosing the cases in thick 
 brown or dark green or red paper, saturated with India-rubber 
 varnish. Where this cannot be procured commercially, it might 
 easily be made by the photographer himself. The joints of the 
 paper must, of course, be pasted down with the varnish also. 
 
 CHAPTEE XYII. 
 
 DRY PROCESSES. 
 
 In the foregoing chapter the writer has endeavored to group 
 together those details that are common to all dry processes. 
 Therefore, before undertaking any of the following methods, it 
 is presumed that the photographer has made himself acquainted 
 with its contents. 
 
 In learning any one dry process a step will have been made 
 towards all, so much have they in common. At the same time 
 they are nevertheless very distinct. The best advice that can be 
 given is to hold persistently to some one process until it is com- 
 pletely mastered. Then, if desired, others can be experimented 
 with, with the view of settling down upon some one. It is an 
 important matter to be able to judge by the inspection of a drv 
 plate whether it has the right density and modulation to print 
 well. This can scarcely be done if the photographer changes 
 about, because some dry plates are very non-actinic, whilst others, 
 equally dense to the eye, are comparatively very transparent to 
 the chemical rays. Hence much changing will lead to continued 
 mistakes in development. 
 
 As, in the writer's opinion, the collodio-bromide process gives 
 the most sensitive plates and the softest negatives, and as these 
 plates are the most easily and rapidly prepared, it will be placed 
 first. 
 
DRY PROCESSES. 
 
 365 
 
 § 1. — CoUodio-Bromide Dry Process. 
 
 The first idea of adding nitrate of silver to a bromised collo- 
 dion, and of thus dispensing with the negative bath, originated 
 with Messrs. Sayce and Bolton, and was by them put into a prac- 
 tical and workable shape. After several years of constant use 
 and experiment, however, the writer has been enabled to greatly 
 increase both the rapidity and the certainty of the process by 
 radical changes made in every pS,rt of the mode of proceeding, viz., 
 by introducing aqua regia into the collodion, by adding the 
 nitrate of silver in a state of solution, and also by changing the 
 preservative. The tedious washings are done away with, and a 
 better and more sensitive plate is made with greatly diminished 
 trouble and manipulation. 
 
 The Pyroxyline. — For collodion to be used in this process, a 
 very intense cotton is desirable. The best course is to obtain 
 specimens from two or three sources, of cotton believed to be 
 intense, and to try them, securing a good supply of that which 
 answers best. 
 
 Formula for Collodion. 
 
 Ether 3 ounces. 
 
 Alcohol . . .1 ounce. 
 
 Bromide of cadmium 15 grains. 
 
 Bromide of ammonium 3 " 
 
 Pyroxyline 31 " 
 
 The two bromides should be placed together in a test-tube or 
 flask, and dissolved in part of the alcohol, with heat if necessary. 
 Previously dissolve the pyroxyline in the ether and rest of alco- 
 hol. Set the bottle in a light warm room, where the sun will 
 fall on it for several hours a day. It will be fit for use in three 
 weeks, and be good for three or four months, after which the 
 film is more apt to be weak, that is, to split in washing. 
 
 Aqua Regia. — Put into a stoppered bottle an ounce of ordinary 
 hydrochloric acid and half an ounce of ordinary nitric acid. 
 Stand in a warm place ; as soon as the mixture takes an orange 
 color, remove it and keep it well stoppered. 
 
 Gum Solution. — Several different preservatives may be used, 
 but in all the best, gum makes an essential part. It should be 
 dissolved and kept in quantity. Upon one-quarter pound (avoir- 
 dupois) of good clean gum-arabic pour six or eight ounces of hot 
 
866 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 water, stir well, and, after a portion of gum has dissolved, pour 
 the liquid on a filter, add more hot water, and continue till the 
 gum is got in solution in thirty ounces water. Take an equal 
 quantity of clear white sugar (one-quarter pound), and dissolve 
 this in portions in the gum-water before filtering. After filter- 
 ing, add about two-thirds of a drachm of carbolic acid, and the 
 mixture will keep for a year in perfect condition. 
 
 As gum-water is very slow and troublesome in filtration, it 
 will be well to use a percolator. (See Part Y., Chapter II.) 
 
 Sensitizing the Collodion. — Measure out into a graduate as much 
 collodion as is expected to be wanted, and add to each ounce, in 
 hot weather, two drops of aqua regia. The easiest and safest way 
 •to drop it is to plunge a glass rod in the acid bottle, and let drops 
 fall from the end into the collodion. 
 
 Weigh out ten grains (10 grains) of finely powdered nitrate of 
 silver (fused is best, but crystallized will do) for each ounce of 
 collodion taken, and place it in a small flask. Measure some 95 
 per cent, alcohol in a graduate, allowing a quarter of an ounce to 
 each ounce of collodion taken. Pour about half of this into the 
 flask upon the nitrate of silver, warm it over a Bunsen's burner 
 or other gas flame, agitating gently all the while. As soon as 
 the alcohol boils, remove it and continue to agitate. In a few 
 moments return the flask or tube to the lamp till boiling recom- 
 mences. In this way most of the nitrate will dissolve ; this is 
 poured into the collodion, and the operation is repeated with 
 some more of the alcohol, leaving a little for a third application. 
 All of the silver will thus be easily got into solution. 
 
 The addition of the nitrate solution to the collodion should be 
 made in the dark room ; all the previous operations may be con- 
 ducted by ordinary light. In adding the nitrate solution, a little 
 should be poured in at each time, shaking a little between each. 
 The hot solution should not go down the sides of the bottle, but 
 straight into the collodion. On the sides it might chill and crys- 
 tallize a little. 
 
 Most of the nitrate dissolves in the first portion of the alcohol ; 
 as soon as this is all in the collodion, shake up well for a couple 
 of minutes. After adding each following portion, half a minute's 
 shaking will be ample. 
 
 A long narrow vial is preferable for this operation, and should 
 not be more than about half full, otherwise the shaking will act 
 
DRY PROCESSES. 
 
 367 
 
 less effectually, and must be continued longer. It is a good plan 
 to keep the bottle rolled up in yellow paper, to exclude all light. 
 
 After the last addition has been made, and the contents shaken, 
 the bottle is to be put aside. Too much shaking is more likely 
 to do harm than good. 
 
 The mixture should stand for a time that depends somewhat 
 upon the temperature of the room and the season, and may vary 
 from ten hours to sixteen. It is then ready for use as soon as 
 filtered. 
 
 No more should be made than is intended to be used up, and 
 the residues should be rejected. If kept over about sixteen 
 hours, there is no certainty of the working of the plates, whereas, 
 when made as here directed, they are more uniformly successful, 
 and free from fog and stains, than are wet plates. 
 
 Filiering. — Before using, the sensitive mixture will need to be 
 filtered through a bit of clean sponge forced into the neck of a 
 funnel. This should neither be put in too tight nor too loose, the 
 collodion should run through in a very thin stream, or a rapid 
 succession of drops. The mixture filters quite as easily as plain 
 collodion, the bromide of silver in suspension being apparently 
 entirely without effect upon the filtration. In addition to the 
 sponge, the writer likes to use a linen filter. A yard of the 
 finest and closest linen is boiled for a few minutes in a gallon of 
 water, with an ounce of common crystallized carbonate of sodium. 
 It is then thoroughly washed out with clean water, and left to 
 soak, then well wrung out with clean water. This furnishes a 
 large number of excellent collodion filters, and one has more 
 certainty of getting films free from specks when this is used in 
 addition to the sponge. 
 
 Coating the Plate. — More care is necessary than in ordinary 
 coating, as the collodion has more tendency to set unevenly. 
 Pour on in the same way as usual, but without sending back to 
 the far corner, put on plenty, cover the plate rapidly. Raise the 
 far end of the plate as Utile as possible, just enough to enable the 
 surplus to drain off. Keep it so, and rock steadily. In ordinary 
 coating, at the end of the draining we raise the plate almost ver- 
 tically : this is exactly what is not to be done here, the plate is 
 kept almost horizontal until the collodion has set. 
 
 Operating in this way, if we do not get an even plate the mix- 
 ture is too thick and will require to be diluted. This may be 
 done either with plain collodion or with ether. Generally the 
 
868 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 former is the best ; but it must be plain collodion 'made with the 
 same cotton : this is essential. In hot summer weather the sen- 
 sitive mixture is much more difficult to manage, and will some- 
 times need the addition of ether before it will work smoothly. 
 
 It is impossible to judge of the character of the plate by hold- 
 ing it between the eyes and the light. But if held a little to one 
 side of the light, every slightest inequality will become con- 
 spicuous. A perfect plate will look perfectly smooth, but plates 
 that show only a slight irregular cloudiness will give perfect 
 negatives. If the cloudiness reaches a certain point, it will be 
 liable to show in the flat tints, sky, water, &c. "When the cloudi- 
 ness reaches to a still greater extent, it is liable to produce mottling, 
 which shows especially in the skies. 
 
 Before proceeding to coat the plates, they will need to be edged. 
 (See p. 352.) As the coating should not instantly follow 
 the edging, it is best to edge half a dozen or a dozen, and stand 
 them in a rack. Each plate, before coating, should be carefully 
 brushed with a broad flat brush, and a piece of folded paper 
 should be interposed between the fingers of the left hand and the 
 under side of the plate, or else a pneumatic holder should be 
 used. 
 
 As soon as the plate is set, it is thrown into a pan of water and 
 lies there until it no longer shows greasy marks when taken out, 
 but exhibits a perfectly uniform surface. It is best to have three 
 or four pans of water, and coat a plate for each in succession, 
 agitating the pans gently from time to time. As soon as they 
 cease to show greasy marks and are smooth, they are ready to 
 transfer into the pans of " preservative." In these they remain 
 from five to eight or ten minutes, at the convenience of the 
 operator. The time is not very material, provided it is not less 
 than five minutes nor much over ten. 
 
 If the plates are not to be dried by heat, they may be backed 
 at once. The plate is taken out of the preservative bath, reared 
 on end, and the back wiped with blotting-paper, because if the 
 wet is left on, it thins the backing too much. The colored paste 
 (see p. 856) should be as thick as possible to manage; it is 
 put on thickly and carried up to within an eighth, or, at least, a 
 quarter of an inch of the edge. 
 
 If they are to be dried by heat, the backing, if applied first, 
 will be apt to liquefy and run. 
 
DRY PROCESSES. 
 
 369 
 
 When plates are to be dried bj heat, thej should drain five or 
 ten minutes before the heat is applied, or surface marhings may 
 be expected. 
 
 Preservatives. 
 
 Almost any preservative that can be used with common dry 
 plates made with a bath, can be used also with collodio-bromide 
 plates. 
 
 The writer of this manual has devoted a great amount of time 
 to investigating the qualities of a great range of substances as 
 preservatives. He finally adopted two as being superior to any 
 of those previously proposed or used. These are, first, pyrogaUio 
 acid ; and second, a special preservative made from cochineal. 
 
 Pyrogallic Preservative. 
 
 The writer uses for all purposes in which pyrogallic acid is 
 employed, a solution made by pouring alcohol into an ounce 
 bottle of pyrogallic acid till it reaches the neck. A bottle hold- 
 ing just 8 ounces (or marked with a diamond on the side at the 
 point to which 8 ounces fill it) is adopted for regular use, and 
 the above strong solution placed in it. More alcohol is poured 
 into the original pyrogallic acid bottle to rinse it, and this is 
 poured upon the filter and so on, till the filtrate amounts to 8 
 ounces. This is the simplest mode of operating and avoids all 
 waste of material, as both the bottle and filter are well washed 
 out. Shake well to mix the different portions. 
 
 To make the pyrogallic preservative, take 
 
 Of above solution 1 drachm. 
 
 Of gum and sugar solution, already described (p. 365) 10 drachms. 
 Of water 6 ounces. 
 
 In making a batch of plates, it is convenient to prepare three 
 such baths to save time, as the plates are rapidly worked through. 
 Each plate, as soon as set, is slid into a pan of water ; as soon as 
 the oily appearance is gone, it goes into the preservative bath, 
 and then in five minutes is ready for drying. Both the water 
 pans and the preservative pans should be occasionally agitated a 
 little by lifting one end and letting the liquid pass in waves over 
 the plate. 
 
 The writer has never been in the habit of making more than 
 
370 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 six or eight plates in one bath. Using three baths, and making 
 a batch not exceeding two dozen plates, there will have been 
 eight to each bath. 
 
 If the plates are to be dried without heat, it is always most 
 convenient to back them as already described, as soon as they 
 are out of the preservative bath. 
 
 Cochineal Preservative. 
 
 Grind one and a half ounce of good clean cochineal in a mor- 
 tar with one fluidounce of fuming sulphuric acid. As the paste 
 gets gradually thicker, add more acid, until in all two fluidounces 
 have been added. When well mixed, transfer into a wide-mouth 
 bottle, wipe the neck clean inside, set in a vessel of hot water, 
 and leave till cold. Let it stand for a week, then pour out into 
 about a quart of water. Add slaked lime until a piece of litmus 
 paper dipped into the solution turns blue. Then filter and pour 
 water upon the filter until the filtrate amounts to eighty ounces. 
 Add a quarter of an ounce of carbolic acid, and the mixture will 
 keep indefinitely. As but little of it is needed, one making such 
 as the above will be sufl&cient for a season's work. 
 
 To apply it as a preservative, take of the above 
 
 Solution 6 drachms. 
 
 Gum and sugar solution (p. 365) . . . .10 " 
 Water 6 ounces. 
 
 This, placed in a pan just large enough to hold a plate of 6J 
 by 8|, will make a convenient bath for that size of plate ; or the 
 quantity may be increased or diminished for larger or smaller 
 sizes. 
 
 As to the choice between these two excellent preservatives, it 
 is not easy to decide. The cochineal gives very dark, blackish 
 plates ; the pyrogallic acid, light brown, not unlike wet plates. 
 The cochineal gives the softest, the pyrogallic acid the brightest 
 negatives. The writer has had much more experience with the 
 cochineal, having used it exclusively for view-taking through an 
 entire season, and with great satisfaction. He has kept plates as 
 long as three and a half months in good order. 
 
 The pyrogallic preservative he has only discovered much 
 more lately, and cannot as yet report upon its keeping qualities. 
 Judging by analogy, they ought to be excellent. 
 
 Either of these processes, by increasing the dose of bromide in 
 
DRY PROCESSES. 
 
 871 
 
 the development, will give more and more contrast and absence 
 of deposit in the shadows, so that it is easy in this way to give 
 the negatives an ambrotype appearance. For a soft printing 
 negative this is not desirable, but this property might be useful 
 in making transparencies for the lantern, for which the pyrogallic 
 process seems particularly applicable — more so than the other. 
 
 Other Preservatives for the Author'' s Gollodio- Bromide Process. 
 
 As already said, almost any preservative that will work with a 
 common dry plate is suitable for collodio-bromide plates. Next 
 in order of excellence to the foregoing the writer places the Tea 
 preservative, first proposed by Mr. Newton. This preservative is 
 undoubtedly superior to tannin, to coffee, or to gallic acid. 
 
 In the writer's hands, tea has worked better without gum and 
 sugar than with them. It is sufficient to take a tablespoonful of 
 good black tea, let it infuse in boiling water in a covered cup in 
 a warm place for an hour or two, filter and dilute until the liquid 
 amounts to eight ounces. As before, the plate, as soon as the 
 water has rendered it smooth and uniform, is put into this bath 
 for five or ten minutes, and then backed and dried. The results 
 are good, but distinctly inferior to the foregoing. 
 
 Coffee Preservative. — Make a decoction of an ounce of coffee in 
 eight of water, and filter. This preservative does best with gum 
 and sugar. To the above quantity, an ounce and a half of the 
 gum and sugar solution may be used. 
 
 Tannin. — In the use of tannin a great mistake has been gene- 
 rally made by using too much of it. The writer prefers — 
 
 Good tannin 16 grains. 
 
 Gum and sugar solution 10 drachms. 
 
 "Water 7 ounces. 
 
 This is about one-eighth as much tannin as generally directed, 
 and gives much softer and more harmonious pictures. If a de- 
 ficiency in brightness and density is found, increase the tannin. 
 
 Exposures. 
 
 ■ For the author's preservatives, two first described, give with a 
 good light the same exposures as for wet plates ; with an inferior 
 light, the exposure must be longer than for the wet. For the 
 tea plates, give once and a half as long as for the wet. For the 
 coffee and tannin plates, give twice as long as for the wet. 
 
872 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 It will be observed that tbrough all these various treatments 
 the writer's collodio-bromide process gives much greater sensi- 
 tiveness than is attained with the ordinary dry processes used 
 with the same preservative. 
 
 For Drying, see p. 354. 
 
 For Development, see p. 358. 
 
 § 2. — Dry Plates made with a Negative Bath. 
 
 This is the older way of managing dry plate work, and for 
 those who habitually use the wet process, and occasionally need 
 a dry plate, it is the more convenient. It is also preferred by 
 many habitual dry-plate workers. 
 
 For this method of dry-plate work the regular negative bath 
 suffices, though it is an advantage to have it a little more acid. 
 Ordinary collodions may be used if they are pretty old ; generally 
 they are improved by adding a little simply bromised collodion 
 to them, or a grain or two of bromide of cadmium to the ounce. 
 
 But they will work still better with a very intense cotton, 
 giving a porous and not a skinny film. If made specially, the 
 collodion may be salted as follows : — 
 
 Iodide of ammonium 2 grains. 
 
 Iodide of cadmium 2 " 
 
 Bromide of cadmium 3 " 
 
 Add a little tincture of iodine and keep in a warm light room 
 for several week. If the pyroxyline has a good deal of intensity, 
 it may be used sooner, but age and ripeness have much to do 
 with success in dry plates. 
 
 The plate should be edged with rubber solution, as described 
 at p. 352, remembering that the collodion must not be poured 
 on till the edging is dry. When set, the plate is to be slid into 
 a pan of water until the greasiness disappears, and is next to be 
 washed thoroughly under the tap until all free nitrate of silver 
 is removed. It is then plunged into the bath of preservative, 
 whichever it may be intended to use, and is finally backed and 
 dried, or dried first and backed afterwards. 
 
 The preservatives have been already described pretty fully 
 under the head of the collodio-bromide process, and the manipu- 
 lation is much the same in both cases, except that, in the present 
 case, the work is much more laborious. The collodio-bromide 
 
DRY PROCESSES. 
 
 373 
 
 plate was put into the pan of water- immediately after coating, 
 whereas the present sort must first be sensitized in the nitrate 
 bath. Again, the collodio-bromide plate goes direct form the 
 water-pan into the preservative, whereas the ordinary dry plate 
 requires a thorough washing under the water faucet to be inter- 
 posed between these two operations. 
 
 Thus it requires twice the time and trouble to prepare an infe- 
 rior and less sensitive plate. 
 
 Pyrogallic Preservative. See p. 369. 
 
 Tea Preservative. "| 
 
 Tannin Preservative. V See p. 371. 
 
 Coffee Preservative. J 
 
 Clove Process. 
 
 The writer has found that a preservative of cloves gives most 
 excellent plates. Clove nuts, not the ground cloves, are taken 
 and broken up. Over a quarter pound, pour a quart of hot water, 
 and, after some hours, filter. To seven ounces of water add one 
 ounce of this decoction and one hundred grains of gum. Treat- 
 ment in all respects the same as with tannin. 
 
 A decoction of Malt is with some a favorite process. 
 
 Eesin Process. 
 
 Despratz first showed that if common rosin, or some other 
 sorts of resin, be added to the collodion, the plates need no pre- 
 servative, but may be simply washed and dried, after going 
 through the negative bath. At first the process was much ob- 
 jected to on the ground that it rapidly deteriorated the negative 
 bath. But it appears that this may be easily restored to working 
 order by adding a thirty-grain solution of permanganate of potas- 
 sium until the bath retains a faint reddish coloration ; then filter 
 and acidulate. The collodion should be of an intense character 
 and porous structure, and to it is added two grains to the ounce 
 of common rosin, or one grain rosin and one grain Canada balsam. 
 After passing through an ordinary nitrate bath, wash it tho- 
 roughly. It is advisable to use distilled water for the first and 
 last washings. The plates are more sensitive when newly pre- 
 pared than after keeping. 
 
 Development same as tannin; or a weak iron development. 
 
374 
 
 PHOTOGRAPHIC M ANIP IT L ATI ONS. 
 
 Morphia Process. 
 
 By Bartholomew. Said to be more sensitive than many other 
 processes. Proceed exactly as in the tannin process, but make 
 the preservative bath a solution of acetate of morphia^ one grain 
 to the ounce. The writer has found it advantageous to add to 
 the bath acetic acid No. 8 (Beaufoy's), two or three minims to 
 the ounce. Plates keep only from five to twelve days. 
 
