THE W. K. BURTON, C.E., Professor of Sanitary Engineering Imperial University of Japan, Author of "Modern Photography" "Photographic Printing, ' ' Etc. , ANDREW PRINGLE, President of the Photographic Convention of the United Kingdom, 1889, Fellow of the Royal Microscopical Society, Etc. NEW YORK: THE SCOVILL & ADAMS COMPANY, 423 BROOM.E STREET. Copyright, 1889, THE SCOVILL & ADAMS COMPANY. TR [45 PREFACE. OF the two writers, both have zealously followed photog- raphy as something more than a mere amusement, for a con- siderable number of years. One of the writers has studied the science from a theoretical and experimental point, while the other writer's attention has been almost entirely directed to the production of practical results by the processes known, and by each process as it has been given to the world. As joint authors, therefore, we trust that our joint work may be acceptable to the photographic public ; not as replacing, or superior to, other works, but rather as filling a place not occu- pied by any other work. The chief claim made for our work is that every word we have written in it refers to subjects with which we are personally and intimately acquainted; not a direction nor a formula is given on trust, every one has been successfully used by one or other of us, in most cases we have both used the formulae found in this book. At first our MSS. extended to a very considerable length, and treated photography completely as theoretical, practical, and artistic ; but circumstances caused us to abridge our work, and to produce a book less complete, and, perhaps, less inter- esting, but, as we hope, more generally useful, not only to ama- teurs and beginners, but also to those who desire authentic in- structions and formula for every -day work. Such instructions and formulae, tested carefully by ourselves, and likely to be useful to our readers, it has been our ambition to give the pub- lic. Whether or not our aspirations have been fulfilled, each member of the public may judge for himself, by application (suitably accompanied) to the publishers of our little book ! W. K B. A. P. 861635 CONTENTS. PAGE PREFACE, 3 CHAPTER 1. INTRODUCTORY AND HISTORICAL, - 7 CHAPTER II. THE THEORY OF PHOTOGRAPHY, - - 12 CHAPTER III. APPARATUS, - 16 CHAPTER IV. THE DARK-ROOM, - - 80 CHAPTER V. "NEGATIVE" AND "POSITIVE," - - 34 CHAPTER VI. THE WET COLLODION PROCESS, - - > 36 CHAPTER VII. A DRY COLLODION PROCESS, - - 46 CHAPTER VIII. GELATINE EMULSION PROCESSES, PRELIMINARY, - - 50 CHAPTER IX. GELATINE-BROMIDE EMULSION, - - 55 CHAPTER X. GELATINE-BROMIDE EMULSION, BY THE AMMONIO-NITRATE PROCESS, AND PRECIPITATION BY ALCOHOL. CENTRIFUGAL SEPARATION, 60 CHAPTER XI. COATING PLATES WITH GELATINE-BROMIDE EMULSION, DRYING, ETC., 69 CHAPTER XII. THE CAMERA IN THE FIELD, - - 73 CHAPTER XIII. EXPOSURE AND DEVELOPMENT GENERALLY TREATED, - - - 81 6 CONTENTS. CHAPTER XIV. PAGE DEVELOPMENT OF GELATINE-BROMIDE PLATES, CHAPTER XV. GELATINE-BROMIDE PI.ATKS FIXING, INTENSIFICATION, REDUCTION, ETC., - 96 CHAPTER XVI. DEFECTS IN GELATINE-BROMIDE NEGATIVES, - CHAPTER XVII. PAPER NEGATIVES AND STRIPPING FILMS, - - 104 CHAPTER XVIII. "COLOR CORRECT" OR "ORTHOCHROMATIC" PHOTOGRAPHY, - 110 CHAPTER XIX. STEREOSCOPIC PHOTOGRAPHY, - 115 CHAPTER XX. PART II. PRINTING PROCESSES, PRELIMINARY, - - 118 CHAPTER XXL PRINTING ON ALBUMENIZED PAPER WITH SILVER CHLORIDE. - 121 CHAPTER XXII. PREPARATION OF NEGATIVES FOR PRINTING, COMBINATION PRINTING, |S3 VIGNETTING, - - 188 CHAPTER XXIII. PRINTING ON PLAIN SALTED PAPER, - 133 CHAPTER XXIV. GELATINE-CHLORIDE PAPER FOR PRINTING-OUT, - 140 CHAPTER XXV. CONTACT PRINTING ON GELATINE BROMIDE PAPER, - - 142 CHAPTER XXVI. RAPID PRINTING PAPER, . 148 CHAPTER XXVII. PLANTINOTYPE, OR PRINTING IN PLATINUM, - 150 CHAPTER XXVIII. THE "CARBON " PROCESS, OR "PIGMENT PRINTING. " - 156 CHAPTER XXIX. POSITIVES AND NEGATIVES BY ENLARGEMENTS, - - 164 CHAPTER XXX. LANTERN-SLIDES, - ------ 171 RESIDUES, CHAPTER XXXI. 182 The Processes of Pure Photography. CHAPTER I. INTRODUCTORY AND HISTORICAL. PHOTOGRAPHY is one of the greatest facts of the present day. Its influence is of very wide scope, because it is not only an almost infallible means of recording facts, but also a simple means whereby the artistically inclined may, to a cer- tain extent, find expression for their fancy. Photography not only affords us evidence of what we, and nature, appear, but enables us to depict, within limits, what we, and the rest of nature, might be. Briefly, photography is at once a science and an art. Without a certain knowledge of the science, we can- not produce any effect at all, artistic or otherwise ; but we may master the science, stop there, and still have in our hands a most potent agent for depicting, graphically, facts. Again, if our ultimate object be to use photography as an art, we must master the science, first of all, that we may be able to produce a graphic result, and next, that we may control our result, so that our scientific means may lend themselves to our artistic aspirations; and the more control over, and facility in, our scientific operations we have, the more fully shall we be able to give our minds to the realization of our artistic conceptions. In the same way, if our ultimate object be purely scientific, if our sole ambition is to give true photographic copies of what 8 THE PROCESSES OF PUKE PHOTOGRAPHY. we see, especially if we see it under difficulties, such as those of great magnification, or reduction in size, we must still master our photographic science, so that the combined difficulties of seeing and depicting what we see may not overpower and conquer us, In this book we do not propose to deal with art, nor with any science except purely photographic science ; and our aim is to lay bare, as clearly as space will permit us, the principles regulating, and the practices most suitable for, successful photography. We are prevented by circumstances from fully entering into the theories, or touching on more than very few of the practices which control successful photography, but it is our ambition to so lay down the practice that close elucida- tion of the theories will not be essential to the intelligent reader, or, at least, so that the reader may, while acquiring the power of producing photographs, be only tickled, and not driven to study the theories. On the above basis it is clearly unnecessary for us to give more than a cursory resume of the chief results that mark the history of photography. The great landmarks are those fol- lowing. We can attach no date to the first observation of light action on silver chloride, but to do so we should have to go back at least 300 years. That different parts of the solar spectrum affected silver chloride in different ways was observed by Kitter and Seebeck, in 1801 and' 1810. Wedgewood and Davey observed more energetic light action on the silver salt on a basis of white leather than on paper. This contained the germ of development processes acting by reduction of the sil- ver salt, the tannin of the leather playing the important part. Camera photography may be attributed to Joseph Nicephore de Niepce, who gave the first authentic account of it. He used bitumen spread on a metal plate. Bitumen, on exposure to light, loses its pristine solubility in certain oils. With de Nu>pce, Daguerre, a miniature portrait painter, in 1829, en- tered into partnership ; in 1839 the Daguerreotype process was announced. Between these dates Kiepce had died, and what- ever share of the credit was due to him Daguerre claimed the whole of it, and attached his name to the process. Then fol- THE PROCESSES OF PURE PHOTOGRAPHY. 9 lowed the addition to the silver iodide of Niepce, of silver bromide, by Goddard, in 1810 ; also, in 1840, Sir J. Herschell added an important step to the progress, discovering the solu- bility of silver salts in sodic hyposulphite, so that a method was no longer wanting to fix the image. This sodic salt is an important item in the photographic laboratory of the present day. In 1839 that eventful year for photography Fox Talbot published his first process, wherein he coated paper with sodic chloride, and thereafter brushed over it silver nitrate, thereby forming silver chloride in presence of excess of silver nitrate, the basis, with the addition of albumen, also suggested by Talbot, of our " silver printing ".process of to-day Talbot again comes to the front with an enormous stride in his negative process, whereby, in place of one positive picture being the ultimatum of a whole set of operations, we produce by one set of operations a negative, forming a matrix for a theoretically unlimited number of positive pictures. (See chapter on Positive and Negative, p. 34). This process, which Talbot called " calotype," was a development process, the reagents being silver nitrate and gallic acid, the latter due to the Rev. J. B. Eeade. About 1850, Le Gray seems to have suggested the use of collodion as a " vehicle " for the sensitive silver salts ; Scott Archer certainly published the first collodion process. It is worthy of note, however, that the lately deceased Mr. J. G. Tunny, of Edinburgh, has stated in our hearing, that Le Gray furnished him with a good practical collodion process before Archer's was published ; and, further, that he (Mr. Tunny) used Le Gray's process in conjunction with the "iron de- veloper." For many years, and with great reason, the wet-collodion process reigned supreme ; but, grand as its qualities were, it had the drawback that the plates had to be used wet, and a great load of paraphernalia had to be carried -afield for the work. The advent of dry-collodion processes was felt, as a matter of convenience at least, to be a marked advance. The free silver nitrate of the wet process was replaced by other ]0 Till. l'Un( I-SKS OF PUKE PHOTOGRAPHY. iodine absorbents of organic nature, and photographers " ran riot " among such substances as beer, tea, coffee, tannin, beef- tea, tobacco and who knows what besides ! j The discovery, in 1862, of the alkaline developer gave a great " fillip " to dry processes, for by it not only the free sil- ver nitrate on the film is reduced, but also the silver haloids in the film. The bath was dispensed with, at last, in favor of emulsion processes, the joint invention of Messrs. B. J. Sayce and W. B. Bolton, both of whom are to be credited with the advance. Finally, gelatine replaced collodion, the first published gela- tine emulsion process being that of