 Gum Gallic Process. 
 Gordon recommends for collodion : — 
 
 Alcohol and ether, each ^ ounce. 
 
 Iodide of cadmium 3 grains. 
 
 Bromide of cadmium 3 " 
 
 Iodide ammonium 1 grain. 
 
 Pyroxyline, not over 6 grains. 
 
 Negative bath forty grains. Leave in ten to fifteen minutes ; 
 plunge into two successive baths of distilled water ; leave two 
 hours in a third. Or use four successive pans. 
 
 Preservative Bath. 
 
 Water (warm) 8 ounces. 
 
 Gum-arabic 160 grains. 
 
 Sugar candy 40 " 
 
 Gallic acid 24 " 
 
 It is advised to apply a substratum of albumen, and, before 
 developing, to edge with India-rubber. Probably edging at first 
 with India-rubber would be sufficient. 
 
 Development may be either alkaline (managed as in the tannin 
 process), or an iron developer containing two grains of gelatine 
 to the ounce of developer may be employed. The gelatine should 
 be first dissolved in the acetic acid. A redevelopment with acid 
 pyro and silver is needed. Fix in hyposulphite. Exposure three 
 times as long as for the wet. Should the alkaline developer veil, 
 use more bromide in it, adopting the proportions given for col- 
 lodio-bromide plates. 
 
NEGATIVE VARNISHES. 
 
 375 
 
 CHAPTER XVIII. 
 
 NEGATIVE VAKNISHES. 
 
 It is of the very highest importance to the photographer to 
 obtain a varnish as nearly perfect as possible. Upon it he must 
 depend for the preservation of all his work, and it would be 
 difficult to adequately describe the losses that some have suffered 
 in consequence of trusting their negatives to varnishes of a de- 
 fective character. 
 
 This consideration, and the very contradictory nature of the 
 opinions held by good judges, have led the writer of this manual 
 (although fortunate enough in his own case never to have used a 
 bad varnish) to undertake a very thorough and careful study oi 
 the subject within a short time past. The results which were 
 reached proved not only very important, but were to a consider- 
 able extent contrary to opinions which have obtained general 
 acceptance, and which had been up to that time entertained by 
 the author himself. 
 
 Five different varnishes formed the subject of this study, each 
 one of a sort that has been highly recommended. One was a 
 bleached lac varnish^ two were of unbleached lac, one of sandarac ; 
 these four were spirit varnishes. To these was added a benzole 
 varnish, and as the writer has never been in the habit of making 
 benzole varnish for his own use, a commercial benzole varnish 
 was selected, of a high character and largely used. The four 
 spirit varnishes were made by the following formulae : — 
 
 No. 1. — Bleached Lac Varnish. 
 
 Bleached lac, best quality 9 ounces, 
 
 Sandarac 3 " 
 
 Essence lavender 5 " 
 
 Alcohol 69 " 
 
 Filter. 
 
 No. 2. — Unbleached Lac Varnish. 
 
 Orange lac, best 220 grains. 
 
 Sandarac 80 " 
 
 Essence lavender i ounce. 
 
 Alcohol 4 ounces. 
 
 All the ingredients mixed at once. 
 
376 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 No. 3. — Unbleached Lac Varnish. 
 
 Best orange lac 200 grains. 
 
 Alcohol . . • 4 ounces. 
 
 Dissolve, filter, and add 
 
 Sandarac 80 grains. 
 
 Essence lavender 1^ fluidrachm. 
 
 Filter again. 
 
 No. 4. — Sandarac Varnish} 
 
 Sandarac 10 ounces. 
 
 Canada balsam 1 fluidounce. 
 
 Essence lavender 2 ounces. 
 
 Alcohol 64 " 
 
 No. 5 was the commercial benzole varnish before mentioned, 
 and of "which the writer has not the formula. 
 
 These varnishes were applied- on waste negatives with heat 
 before and after, and exhibited the following characteristics : — 
 
 Smoothness. — Nos. 1, 3, 5, perfectly smooth; 4 was somewhat 
 thready and more difiicult to work ; 2 a little irregular, but less 
 .so tjaan 4. 
 
 Clearness. — Excepting that 5 showed a very slight tendency to 
 dry dead, all were perfectly clear. 
 
 Hardness. — This important quality was tested by rubbing 
 steadily with a moderately soft lead-pencil, in one place, until 
 the film was cut through, and noticing how much resistance each 
 exhibited. It was found necessary to make this test with great 
 care, as one and the same film varied much in difi'erent parts, 
 resisting best always where the image was densest (because there 
 was more varnish absorbed and retained there). It was, there- 
 fore, necessary to choose a portion of each of equal density, and 
 to repeat the trial many times to avoid error. Eesult: No. 4 the 
 hardest and No. 5 the softest by a good deal, the rest inter- 
 mediate. No. 3 was harder than 1 and 2, evidently because of 
 the more sandarac and less lavender. It was estimated that No. 4 
 resisted four times as much friction as No. 6; that No. 2 was 
 half-way between. No. 3 was intermediate between 2 and 4, and 
 No. 1 was next in softness to No. 5. 
 
 Resistance to Heat. — The amount of resistance to heat exhibited 
 by a varnish is of very great importance. In our hot summer 
 weather negatives in the direct rays of the sun may become 
 
 ' For this formula the writer is indebted to Mr. Fennemore. 
 
NEGATIVE VARNISHES. 
 
 377 
 
 greatly heated. It is a fact well established in physics, that glass 
 allows the heat rays direct from the sun a much freer passage 
 than the dark rays returning from an object beneath the glass. 
 Therefore there is a tendency for the heat to accumulate in the 
 film, paper, and packing, and thus to subject the varnish to a 
 most severe trial. If it softens in the least, adhesion of the paper 
 takes place, and the negative may easily be destroyed. 
 
 In order to subject the varnishes in question to a decisive test, 
 they were placed on a metal vessel filled with hot water, and 
 heat was applied below till the water boiled. From time to time- 
 slips of paper were pressed forcibly upon the varnished surface, 
 and then were gently raised to observe if the slightest adhesion 
 took place. 
 
 One curious result observed was that when the heat was mode- 
 rately raised, Nos. 1 and 2 showed signs of slight adhesiveness, 
 which, when the heat was raised higher, instead of increasing, en- 
 tirely disappeared. This evidently indicated that, in applying heat 
 immediately after varnishing, the heat had not been applied long 
 enough to drive off all the essential oil. So that when, in .this, 
 experiment, a considerable heat was applied, the remaining essen- 
 tial oil softened the resins, but presently evaporated, leaving the 
 film more solid. This shows how much depends upon a thorough 
 application of heat after varnishing. 
 
 It was found that, as all these varnishes were good, a higher 
 degree of heat than that which could be obtained by boiling the 
 water in the vessel was necessary to decide as to the superiority. 
 Therefore fresh pieces were taken, cut from the same negatives, 
 and these, without a gradual heating, as in the former case, were 
 suddenly placed upon a piece of iron so hot that a drop of water 
 let fall on it instantly boiled away. This high heat brought out 
 the differences in a very decisive way. Nos, 4 and 5 were still 
 almost wholly free from any tendency to stickiness. Nos. 1, 2, 
 and 3 did decidedly less well. 
 
 Resistance to Moisture. — When varnished films crack and break 
 away in progress of time, this evil generally results from damp- 
 ness penetrating the film. Under its influence the collodion film 
 would naturally swell, the varnish not, and this unequal action 
 tends to detacb the film from the glass and crack the varnish. 
 As this action generally requires years to become apparent, it 
 was thought that the most expeditious, as well as severe, test of 
 25 
 
378 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 resistance to moisture would be made by plunging the negatives 
 under water. 
 
 Accordingly pieces of the same size in each case were cut out 
 of negatives varnished with the different varnishes, applying the 
 same quantity, as nearly as possible, of each, and drying by equal 
 heat. These were placed side by side in a large deep porcelain 
 pan and kept covered with water. 
 
 At the end of four days No. 5 gave way ; the rest were all in 
 good order. 
 
 They were examined from time to time, and all appeared per- 
 fectly sound, until, at the end of six full tveeks, it was noticed 
 that Nos. 1 and 3 showed a very slight puckering at one corner, 
 as if there might be a commencement of detaching. Nos. 2 and 
 4 appeared to be in as good condition aft^ six weeks' immer- 
 sion as they were before they were placed in the pan. 
 
 The writer cannot but consider this result very remarkable. 
 It indicates that, with several of the varnishes of which the for- 
 mulas are here given, the action of moisture amounts virtually 
 to nothing. 
 
 To sum up : If we examine which of all the varnishes ex- 
 hibited the greatest number of good points, we shall find it to be 
 the much condemned sandarac varnish (No. 4). It was the hardest 
 in resistance to mechanical injury, one of the two best resisting to 
 heat, and one of the two best resisting to moisture. Its only fault 
 was a tendency to th readiness when applied, requiring a little 
 more dexterity to make a good even coating. 
 
 The benzole varnish did not stand high at all, its only good 
 points being its resistance to heat, in which it was equalled by the 
 sandarac, and in hardness, in which it was excelled by the same. 
 In resistance to moisture it was very far behind all the rest. 
 
 The two orange-lac varnishes (Formulas 2 and 3) exhibited 
 good qualities. Number two resisted moisture for six weeks as 
 well as the sandarac. Both were easily applied, and gave 
 smooth, even films without trouble. But they were deficient 
 in hardness, and their resistance to heat, though fair, was infe- 
 rior to Nos. 4 and 5. * 
 
 In view of these objections to the lac varnishes, and of the 
 very poor resistance of the benzole varnish to moisture, the pre- 
 ference must evidently be given very decidedly to No. 4, the 
 sandarac, a most excellent varnish. 
 
TREATMENT OF RESIDUES. 
 
 379 
 
 Varnisli is generally best left to clear itself by standing. It 
 quickly clogs a filter, especially if it contains lac. 
 
 Varnishes will dissolve some collodions, it is said, though the 
 writer never saw this happen. In such cases it is recommended 
 to add about one or two per cent, of water. The addition of 
 water, even to a small extent, will often diminish the solvent 
 powers of the alcohol for some of the constituent parts of the 
 varnish, and cause a cloud to form, rendering filtration necessary, 
 and perhaps changing the character of the varnish. It should, 
 therefore, never be done unnecessarily. 
 
 In view of the results of the above careful examinations, there 
 would be no advantage in giving additional formulas for other 
 and comparatively untried varnishes, when qualities so excel- 
 lent have been proved to exist in some of the foregoing. 
 
 The highly polished surface of a heat-dried negative does not 
 easily take color or shading. In addition to the methods already 
 given for overcoming this difficulty, it may be mentioned here 
 that finely powdered resiri, rubbed on the part of the film to be 
 operated upon, has been found to be an excellent treatment. 
 
 CHAPTER XIX. 
 TREATMENT OF RESIDUES. 
 
 Every photographer should endeavor to avoid wasting the 
 valuable metals that he employs, but the extent to which this 
 care should be carried will depend largely upon the scale on 
 which he carries his operations. It would be, for example, a 
 waste of time for the amateur to attempt to extract the silver 
 from his hyposulphite solutions, but the professional photo- 
 grapher should never reject them without first removing the 
 silver, unless indeed he operates upon a very small scale. But 
 the amateur will always wish to recover the silver from baths, 
 positive ajid negative, that have become useless. 
 
 Residues may be worked in two ways, either the dry or the 
 wet. Both are chemical manipulations of the very simplest 
 order, can be explained in a few paragraphs, and can be readily 
 mastered by any man of ordinary intelligence. The writer would 
 
380 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 recommend the professional photographer to use the dry way, 
 and the amateur, the wet. 
 
 § 1.— The Dry Way. 
 
 Old Baths. — These will be thrown down with common salt. 
 Take good coarse but clean salt, make a strong solution of it in 
 any convenient vessel of glass or wood. Pour in the baths with 
 constant stirring. Make sure that the salt has been added in 
 excess, or large quantities of silver may be wasted unknowingly. 
 To make this certain, let the whole have a most thorough agita- 
 tion, then let stand some hours to settle, take olf some of the 
 supernatant liquid, and add to it a little clear solution of salt. 
 If no precipitate falls and no cloudiness is produced, the operator 
 may feel assured that all the silver is thrown down as white 
 chloride of silver, changing to violet whenever exposed to the air. 
 
 This chloride must next be washed. The liquid over it is 
 carefully and completely drained off, clean water added in abun- 
 dance, the whole thoroughly well stirred up and allowed to settle, 
 then poured off, and this is repeated several times ; the oftener 
 the better. The vessel should be capacious, so that the chloride 
 of silver, after settling for some hours, should not form a layer 
 extending one-tenth the height of the water in the vessel. (It 
 should be carefully borne in mind that if any hyposulphite baths 
 are poured into this, that, so far from anything being precipitated 
 from them, the hyposulphite will dissolve large quantities of 
 chloride of silver, if this has been already thrown down, or pre- 
 vent its precipitation^ if added earlier.) 
 
 The chloride of silver, after being washed and dried, is put into 
 a crucible, after being mixed thoroughly with half its weight of 
 dry carbonate of soda and one-quarter its weight of clean sand. 
 The crucible should not be plunged suddenly into a hot fire, or 
 it will almost surely crack. But a few live coals should be put- 
 into the furnace, then a thin layer of fresh coal, then the crucible 
 on that, and more fresh coal heaped round it. Bring the fire 
 gradually up to a bright red heat, and when the silver is melted, 
 stir it up with an iron rod. The most suitable crucibles are of 
 Paris clay, to be had of the dealers in chemical apparatus. Com- 
 mon sand or "Hessian" crucibles are porous: if these are used, 
 they should have the pores filled lip beforehand by fusing a little 
 borax in them, to prevent the silver from sinking in. 
 
TREATMENT OF RESIDUES. 
 
 881 
 
 Cuttings and Spoiled Prints. — These should be carefully burned 
 in any convenient vessel, the ashes gathered up, and these may 
 be added to the foregoing. Some have advised to heat the ashes 
 with nitric acid, but this does not exhaust all the silver, and the 
 nitrate of silver obtained is too impure for use without re- 
 ducing it. 
 
 Hyposulphite Baths. — The silver is best extracted from the old 
 fixing baths, positive and negative, by precipitation with liver 
 of sulphur (sulphide of potassium). The silver is thus thrown 
 down as sulphide of silver. This sulphide of silver is a heavy 
 black powder, from which the sttipirtn" is recovered by melting 
 with an equal weight of saltpetre. But in doing this, two pre- 
 cautions must never be omitted. 
 
 First, the sulphide must be heated red-hot hy itself (that is, 
 before the admixture of the saltpetre) in an iron pot. The object 
 of this is to burn off the sulphur powder thrown down along 
 with the sulphide of silver, and which, if it remained with the 
 sulphide of silver when melted with the saltpetre, might cause 
 dangerous explosions. 
 
 And secondly, it is necessary to be certain that the whole of 
 the sulphide of silver is decomposed. This may be materially 
 aided by stirring the mixture after it has been some time fused, 
 with an iron rod, and continuing this for some time. 
 
 The writer, believing that all photographic operations should 
 be carried on with nitrate of silver of the best quality, not only 
 advises not to mix the silver got from the sulphide with that re- 
 duced from the chloride, but either to dispose of it to a refiner 
 for further purification, or else to purify it by dissolving it in 
 nitric acid, and adding this solution to the spent baths, to be with 
 them precipitated as chloride. Many will doubtless hold this to 
 be excess of caution, but a bath, and especially all negative baths, 
 ought to be beyond suspicion. 
 
 Oold- Residues. — The least troublesome way of managing them 
 is undoubtedly that recommended by Davanne, to acidulate the 
 spent toning baths ; add thereto solution of persulphate of iron, 
 and to add the precipitate obtained by the addition of the iron 
 solution to the chloride of silver, and place them in the crucible 
 together. Then the lump of silver contains the gold alloyed 
 with it, and, when the silver is dissolved in nitric acid, the gold 
 remains behind. 
 
 The residue containing the gold, after nitric acid has dissolved 
 
332 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 all that it can dissolve, is a dark-colored powder, which may be 
 treated with hot nitro-hydrochloric acid (nitric acid one part, 
 hydrochloric acid two parts), in which it easily dissolves. 
 
 § 3.— The Wet Way. 
 
 This method is here recommended chiefly for amateurs who 
 wish to work over their positive and negative baths. A gallon 
 precipitating jar is to be about one-third filled with a solution of 
 clean salt, and the baths are turned into it and thoroughly stirred 
 up. After the chloride has settled, and leaves the liquid clear, a 
 portion of it is placed in a clean glass, and tested with more solu- 
 tion of salt, to make sure that the precipitation is complete. 
 After being, well washed by repeatedly stirring up with water, 
 and pouring oiff again, the water is finally poured ofi* closely, a 
 little sulphuric acid is added, and then a lump of good zinc. 
 For each pound of silver an ounce of sulphuric acid and a half- 
 pound of zinc will be ample. The chloride rapidly shows signs 
 of blackening, and this slowly proceeds until the whole of the 
 metallic silver is revived in the form of a grayish-black powder. 
 
 At the end of about two days, during which the contents of 
 the vessel should be occasionally shaken, the operation will be 
 complete. The lump of zinc is removed, a little more sulphuric 
 acid is added, stirred up, and the whole left for some hours. 
 The revived silver is then washed precisely in the same way as 
 the chloride, with eight or ten waters (first breaking it well up 
 with the fingers), and is then ready to dissolve in nitric acid. To 
 effect this solution, place a quantity of nitric acid of good quality 
 in a vessel of which it does not fill over one-fifth or one-sixth. 
 Throw in the silver powder, waiting between each addition till 
 the effervescence subsides, and avoiding most carefully to inhale 
 any of the red fumes evolved ; to which end the operation should 
 be performed under a well-drawing chimney. When all the 
 silver is dissolved, the solution, which is always very acid, is to 
 be filtered, evaporated down, and either crystallized or fased ; 
 the writer decidedly prefers the latter. 
 
 In fusing nitrate of silver, care must be taken to use a suffi- 
 ciently large porcelain basin ; for if, when the solution is very 
 much concentrated, i,t reaches nearly to the edge of the basin, it is 
 liable to perform what is known to chemists as "travelling" — 
 that is, it will creep over the sides, and a crust once established, 
 
VARIOUS PHOTOGRAPHIC PROCESSES. 
 
 383 
 
 more and more will get over by capillary attraction, make a crust 
 on the outside, and run down, half crystallizing and half fused, 
 upon the table. The writer once left a capsule with nitrate pre- 
 paring for fusion, for a short time, and, on returning, found over 
 half a pound outside. Capsules of Berlin or Meissen porcelain 
 only can be trusted for fusing nitrate of silver. 
 
 This method of operating gives satisfactory results if carefully 
 carried out. The zinc used should be pure. The Bethlehem 
 zinc, sold in the Atlantic cities of America, is excellent for this 
 purpose. Granulated zinc is not near so good for use as zinc in 
 lumps, for, though it may work a little faster, there is always 
 danger of small portions being overlooked and remaining in the 
 silver, failing to be dissolved by the acid. The Bethlehem zinc 
 comes in ten-pound ingots. Instead of granulating it, set it on a 
 good fire till it is nearly ready to melt at the corners ; remove 
 it, and it will be found that, when thus hot, it will break up 
 under a hammer with the utmost facility. 
 
 With many photographers it will be an object to have as little 
 to do with chemical manipulations as possible. Such cannot do 
 better than to sell their residues to some fair-dealing reducer. 
 The residues should be kept in good condition, and the three sorts 
 kept separate, viz., chloride, from throwing down old baths with 
 salt ; sulphide obtained from fixing baths by precipitating with 
 liver of sulphur; and lastly, ashes from clippings, failures, etc. 
 
 CHAPTER XX. 
 
 PHOTOGEAPHY ON GLASS AND ENAMEL, AND COLLODIO- 
 CHLORIDE PRINTING. 
 
 § 1.— Printing on Glass by Development. 
 
 Positives may be obtained on glass in a variety of ways, both 
 by development and sun-printing, and each different method has 
 its advocates, and is capable of giving good results. These posi- 
 tives, when made on ordinary transparent glass, are known as 
 Transparencies, when printed on white dpaque glass they are 
 known as opal pictures or opalotypes. The difference depends 
 
384 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 solely upon the material used as a support, and either may be 
 obtained by development or by the direct action of sunlight. 
 
 When made hy development, two different methods may be em- 
 ployed. An image may be obtained in the camera, and be sub- 
 sequently developed, or the negative may be laid on the sensitive 
 plate and exposed to a weak light, and followed by development. 
 
 Printing in the Camera. — When it is intended to print in the 
 camera, by far the best method is to have a camera expressly 
 constructed for this purpose, with two bellows and two racks 
 and pinions. Suppose the bottom of an ordinary camera to be 
 extended in front, another camera to be attached, and beyond, a 
 frame to receive the negative. In this way a total exclusion of 
 diffuse light is effected ; no ray can reach the lens except through 
 the negative. The frame containing the negative at the front can 
 be racked in and out, as also can the dark slide and focussing 
 screen at the back ; the lens occupies a stationary position be- 
 tween the two. 
 