Dr. R. L. Maddox, in 1871. In 1874, Mr. R. Kennett made gelatine pellicle, and, in 1878, gelatine began to leave all other ".vehicles" behind it. In this year, 1878, in March, Mr. Charles Bennett published liis process, whereby he produced gelatino-bromide emulsion of a sensitiveness that utterly overshadowed all previous prepara- tions ; this he achieved by prolonged digestion of the emulsion at medium temperature. Mr. Bolton is again heard of in his ' suggestion to gain sensitiveness by short boiling in presence of a minimum of gelatine in place of long digestion with the full bulk of gelatine. The only really important modification since that was the ammonio- nitrate process, of which full de- tails will be found in our chapter dealing with the subject. In development, since the " alkaline developer " was pub- lished, we have to record no striking variation, save the fer- rous oxalate developer of Messrs. Carey Lea and W. Willis. Mr. Lea's process was first published, but we are able to state that Mr. Willis' memorandum of the process was in the hands of the editor of a periodical three months before Mr. Lea's process was published, accident only depriving Mr. Willis of the credit. The advances in printing processes have been of no less im- portance than those in negative processes. For a long time the production of prints more stable than those formed from silver chloride on paper was a problem, but the discovery by Mungo Ponton, in 1838, of the sensitiveness to light of potas- sic bichromate in presence of certain organic substances, led THE PROCESSES OF PURE PHOTOGRAPHY. 11 up after a course of experiments by Becquerel, Poitevin, Pouncey, and others, to the publication, by Swan, of the "car- bon " or " pigment " printing process, certainly the first that could go under the name of " permanent." Out of certain other qualities of chromates, in presence of organic matter, arose a long series of photo-mechanical pro- cesses with which we cannot here deal. The platinotype process, treated later by us, is due to Mr. W. Willis. The latest advances in photography are connected with " orthochromatics " or color correct photography, and in this field the labors of Vogel, Ives, Eder, Schumann, and Botham- ley are conspicuous. To those interested in the historical development of photog- raphy, we recommend the " History of Photography," by "W. J. Harrison. CHAPTER II. THE THEORIES OF PHOTOGRAPHY. LIGHT is supposed to consist of, or to be produced by, waves of a substance known as ether, all-pervading and imponder- able. Light is merely the name by which we call the sensa- tion produced upon our senses by these ether waves. Matter is supposed to consist of atoms, particles so infmites- imally small as to be incapable of division and in constant motion among each other. " Molecule " is the name we give to an aggregation of two or more atoms of different kinds in combination. The waves constituting light are not all equal in length from crest to crest, nor do they travel from their source at equal paces. Some light waves are very much shorter than others, and, moreover, when in their course they pass from a medium of one density into a medium of another density, some waves or "rays" are turned out of their course ("refracted") more than others. The rays formed by short waves are turned out of then* course more than the rays formed by longer waves. A ray of white light is composed of a vast number of waves of different lengths and different " refrangibilities," and, more- over, at each extremity of the scale of visible wave-lengths are rays which our eye cannot appreciate, just as in sound there are waves so frequent and others so distant from each other that our ear fails to record them to our brain. The visible light rays which are shortest from crest to crest, and which are the most "refracted" on changing the medium through which they travel, convey to our mind the sensations of what we call blue or violet colors. Still shorter and still more refrangible are many rays invisible to us. These short, THE PROCESSES OF PUKE PHOTOGRAPHY. 13 highly refrangible, visible rays, and the still shorter and more refrangible invisible rays are remarkable for the energy with which they exert chemical action, and to the chemical action exerted by these rays specially we owe the power of producing a photographic image. The usually accepted theory is that the wave length of these chemical rays is of such a "measure" as to produce vibration synchronous with the vibrations already mentioned as taking place among atoms, and so either causing entire severance between the atoms forming a molecule, or else placing these atoms in such a condition that the severance is ready to take place when suitable steps are taken or conditions observed to complete the inchoate process of separation. In photography with silver salts the molecule consists of an atom of silver and an atom or atoms of some other substance, photo- graphic action consisting in this case of a severance between the silver atom and the other atom. If all the rays composing visible light exerted anything like an equal amount of chemical activity, it is evident that photo- graphic action might take place and yet be totally useless to us, because