 In Fig. 138 the portion A receives the dark slide in the usual 
 manner. B is similar to the front of an ordinary camera ; it car- 
 ries the flange, and into it the lens is screwed. At N is a special 
 
 Fig. 138. 
 
 arrangement to receive the negative which is to be printed. The 
 front, N, is raised and pointed at a bright cloud, or a mirror may 
 be placed in front of it, inclined so as to send light from the sky 
 directly upon the negative, and the focussing is done by racking 
 the back, A, in or out. The space from A to B is shorter than 
 from B to N, because the centre of the tube of the lens (which 
 projects beyond B towards N) should correspond with the middle 
 of the base-board. To copy a whole size plate of equal size with 
 the original, the space from A to N must be fully four times the 
 focal length of the lens* employed. A ten-inch Steinheil aplanatic 
 will be useful for the purpose. In this case the space from the 
 
VARIOUS PHOTOGRAPHIC PROCESSES. 
 
 385 
 
 negative frame to tlie focussing glass should be from three feet 
 six to four feet. B is stationary, A and N rack backwards and 
 forwards. If the photographer has two cameras of suitable size, 
 they may be combined so as to give very much the effect of the 
 double camera, shown in the figure. The second camera has its 
 lens removed, its front is turned towards the front of the other 
 camera, and the end of the tube of the one is thrust through the 
 flange of the. other. The ground glass is also removed, the nega- 
 tive to be copied is secured in the focussing frame in its place. 
 
 Or the arrangement represented at Fig. 189 may be used. 
 Four strips of wood extending from the camera support a light 
 
 frame, in which the negative is to be secured, and during the 
 operation the space between the camera and the lens is covered 
 over with a piece of black muslin or a focussing cloth. A mirror 
 placed in an inclined position throws light through the negative. 
 The object of arranging the legs as shown in the figure, is to 
 admit of pushing the portion supporting the mirror outside of a 
 window, in order to receive light direct from the sky above. The 
 same object may be attained by nailing a board of the proper 
 width and length upon an ordinary table, and making it project 
 at one end in the same manner. 
 
 The larger the size of the transparency, in proportion to the 
 original negative, the greater must be the distance between the 
 ground glass of the camera, and the frame -holding the negative. 
 It has been already said, that when the copy is to be of the same 
 size as the original, the distance will be approximately four 
 
 Fig. 139. 
 
386 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 times the focal length of the lens when focussed on a distant 
 object. 
 
 The transparency will need to have the same brilliant clear- 
 ness as the negative, which will be got in the same way — a fall 
 exposure, a rapid development with plenty of restraining acid, 
 and fixing immediately. 
 
 It is scarcely necessary to say that the negative for this pur- 
 pose must have precisely the same properties as those intended 
 for enlargement (see p. 177.) It must not be dense ; print must 
 be easily legible through the densest parts. The deep shadows 
 must be represented by clear glass, free from all trace of veiling. 
 
 Contact Printing followed by Development. — Transparencies may 
 also be obtained by the wet process without the use of the camera. 
 A wet plate is prepared in the ordinary way, and after thorough 
 draining, strips of thin letter paper are laid on its face near the 
 edges where it is not important to get the image, and the nega- 
 tive is laid face down on these, which preserve it from actual 
 contact. It is then held for half a minute or thereabouts, accord- 
 ing to the density of the negative, under an argand burner, and 
 development is effected in the usual way. A dense negative will 
 not answer. 
 
 The treatment of the positive after development will depend 
 upon the object in view. If the object be to produce a picture to 
 be viewed in the stereoscope or hung against a window, the plate 
 after fixing will be blackened with corrosive sublimate, or, better, 
 will be treated with iodine and then with sulphide of potassium. 
 (See p. 171.) 
 
 If the intention is to produce an enamel by Griine's process 
 (which see), the plates will be toned with bichloride of platinum. 
 
 The same results as the above are got by using a dry plate, 
 exposing under the negative in a frame for a few seconds to diffuse 
 daylight, or for about a minute under an argand gas-burner, or to 
 magnesium light; the latter being the most certain, as when the 
 quantity of magnesium required for one operation has been once 
 determined, it is easy to repeat without danger of error. 
 
 Transparencies for the Magic Lantern^ or " Stereopticon,^^ may be 
 made in several ways. Contact printing on wet collodion, as 
 just described, may be used, or they may be printed on the 
 camera, as above, or dry plates may be used ; the latter method 
 was habitually employed by a photographer who for a long time 
 supplied most of our dealers with lantern slides. Equally good 
 
VARIOUS PHOTOGRAPHIC PROCESSES. 
 
 387 
 
 results are got by wet collodion, Tn any case tlie lights must be 
 perfectly transparent. A long exposure, rapid and very acid 
 development, quick fixing, and then a treatment with corrosive 
 sublimate, followed by cyanide of potassium or sulphide of po- 
 tassium, will be suitable. (See p. 172 for details.) 
 
 The Albumen Process. — The albumen process, which was used 
 for making negatives before the discovery of the collodion method, 
 and which was superseded by it, gives finer transparencies on 
 glass than any other method in use. A good deal, however, 
 depends upon the personal skill of the operator. It was, for ex- 
 ample, long believed that Ferrier's magnificent specimens were 
 produced by some secret process of his own, but eventually it 
 appeared that he used the regular method, as follows : — 
 
 The whites of twenty fresh eggs are taken, clear of yelk. 
 Iodide of potassium one hundred grains, and five grains of iodine, 
 are dissolved in a little water and added to the albumen, and the 
 whole is beaten up to a froth, and set in a cool place to subside. 
 As in this process it is of the greatest importance that no dust 
 shall settle on the plates, it is necessary that the operating-room 
 should be cleaned the day before by wiping off the floor, walls, 
 and woodwork, with a wet cloth. Shortly before commencing, 
 the floor is to be sprinkled with water. 
 
 A stout iron plate is fixed in a horizontal position over a gas- 
 burner, or any other efficient lamp. The albumen having been 
 poured off perfectly clear, is then extended over 
 the plate (absolutely clean), an operation which 
 is aided by first breathing gently on it so as to 
 let the moisture condense. Four silk cords 
 have each a little hook at the end, the other 
 ends are tied together and held in the hand ; the 
 hooks are slipped under the plate, which is then 
 supported by the cords. In this way it is sus- 
 pended over the hot plate and a rotating motion 
 is given to the threads, which keeps the albumen 
 distributed over the plate ; presently it is dry. 
 
 These plates are stored away, and when wanted- for use are 
 sensitized in an acid silver bath prepared as follows: — 
 
 Nitrate of silver j ' ' ' ^ ounce. 
 
 Acetic acid (glacial) J . .2 ounces. 
 
 Iodide of potassium . . . . . . ^ . . 2 grains. 
 
 Distilled water . 14 ounces. 
 
388 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 From a quarter of a minute to a minute is needed for sensi- 
 tizing, after whicli the plate is rinsed under a tap, and laid in 
 fresh water ; then dried in any suitable way (p. 353), 
 
 The exposure is made in a suitable frame under a negative, for 
 a few seconds, to diffuse light. The development is effected by 
 plunging into a bath of gallic acid, one grain to the ounce. 
 Silver is gradually added until the plate acquires the desired 
 density. Ferrier is said to have toned his transparencies by first 
 plunging them in a weak sublimate solution, and then, after' 
 washing, into a one-grain solution of chloride of gold. 
 
 § 2. — Sun-Printing on Glass by the Collodio-Chloride Process. 
 
 Instead of developing a weak image on glass, we may carry it 
 to its full strength by direct printing. There are two methods; 
 usually employed for this purpose, the collodio-chloride process; 
 of Mr. Simpson, and the albumen process; the first is the easier' 
 and most generally employed, the second (to be described in next 
 section) is more difficult, but gives richer effects. 
 
 When a collodion containing chlorides only, instead of iodidess 
 and bromides, has nitrate of silver added directly to it, the; 
 chloride of silver which is formed, in place of falling at once to- 
 the bottom, remains for a long time suspended in the collodion,, 
 giving it a milky appearance. The nitrate of silver is kept a, 
 little in excess, and when this liquid is coated upon glass or 
 paper, a surface is obtained which may be printed upon very- 
 much in the same way as albumenized paper. (Eespecting; 
 collodio-chloride on paper, see § 4.) 
 
 ■Mr. Gr. W. Simpson, who first proposed this method, directed! 
 to make an ordinary plain collodion with equal parts alcohol andi 
 ether and six grains of pyroxyline to the ounce, and salt it withi 
 
 Chloride of strontium .2 grains. 
 
 Citric acid 1 grain. 
 
 to each ounce, and to sensitize by adding nitrate of silver im 
 the proportion of 7| grains to each ounce, in fine powder, shaking; 
 up well. 
 
 Chloride of strontium has the advantage of easy solubility in- 
 mixed alcohol and ether (the chlorides as a rule are less soluble) 
 in this mixture than the iodides and bromides), but experience) 
 has shown that it does not give as good a tone as some other 
 chlorides. 
 
VAEIOUS PHOTOGRAPHIC PROCESSES. S8d 
 
 The writer finds as the result of his experiments with this 
 process, that it is better to use considerably more pyroxyline in 
 the collodion than six grains, especially when the surfaces are 
 not very large. With glass plates of quarter and half size /uUt/ 
 nine grains to the ounce may be used, and the effects are much 
 richer than with less quantities. He has also found that the 
 addition of carhoUc acid greatly improves the richness and depth 
 of effect, but unfortunately this treatment can only be used with 
 collodio-chloride on paper; it does not answer on glass, as the 
 carbolic acid separates out in drying on glass. 
 
 The writer also finds it a material improvement to dissolve 
 the nitrate of silver in a part of the alcohol. When put in in 
 powder, part does not dissolve. Some have tried dissolving the 
 nitrate in water, but this renders the collodion much less manage- 
 able and more apt to give irregular films and mottled and spotty 
 effects. 
 
 Dr. Liesegang has lately published the following formula : — 
 
 Alcohol and ether, equal parts 1 ounce. 
 
 Pyroxyline 9 grains. 
 
 Chloride of lithium 1 grain. 
 
 Citric or tartaric acid 2 grains. 
 
 Nitrate of silver 8 " 
 
 Where chloride of lithium is not to be had, chloride of cadmium 
 may be substituted, using twice the quantity. For pyroxyline, 
 Dr. Liesegang recommends one-half of his pyroxyline and one- 
 half ordinary soluble cott9n. He shakes up the nitrate of silver 
 in crystals, and at the end of a day removes the undissolved part, 
 powders it in a mortar, and returns it. 
 
 The author recommends to dissolve whichever chloride is used 
 in half the alcohol, adding to it the ether, and dissolving in the 
 mixture the pyroxyline. The powdered nitrate of silver is to 
 be put into a large test-tube or small flask, and the alcohol added 
 in separate portions and boiled. In this way the nitrate is 
 speedily got into solution, and this solution is poured into the 
 collodion and shaken up. Operating in this new way, all the diffi- 
 culties encountered of having the chloride of silver to fall in 
 clots are done away with, and a clear, smooth emulsion is ob- 
 tained, w;hich keeps in excellent order for weeks. 
 
 The author has obtained good results /with fused chloride of 
 calcium in the collodion, instead of chloride of lithium or cad- 
 mium. Of the calcium salt, one and a half grain to the ounce 
 
390 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 of collodion will be proper, and eight grains of nitrate of silver. 
 With chloride of calcium, tartaric acid must not be used, or a 
 gradual precipitation takes place which ruins the collodion. 
 
 To keep the film from slipping from the glass, edge it with 
 India-rubber dissolved in benzine, as described for dry plates 
 (see p. 852), or with albumen, but in neither case should the ap- 
 plication extend beyond the edges, a full substratum is injurious. 
 Print till the shadows are bronzed, but not too deeply, remem- 
 bering, however, that an under-printed plate is wholly worthless, 
 whilst an over-printed one can be reduced by using a stronger 
 fixing solution and leaving longer in it. Tone in any gold toning 
 bath, using it very weak. 
 
 To fix, leave for five minutes in a weak fixing bath, one and a 
 half ounce of hyposulphite to the pint of water. 
 
 M. de Constant first proposed fuming the plates, and certainly 
 they print more quickly and deeply when so treated. The ques- 
 tion whether fuming is necessary will depend very much on the 
 character of the cotton. When a deep tone cannot easily be got, 
 fuming will be found to help. Eemove the stopper of an am- 
 monia bottle and pass the plate a few times over the mouth. 
 
 Special frames are made for printing on glass which permit of 
 examining the print. The sensitized glass plate is held between 
 two iron straps which are secured by screws. The vignetting 
 boards furnished with the frames rarely fit as closely as they 
 should do. Any motion is of course fatal to the sharpness of the 
 print, therefore the boards should be well wedged up. 
 
 Miniature Effects on Ivory are best got by transferring collodion 
 films to the ivory, the surface of which is to be prepared before- 
 hand by polishing it with a little fine cuttle or pumice powder, 
 and then immersing for a minute in a warm solution of gelatine 
 (about 20 grains to the ounce). The image is printed on glass 
 first coated with gelatine, and then with collodio-chloride (or on 
 enamel or collodio-chloride transfer paper). After toning and 
 fixing in the usual way, wash in a few changes of cold water, 
 then immerse In warm, when the film will float off. (Acidulating 
 the water with a drop or two of sulphuric acid to the ounce will 
 facilitate separation.) Eemove the film to a vessel of cold water, 
 and float on to the prepared ivory surface. (B. J. Edwards.) 
 
VARIOUS PHOTOGRAPHIC PROCESSES. 
 
 891 
 
 § 3. — Albumen Positives on Glass. 
 
 Clear white of egg by beating it to a froth, adding first to 
 twelve ounces of albumen a quarter of an ounce of clean, pure 
 sal-amnaouiac dissolved in an ounce and a half of water. Coat 
 the plates, dry, and sensitize. 
 
 The silver bath is made by dissolving two ounces of nitrate of 
 silver in sixteen of water, acidulating with acetic acid. 
 
 When albumen positives on opal glass are thoroughly well 
 made, they exhibit greater force and more transparency of shadow 
 than collodio-chloride work. They are, however, extremely 
 slow in printing, and the success of different operators has been 
 very various. 
 
 Positives on glass appear to require longer and more thorough 
 washing than negative glass work, to preserve them from fading. 
 
 § 4. — Collodio-Chloride Printing on Paper. 
 
 The sensitive collodio-chloride mixture (p. 389) may be coated 
 on paper instead of glass, and be printed and toned in the same 
 way. But as the film is very apt to detach itself from the paper, 
 this last must be prepared with a coating of gelatine. The writer 
 has never met with any paper of which the sizing was qualified 
 to .take the place of this coating, which may be prepared as 
 follows : — 
 
 Nelson or Coxe's sparkling gelatine . . . 400 grains. 
 
 Syrupy glycerine ^ flnidounce. 
 
 Water 16 fluidojinces. 
 
 The gelatine used alone renders the paper excessively stiff; 
 this led the writer to experiment with glycerine added, the efi'ect 
 of which is to greatly reduce the stiffness. Sven with this addi- 
 tion, however, the paper curls up somewhat, and therefore, after 
 it is quite dry, it should be laid in press for some time, and 
 comes out exceedingly flat. 
 
 The annexed cut represents a piece of the coated paper laid on 
 a convenient piece of thin flat board, provided with a handle at 
 one corner. The two farther corners of the paper to be collo- 
 dionized are secured with pins, the thumb keeps down one other 
 corner, whilst the fourth is left open, from which to pour off" the 
 excess. \ 
 
892 PHOTOGRAPHIC MANIPULATIONS. 
 
 Fig. 141. 
 
 It is, however, very convenient to lay the paper on such a 
 board, and, instead of pinning it, to fold np the edges about an 
 eighth of an inch high, in order to keep the collodion from work- 
 ing over, and especially from getting upon the back of the paper, 
 which result quickly follows if the collodion is carried all round 
 the sides without turning them up. 
 
 The writer has found that a considerable increase of richness 
 and tone is got by the addition of plienic {carhoUc) acid. To a 
 measured quantity of the sensitized collodion add about ten per 
 cent, of this acid, and it will be found that a much richer tint is 
 produced than when the carbolic acid is omitted. This method 
 works well upon paper, but not upon glass. The printing is 
 done in the ordinary way, and the succeeding operations are the 
 same as when glass is the support. (See sec. 2.) 
 
 § 5.— Photographic Enamelling. 
 
 Of all- forms of picture-making, the enamel may be considered 
 the most permanent. Even the carbon process is liable to the 
 objection that the paper on which the print is made is a very 
 perishabl-e substance, and positives on glass by the collodion 
 process are liable at best to many injurious influences from which 
 an enamel, burnt in upon glass or porcelain, is evidently free. 
 
 For reproducing photographs in enamel, several ingenious pro- 
 cesses have been proposed. Two at least have been worked 
 commercially upon a large scale : that of Lafon de Camarsac, in 
 Paris, and that of Grune, in Berlin. Lafon has maintained his a 
 close secret, whilst Griine, with commendable liberality, has given 
 his to the public. It is his that will be here first given. 
 
 There exists no difficulty whatever in transferring a collodion 
 film to any other support. For this purpose it is best to diminish 
 
VARIOUS PHOTOGRAPHIC PROCESSES. 
 
 393 
 
 the adhesion of the collodion, by rubbing the glass beforehand 
 with a little wax dissolved in ether; or, as proposed bj Mr. 
 Woodbury, add to the collodion two or three drops to the ounce 
 of a saturated solution of beeswax in ether, which renders the 
 film easily transferred without afiecting the photographic proper- 
 ties of the collodion. 
 
 The operator prepares a glass collodion positive, which must, 
 of course, be a positive by transparency, and not an arabrotype. 
 This may be done in several ways (for which see the previous 
 sections of this chapter). 
 
 The next step will be to tone with weak solution of bichloride 
 of platinum instead of chloride of gold ; wash and dry. Eun a 
 penknife round the edges, plunge the negative in water, and 
 float off the film. It will be advisable to add a little acetic acid 
 to the water; acids tend to loosen films from their supports, 
 alkalies to increase the attachment. Eeceive the film on the 
 porcelain surface, and, after allowing it to dry, dissolve out the 
 collodion film with mixed alcohol and ether. The image in pla- 
 tinum will remain upon the porcelain. It then only remains to 
 apply a suitable flux, and burn in the picture in a muffle. Griine 
 has not given the composition of the flux that he uses, but it is 
 probable that Leth's flux will be found satisfactory. It is made 
 as follows : — 
 
 I^f <i lead 6 ounces. 
 
 Fine quartz sand, or pounded quartz . . . 3 " 
 I^oi'ax 1 ounce. 
 
 Melt in a crucible, and, after cooling, reduce the glass formed 
 to a fine powder. Strew this over the plate, place in a muffle, 
 and raise the heat just high enough to fuse the coat of flux into 
 a transparent glass over the picture. 
 
 This process can also be used for producing designs in gold 
 upon glass or porcelain. To effect this, the pos-itive is toned 
 with gold, thoroughly, and the rest of the treatment remains the 
 same, except that a reducing flux must be used. No half-tone 
 can be obtained in this way, because the gold, no matter how 
 thin, exhibits its full metallic color. It easily acquires a brilliant 
 surface by polishing. Beautiful designs in gold of the most com- 
 plicated figures, have been burnt into porcelain by Griine by this 
 process. 
 
 Those desiring further details may consult the Photographisches 
 26 
 
394 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 Archiv, Band VI., 346 ; Photog. News, IX., 457 ; or Martin's 
 Handhuch der Email-photographie, Weimar, 1867. 
 
 § 6. — Photolithography. 
 
 To be able to tranfer a pbotograpb to stone or metal, and to 
 print a large number of copies therefrom, is evidently a most 
 valuable application of the science; and this is now accomplished 
 in a very admirable manner. 
 
 It is evident that the production of half-tone is more difficult 
 than the simple obtaining of black and white, and that different 
 means must be employed. The processes therefore will be classi- 
 fied under these two different heads: — 
 
 A. — PROCESS GIVING ONLY WHITE AND BLACK. 
 
 Liesegangh Process. — Liesegang floats ordinary albumenized 
 paper (the salting is not objectionable) upon a solution of chro- 
 mate of ammonium. Then exposes under a strong, clear negative, 
 till a strong image is got. Next lays it against a zinc plate, and 
 passes through a press. Next lays it, face up, on cold water, till 
 the image becomes visible. Takes a clean sponge, previously 
 cleaned well with chlorhydric acid to get rid of grit, and removes 
 the excess of ink. Then transfers in the usual way of litho- 
 graphic transfers. 
 