uncontrollable by us ; for in that case we should be unable to see any of our processes. But it so happens that while we have some of the rays composing white light exert- ing strong chemical action, we have other rays of much greater wave-length and much less refrangibility marked by much in- ferior chemical energy, though their wave-lengths are still great enough for our eye to appreciate. These rays which produce on our mind, tutored by our eyes, the sensations of orange and red colors are called " heat rays," and beyond the scale of visible heat rays there are other rays even longer and even less refrangible, and possessing even less chemical energy than the visible red rays. So that while we can use the " chemical rays " of light to obtain photographic action, we can use the " heat rays " to enable us to see sufficiently well to manipulate our photographic materials while we prepare our " sensitive " substances, and while we complete the pro- cesses started by the chemical agency of light, referred to by us as " inchoate," but ready to be completed under certain conditions. 14 THE PROCESSES OF PURE PHOTOGRAPHY. In short, by a non-chemical or "non-actinic" light, we pre- pare our sensitive material ; to chemical action of light we ex- pose it, and by non-actinic light we "develop" the action started by the light ; a "sensitive " material being one capable of being acted upon by light. There are other rays forming components of white light in- termediate between the heat rays and chemical rays, in points of wave length and refrangibility. These intermediate rays have a speciality of their own, viz., visual brightness, and we call them "yellow" or "green." The yellow is not so much en- dowed with heat characteristics as the red rays, nor is the green so remarkable for chemical activity as the violet rays ; but all the component parts of a ray of white light have a cer- tain amount of chemical power, and a certain amount of heat- ing power, just as all the visible component rays of white light have a certain amount of visual brightness. If an opaque object appears to us " red," it appears so in virtue of its absorbing the other rays and reflecting to our eyes red alone. If a sheet of glass were stained really and purely red, no visible rays would pass through it except red. An opaque object "reflects," a transparent object "transmits," light ; but, so far as color is concerned, the theory holds good for reflection as for transmission. A beam of white light caused to change its course by being passed out of one medium through another of different density in a certain simple man- ner, may be analyzed or broken up into its component rays, so that these rays can be distinguished ocularly from each other from their different colors and by the different directions in which they travel after " refraction," and an instrument made for the purpose of facilitating the observation of these differ- entiations is called a spectroscope, the analyzed or separated and colored band of rays being called a " spectrum." The science of optics depends, equally with the science of photographic chemistry, on these qualities of light, and while the refraction per se is the action most useful in optics, the coloring dependent on the " bending " is a factor that requires to be carefully minimized or totally counteracted. The chief processes of photography depend on what is called THE PROCESSES OF PURE PHOTOGRAPHY. 15 "reduction," We start with a compound of (say) silver and something else. Actinic light either " reduces," or prepares for "reduction," our compound, and the "reduction" consists in removing the something else, and leaving the silver alone to form the visible photographic image. The optics of photography are directed chiefly to regulating the size of our image, light unaided is quite able to effect all our purposes, but without the aid of optical appliances light would be for us an unmanageable and unprofitable servant. We do not expect, and still less wish, this summary to be taken as touching more than the extreme outskirts of the sub- ject of photographic theory. We believe that a thorough mastery of the whole theory is almost essential to a thorough mastery over the practice, but our limits absolutely preclude other explanation. Certain processes are not even touched by the above remarks ; on encountering these processes in their turn, we shall say a word or two on the special theories regulating them. CHAPTER III. APPARATUS. THE apparatus required for the production of a photograph, by the usual processes, may be summed up under two heads : 1st. Apparatus for producing a negative, or a direct positive. 