 Liesegang attaches importance to the nature of the ink used 
 for inking in the zinc as above mentioned. He takes — 
 
 Venice turpentine 8| ounces. 
 
 Wax . .1 ounce. 
 
 Palm oil 1 " 
 
 These are to be heated in an iron pot until they take fire. Then 
 stir in — 
 
 Lithographic transfer varnish 83 ounces. 
 
 Linseed oil varnish, No. 2 16^ " 
 
 ■B. — PROCESS^ GIVING HALF-TONES. 
 
 ATbertype. — The older processes are likely to be quite super- 
 seded by the albe'rtype, of which the following is the specifica- 
 tion for the Erench patent. Coat in the dark room a heavy glass 
 plate with — 
 
VARIOUS PHOTOGRAPHIC PROCESSES. 
 
 895 
 
 Filtered water 300 parts. 
 
 Albumen 150 " 
 
 Gelatine 15 " 
 
 Bichromate of potash 8 " 
 
 Dry in the dark, and then expose to light through the glass, care- 
 fully protecting the other face in order that the hardening may 
 proceed from the bottom (next the glass) to the surface, and be 
 perfectly solid. Half an hour to two hours' exposure. Coat 
 again with — 
 
 Gelatine 80 parts. 
 
 Bichromate . 10 " 
 
 "Water 180 " 
 
 Expose under a negative, wash for about fifteen minutes, and 
 dry. Then slightly wet it and work it on a lithographic press in 
 the ordinary way with ordinary printing ink. 
 
 § 7. — Photo galvanography. 
 
 It has been known for a period of years that when a mixture 
 of gelatine and bichromate was extended on glass and exposed 
 under a negative, all those parts protected from the light could 
 be made to swell up by soaking the film in water. Consequently 
 the image is produced in relief. 
 
 The writer of this manual worked out the details of a process 
 himself, and was the first to publish any practicable method, 
 which will be found in full detail in the British Journal of Pho- 
 tography for February 10th, 1865. Briefly, the process consists 
 in coating glass with a film of — 
 
 Gelatine . . . 200 grains. 
 
 Water 4 ounces. 
 
 Cold saturated solution bichromate of potash . 5 drachms. 
 
 When dry, expose under an average negative to direct sun- 
 light for two to three minutes. Then leave in water for aobut 
 two hours, changing frequently, then let dry. 
 
 The surface may receive a conductor in several ways. Brush 
 over with an ethereal solution of chloride of gold, let dry, place 
 in sunshine, and apply a solution of protosulphat« of iron. This 
 is the writer's method of gilding the film, which takes a brilliant 
 gold surface, and is then ready to be plunged into the electrotype 
 bath. 
 
 But, on the whole, the writer preferred to treat the dry gelatine 
 
396 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 film (after the bichromate, of course, had been thoroughly re- 
 moved) with alcoholic solution of nitrate of silver, and then to 
 fog it with pyrogallic acid. 
 
 By means of the electrotype bath, a copper reproduction of the 
 relief is obtained from which to print. 
 
 Woodbury^ s Relievo Process. — The above method is evidently 
 applicable only to the reproduction of engravings and wood-cuts ; 
 negatives of natural objects, made up of half-tones, cannot be used 
 for it. Woodbury ingeniously avoids this difficulty by a very 
 valuable process, which has been patented. 
 
 It is easy enough, by the process just above described, to obtain 
 a reproduction in copper of a gelatine relief of objects containing 
 half-tones. This reproduction will not, of course, have lines like 
 a copperplate, but will consist of undulating depressions and 
 elevations. The difficulty lay in making this to print. Mr. Wood- 
 bury's idea was to mix a little black pigment with gelatine, to 
 spread this over the plate, and then with a flat surface to remove 
 the excess. A piece of paper being then pressed against the 
 plate, receives the remaining gelatine. In the portions but little 
 sunk, there will have been but little pigment, and these will 
 print light, and just in proportion to the depth of the sunk por- 
 tion will be the blackness of the print. 
 
 Work of remarkable beauty has been executed by this process, 
 which is applicable to printing on paper, glass, wood, or any 
 other surface. 
 
 § 8. — Various Processes. 
 
 Willis's Aniline Process. — This process has likewise been pa- 
 tented. The work produced by it is of rather a common order ; 
 its recommendation is its extreme facility and cheapness. 
 
 Paper is impregnated with solution of bichromate of potash, to 
 which a little phosphoric acid has been added. After exposure 
 under a transparent positive, it is exposed to vapors of aniline, 
 which develop a grayish image. The print is then merely fixed 
 by simple washing. As a positive affords a positive, plates, draw- 
 ings, &c., can be copied without the intervention of a negative or 
 the use of a camera. The process is carried on commercially by 
 the patentee in England. 
 
 Prints in Color. — Float close-grained, fine photographic paper, 
 plain or albumenized, on a warm solution of gelatine, six hundred 
 
VARIOUS PHOTOGRAPHIC PROCESSES. 
 
 897 
 
 and fifty grains ; water, twelve ounces ; bichromate potash, three 
 drachms ; glycerine, half fluidounce ; letting the gelatine swell 
 first in part of the water. Dissolve the bichromate in the rest. 
 When the gelatine has well swelled, dissolve it by heating, and 
 add (in the dark room) the bichromate solution. Dry the paper 
 in the dark. Expose briefly to direct sunshine under a positive. 
 A light picture results on a brown ground. Throw into water 
 for thirty-six hours : the whole disappears, and the back must be 
 marked to distinguish it. Now blot off the exposed surface gently 
 with bibulous paper, leaving it very moist, and rub on powdered 
 color with a wet hift of cotton. The color adheres to the parts 
 protected from the oven, and thus a. positive results.^ 
 
 Very pretty effects are obtained by laying on the paper ferns^ 
 grasses, &c., and developing with a green powder, " chrome green" 
 (chrome yellow and Prussian blue, sold ready mixed under this 
 name) answers very well. In this way, positives of a green color 
 are obtained at a single operation. They are perfectly permanent. 
 If the color does not adhere on the image, the exposure has been 
 too long; if it adheres on the image, and elsewhere also, too 
 short. When the color has been applied, hold the print a few 
 moments under a stream of water to clean the whites. 
 
 Printing Processes with Salts of Iron. — Most of the salts of the 
 peroxide of iron are reduced by light to the corresponding salts 
 of the protoxide, with a loss of one-third of their oxygen. By 
 applying reagents which act differently on the two oxides of iron, 
 this reduction is made apparent, and a colored picture is pro- 
 duced. Thus, if red prussiate of potash be applied, all the part 
 acted upon by the sun becomes blue; with gallic acid the unex- 
 posed part becomes black, and so on. 
 
 Chloride of Iron. — Take 
 
 Perchloride of iron 50 grains. 
 
 Tartaric acid 15 " 
 
 Water 1 ounce. 
 
 Expose under the object itself or under a transparent positive. 
 Plunge for an instant in distilled water, and then in a saturated 
 solution of gallic acid, a decoction of nutgalls, or a mixture of 
 gallic and pyrogallic acids, according to the time allowed. The 
 
 ' This method of operating, described by the writer in the Philadelphia Pho- 
 tographer for May, 1865, has sinqe been published as new in Berlin, and, with 
 trifling alterations, patented in England. 
 
398 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 impression is here in ordinary ink, gallo-tannate of peroxide of 
 iron. 
 
 Oxalate of Iron and Ammonia. — Exactly saturate one ounce of 
 oxalic acid with ammonia, add another ounce, and digest the 
 mixture with freshly-precipitated and still moist peroxide of 
 iron. The filtrate, after the liquid is fully saturated with per- 
 oxide, gives, by evaporation in the dark, large and splendid 
 green crystals of the double salt. 
 
 Paper is sensitized by floating in a minute or two upon a tolera- 
 bly strong solution of these crystals, seventy to one hundred 
 grains to the ounce, and dried, in which state it will keep for a 
 long time. Exposed under a negative, an almost invisible image 
 is obtained after a brief exposure, which, by ferridcyanide of 
 potassium, becomes a blue picture. This process is due to 
 Herschel. It has the disadvantage that it does not give clean 
 whites. 
 
 The writer imagined a remedy for this, which has been very 
 successful ; it consists in adding a little oxalic acid to the solution 
 of ferridcyanide, the whites thus remain brilliantly clear. It is 
 necessary, however, to be careful about putting the fingers into 
 the bath. The free ferriprussic acid liberated by the oxalic acid 
 continually decomposes, with production of prussic acid, in a 
 very dilute form, it is true, but still active enough to render care 
 advisable. 
 
 CHAPTER XXI. 
 CAEBON FEINTING. 
 
 I 1. — Introductory Remarks. 
 
 Carbon printing, in the form now in use, has been the result 
 of the action of many minds, and the honor of its discovery can- 
 not be ascribed to the ingenuity of any one person. It may be 
 traced back as follows : — 
 
 The first step was th© remark that paper imbued with solution 
 of bichromate of potash, darkened when exposed to light. This 
 was made in 1839 by Mr. Mungo Ponton. 
 
 The next was the discovery that gelatine, gum, and some other 
 
CARBON PRINTING. 
 
 399 
 
 bodies, were rendered wliolly insoluble when exposed to light in 
 presence of bichromate of potash. This observation was first 
 made by M, Becquerel; subsequently Mr. Fox Talbot patented 
 a method of photo-engraving based on it. 
 
 The next idea evolved was, that the gelatine, made insoluble 
 by light, might be made to imprison particles of coloring matter. 
 Thus, where light acted, these would remain ; where it did not 
 act, they would wash out by reason of the solubility of the por- 
 tion of the film in which they were contained. This was an 
 important step, and was made by M. Poitevin in 1855. 
 
 This was, in fact, a carbon process ; but in this, and in all the 
 efforts made for some time subsequently, the half-tone was ex- 
 tremely defective. 
 
 M. Laborde seems to have been the first to perceive that the 
 action of the sun was at first superficial, and only by degrees 
 penetrating through the layer of gelatine. Thus those portions 
 under the transparent parts of the negative became deep black, 
 because the sun rendered the layer of gelatine insoluble through 
 and through, and so attached it fully to the paper. But in the 
 half-tones this penetration did not take place ; the action was 
 comparatively superficial ; the lower part of the film remained 
 soluble, so that the impressed portion above it was undermined 
 in developing, and broken away. The only indications of half- 
 tone obtained seem to have been due to inequalities in the paper . 
 M. Laborde, though he perceived the evil, did not find a remedy 
 for it except to suggest exposing from the back. 
 
 The honor of devising the method of transferring is due to 
 Mr, Swan. He showed that the true plan of developing lay in 
 attaching the exposed surface to paper or other support, remov- 
 ing the original paper support, and so developing on the under side. 
 Thus all the half-tone was excellently preserved, and the picture 
 was re-transferred to another and final sheet of paper. 
 
 Details. — Since the first' edition of this manual was published, 
 the carbon process has been somewhat simplified, and is passing 
 more and more into use in England, where it is better understood 
 than anywhere else. 
 
 " Tissue" for carbon printing is' sold ready prepared, and is to 
 be sensitized by plunging into a solution of bichromate of potasb, 
 one ounce in thirty of water. If more sensitive paper is wanted, 
 the proportion may be increased. • As tissue so prepared is liable 
 
400 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 to spontaneously harden, and at best keeps but for a day or two, 
 the writer pointed out some years ago the advantage of adding 
 liquid ammonia to the bichromate solution, whereby the sensi- 
 tive properties are preserved for several weeks. Lately this 
 method seems to have come into commercial use. 
 
 After the sensitized tissue has been dried, which operation 
 must be performed rapidly, but not at too high a heat, lest the 
 gelatine melt and run, it is exposed under a negative ; the exposed 
 surface is next moistened and pressed against another sheet of 
 paper. With some sorts of highly sized papers, the exposed and 
 moistened surface of the gelatine will adhere without difficulty. 
 Other paper will require a coating of gelatine, or albumenized 
 paper may be employed of which the albumen has been coagu- 
 lated. The adhesion is made complete by pressure with a wet 
 sponge, or a roller or " squeegee," and then the two papers, with 
 the layer of gelatine between, are thrown into water scarcely 
 lukewarm ; presently the original support can be removed, and 
 the print, by lying in the water for a short time, becomes deve- 
 loped. It is finally cleaned off" by gentle agitation in cold water. 
 
 Under and Over-exposure.— li is of course very desirable that the 
 right exposure should be hit, but a certain latitude of error can 
 be compensated for in the development. If the print clear itself 
 with difficulty, hotter water may be cautiously applied, not, how- 
 ever, until its necessity has become apparent. 
 
 On the contrary, under-exposure will show itself by a tendency 
 to clear rapidly as soon as the temperature of the water has been 
 a little raised and when it is barely tepid. This will indicate the 
 necessity of keeping down the temperature and finishing the print 
 in water as cool as will clean the lights. 
 
 The print thus obtained is of course reversed. In some cases 
 this is a matter of indifference, but more frequently it is neces- 
 sary that the print should correspond with the object itself, as 
 does an ordinary silver print. This correspondence is obtained 
 in either of twoVays: — 
 
 By taking Reversed Negatives. — A reversed negative bears the 
 same relation to.an ordinary one as an image in the looking-glass 
 does to the object- itself. Accordingly, one method of reversing 
 negatives is to have a small mirror placed just in front of the 
 lens, making an angle of forty-five degrees, so that the reflection 
 in the mirror, not the object itself, is taken on the film. The 
 
CARBON" PRINTING. 
 
 401 
 
 mirror must have only one reflecting surface ; must be silvered 
 on the face instead of the back. 
 
 Another method is to put the film side of the negative away 
 from the lens. Two precautions are here necessary : the glass 
 must be plate, and perfectly free from scratches and faults ; the 
 ordinary brass spring at the back of the plate must be removed, 
 and long springs of silver be placed at the ends, so that tips of 
 the springs will rest upon the corners of the plate. 
 
 In practice, the first system has been the most successful. 
 
 By Double Transfer. — With non-reversed (ordinary) negatives, 
 if the final print is required to be non-reversed, a re-transfer 
 must be made on paper prepared with gelatine. 
 
 Evidently it will be prudent to keep down the temperature in 
 the early stages of the operation, and to raise it only as far as 
 becomes manifestly necessary. 
 
 Re-transferring. — This is done with gelatine solution. 
 
 Water 40 ounces. 
 
 Glycerine 1 ounce. 
 
 Gelatine 4 ounces. 
 
 Heat this long enough to expel all air-bubbles, but do not keep 
 unnecessarily long in fusion, as by such treatment gelatine loses 
 to some extent its power of setting. 
 
 Cover the surface of the print very carefully and evenly with 
 solution, either by floating or brushing, then hang up to dry. 
 Dampen carefully the mount, whether this be paper or cardboard, 
 avoiding to dampen too much, lay the print on face down, and 
 pass at once through the rolling press. 
 
 The print is now left for a day to dry thoroughly before under- 
 taking the last operation, that of removing the paper which has 
 acted as a support during development. This is done by vigor- 
 ously rubbing with tufts of cotton dipped in benzine. Then 
 raise a corner, selecting one of the deep shadows where the film 
 is thick, with a blunt knife, bend it well back and peel it gently 
 off. In mounting on paper, Mr. Swan is in the habit of subse- 
 quently laying the print for an hour in a five per cent, solution 
 of alum, a step which the writer believes he .was the first to 
 suggest. 
 
 % 
 
402 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 § 3.— Other Methods. 
 
 Carbon Direct Printing. — In the case of objects devoid of half- 
 tone, and consisting altogether of white and black, the transferring 
 is unnecessary. If gelatine or gum be mixed up with solution 
 of bichromate of potash, and a pigment be incorporated with it, 
 this mixture may be spread evenly on sized paper, and, if exposed 
 under a negative, a positive copy is obtained. 
 
 The writer has shown elsewhere that gum is preferable to gela- 
 tine for this purpose, inasmuch as it may be spread evenly over 
 the paper with a brush ; gelatine mixtures cannot, as they con- 
 geal in the operation. He also showed that the perfectly pure 
 whites could be obtained by adding albumen to the mixture, and 
 not without it. 
 
 Printing through the Paper^ etc. — Laborde first suggested this 
 idea, but, in spite of many efforts, it has never been practically 
 successful, the grain of the paper interfering, unless, indeed, Mr. 
 Pouncy's prints have been, as stated, so obtained. 
 
 Pouncy's Process. — Excellent prints have been obtained by Mr. 
 Pouncy, an early and unwearied laborer in the field of carbon 
 printing. In this process the sensitive pigment is composed of 
 asphaltum, printer's ink, and a fatty matter, with or without bi- 
 chromate of potash. The matters are incorporated with the aid 
 of heat, and strained. All the information given by Mr. Pouncy 
 is that there must be more ink than asphaltum, that it should be 
 as thick as cream, and give an opaque coating when applied to 
 glass. Only some sorts of asphaltum give good results. 
 
 The sensitive pigment is to be applied to paper with a broad 
 camel's-hair brush, leaving the brush in the pigment when not in 
 use. The paper dries in a few minutes, and keeps for months. 
 
 The paper to be used should be a very transparent tracing 
 paper, or bank-post rendered transparent with poppy oil. Ex- 
 pose with the paper side next to the negative, and develop by 
 immersion in turpentine. 
 
 These prints are advantageously transferred to white paper. 
 After the print has become thoroughly hard by exposure to light 
 and air, after development, varnish the surface with a broad 
 camel's-hair brush, and lay the picture face down on the surface 
 to which it is to be transferred, and press in a copying press ; 
 when dry, moisten the transparent paper, and it will come off, 
 leaving the print behind. 
 
CAKBON FEINTING. 
 
 403 
 
 The exposures in this process are long; from three to five 
 times those of chloride paper. The prints are very beautiful, 
 and probably have the highest claim to permanence of any pho- 
 tographic work on paper, without exception. 
 
 Carbon Printing on Glass. — The writer has devised an extremely 
 simple mode of operating. " Tissue," as sold, is placed in a solu- 
 tion of bichromate of potash, one ounce to twelve of water, a 
 clean piece of plate glass is slipped under it, the tissue pressed 
 close, and thus contact is secured without bubbles. After drying, 
 the glass face is cleaned, the negative placed against it (the glass 
 side), and the printing is done by reflected sunlight, or by placing 
 in the bottom of a box three or four feet long, so as to exclude 
 diffused light. Develop in tepid water. No transferring is 
 needed. This method, when well managed, gives a clean, sharp 
 image, and involves but very little trouble. 
 
PART TV. 
 
 THEORETICAL CONSIDERATIONS. 
 
 CHAPTER I. 
 
 GENEKAL OBSEEVATIONS. 
 
 "When we attempt to study the functions of liglit, we find our- 
 selves face to face with questions which continually extend and 
 expand as we consider them, until we are lost in the immensity 
 of the subject. 
 
 For all life, such as we know it on this planet, has been ordained 
 by its Creator to exist only under the influence of light. By that 
 agency, carbon is separated from the carbonic acid of the atmo- 
 sphere, and is combined into all those organic forms of nutriment 
 upon which we rely to support life, either directly as food, or 
 indirectly to nourish those animals which are eventually to con- 
 stitute our food. Thus, everything that lives upon the face of 
 our planet owes its existence to light. 
 
 Light is so powerful in its influence upon organic bodies that 
 there exists scarcely one which is not directly affected by it. If 
 an organic body be formed by the affinities of its component parts 
 acting in the absence of light, then when that body so formed is 
 submitted to the action of light, the afl&nities of its elements are 
 in a vast number of cases so altered that decomposition results, at 
 least if moisture b.e present. As familiar examples may be men- 
 tioned that almost all colors are bleached by exposure to sun- 
 light, almost all organic substances are essentially altered in their 
 nature by. long action of sunlight. Perhaps no more striking 
 instances can be adduced than those of the whole vegetable 
 world. Plants of every description undergo incessant changes 
 under the action of light ; these changes take one course so long 
 as the plant lives ; with its death a new order of changes sets in. 
 
GENERAL OBSERVATIONS. 
 
 405 
 
 During its life it not only forms cellular and woody tissues and 
 chlorophyl, &c., characteristic of vegetable life generally, but 
 also vast numbers of complex organic bodies, such as the vege- 
 table alkaloids, the gums, the resins, the sugars, the vegetable 
 oils, the essential oils, &c. &c. After the death of the plant, an 
 inverse action is set up, and these substances tend to resolve 
 themselves, under the influence of light, heat, and moisture, 
 more or less completely into carbonic acid and water. 
 
 Inorganic bodies as a class are less sensitive to light, but there 
 are, nevertheless, very many even of these in which a change of 
 affinities is brought about by its agency. 
 
 Most commonly the action of light is a reducing one, that is, 
 there is a tendency to part with oxygen (similarly with other 
 chlorous bodies, as iodine, bromine, and chlorine). This is analo- 
 gical with the action of light in producing vegetation by which 
 the carbonic acid of the atmosphere is made to part with oxygen, 
 and enter into new forms of combination. So that the regular 
 and normal action of light may be said to be the reducing one. 
 
 Occasionally, however, the action is contrary, and a combina- 
 tion with the oxygen of the atmosphere is promoted. Phosphorus 
 is an example of this exceptional action, its union with oxygen 
 is accelerated by light. Another prominent exception may be 
 cited in the action of light upon a mixture of hydrogen and 
 chlorine, bodies which, when mixed together, show no tendency 
 to unite in the dark, but do so with explosion when light is 
 allowed to fall upon the glass vessel in which these gases are 
 mixed in proper proportions. 
 
 An examination into the action of light in those processes 
 which the photographer employs, shows that so far as it is chemi- 
 cal, it is invariably reducing. Thus, when a bichromate is ex- 
 posed to light in the presence of organic matter, the agency of 
 the light enables the organic matter to oxidize itself at the ex- 
 pense of a part of the oxygen of the chromic acid. When a 
 per-salt of iron is exposed to light, it tends to lose one-third of its 
 oxygen, and to pass to the condition of a proto-salt. The same 
 thing takes place in the salts of uranium, which principle forms 
 the basis of the so-called Wothlytype process. Some other metals 
 are acted upon similarly : the salts of mercury tend to lose half 
 their oxygen, chloride of gold may lose the whole of its chlorine, 
 and the gold may be revived in metallic form. 
 
406 
 
 PHOTOGRAPHIC 
 
 MANIPULATIONS. 
 
 CHAPTEE II. 
 
 ACTION OF LIGHT ON COMPOUNDS OF SILVER. 
 
 § 1.— Chloride of Silver. 
 
 Light exerts a distinct chemical action upon chloride of silver, 
 of a reducing nature, that is, the chloride passes into sub-chloride 
 with elimination of free chlorine, or of hypochlorous acid. If 
 pure precipitated chloride of silver, well washed and freed from 
 all organic matter, be exposed to light in a sealed glass tube, it 
 gradually assumes a violet color, and loses chlorine. In the dark 
 it regains its whiteness by recovering the chlorine lost. If free 
 nitrate of silver be present, that is, if the chloride of silver be 
 moistened by solution of nitrate of silver, the coloration proceeds 
 much more rapidly. 
 
 If organic matter be present, the decomposition is more rapid 
 still, and in many cases the sub-chloride of silver appears to unite 
 with the organic matter, giving risd to the production of com- 
 pounds much more deeply colored than the simple sub-chloride. 
 Of these is the dark chocolate-colored substance, passing almost 
 to black, which constitutes the body of an albumenized paper 
 print before toning. 
 
 § 2.— Iodide of Silver. 
 
 The study of the action of light upon iodide of silver presents 
 very great difficulties, and has given rise to considerable differ- 
 ence of opinion. 
 
 In studying this subject, it becomes necessary, as the writer of 
 this manual has more particularly pointed out elsewhere, to con- 
 sider the question in two different forms, and distinguish between 
 the action of light upon iodide of silver in the presence, and also 
 in the absence of organic or other bodies capable of exerting 
 special influences on it. 
 
 To be able fully to eliminate the effect of these latter, the 
 writer devised the method of precipitating metallic silver upon 
 
ACTION OF LIGHT ON COMPOUNDS OF SILVER. 407 
 
 films of glass, and then iodizing these films with iodine dissolved 
 in solution of iodide of potassium. It had been held, indeed, that 
 iodide of silver formed in presence of excess of iodide of potas- 
 sium was insensitive to light ; this view, however, the writer dis- 
 proved by decisive experiments, and it is now abandoned. 
 
 As the film of iodide of silver upon glass was very liable to 
 slip about, an expedient was found to fix it, but substituting ground 
 glass, and this method of experimenting is now the only one 
 known that is capable of affording reliable results. 
 
 By these experiments, which cannot be detailed here, the 
 writer was enabled to show — 
 
 1. That pure iodide of silver isolated undergoes no chemical 
 decomposition even by very prolonged action of light. Thus a 
 film exposed for many hours to brilliant sunshine was placed 
 aside for a day or two in the dark. It was exposed for a second 
 or two under a negative, and the image of that negative was then 
 developed upon it without difficulty. 
 
 2. But if an organic substance be present, then chemical de- 
 composition does take place. Thus, if a film of iodide of silver 
 upon ground glass be washed over with a solution of tannin, and 
 then be exposed for a sufficient time under a negative, a visible 
 image of the negative is obtained. 
 
 Development on Iodide of ^Iver. — Very erroneous notions of the 
 nature of development on iodide of silver have often been enter- 
 tained, and the writer himself was at one time under the convic- 
 tion that iodide of silver might undergo such a physical impression 
 as to predispose it to decomposition when brought into contact 
 with certain substances. Careful and extended experiment has 
 led him to return to his older opinion, that the physical impres- 
 sion of light upon iodide of silver is such as merely to predis- 
 pose it to receive a falling precipitate. This-conception should 
 be fully mastered by the student, and may be explained as fol- 
 lows: — ■ 
 
 If we take a saline solution which is just ready to let fall a 
 precipitate, and stir it well in a glass vessel, allowing the end of 
 the glass rod to touch the sides of the vessel in stirring, we shall 
 find that (in many cases) the precipitate will form first and in 
 preference on all those parts of the glass which have been touched 
 by the rod. Thus it may be said that the previously invisible 
 path of the rod over the glass has been developed by the precipi- 
 tate. The surface of the glass was only physically, not chemi- 
 
408 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 cally, altered by the passage of the rod over it; and yet it 
 attracted, more powerfully than the rest, the descending precipi- 
 tate. Just so the part of the iodide film which has been touched 
 by light, exerts a more powerful attraction upon the descending 
 precipitate of metallic silver from the developer than those por- 
 tions which have not been touched. 
 
 It appeared to the writer that although the similarity of these 
 phenomena was sufficiently obvious, yet the two might be brought 
 closer together if he could show that an iodide film could receive 
 a species of latent image by mere pressure, independently of light, 
 capable of being developed by an ordinary developer. Experi- 
 ment realized this without difficulty. Sensitive collodion films 
 were pressed with various surfaces having raised or sunk devices. 
 Then a developer poured over them brought out these devices 
 with great distinctness, the silver being attracted always in prefer- 
 ence to those parts which had received the pressure. The writer does 
 not, however, mean to affirm that the action of light is necessarily 
 mechanical, as in the foregoing illustration and experiment. 
 
 It is very remarkable that although invisible images may be 
 developed on both chloride and bromide of silver, yet the phe- 
 nomena are of quite a diff'erent nature. Development on pure 
 iodide of silver results simply from| power in the film to attract 
 to itself a descending precipitate, and is independent of any de- 
 composition of the iodide in the film, either under the action of 
 light, as may take place in the case of chloride of silver and 
 bromide of silver, or under that of a developer, as may happen in 
 the case of bromide, of silver. 
 
 That the development in the case of iodide of silver is perfectly 
 independent of any decomposition of the iodide film, is shown by 
 experiments published by the writer, together with Dr. Shepard, 
 of Providence, in which, after an image had been developed on an 
 iodide film, it was dissolved away with solution of acid pernitrate 
 of mercury, and was then, after washing, reproduced hy a second 
 application of a developer. This exhibits in a striking light what 
 the writer holds to be the peculiar and characteristic action of 
 iodide of silver, viz., that it is so modified by the action of light 
 as to be capable of forming an image out of the silver in the 
 developer, without itself having undergone decomposition either 
 during exposure or under development. In this way only does 
 it seem possible to explain the fact that a developed image may 
 
ACTION OF LIGHT ON COMPOUNDS OF SILVER. 409 
 
 be dissolved away, and the power nevertheless be left in the film 
 to reproduce the image bj a second development. 
 
 It has been already explained that in the presence of certain 
 organic and other bodies, iodide of silver undergoes chemical 
 decomposition, and the same seems to be true when nitrate of 
 silver is present. When, therefore, instead of experimenting 
 upon a film of iodide of silver, isolated on glass, we take a com- 
 mon sensitized plate in which both nitrate of silver and an 
 organic body (collodion) are present, the conditions are essen- 
 tially changed, and chemical decomposition undoubtedly takes 
 place. Consequently, in the ordinary wet collodion process, 
 there appear to be two invisible images simultaneously present 
 in the film — one a latent physical image due to the action of 
 light upon the iodide, the other a chemical image, invisible 
 simply by reason of its tenuity. Both of these may serve as 
 bases of development. 
 
 For want of distinguishing clearly between these conditions, 
 and of remembering that what takes place in the case of iodide 
 of silver isolated from all other bodies is very different from 
 what takes place when free nitrate of silver or certain organic 
 bodies are present — for want of bearing this steadily in mind, 
 much that has been written on the subject of this latent image 
 has little or no real value. ^ 
 
 The above are the views which the writer has entertained and 
 endeavored to prove. In the opinion of some photo-chemists, 
 however, the action of light upon iodide of silver is always 
 chemical, and no impression is formed except by actual decom- 
 position. But this opinion seems to be at variance with observed 
 facts, and the reactions of iodide of silver cannot be satisfactorily 
 explained by it. 
 
 It will be interesting to note that in the case of iodide of silver 
 the chemical latent image always offers a stronger basis of develop- 
 ment than the physical. Now it has been already explained that, 
 according to the view entertained by the writer, the chemical 
 image is never produced upon isolated iodide of silver, but only 
 when some suitable body is present to give rise to its production, 
 consequently it follows that the presence of that body capable of 
 giving rise to the production of a chemical- image, may greatly 
 exalt the sensibility of the iodide. It is for this reason that the 
 presence of the bath solution (containing free nitrate of silver) 
 in wet plates, and certain bodies, such as tannin, gum, gallic acid 
 27 
 
410 PHOTOGRAPHIC MANIPULATIONS. 
 
 etc., in dry plates, greatly diminishes the exposure needed. These 
 latter substances have been G&Ued preservatives, though it is evi- 
 dent that they are sensitizers precisely as nitrate of silver is a 
 sensitizer. 
 
 As the production of a " chemical image," i. e., one depending 
 upon the actual decomposition of the iodide, must always arise 
 from a separation of iodine to a greater or less extent from the 
 silver present, so it seemed natural to suppose that the greater sen- 
 sitiveness, or, in other words, greater prooeness to decomposition 
 resulting from the presence of so-called preservatives, had its 
 origin in an afiinity of the preservative for iodine, which affinity, 
 insufficient in itself to produce decomposition, would neverthe- 
 less aid the action of the light. This explanation was first made 
 by Poitevin, and has received general acceptance. Yogel has 
 affirmed that all preservatives have this characteristic, that they 
 show their affinity for iodine by decolorizing the blue solution 
 of iodide of starch. 
 
 But few experiments appear to have been made to test this 
 view. The writer, at a time when he was experimenting with 
 many new preservatives, tested many of those which had shown 
 therriselves useful, with the iodide of starch, found that they all 
 decolorized it. What tends, however, somewhat to weaken this 
 argument, is that the most powerful sensitizers were not always 
 . those that most rapidly decolorized the blue test. Thus tincture 
 of stramonium showed itself to be a most powerful sensitizer, 
 but exhibited so little action upon the blue solution, that twenty- 
 four hours were necessary to render the action visible. 
 
 § 3.— Bromide of Silver. 
 
 The action of light upon bromide of silver has been less studied 
 than that of iodide, because the difficulties which it presents have 
 been less evident than those in the case of the iodide. For it was 
 easily shown in the case of bromide of silver that a chemical 
 decomposition does.tftke place by continued action of light.^ 
 Hence it was supposed that no physical action of light took place, 
 inasmuch as none was apparently needed to explain the pheno- 
 mena observed. 
 
 • This fact the writer has carefully verified \ipon films of bromide of silver 
 isolated upon surfaces of ground glass. 
 
 ( 
 
t 
 
 ACTION OF LIGHT ON COMPOUNDS OF SILVER. 411 
 
 But the writer has pointed out elsewhere that the mere fact of 
 the possibility of development hy pyrogallic acid in the absence of any 
 free soluble silver cornpound^ is in itself an unanswerable argument 
 for the existence of such a physical image. 
 
 Upon a dry collodio-bromide plate perfectly washed and hav- 
 ing present no trace of the nitrate of silver, the application of 
 pyrogallic acid will develop a visible image. Whence does this 
 come ? The image is evidently a sub-bromide of silver, perhaps 
 combined with organic matter, but that the bromide of silver in 
 the film afforded the sub-bromide by decomposition is sufiSciently 
 clear. 
 
 Now although this image may be developed where there was 
 no image visible upon the plate after its exposure, let us even 
 suppose for argument that there was a faint visible image. If 
 the development were conducted with nitrate of silver present, 
 this faint visible image might certainly act as a foundation upon 
 which the strong image was built up. But nothing of the sort 
 can take place where the alkaline development is conducted in 
 the absence of all silver compounds except those in the plate. 
 
 It, therefore, appears clear that a latent physical image may 
 exist on bromide as well as on iodide of silver. 
 
 But the difference between these compounds in respect of the 
 action of light upon them is very striking. 
 
 On iodide of silver the latent physical image is produced where 
 the iodide is isolated. 
 
 But on bromide only where a "sensitizer" is present. 
 
 On bromide isolated, the action of the light can only produce 
 a chemical image ; on iodide isolated, it can produce a physical 
 image only. 
 
 The action of the light upon bromide of silver, isolated, must 
 be enormously long to produce an impression capable of being 
 developed ; the sensitizer abridges this'period vastly more than 
 in the case of iodide. 
 
 But on bromide isolated, the long-continued action of light 
 may produce a strong, visible image (in 'aii experiment by the 
 writer this was attained by four hours' exposure to strong sun 
 under a negative), which cannot take place in the case of iodide. 
 
 Development on Bromide of Silver— In the case of iodide of 
 silver, we have seen that development is essentially the attraction 
 to the film of a descending precipitate, the film itself remaining 
 (chemically) unaltered. But in the case of bromide of silver 
 
412 PHOTOGKAPHIC MANIPULATIONS 
 
 (acted on by light in the presence of tannin, or other sensitizer) 
 the alkaline development consists essentially in a reduction of the 
 bromide in the film, and the production thereby of a more or less 
 complex, deeply-colored substance, forming the image. 
 
 The remarkable distinctions between these two developments, 
 as respects their essential characters, correspond to equally great 
 differences in the practical operations based upon them. So that 
 in the wet processes, in which iodide of silver is the altogether 
 essential body, we see those forms succeed best in which a de- 
 scending precipitate is applied to the invisible image. 
 
 But in the dry bromide processes we find only one thing essen- 
 tial : that to the exposed plate there shall be presented a substance 
 like pyrogallic acid, which has a natural tendency to provoke 
 reduction. This substance at once starts a decomposition in those 
 parts that have been exposed to light. "We may enhance its 
 decomposing action by alkalies, and so exalt that decomposing 
 agency until it is alone sufiicient to produce such an image as we 
 want ; or, we take the image so produced, and by adding silver 
 and acetic acid, we may huild upon it a denser image for our pur- 
 pose. So far as this building up is concerned, we proceed upon 
 the same principles as in the wet process, but this second step 
 does not in the least affect the character of the first, and that first 
 step differs absolutely and essentially from anything that belongs 
 to the wet development. 
 
 It is then (and this is what, if the writer is not mistaken, has 
 not before been correctly presented) by a careful consideration of 
 the essential characters of these two developments, that we arrive 
 at the essential differences between the invisible image as formed 
 on iodide, and on bromide of silver. Each in its absolute essence 
 and freed from such accidental phenomena as may accompany it 
 (and may lead to the production of a chemical image), is physical 
 and not chemicEtl in its nature. But in the iodide the physical 
 impression is one tending to cause the attraction of a descending 
 precipitate, in th-e bromide it is one predisposing to decomposition 
 when a reducing. ag.ent of a proper character is presented. 
 
• 
 
 ACTION OF POETIONS OP THE SPECTRUM. 413 
 
 CHAPTER III. 
 ACTION OP VARIOUS PORTIONS OP THE SPECTRUM. 
 
 When, instead of exposing sensitive bodies to ordinary light, 
 we let fall upon them a solar spectrum, we find that its different 
 portions exercise widely different influences. 
 
 We find, also, that the nature of the prism used singularly 
 affects the influences exerted by the different portions into which 
 it separates white light. Thus, for example, with a flint glass 
 prism, the most powerful actinic force is exerted by the invisible 
 rays just beyond the violet. But if a prism filled with sulphide 
 of carbon be used, a spectrum is formed, devoid, or nearly so, of 
 invisible ultra violet rays, capable of acting upon sensitive paper. 
 A series of very interesting experiments, chiefly made by Her- 
 schel, on the action of different portions of the spectrum, have 
 been tabulated, and will be found in Hunt's valuable Researches 
 on Light. 
 
 As respects the silver haloids, the action of light commences 
 far beyond the visible rays, and extends some distance into the 
 visible spectrum. Bromide of silver is very faintly affected by 
 green rays, which do not act upon iodide. It has, therefore, a 
 slightly wider range of sensitiveness than iodide. 
 
 Below the green come those brighter rays which form the 
 principal illuminating part of white light. These are without 
 effect upon sensitive films of the silver haloids that have never 
 been exposed to light. But Ed. Becquerel has shown that these 
 less refrangible rays have a " continuing" pow.er, that is, that 
 although incapable of themselves to commence q^ti impression upon 
 a sensitive surface, even by a very prolonged action, yet if that 
 action be set up by the more refrangible rays; these less re- 
 frangible ones can continue and increase It. Thus, if paper pre- 
 pared with iodide of silver be exposed to the spectrum, the im- 
 pression ends with the blue rays. But if it be but exposed for 
 a second or two to light, and then to the spectrum, and if a de- 
 veloper be applied, an impression is found to have been made 
 extending to the very end of the visible spectrum. 
 
41i 
 
 PHOTOGRAPHIC MANIPULATIONS. 
 
 What is also remarkable in this very interesting investigation 
 is, that the bodies which act as a support to the silver compound 
 may exercise an important influence on the effects produced. 
 Thus the iodide and chloride of silver in collodion or paper, or 
 on a metallic film, are subject to this "continuing" power. 
 Bromide of silver, when formed on a daguerreotype plate, is not; 
 formed on collodion or on paper, it is. The image of the spectrum, 
 when formed on bromide' of silver on a j^lciie, is much longer 
 than the image upon chloride or iodide also on a plate, whereas 
 bromide in collodion or on paper gives a spectrum no longer 
 than iodide or chloride.' 
 
 These results are as important in their relations to photo- 
 graphy as they are interesting in themselves, and their bearing 
 on the negative process is too evident to need that the writer 
 should dwell on it. Only it may be remarked that they explain 
 in part some of Mr. Eutherfurd's results in photographing spectra 
 on collodion ; they seem, however, to indicate that in his ex- 
 periments the spectrum was not wholly purified from white light, 
 for in these experiments impressions of many of the less refran- 
 gible portions of the spectrum were obtained in collodions con- 
 taining the silver haloids. 
 
 Heliochromy. 
 
 It has been long known that the various colors of the spectrum 
 had the power of impressing themselves upon certain sensitive 
 surfaces, especially upon sub-chloride of silver. So that if a piece 
 of paper be impregnated with chloride of silver and then be ex- 
 posed to light till it darkens somewhat, it may in this condition 
 be exposed to daylight' under colored glasses, and after a certain 
 amount of exposure, will be found to assume the color of the 
 glass under which it was exposed. Becquerel has varied the ex- 
 periment by using metallic plates^ on which a coating of chloride 
 of silver was formed. Poitevin discovered that bichromate of 
 potash aided chloride paper in reproducing natural colors. 
 
 But neither have the results so far obtained been at all beauti- 
 ful, nor has it been found possible to render them permanent. 
 At the same time, the experiments above referred to are curious 
 and interesting, and there is no doubt that it is in the power of 
 photography to reproduce all the colors of nature. 
 
 ' Becquerel, La Lumiere, II. pp. 89-92, 
 
 I 
 
 r ■ • 
 
# 
 
 PART Y. 
 
 CHAPTER I. 
 PHOTOGRAPHY IN ITS RELATIONS TO HEALTH. 
 § 1. — Poisons. 
 
 In adopting a pursuit, whether simply with a view to interest 
 and amusement, or with the design of serious study and investi- 
 gation, or as a business enterprise, every one should attentively 
 consider its relations to his health. Permanent injury to bodily 
 health is an evil so serious that its full magnitude is appreciated 
 by none who have not learned by their own bitter experience. 
 The writer, therefore, appeals to the good sense of every one 
 who may adopt this manual as his guide through the study of 
 photography, in the first place to neglect none of the general 
 precautions which will be here recommended ; and in the second, 
 should he find his health in any way suffer, to ascertain at once 
 to what that injury is ascribable, and to lose no time in taking 
 such special action as the case may need. Speaking from per- 
 sonal experience, and having witnessed evil results in others, the 
 writer earnestly desires to induce the habitual adoption of effec- 
 tive precautions. 
 
 It is not that photography is necessarily a hurtful art, but its 
 practice brings its votaries into contact with several very strong- 
 poisons, which, if used without great care, and still more, if used 
 with the heedlessness that is only too common, are liable to pro- 
 duce the very worst effects. These substances are principally 
 ether ^ collodion^ cyanide of potassium,, corrosive sublimate, chloride of 
 gold, nitric acid, acetic acid, and ammonia. 
 
 Ether, whether swallowed or inhaled as vapor, has a remark- 
 able effect, which, like that of many other active agents, is 
 twofold, stimulating and sedative. The first tendency is to pro- 
 
416 PHOTOGRAPHY IN ITS RELATIONS TO HEALTH. 
 
 duce a species of imperfect intoxication, soon followed by more 
 or less prostration ; this sedative effect has led to its being used 
 in medicine under the name of " Hoffmann's Anodyne." The 
 effect of its continued use is to produce languor, depression of 
 spirits, and bodily prostration. 
 
 Collodion^ from the large quantity of ether which it contains, 
 produces the specific effects characteristic of that substance, but 
 also other effects, the precise source of which is not well under- 
 stood. When collodion becomes much ripened, and especially 
 when it takes on a deep color, it is found to give off a very irri- 
 tating vapor, which attacks the face, and especially the eyelids, 
 producing severe inflammation. Cases have been cited in which 
 photographers have been in this way obliged to interrupt their 
 pursuit for times varying from a few days to many months. 
 When the photographer perceives a disposition to irritation and 
 inflammation in the face, he may at once suspect his collodion of 
 being the cause. 
 
 Cyanide of potassium is, of course, the most dangerous chemical 
 with which the photographer comes into contact. For clearing 
 both positives and negatives, especially the former, it keeps its 
 hold upon photographers, particularly amongst careless manipu- 
 lators, through two causes. First, if by mismanagement the nega- 
 tive is a little fogged, cyanide, which has a stronger solvent action 
 than hyposulphite, tends to clear it up. Second, the transfer of 
 small portions of cyanide to other solutions by dirty fingers, has 
 not the absolutely disastrous results that follow such transfers of 
 hyposulphite. These considerations are not in the least credit- 
 able to the photographer who is influenced by them. 
 
 Cyanide of potassium is a compound of prussic acid with 
 potash. In this compound it retains all the dangerous proper- 
 ties that characterize if in the free state. In fact, a solution of 
 cyanide slowly but continually decomposes, absorbing carbonic 
 acid from the air and giving off prussic acid in the form of gas. 
 
 This poison may act in three ways. Leaning over a bath of it, 
 or even remaining in a room containing a solution of it exposed 
 on a considerable surface to the air, a small quantity of prussic 
 acid is continually inhaled. 
 
 In manipulating with its solutions, the hands come into contact 
 with it. How far chemical solutions are taken up by a perfectly 
 sound skin has been a matter of considerable discussion among 
 physicians, but recent careful experiments made in Paris leave . 
 
POISONS. 
 
 417 
 
 no doubt that the skin continually absorbs liquids which remain 
 in contact with it. 
 
 If, however, the continuity of the skin be broken by a scratch, 
 cut, pimple, or otherwise, cyanide is readily absorbed at such 
 places, and a considerable amount of local inflammation may be 
 produced. In some cases paralysis of the limbs has been afiS.rmed 
 to have resulted, and even paralysis of the whole side. 
 
 For several years past the photographic journals have pub- 
 lished numbers of letters from photographers who have had 
 their health injured, or, in many cases, ruined by the action of 
 their chemicals, and especially by cyanide. Paralysis is the most 
 common result, attacking most frequently an arm, but sometimes 
 the entire side. One describes his hands as for months continu- 
 ally exuding some anomalous secretion, sticking them fast to his 
 gloves, and interfering with their use. Another complains of 
 intense pains in the fingers, only to be rendered endurable by 
 keeping them for hours in cold water. Others find the whole 
 bodily health broken down, and no help to be obtained from 
 medicine. One photographer (M. Davanne), after having had his 
 hands wet with cyanide solution, moistened them with acetic 
 acid, and was almost instantly struck down insensible with symp- 
 toms of violent poisoning. His friends barely saved him by long- 
 continued pouring of cold water on the head. 
 
 It should always be remembered that when any substance or 
 compound having an acid reaction comes into contact with cyan- 
 ide of potassium, the dangerous tendencies of the latter are greatly 
 increased — in fact, prussic acid is at once set free. 
 
 A very painful class of casualties are those resulting from care- 
 lessness with cyanide. Solutions are left about ; sometimes the 
 incredible carelessness of leaving them in drinking tumblers is 
 committed. For all lives lost in this way (and there have been 
 many), he who left the solution about is morally responsible. 
 Once for all, the use of this chemical should be abandoned totally 
 by photographers. If any insist on using it, the least such can 
 do is to keep it exclusively in vessels marked conspicuously, 
 
 POISON". 
 
 Corrosive sublimate is another dangerous chemical, but not 
 capable of acting by inspiration through the lungs. Accidents 
 with sublimate arise either from absorption or internal adminis- 
 tration. 
 
 Absorption through the skin takes place slowly, and the fingers 
 
418 PHOTOGRAPHY IN ITS RELATIONS TO HEALTH. 
 
 may be occasionally wetted with sublimate 'solution without any 
 noticeable bad results ; the danger lies in this, that there is no safe 
 line that can be drawn, and that the photographer can form no 
 conception as to the point to which he may go with impunity. 
 Evil must be done before its danger can be recognized. 
 
 Administered internally, sublimate is a powerful corrosive 
 poison. 
 
 Chloride of gold acts as a poison by causing deep and severe 
 ulcerations upon the fingers of those who are continually working 
 in toning baths. Such manipulation should be managed by means 
 of spatulas and forceps of glass or whalebone. 
 
 Nitric acid acts toxically through the lungs. It stains the skin 
 a deep yellow, which lasts until the epidermis is worn off, but no 
 other evil seems to result from contact. It is possible that it is 
 not absorbed, but that it kills the skin too quickly for such an 
 effect. Nitric acid diffused through the atmosphere and inhaled, 
 acts as a direct poison. Some years since, Mr. Stevens, together 
 with an assistant, undertook to sop up a quantity of nitric acid 
 spilt by the breaking of a large vessel, an act which resulted 
 fatally to the one and nearly so to the other. 
 
 In less quantities, and inhaled over a longer time, it may pro- 
 duce irritation of the lungs and chest diseases. 
 
 Acetic acid acts similarly to nitric, but in a less degree. Its 
 fumes are very irritating to the lungs, especially to weak ones. 
 The quantity of acetic acid used in photographic operations is 
 often very large, so that in many professional establishments 
 there is always a strong smell of this acid. Such a state of affairs 
 must be hurtful to every one connected with the place, and ought 
 to be done away with at any cost. 
 
 Pyrogallic acid has been stated lately to be an active poison, 
 having, in its action on the system, certain analogies with phos- 
 phorus. 
 
 § 3. — Remedies. 
 
 General. — It is evident that all poisons which are liable to be 
 carried upon the atmosphere should, as far as possible, be kept in 
 closed vessels. Cyanide should never be left in open pans or 
 baths. Nitric acid baths used for cleaning (for which purpose 
 bichromate and sulphuric acid is far preferable ; see article on 
 cleaning plates) should never be left exposed to the atmosphere. 
 
 r 
 
REMEDIES. 
 
 419 
 
 but the pans or baths should be protected, and be kept under a 
 chimney or a draught of some sort. 
 
 Next to avoiding the production of fumes, the best thing is 
 ventilation. In the case of ether and collodion, this is the only 
 efficient means, as the fumes of collodion cannot be kept out of 
 the air. For this reason plates should be collodionizeft, not in the 
 open air of the dark room, but in a sort of closet partitioned off 
 and provided with a vent above and below. The operator is 
 outside of such a closet, and the fumes are not inhaled as the 
 plate is coated. This is a very important precaution. 
 
 When acid fumes have got into the air, their removal can often 
 be expedited by pouring out ammonia. This, though eflScient, 
 has the disadvantage of causing thick white clouds, which sub- 
 side by degrees only. Still, its use is occasionally valuable. 
 
 jSpecial. — Poisons taken internally must be treated with specific 
 remedies; the object is always to bring the poisonous matter into 
 some inert compound. 
 
 Cyanide of potassium has the remarkable property of taking 
 up iron and forming a perfectly innocuous substance known as 
 yellow prussiate of potash, ferrocyanide of potassium. Proto- 
 sulphate of iron may, therefore, be taken internally in consider- 
 able quantity. Cyanide of potassium, in presence of a mixture 
 of a protosalt and persalt of iron, is converted instantly into 
 Prussian blue, a substance not at all injurious to the system. 
 Those who use cyanide habitually, will do well to keep the mix- 
 ture of proto and persulphate of iron in readiness for accidents to 
 others, if not to themselves. Common sulphate of iron in solu- 
 tion, by continued exposure to air, peroxidizes, and may be used 
 for this purpose. 
 
 For corrosive suUimate when taken internally, white of egg is 
 usually administered. The quantity of the remedy must be con- 
 siderable — the raw white of one egg to each three or four grains 
 of the poison swallowed. 
 
 Poisons in cuts and scratches should be immediately treated with 
 the same remedies as those advised where the poison has been 
 taken into the stomach. For injuries occasioned by the continuous 
 absorption of poisons, no satisfactory remedies can be recom- 
 mended, recourse must be had to the advice of an educated and 
 intelligent physician. 
 
 The writer feels that he cannot leave this subject without again 
 advising photographers to pay more attention to the conditions 
 
420 
 
 CHEMICAL MANIPULATIONS. 
 
 of health than is generally done. Those who have the direction 
 and management of establishments, should never forget that 
 those whom they employ are often much more exposed to these 
 dangers than themselves, without having the opportunity or the 
 privilege of introducing better arrangements and precautions. 
 And that, liowever employers may feel disposed to risk their own 
 health, they are not justified in causing others, either ignorantly 
 or knowingly, to share such dangers. Many a man, when he has 
 found his nervous system permanently injured, or his lungs 
 weakened, commences care-taking when it is too late. The need- 
 ful precautions are neither many nor troublesome ; they should 
 be taken from the outset, and steadily persevered in. 
 
 CHAPTEE II. 
 
 CHEMICAL MANIPULATIONS. 
 
 Some of the simpler chemical manipulations are frequently 
 needed in photography, and deserve a brief description here. 
 
 § 1. — Weighing and Measuring. 
 
 No operations are commoner or seem easier than these, and yet 
 in none are mistakes more frequent. 
 
 WEiGHiNG.—^For the operations of photography, a small bal- 
 ance like that on page 421, having a nine or ten inch beam, will 
 be the most suitable, using a heavier and commoner pair of scales 
 for weights over one or two ounces. Fig. 142 represents the 
 French pattern of " trehichef^ or tilting scale, now largely manu- 
 factured here. The panS- rest on the box until the lever is 
 pressed, when they swing loose. 
 
 In weighing, it is -necessary always to beware of "sticking." 
 When the pans are nearly equally loaded, but not exactly; the 
 needle may point at the centre by reason of the beam not moving 
 with^entire freedom. By making the pans oscillate a little, it 
 will bfe, easy to see if the needle moves on each side to the same 
 distanq^from the centre. 
 
WEIGHING AND MEASURING. 421 
 Fig. 143. 
 
 Inattention to reckoning the weights is another common source 
 of mistakes, especially with our defective system. 
 
 The following are the details of the weights as now used. The 
 grain is the same always. 
 
 Avoirdupois. 
 1 drachm =-647^^ grains nearly, 
 1 ounce =4372^ grains. ^ / t> diy~a.c]xrr\ S 
 1 pound = 16 ounces = 7000 grains. 
 
 Apothecaries. 
 1 drachm = 60 grains. 
 1 ounce = 480 grains. 
 1 pound = 13 ounces = 5760 grains. 
 
 Troy. •■■ ■ 
 
 1 pennyweight = 24 grains. 
 1 ounce = 30 dwt. = 480 grains. 
 1 pound = 13 ounces =57'60 grains. 
 
 Decimal Weights authorized hy Congress. 
 A tliousand milligrammes make one gramme. 
 ■ A thousand grammes " ." kilogramme. , 
 
 One grain corresponds to 65 milligrammes nearly (64.8). ^ 
 One drachm apothecaries' weight to 3.883 grammes. ^ 
 «' ounce " 31.1035 " 
 
 " " avoirdupois -."'38.349 " 
 " pound " " 453.59 " 
 
 " " apoth. or troy ^' 373.243 " 
 
 1 gramme = 15.43334 grains. 
 
 1 kilogramme =3 lbs. 3 oz. 119.85 gfs., or 15,433.35 g^ 
 
 ■mt. 
 
422 
 
 CHEMICAL MANIPULATIONS. 
 
 Fig, 143. 
 
 Measueing is still more liable to error 
 than weighing. The vessel must be kept 
 carefully perpendicular, and be examined 
 by a level light. The surface of the liquid 
 is always curved, being higher at the edges. 
 The lower level is that to be used, that is, 
 the lower part of the curved surface must 
 correspond with the lines ruled on the 
 glass, as shown by the dotted line on the 
 figure, which represents a "minim glass." 
 
 Liquid Measure. 
 1 fluidrachm = 60 minims. 
 1 fluidounce = 8 fluidraclims. 
 1 pint= 16 fluidounces. 
 1 gallon = 8 pints. 
 
 § 2.— Heating. 
 
 The alcohol lamp was for a long time the favorite source of heat 
 when needed on a small scale ; its advantage lies in its high tem- 
 perature and freedom from smoke. As alcohol both evaporates 
 and absorbs water from the air, the wick should be kept covered. 
 If the wick-tube is passed through a cork, this should always 
 have a groove to permit escape of vapor, or it will be liable to 
 be driven out with a dangerous explosion. 
 
 But whenever gas can be had, the Bunsen Iwner (see Fig. 144) 
 conveniently and economically replaces alcohol. 
 
 The sand-hath is an excellent means of applying a gentle heat 
 to large surfaces. 
 
 A very simple and convenient form of sand-bath is to have a 
 circular rim on top of a stove, filled with clean building sand. 
 The beat is thus applied much more evenly than if the vessel were 
 set directly on the stove without the interposition of the sand, and 
 the danger of breakage is greatly diminished. 
 
 A sand-bath may also be established over a Bunsen burner. 
 Get a worker in sheet-iron to make a cylinder of stout galvanized 
 iron, about twelve inches in diameter, and ten high. The top 
 and bottom are turned over heavy iron wire, and curved pieces 
 are cut out at top and bottom, to serve as air-passages. A circular 
 piece of sheet-iron is hammered into a basin thirteen inches 
 across, and this, filled with sand, rests on the top of the cylinder. 
 Such a . .cylinder will support a very heavy weight. 
 
EVAPORATION". 
 
 423 
 
 § 3. — Evaporation. 
 
 In evaporating, two important points are to be borne in mind. 
 First, the heat should not be contracted to a single point ; and 
 second, it should not be so diffused as to strike that part of the 
 vessel that is above the liquid. In either case fracture is apt to 
 occur; in the latter case, almost certainly. 
 
 For large operations the sand-bath will be proper ; that is, for 
 evaporating negative baths, and such work. For small operations 
 the following arrangement is capital. 
 Procure a lampstand, with a strong ^'^S- 144. 
 
 ring about five inches in diameter; 
 take a piece of strong but fine and 
 close-meshed brass wire gauze, six 
 inches square, lay it on the ring and 
 press the corners down under the ring, 
 so as to fix it firmly to it. This 
 wire gauze forms a support which will 
 carry anything from a capsule an inch 
 in diameter to a basin of twelve or 
 fifteen inches, provided the lampstand 
 be strong and stout as it should be, as 
 well as flasks, beakers, or, in fact, any utensil whatever. The 
 Bunsen's burner stands under this, always ready for service at a 
 moment's notice. The wire gauze stops the 
 flame, and permits only the hot air to pass 
 through, thus giving a great protection against 
 accident, whilst scarcely interfering with the 
 heating. 
 
 A tripod, if made strong and stout, is also 
 a good support, but far less convenient than 
 the foregoing, inasmuch as it cannot be raised 
 and lowered, and is never so strong as the lampstand. In this 
 case, also, a piece of wire gauze, should be interposed between 
 the vessel and the source of heat. 
 
 § 4.— Filtration. 
 
 Of filtration, all that need be said is, make the filter always a 
 little smaller than the funnel, and always wet it before pouring 
 in the liquid to be filtered. Select a gQod paper, which filters 
 
 / 
 
424 
 
 CHEMICAL MANIPULATIONS. 
 
 clean and quickly, and when that which exactly suits is found, 
 a good supply should be laid in. Nothing is more vexatious 
 than to wait for a slow filtration. 
 
 § 5. — Pouring. 
 
 In transferring liquids from one vessel to another, there are 
 two contrivances by which the clean 
 ^^S- 146. performance of the operation without 
 
 loss may be greatly facilitated. These 
 are greasing and rod-pouring. 
 
 Greasing is the application of a little 
 tallow on the finger under the lip over 
 which the liquid is to be poured. For 
 pouring valuable liquids out of large 
 vessels, especially if nearly full, this 
 mode is very useful. 
 
 In rod-pouring^ the glass rod is first 
 wetted with the liquid, and is then held 
 to the lip of the vessel, which is so in- 
 clined as to pour slowly, the stream following the rod (Fig. 146). 
 Both methods may be combined. 
 
 § 6. — Fusing. 
 
 For reducing chloride of silver in the dry way, a Hessian cru- 
 cible may be used. The chloride is intimately mixed with twice 
 its weight of dry carbonate of sodium ; this mixture is rammed 
 tightly into the crucible, which is by degrees raised to a white 
 heat. As the Hessian crucibles are porous, some of the silver 
 may sink in. To obviate this, fuse a little borax in it, or use a 
 Paris day crucible, which is not liable to this objection. 
 
 For fusing nitrate of silver, a Berlin or Meissen porcelain basin 
 will be required ; none other can be depended upon. The Ber- 
 lin are the best, and are stamped in blue ; some with the letters 
 K P M, some with a Prussian €agle inside of a circle. Both of 
 these sorts are excellent. With care, the operation is perfectly 
 safe, and fracture need not be feared. The Bunsen burner will 
 give the necessary heat for small quantities, or combined burners 
 for large. C 
 
NEUTRALIZATION. 
 
 425 
 
 I 7. — Neutralization. 
 
 Where tbe object is merely to render an alkaline liquid acid, or 
 an acid one alkaline, it will be sufficient to add the appropriate 
 reagent, until blue litmus-paper, by turning red, indicates acidity ; 
 or red, by becoming blue, shows alkalinity, as the case may be. 
 
 But an exact neutralization, as where an acid or an alkaline 
 liquid is to be rendered exactly neutral, is an operation requiring 
 some circumspection. If, for example, an acid liquid is to be 
 neutralized with ammonia, and the latter liquid is added a few 
 drops at a time, the operation will be very tedious, and will be 
 almost certain to fail, an excess of ammonia will almost certainly 
 be at last introduced. The operator, therefore, feels his way. He 
 pours off a part, say a third, of the acid liquid, and adds boldly 
 enough ammonia to make it quite alkaline. He then adds enough 
 of the remainder of the original liquid to render the mixture 
 decidedly acid. Eepeating this several times, he gets a pretty 
 clear idea of the proportion of ammonia, unknown at first, which 
 is required. Towards the end he diminishes the quantity of each 
 successive addition, till with the last drops, with care, he obtains 
 an exact neutralization. 
 
 There are some cases in which the neutralization is effected 
 by the addition of a substance which, even if added in excess, 
 produces a precipitate, and so leaves the solution neutral, so that 
 the addition of an excess of the precipitant is without much im- 
 portance. An example of this is presented in the neutralization 
 of an acid negative bath with carbonate of sodium. If an excess 
 of carbonate of sodium be added beyond what is necessary to 
 neutralize the free acid, carbonate of silver is formed, and this 
 being but very sparingly soluble in water,i is precipitated. The 
 addition, therefore, of a slight excess of carbonate of sodium does 
 not render the liquid more than very faintly alkaline. 
 
 In other cases, the neutralization is effected by a substance 
 insoluble in the solution after neutralization. This is the simplest 
 case of all : it is sufficient to add the neutralizing substance in 
 excess, and then to remove that excess by filtration. An example 
 of this is afforded in the preparation of a neutral gold toning- 
 bath. The acid solution of perchloride of gold is agitated with 
 excess of precipitated chalk ; as much chalk dissolves as is neces- 
 
 ' Soluble in 31,978 parts of water at 12° C. (Kremers.) 
 
426 
 
 CHEMICAL MANIPULATIONS. 
 
 sary to neutralize the excess of hydrocliloric acicl, and the rest 
 is got rid of by filtration. 
 
 Negative baths requiring neutralization must always be treated 
 with bicarbonate of sodium, never with chalk. 
 
 § 8. — Decantation. 
 
 Fig. 147. In all cases where a precipitate is to subside, that ope- 
 ration takes place best in vessels larger at the bottom 
 than at the top, tolerably well in vessels with straight 
 sides, and very badly in conical vessels, widening 
 towards the top. Those of this last shape should, there- 
 fore, never be employed for decantation. The shape 
 shown in the margin is the proper one. 
 
 g 9. — Cleaning Glass and Porcelain Vessels. 
 
 The bichromate mixture already recommended for cleaning 
 glass plates is most excellent for vessels. It should be pretty 
 strong. A most useful plan is to take cold saturated solution of 
 bichromate of potash, and add about one-eighth its bulk of sul- 
 phuric acid (or one-fourth its bulk of the dilute acid that comes 
 from the drying-box). If the ordinary acid is used, it must be 
 mixed in a porcelain or thin glass vessel ; a bottle will probably 
 break by the sudden heat evolved. For a few moments a corro- 
 sive vapor is thrown off; after cooling, however, this trouble 
 disappears. 
 
 About a quart of this mixture is to be kept on hand and poured 
 into vessels needing cleaning, which it does very effectually. It 
 mav be used again and again until it takes a brownish-violet 
 color, when it should be rejected as spent. 
 
 § 10. — Marking Negatives. 
 
 The photographer will often desire to mark his negatives, es- 
 pecially landscapes, with the name of the place, the lens used, or 
 other note of interest. With portraits there are always places 
 convenient for either marking with black varnish, or marking 
 with a sharp point through a dense place, on portions not to be 
 used in the print. But with a landscape negative, good to the 
 very edge, one is not disposed to sacrifice a place for marking. 
 
 "'V 
 
BENDING glass; 
 
 427 
 
 An excellent plan is to use a writing diamond^ which is quite dif- 
 ferent from a glazier's, and may be had of the philosophical 
 instrument makers. With one of these one may write legibly 
 on the back, over a very thin or a very thick portion, without 
 the marks showing in the print, as is the case when a glazier's 
 diamond is used. These writing diamonds are sparks set in steel 
 tubes much like everpoint pencils. They are mostly made in 
 Amsterdam, the great centre of diamond-cutting. 
 
 § 11.— Bending Glass. 
 
 An ordinary gas flame is sufficient for bending glass tubes up 
 to half-inch diameter. No particular care is necessary except to 
 apply the heat equally by slowly turning the tube round, and to 
 avoid commencing to bend until the glass is quite soft, otherwise 
 the tube will almost certainly break. The black from the flame 
 will easily wipe off. Lay the bent tube on some non-conducting 
 surface to cool slowly. 
 
 § 13. — Piercing Holes in Corks. 
 
 This is best done with borers Fig. 148. 
 
 consisting of tubes of brass or 
 tinned iron. The former are to 
 be had of the instrument makers, 
 in sets of different sizes sliding 
 into each other. The tin tubes 
 can be made by any tinsmith, and 
 should have a cross-piece as a 
 handle across one end. This end- 
 piece has a hole cut into it of the 
 same size as the tube, in order 
 that the pieces of cork punched out may pass freely through. 
 Several sizes will be wanted, say ^% /g, i |, 1 inch. A set 
 of a dozen comprising other intermediate sizes is still more satis- 
 factory. The edges should be occasionally sharpened with a rat- 
 tail file. 
 
428 
 
 CHEMICAL MANIPULATIONS. 
 
 § 13.— Softening Corks. 
 
 All corks are the better for softening. The cork-pressers 
 usually sold are next to worthless. To roll the cork under the 
 foot, with a piece of clean paper above and below it, is not a bad 
 way, but the circular cork-pressers, consisting of a notched wheel 
 and excentric band, are most excellent. A cork should be soft- 
 ened before boring, not after. 
 
 § 14. — Blackening Brass and Wood Surfaces. 
 
 Brass. — Dissolve a drachm of bichloride of platinum in one 
 ounce or one and a half ounce of water, and add a grain of nitrate 
 of silver. Clean and polish the brass surface, warm it, and apply 
 the solution with a small tuft of cotton. Eub till dry, and then 
 finish oft' with a little dust of graphite, avoiding to put on any 
 polish, which would convert the surface into a reflecting one, 
 and enable it, though black, to send back white light. 
 
 Brass surfaces are cleaned for these purposes, either by rubbing 
 with sand and polishing powder, or by applying nitric acid. The 
 fumes that rise should be carefully avoided, an^^ the acid be only 
 left on till a bright surface is obtained. 
 
 Wood. — Take five parts of lampblack, two of finely pulverized 
 gum-arabic, and one of brown sugar ; mix to a thick paste with 
 water, and rub on with a piece of flannel. This is excellent for 
 the insides of cameras and drying-boxes ; it does not come oft" on 
 the fingers. A second coat aids in obtaining a perfect blackness. 
 If it soils the finger when rubbed on it, there was too much 
 lampblack; if there show itself any reflection, there was too little. 
 
 § 15.— Paste. 
 
 Paste is far preferable to mucilage for attaching labels. If 
 well boiled, and then mixed with a little carbolic acid (one 
 drachm to eight or ten ounces of paste), and placed in a bottle 
 with a cork pierced to carry a brush, it will keep in excellent 
 condition for a year or more. When gum mucilage is used, the 
 addition of a very little glycerine will make it hold better, and 
 diminish its tendency to separate or "scroll." 
 
buckle's brush. 
 
 429 
 
 § 16.— Filtration of Viscid Liquids— the Percolator. 
 
 Solutions of gum, of gelatine, and other viscid liquids, are best 
 filtered through a percolator. This is a porcelain 
 funnel without a neck, and pierced with twelve 
 oval openings. It is so set into a jar that all 
 the openings shall be below the upper rim of 
 the jar. A paper or other filter is placed inside. 
 When paper is used, it is best to make the 
 lower part of the paper double, by putting in a 
 second and smaller filter to prevent bursting at 
 the bottom. The facility of filtering through 
 the percolator greatly exceeds that of an ordinary filterin 
 funnel. 
 
 § 17.— Buckle's Brush. 
 
 A string is passed over a tuft of cotton, and the end of the tuft 
 is pulled by the string into a glass tube. This sort of brush has 
 
 Fig. 150. 
 
 been largely used for extending solution of nitrate of silver, and 
 other solutions, over paper. When soiled, it is easy to change 
 the cotton for a fresh piece. 
 
NOTES AND ADDENDA. 
 
 Permanent Silvered Paper (see p. 277). — At the time wlien the article on the 
 author' s new process in the body of this manual went to press, there had been 
 so far time only for testing its keeping qualities about seven weeks. Since then, 
 the paper has been used after keeping it /or over three months, with entire success, 
 and the great value of the -method has been fully confirmed. As already men- 
 tioned, when the paper is long kept, it acquires a slight yellowish tinge on the 
 face, and a light broAvnish coloration on the back ; but as these disappear in 
 the operations of toning and fixing, when carried through precisely in the ordi- 
 nary manner, they have no importance. The prints executed on paper kept 
 over this long period are not to be distinguished from those made immediately 
 after sensitizing. 
 
 The object of this process is not, however, so much to keep paper over these 
 long periods, as to enable those who work on a small, or even on a moderate 
 scale, to avoid the trouble of daily, or almost daily, preparation of small quantities 
 of paper ; even, however, for those who operate more largely the process has its 
 advantages in the avoidance of waste such as constantly results from miscalcula- 
 tion and from unexpected changes of weather, by which vexatious losses are a 
 common experience. It should be remarked that the experiments here described 
 were made during the moderate weather of spring, and that in hot summer 
 weather the time during which the paper can be kept may not reach so great a 
 length. 
 
 The writer desires also again to call attention to the fact, that all paper prepared 
 by any process with the intention of long keeping, should be sensitized with much 
 more careful exclusion of light than is necessary for paper intended for immediate 
 use. Similar care is necessary when the box containing it is opened to take out 
 part of the paper, in order that what remains over shall not have been exposed 
 to light. It is best to do this in the dark room. 
 
 Water-proof Negative Varnish. — Since the remarks on p. 375, &c., went to 
 press, there has been time to extend the observations on the resistance of these 
 varnishes over a longer period. After the plates had been left for three months 
 under water, they were in the following conditions : — 
 
 The bleached lac varnish (No. 1), and one of the orange lac varnishes 
 (No. 3), were in good condition, and exhibited no signs of injury except that each 
 had a small pucker or fold at one corner, so slight as to have no real importance. 
 
 The other orange lac varnish (No. 2) was in an entirely perfect condition. 
 
 Sandarac varnish (No. 4) was badly torn, about one-third the film was off the 
 plate. 
 
 The resisting powers of all these four varnishes cannot be considered as 
 
432 
 
 NOTES AND ADDENDA. 
 
 otliervs'ise than very remarkable, for even the Sandarac stood for a long time, 
 and though inferior to the other three in its resistance to moisture, excelled 
 them in resistance to heat and to mechanical injuries. 
 
 The observation has been often made, that out of a lot of negatives made at 
 the same time, and varnished "with the same varnish, and kept under identical 
 conditions, some will be ruined with honeycomb cracks and others escape, and 
 this fact has occasioned much surprise, and has remained unexplained. The 
 writer is satistied, from his examination, that the explanation is very simple. 
 
 Varnish penetrates but slowly through a collodion film, and if it is poured off 
 too soon, the negative may appear to be all right, and yet the varnish have 
 really no sufBcient hold upon the glass. The importance of this point has, the 
 writer believes, never before been pointed out. In the directions for varnishes 
 given in this manual, it is advised to wait ten or twelve seconds after the plate is 
 completely covered, before commencing to pour oflF. This gives the varnish time 
 to completely saturate the film and to cover the glass under the film with an even 
 stratum. Attention to these directions is important, especially for those who wish 
 to feel that their negatives are safe for a long period of years. 
 
 It seems scarcely necessary to say that if the hyposulphite has not been 
 thoroughly w^ashed out, the dangers to the negative are thereby much aggra- 
 vated. Experience is also constantly accumulating to show that when negatives 
 have been carelessly varnished, or where a poor varnish has been used, any 
 sudden change of hygrometric condition may cover the negative with honey- 
 comb cracks. A case has been cited in which a negative in good condition was 
 taken from a warm, dry room and carried for half an hour through a damp 
 Jitmosphere, at the end of which time it was covered with cracks. With any of 
 the above four varnishes properly applied, it is safe to say that such a trial might 
 have been repeated a score or perhaps a hundred times without evil results. 
 
 When this trouble occurs, the writer would advise to revarnish with a thin 
 spirit varnish, leaving it in for twenty or thirty seconds before commencing to 
 pour off. In his own work he has never, met with a single case of cracking. 
 
 Reducing Residues. — Lately the plan of precipitating silver as oxalate and 
 reducing by heat, has been brought forward again. The idea is ingenious, and 
 as oxalate of silver is easily resolved into metallic silver by the simple application 
 of heat, the method would be convenient enough, were it not so dangerous. The 
 oxalate of silver, when heated, is liable to explode with tremendous violence ; an 
 accident of this sort happened some years ago in the laboratoiy of M. Wurtz, in 
 Paris. 
 
 New Developer. — It is stated that the action of pyrogallic acid as a developer is 
 greatly heightened by the addition of sulphate of copper. A three-grain solution 
 of pyrogallic acid is mixed with one-third of its bulk of a cold saturated solution 
 of sulphate of copper just before throwing it over the plate. 
 
 X 
 
INDEX. 
 
 A. 
 
 Aberration, 58, 59 
 Accessories, 203 
 
 arrangement of, 189 
 Acceleration of exposures, 220 
 Acetate toning, 290 
 Adapting flanges, 224 
 Admission, centre of, 69 
 After-intensification, 171 
 Alabastrine positives, 189 
 Albertype, 394 
 
 Albumen positives on glass, by de- 
 velopment, 387 
 
 by sun printing, 391 
 Albumenizing glass, 155 
 
 paper, 270 
 Alcohol, influence of, 131 
 Alkaline carbonate toning, 289 
 
 development, 358 
 Alum in the printing bath, 274 
 Ambrotypes, 42, 188 
 Aniline process, 396 
 Animals photographed, 349 
 Annatto for backing, 356 
 Anthony, H. T., alum in printing 
 bath, 274 
 
 fuming, 279 
 Aplanatic lens, 10, 81 
 Apparent size of objects, 106 
 Architectural photography, 208 
 Arrangement of accessories, 191 
 Arrowroot paper, 272 
 Astigmation, 61 
 Atmospheric effect, 244 
 
 B. 
 
 canopy, 
 conical. 
 
 Backgrounds — 
 
 crayon, 208 
 
 inclined, 204 
 
 pictorial, 208 
 
 rotating, 206 
 Backing dry plates, 356 
 Balance, 421 
 Bar frame, 45 
 Barrel distortion, 65 
 Bases in collodion, 134 
 Bath, fixing, 46 
 
 negative, 19, 155 
 
 positive, 44 
 
 printing, 273, 274 
 
 swinging, 158 * 
 
 toning, 46 
 Bending glass, 427 
 Benzoate toning, 290 
 Berlin portraits, 194, 283 
 Blackening brass and wood sur 
 
 faces, 428 
 Blistering in dry plates, 352 
 
 silver prints, 341 
 Blotting off silvered paper, 274 
 Blue stippling, 121 
 Blurring, 27, 315 
 Brass surfaces, to blacken, 428 
 Brilliancy, how obtained, 231 
 Bromide of ammonium, 134 
 
 of cadmium, 136 
 
 of lithium, 135 
 
 of potassium, 134 
 
 of sodium, 135 
 Bromides in collodion, 137, 168 
 Buckle's brush, 429 
 
 C. 
 
 la 
 
 203 
 204 
 205 
 
 Calcio-chloride toning, 289 
 Camera, landscape, 147 
 levelling the, 147 
 
434 
 
 INDEX. 
 
 Camera — 
 
 red lining to, 221 
 reversing of, 148 
 selection of, 12, 147, 221 
 solar, printing by, 268 
 tested, 13 
 
 for transparencies and opalo- 
 
 types, 384, 385 
 Van Monckhoven's, 266 
 Woodward's solar, 266 
 Canopy background, 204 
 Carbon printing, 298, 402 
 
 on glass, 403 
 Carbonate of silver, printing on, 
 
 282 
 Carriers, 14 
 
 Centre, admission and emission, 69 
 
 optical, 68 
 Chemicals, 15 
 
 in fault, 304 
 Chemical focus, 95 
 Chloride of iron, printing witlf 398 
 
 of silver, development on, 160 
 Chlorine, intensifying by, 172 
 Chromatic aberration, 59 
 Cleaning, 35 
 
 glass, 426 
 Cleanliness, 17 
 Clouds, 219, 239 
 
 printed in, 184 
 
 reflected, 185 
 Clove process, 373 
 Coating the plate, 23 
 Coffee process, 371 
 Collo-developers, 164 
 Collodio-bromide process, 365 
 Collodio-chloride process — 
 
 failures in, 242 
 
 on glass, 388 
 
 on paper, 391 
 Collodion, 131, 231, 305 
 
 decanting, 145 
 
 dry plate, 365 
 
 filtering, 146, 367 
 
 formulas for, 142, 143 
 
 injurious to health, 416 
 
 keeping of, 146 
 
 salting, 132, 134 
 
 thinning, 25 
 Colors obtained in photography, 
 414 
 
 Coma, 63 
 Comets, 324 
 
 Combination prints, 182 
 Composition, 234 
 Conical background, 204 
 Conjugate foci, 75 
 Contact printing on glass, 386 
 Contrast, causes of, 165, 313 
 
 in composition, 243 
 Contrasts, 213 
 Copying, 251 
 
 camera, 253, 255 
 
 cone, 253 
 Corks, to pierce, 427 
 
 to soften, 427 
 Corrosive sublimate for intensify- 
 ing, 172 
 
 Corrosive sublimate, poisonous ef- 
 fects of, 417 
 Cotton, negative, 126 
 Crapy lines, 310 
 Crayon portraits, 194 
 Cross-lights, 193 
 Creamy negatives, 161 
 Curvature of the field, 63 
 Cut-off, 15 
 
 Cyanide for intensifying, 173 
 poisonous nature of, 416 
 
 D. 
 
 Daguerreotypes, copying of, 254 
 Dark room, 109 
 
 arrangement of. 111 
 
 temperature, 113 
 Decantation, 426 
 Defects in the image, 313 
 Developers, CoUo-, 164 
 
 strong and weak, 162 
 
 sugar, 164 
 Developing boxes, 346 
 Development, 30, 132, 162, 305 
 
 aids to, 162, 163 
 
 alkaline, 358 
 
 of dry plates, 358 
 
 management of, 165, 166, 198„ 
 200, 214, 318, 432 
 
 on paper, 260 
 Diagonal line, the, 236 
 Diaphragms, 64, 92 
 
 inclined, 66, 219 
 
INDEX. 
 
 435 
 
 DifBculties in portraiture, 198 
 Dippers, 25 
 Direction, line of, 234 
 Dispersion, 54 
 
 Distance in landscape composition, 
 
 238 
 
 Distance of position, 191 
 
 Distortion, 65 
 
 Double portraits, 181 
 
 Drawings, copying of, 251 
 
 Dress, effect of, 196 
 
 Dry plate photography, 351, 365 
 
 plates, to dry, 353 
 backing of, 356 
 development of, 358 
 failures in, 360 
 Drying box, the author's, 354 
 Drying dead, 330 
 Drying plates by heat, 353 
 
 spontaneously, 356 
 
 by sulphuric acid, 354 
 Dust, 160 
 
 E. 
 
 Edging plates, 352 ' 
 Emission, centre of, 69 
 Enamels burned in, 392 
 Encaustic paste, 300 
 Engravings, copying of, 251 
 Enlargements, 177, 265 
 Equivalent focus, 70 
 Ether, influence of, 131 
 
 injurious effects of, 415 
 Evaporating, 423 
 Exposure, 30, 195 
 
 acceleration of, 220 
 
 of dry plates, 361, 363 
 
 P. 
 
 Failures in dry plate work, 360 
 in photographic operations, 301 
 in silver printing, 337 
 in varnishing, 40, 330 
 
 Faults in spherical lenses, 58 
 
 Feathery markings, 330 
 
 Fennemore's glass room, 118 
 
 Ferrotypes, 42, 188 
 
 Field work, 222 
 
 Figure, relative size of, 192 
 
 Figures in landscapes, 241 
 Filtering collodion, 146, 367 
 Filtration, 423 
 Fixing the print, 293 
 Fixing bath, 46 
 Flanges, 96, 224 
 Flare, 91 
 
 Flat pictures avoided, 199 
 Focal lengths of lenses, 66 
 
 determined, 70, 72, 73, 74 
 Foci, conjugate, 75 
 Focus, chemical, 95 
 
 equivalent or absolute, 70 
 Focussing, 28, 224 
 Fogging, 302 
 
 of dry plates, 362 
 
 sources of, 112, 113 
 Foliage, 219 
 
 Foreground in landscapes, 219, 237 
 Fuming, 279 
 Fusing residues, 424 
 
 G. 
 
 Gallate of lead, 261 
 Ghost in the camera, 91 
 Ghosts, 181 
 
 Glass, cleaning of, 17, 155 
 
 for glass house, 115 
 
 ground, 48, 121 
 
 preparing of, 155 
 
 selection of, 154 
 Glass room, 115 
 Globe lens, 85 
 
 Glycerine and honey process, 350 
 Gold, chloride of, a poison, 418 
 Gold residues saved, 381 
 Groups, 120, 192, 248 
 Granularity in negatives, 310 
 Green color, its actinic value, 139 
 Ground glass, printing under, 180, 
 283 
 
 Gum in dry plate work, 365 
 Gum-gallic process, 374 
 Gurney's glass room, 119 
 
 H. 
 
 Halation, 315 
 
 Half-tone, how obtained, 167, 315 
 
436 
 
 INDEX. 
 
 Harsh pictures avoided, 199 
 Health, 415 
 
 Heat in development, 359 
 Heating, 422 
 Heliochromy, 414 
 Holders, pneumatic, 159, 160 
 Horizon in landscapes, 242 
 Hyposulphite of sodium, testing 
 for, 297 
 
 I. 
 
 Illumination, 201 
 Image defective, 313 
 
 nature of, 97 
 Inclined backgrounds, 203, 204 
 Index of refraction, 54 
 Instantaneous photography, 347 
 Intensifying negatives, 171, 172, 173 
 Intensity, falling off of, at edges, 65 
 Iodides in collodion, 137 
 Iodine for intensifying, 171 
 Irregularity of film, 310 
 Iron, printing with salts of, 397 
 Ivory, miniature effects on, 390 
 
 J. 
 
 Jamin lenses, 80 
 
 L. 
 
 Landscape lenses, 9, 91 
 
 photography, 11, 51, 208, 224 
 Legray's process, 264 
 Lenses, aplanatic, 10, 81 
 
 Blunt' s hemispherical, 88 
 
 care of, 96 
 
 centering of, 93 
 
 comparison of, 92 
 
 focal lengths of, 66 
 
 general remarks on, 90 
 
 globe. So 
 
 images of, 97 
 
 Jamin, 80 
 
 nature of, 56 
 
 orthoscopic, 87 
 
 Pantascope, 88 
 
 Lenses — 
 
 portrait, 79 
 
 quickness of, 95 
 
 rapid rectilinear, 9, 81 
 
 rectilinear, 88 
 
 Ross's doublet, 87 
 
 selection of, 9, 93 
 
 triplet, 83 
 
 view, 9, 78 
 
 Zentmayer, 86 
 Levelling the camera, 29, 209 
 Liesegang, toning formula, 291 
 Light, exclusion from lens, 120 
 
 influence of, 250 
 
 insufficient, 202 
 
 management of, 193, 200 
 
 regulation of, 109, 124 
 Line engravings, copying of, 251 
 Lines in the negative, 326 
 Lithographs, copying of, 251 
 Local redevelopment, 169 
 
 reduction of negatives, 176 
 Loescher & Petzch's glass room, 
 119 
 
 Lumps in the film, 311 
 M. 
 
 Magnesium light, negatives by, 185 
 Management of light, 193 
 Manipulations, 420 
 in the field, 222 
 Marbled stains, 327 
 Materials for landscape work, 221 
 Measuring, 422 
 Meicke's experiments, 275 
 Melainotypes, 189 
 Mercury for intensifying, 172, 174 
 Metrical weights, 421 
 Mezzotint prints, 194, 283 
 Mezzotints, copying of, 251 
 Microphotography, 258 
 Microscopic photography, 259 
 Miniature effects on ivory, 390 
 Minim glass, 422 
 Miscellaneous faults, 333 
 Moonlight effects, 181 
 Morphia process, 374 
 Mottling in the negative, 312 
 J^jjnting prints, 299 
 
INDEX. 
 
 437 
 
 N. 
 
 Negative, the, 147, 158 
 artifices with, 181 
 bath, 19, 155, 304 
 development on paper, 263 
 drying of, 37 
 for enlargement, 177 
 influences on, 167 
 intensifying of, 171, 172, 173, 174 
 by magnesium light, 185 
 marking of, 426 
 paper pasted on, 180 
 printing of, 280 
 
 reducing of over-developed, 176 
 locally, 176 
 
 retouching, 178 
 
 reversed, 400 
 
 scarlet, 173 
 
 storing of, 186 
 
 thin, how printed, 281 
 
 varnished, to intensify, 175 
 
 varnishing of, 37, 375, 431 
 
 washing of, 36 
 Neutralization, 425 
 Nitrate of silver, fused, 157, 305 
 Nitric acid, poisonous effects of, 
 418 
 
 Nitroglucose, 268 
 
 Notman, toning formula, 290 
 
 O. 
 
 Objectives, 9 
 
 Oil paintings, copying of, 251 
 Opalotypes, 383 
 Optical centre, 68 
 Orthoscopic lens, 87 
 Out-door photography, 344 
 Oxalotype, 398 
 Oyster-shell markings, 327 
 
 Pads, 45 
 
 Pad fuming, 279 
 
 Panoramic'camera, 88 
 
 Paper, albumenizing, 270 
 arrowroot, 272 
 enlargements, 265 
 
 Paper — 
 
 negatives, 263 
 
 for positives, 269 
 
 sensitizing of, 273 
 Papyroxyline, Liesegang's, 129 
 Paraffining, 264 
 Paste, 428 
 
 encaustic, 300 
 Pencil drawings, copying of, 251 
 Percolator, 429 
 
 Permanence of silver prints, 300 
 Permanganate of potassium, 174 
 Perspective, atmospheric, 244 
 
 incorrect, 103 
 
 photographic, 97 
 Photo gal vanography, 395 
 Photography, architectural, 208 
 
 landscape, 208 
 Photographs, copying of, 254 
 Photolithography, 394 
 Pinholes, 321 
 Plans, copying of, 255 
 Plate boxes, 187 
 Plates, preserved, 350 
 
 sensitive, keeping of, 344 
 Pneumatic holders, 159, 160 
 Poisons, 415 
 Portrait lenses, 10, 79 
 Portraiture, 90, 106, 190, 247 
 Posing the sitter, 197 
 Position of background, 206 
 
 in landscape work, 240 
 Positive bath, 44, 273 
 Positive paper, new method of pre- 
 paring a paper that will keep, 
 277,431 
 
 paper, washed, 275 
 
 printing, 269, 280 
 Positives, alabastrine, 189 
 Pouncy's carbon process, 402 
 Pouring, 424 
 
 Preservatives for dry plates- 
 clove, 373 
 cochineal, 370 
 coffee, 371 
 gum gallic, 374 
 rnorphia, 374 
 pyrogallic, 309 
 resin, 373 
 
 tannin, 371 ♦ 
 
 .:.,,,.J;ea, 371 
 
438 
 
 INDEX. 
 
 Pressure frame, 283 
 Printing, 280, 284 
 Printing bath, 273 
 
 new, for permanent paper, 
 277, 431 
 Printing in the camera, 384 
 Printing in clouds, 184 
 Printing, failures in, 336 
 frames, 45, 283 
 
 on glass by development, 383. 
 
 silver, 269 
 Prints, combination, 182 
 
 finishing the, 298 
 
 mounting of, 299 
 
 rolling the, 300 
 
 silver, permanence of, 300 
 
 tested if well washed, 297 
 Projection, panoramic, 108 
 
 plane, 106 
 Pyrogallic preservative for dry 
 
 plates, 369 
 Pyroxyline, 126 
 
 alcoholic, 130 
 
 influence of, 130 
 
 treatment with alkali, 132 
 
 variable character of, 168 
 
 Rapid rectilinear lens, 9, 81 
 Red lining to camera, 220 
 Redevelopment, 32 
 
 local, 169 
 Reducing over-developed nega- 
 tives, 176 
 Reflectors, 124 
 Reflection, 52 
 Refraction, 52 
 
 Relievo process, Woodbury's, 396 
 Rembrandt effects, 194 
 Remedies for poisoning, 418 
 Repeating back, 191 
 Repetition in composition, 243 
 Residues, treatment of, 379, 432 
 Resin process, 373 
 Retouching the negative, 178 
 Retouching, use of resin in, 379 
 Revarnishing, how to do, 41 
 Reversed negatives, 400 
 Ridge roof, 115 
 
 inclination of, 117 
 
 Rolling prints, 300 
 Ross's doublet lens, 87 
 Rotating background, 206 
 Rubber varnish, 352 
 Rules, general, 47 
 
 S. 
 
 Salomon's glass room, 120 
 Sarony's glass room, 119 
 Scarlet negatives, 173 
 Schlippe's salt, 173 
 Seasons, influence on landscape 
 
 work, 227 
 Sensitizing paper, 44, 273 
 
 new method, 277, 431 
 Serum of milk, 264 
 Shade printing, 280 
 Shadows, 216 
 Sharpness, want of, 317 
 Shepard, Dr., toning formula, 291 
 Silver, bromide of, 410 
 
 chloride of, 406 
 
 iodide of, 406 
 
 prints, permanence of, 300 
 
 pure, value of, 157 
 Sizing the film, 177 
 Skies, management of, 210, 219, 230 
 Sky shade, 219 
 Slides, 221 
 Sliding front, 29 
 Slipping of film, 317 
 Smeariness of film, 320 
 Snow landscapes, 215 
 Softness, 231 
 
 how obtained, 165 
 Solar cameras, 266 
 Sore hands, to heal, 37 
 Specks in the film, 160 
 Spherical aberration, 58 
 Splitting of film, 316 
 Spots, hazy, 323 
 
 opaque, 324 
 
 transparent, 321 
 Stains, 14, 43, 327 
 Stand, 15 
 
 Steinheil aplanatic, 10, 81 
 Stereopticon slides, 386 
 Stereoscope, 256 
 Storing negatives, 186 
 Stopping out, 180 
 
INDEX. 
 
 439 
 
 Stops, 92, 211, 223 
 Streaks in the negative, 31, 320 
 Sugar in development, 165 
 Sulphide of potassium for intensi- 
 fying, 172 
 Sun printing, 280 
 Sunlight in glass room, 122 
 Surface stains, 327 
 Swan's carbon process, 399 
 Swing-back, 148, 223, 225 
 
 use in landscape work, 151 
 
 portraiture, 130 
 Swinging bath, 158 
 
 lens, 131 
 
 Syrup for keeping negatives moist, 
 
 347 
 
 T. 
 
 Tank, washing, 295 
 
 Tannin process, 371 
 
 Tea process, 371 
 
 Temperature of glass room, 123 
 
 Tents, 346 
 
 Theoretical considerations, 404 
 Thinness of film, 310 
 Tissue, carbon, 399 
 Toning, 232, 288 
 bath, 46 
 
 formulae, 289, 290, 291 
 and fixing baths, 292 
 
 Top-light, excess of, 201 
 
 Transparencies, 386 
 
 Triplet lens, 83 
 
 Tripod, how made, 221 
 chemical, 423 
 
 Tunnel system, 124 
 
 Two-bath system, 155 
 
 U. 
 
 Uranium intensifying, 174 
 Unsatisfactory results in portrait- 
 ure, 200 
 
 V. 
 
 Varnish, 37 
 
 effects of too thin, 41, 432 
 
 Varnish — 
 
 India-rubber, 352 
 
 negative, 375, 431 
 Varnishing, 37, 38,431. 
 
 failures in, 40, 41, 330, 432 
 Veiling, 302 
 
 Velvet drapery, 194, 197 
 Ventilation, 28, 110, 121 
 
 box. 111 
 View lens, 9, 78 
 Vignetting with cotton, 286 
 
 by development, 287 
 
 with a frame, 285 
 
 glasses, 285 
 
 with a lens, 287 
 
 on the negative, 287 
 
 with paper, 286 
 
 by a screen, 288 
 Viscid liquids, to filter, 429 
 
 W. 
 
 Washed sensitive paper, 275 
 Washing the negative, 36, 169 
 
 prints, 46, 295 
 Washing tank, 295 
 Wax-paper process, 264 
 Weakening of negatives in fixing, 
 330 
 
 Weather, indications of, 229 
 Weigliing, 420 
 Weiglits, 421 
 
 Wenderoth's glass room, 118 
 Willis's aniline process, 396 
 Wind, the, 226, 229 
 Wood-cuts, copying of, 251 
 Wood surfaces, to blacken, 428 
 Woodbury's relievo process, 396 
 Woodward, Dr., microscopic pho- 
 tography, 259 
 Woodward's camera, 266 
 
 Xyloidine, 130 
 
 intmayer lens, 86 
 
SUPPLEMENT A^o. 2. 
 
 1876. 
 
 I.— PERMANENT SENSITIZED PAPER. 
 
 During the last three years I have devoted much attention to finding a 
 method of preparing sensitive paper which should be capable of being kept for 
 a long period of time without losing the power of affording good prints. I have 
 I believe completely succeeded, having now in my hands paper which was pre- 
 pared in November, 1873 and which can still be used for printing. Other speci- 
 mens, also in condition, were prepared in March, 1874. In the course of this 
 investigation I have also learned that very much depends on the mode of keeping 
 Not that it is necessary to use chloride of calcium boxes, or any troublesome 
 method of preservation, but that certain causes that have not apparently been 
 hitherto suspected, aid greatly in the rapid deterioration of silvered paper. 
 
 The spontaneous darkening of sensitized paper depends upon the reduction of 
 the silver salts contained in it. Therefore to aid in its keeping it seemed desirable 
 to place in contact with the silver salt, substances capable of affording either 
 oxygen or chlorine. One substance there was which offered both these elements 
 This w^s chlorate of potash, ^ substance which I believe has been suggested for 
 use in the interval since I commenced experimenting with it but had not been 
 before. Neither has the proper method of using it to the best advantage been 
 indicated. Other substances have proved themselves useful, viz ; lactic acid and 
 nitrate of uranium. 
 
 The different formulas from which satisfactory results were obtained were as 
 follows : 
 
 {Formula No. 1 .) 
 Nitrate of silver, - . 40 grains. 
 
 Chlorate of potash, - - - 20 " 
 
 Dilute lactic acid - - 1 drachm. 
 
 ■ Water, - . . .1 ounce. 
 
 The "dilute lactic acid" is that which is met with in commerce under that 
 name and at moderate prices. 
 
 This formula was used in November, 1873 and the paper then prepared was 
 found in April, 1876 to be in condition for use. Though not perfectly white, its 
 color was not more than what disappears of itself in the fixing bath. I feel no 
 doubt that had this paper been preserved under the conditions which will 
 
2 
 
 presently be described, and which I had not made out at the time that this paper 
 was prepared, it would at the end of 30 months have been quite white and pure 
 
 [Formula No. 2.) 
 Nitrate of silver, - - - 45 grains. 
 
 Chlorate of potash, - - 20 " 
 
 Dilute lactic acid, - - - 1 drachm. 
 
 Nitrate of uranium, . - 16 grains. 
 
 Paper after this formula was prepared in March ISH. In April, 1876, 25 months 
 after preparation, it was found to be in good condition. I think the nitrate of 
 uranium has perhaps some tendency to aid in the keeping qualities. It is how- 
 ever by no means an essential, as formula No. 1 sufficiently proves. 
 
 It seems unnecessary to remark that both this paper and the preceding are 
 intended to be fumed but cannot be expected to keep after fuming. 
 
 METHOD OF PRESERVATION. 
 
 In my experiments I was at first under the impression that in a tin roller or 
 cylindrical case with a tightly fitting cap sliding several inches over it, there 
 was a complete exclusion of light. Experience showed this not to be the 
 case. Sensitized paper placed inside of such a case and additionally protected 
 by wrapping, kept better than similar paper lying loose in the case. This fact 
 has proved to be very important, and a disregard of it may prevent the keeping 
 of paper, otherwise capable of very long preservation. 
 
 Another remarkable observation was the following. The dark yellow-brown 
 paper used for making "buff" envelopes seemed by reason of its color par- 
 ticularly well suited for covering rolls of sensitive paper. It proved on the 
 contrary to have a distinctly injurious effect. Thus when a sheet of sensitive 
 paper was rolled up around itself, and then covered with this buff envelope 
 paper, all the parts of the sensitive paper in contact with the buff, darkened 
 much more rapidly than the portions which had a thickness of the sensitive 
 paper between them and the buff. This action showed itself first on the part 
 in contact with buff, that is the back of the sensitive paper changed first, and 
 gradually this action penetrated through to the face. 
 
 I therefore recommend to proceed as follows. Take a wooden roller not over 
 an inch in diameter, and dry it thoroughly. Place two sheets of the sensitive 
 paper face to face, roll them tightly around the roller, and continue with more 
 sheets until a stout roll is made. It is a great mistake to separate the sheets 
 under the supposition that this aids, on the contrary, they help to make each 
 other keep. It is therefore better to make one large roll than many small 
 ones. 
 
 After finishing the rolling, draw the roller out, and stuff the open space with 
 clean dry raw cotton. The object of this is to prevent all circulation of air, 
 air brings with it dampness; which is unfavorable, of course. But besides 
 dampness, there is a certain quality in the air which tfends to deteriorate the 
 paper. This quality is expended in its action : the more the air changes the 
 oftener will this action be renewed. . . 
 
3 
 
 The next step is to cover the roll of sensitized paper with clean paper. But 
 this cover must not only be clean, but pui-e, paper, and therefore the best way 
 in my opinion, is to use plain photographic paper. Thus prepared and covered 
 with an outer roll of opaque hardware paper, the roll may be laid in a perfectly 
 dark and tight drawer. 
 
 If however it is intended to make the paper keep as long as possible, it will 
 be well to enclose the roll in a sheet of paper saturated with solution of rubber 
 and pasted down, and rapidly dried. This should then be placed in a tin 
 roller, and the roller in a dark closet. 
 
 It should never be forgotten that paper which is intended to be kept for 
 some time will need to be sensitized with a much completer exclusion of light 
 than ordinary sensitized paper. The slight influence of weak light admitted 
 during sensitizing will be entirely without effect when the paper is immediately 
 used. But if the paper is to be kept for some time, this slight impression may 
 be the means of completely destroying it. I therefore advise to take the same 
 care as in preparing paper for positive development. 
 
 The method of using nitrate of cobalt given to the first supplement, for 
 obtaining fine sepia tones, cannot be combined with this. Paper containing 
 nitrate of cobalt will not keep for any length of time, even by addition of 
 chlorate of potash. 
 
 I entertain no doubt that paper prepared by either of these formulas, and 
 especially the first, might be advantageouslj- manufactured for sale. 
 
 II.— DRY PLATE WORK. 
 
 CHLORIODOBROMIDE EMULSION PROCESS. 
 
 In the first supplement to this Manual, are full details of the method of preparing 
 and using this emulsion. It remains here to describe an additional improvement 
 made to the process. 
 
 It is a well known fact that wet plates will under trjdng circumstances, 
 suffer from blurring. Landscapes in which very dark objects are thrown against 
 verj' light ones, or interiors with brightly lighted windows, are exposed to this 
 defect. Emulsion plates made with the chlorobromide process are much more 
 exposed to this defect, and from much slighter causes than wet ones and 
 therefore an application to the back of the plate is much more necessary than 
 with wet plates. 
 
 By the introduction of an iodide into the emulsions, as I have already described 
 in the first supplement, I have succeeded in bringing the emulsion plates to 
 approximately the same level as the wet. But even wet plates when used for 
 landscapes and interiors, are the better for protection from behind, and I have 
 during the winter of 1875-76 devoted a great deal of time to studying the best 
 means of obtaining absolute protection from' .blurring. I believe that I may 
 claim to thave been the first, now many years since, to propose the method of 
 coloring the film to accomplish this result. The difiiculty lies in this, that most 
 coloring matters applied to the film, distinctly diminish the sensitiveness. 
 
4 
 
 I have lately compared all the coloring matters that have been suggested for 
 use, and also very many others, and find scarlet coralline to be the best.* 
 Coralline has been before tried, but always VFith a diminution of sensitiveness. 
 In fact, it has been generally understood that all coloring of the film entailed 
 a loss of sensitiveness, and I notice that the Liverpool Dry Plate Company, with 
 commendable frankness state in their advertisements that the colored plates, 
 whilst free from blurring, are less sensitive. I have been so fortunate as to find 
 the method of using coralline which avoids this difficulty wholly. A plate 
 covered one-half with the colored film and the other half with the uncolored, 
 and 'exposed under a stereoscopic negative will give transparencies of exactly 
 equal strength. The most careful comparison fails to detect any inferiority of 
 sensitiveness, even with exposures made purposely so short as to tax the powers 
 of the film to the uttermost. 
 
 This result is accomplished also in the simplest manner. It is only necessary 
 to add the alcoholic solution of coralline to the finished emulsion and employ it 
 precisely as usual. Neither is there any necessity for special means of removing 
 the color from the plate; this I should consider a fatal objection. Coralline has 
 the inestimable advantage that it disappears of itself in the operations of devel- 
 oping, fixing and washing. 
 
 The best scarlet coralline (the yellow coralline sometimes called aurine ig 
 entirely unsuitable) is to be dissolved in alcohol 48 grains to the ounce. The 
 solution takes place rather slowly and several days should be allowed with occa- 
 sional shaking, neither is it ever entirely complete, a small amount of dark resi- 
 due always remains, even after standing for months. To each ounce of finished 
 emulsion, from 6 to 10 minims of this coralline solution is to be added and well 
 shaken. The emulsion is then ready for immediate use. It will not have the 
 strong red color of coralline, but a buff or salmon shade. 
 
 I cannot le.xve the subject of emulsion without again adverting to the fact that 
 without a pyroxyline of the right character it is a mere loss of time to attempt 
 to obtain a good emulsion, and that nine-tenths of the failures that occur, are 
 attributable to this cause. 
 
 *In this connection the author desires strictly to limit his own claims. Having been 
 elsewhere able to prove that the idea of applying color to the film originated with him, he 
 makes no claim to having been the first to suggest the use of this particular color. But he 
 believes that he has been the first to find a method by which it may be employed without a 
 loss of sensitiveness.