2d. Apparatus for producing prints from a negative. The apparatus required essentially for the production of a negative are, a camera, a lens, and an apartment, or box, illu- minated by a non-actinic light. (A lens is not absolutely neces- sary, but is almost always used). For convenience we require a support for the camera, and vessels of suitable size and shape for chemical operations. Cameras are merely light-tight boxes for preventing light, other than that passing through the lens, from reaching the sensitive plate, and cameras further afford a means of varying the distance between the lens and the sensitive surface, so that the plate may be placed at one focus of the lens. As ocular examination is required to enable us accurately to place the plate in that focus, the camera is provided with a piece of ground- glass representing the sensitive plate in position, while the plate itself is securely carried in a light-tight receptacle, known as a "dark-slide," or "carrier," until the light is to act upon it in the camera, at which juncture a shutter is removed from the slide or carrier in situ in the camera, so that the light irom the lens reaches the plate, while no other light can reach it. Evidently the sensitive plate, when undergoing light-action, must in position coincide accurately with the position occupied by the ground-glass, while we were placing the ground-glass in the focus of the lens. This coincidence of position between ground-glass and sensitive plate is known as "register." THE PROCESSES OF PURE PHOTOGRAPHY. 17 As a matter of convenience and efficiency, cameras are made in two types, a camera for outdoor work, and a camera for studio or indoor operations. The studio camera, not requiring to be carried about, should be of strong material, and should have every mechanical convenience without respect to weight. The " outdoor," " landscape " or " tourist's " camera should have every mechanical motion, and be made of the strongest material consistent with portability. Certain conveniences should be found in every camera, irre- spective of weight, and certain qualities are essential to every camera, irrespective of all other considerations. A sufficient amount of stretch, sufficient strength, and complete rigidity are essentials to every camera. In studio cameras these quali- ties are usually present ; in tourist cameras they are frequently neglected in the mania for lightness. A camera, for perfect efficiency, should have a front so made that the lens, the flange of which is attached to the front, may be moved up and down, at least, and across, if possible, parallel to the sensitive surface. It is frequently convenient, for certain reasons, to be able to put the sensitive surface out of perpendicularity to the axis of the lens ; and it is frequently convenient, while tipping the lens upwards, to preserve the parallelism of the sensitive surface with the plane of sight, or with upright objects in the view. These desirable qualities are obtained by what is known as a " swingback." Time and temper are sometimes lost when, on an oblong plate, the view has to be taken with the plate in the vertical position instead of the more usual horizontal. If the camera be not unscrewed from its bearings on the stand and placed bodily in the desired position, a " reversing back " is required, and it is certainly a great convenience. The camera-body has to be made square for a reversing back to be permissible, but the extra weight and expense entailed are usually made up for by the extra convenience. To save weight, the greater portion of camera-body is usually made of leather, in the form of bellows ; and to save bulk, the bellows are often made to taper more or less towards the front. This taper is convenient, but must not be too sud- 18 THE PEOCES8ES OF PURE PHOTOGRAPHY. den or carried to too small a point, otherwise the bellows may interfere with the image. In some tourist cameras the stretching operation is effected upon the front, in others upon the back of the camera. Each system has its advantages, and each its disadvantages. If the front part of the base-board projects too far in front of the lens, there is, at certain times, a danger of the projecting front trespassing on the field of the lens. We figure a camera of FIG. 1. each of the types in general demand, No. 1 being a tourist camera, No. 2 a studio camera. It is not within our province minutely to describe any special camera ; we have suggested what we consider the essentials of a good camera. The pur- chaser must rely upon the honesty of the parties with whom he deals. Our remarks are only intended to prime the tyro, so that when he goes to make a purchase he may have at least a faint idea of what he ought to ask for. A regular studio camera, as Fig. 2, will probably be suitable only 'to a professional portraitist, but as there are many ama- teurs who lay themselves out for portraiture, and as to prevent fatigue on the part of either and confusion on the part of operator, it is well to have every convenience. We have shown the general appearance of a studio camera that will fulfill every condition of perfection. Not the least important part of the camera is the "dark slide" or "carrier" already mentioned. As it is the recep- tacle wherein the sensitive plate is carried, and as it comes into play at a time when the operator needs all his faculties about him, the dark slide must not only be thoroughly strong and ab- THE PROCESSES OF PURE PHOTOGRAPHY. 19 solutely liglit-tiglit, but sliould be of such neat workmanship as to work certainly and " sweetly " under all circumstances. FIG. 2. For dry-plates, now almost universally used, the slide is usually made ' double," carrying two plates back .to back, with an opaque partition between them. The double slide, as a rule, opens at one end, after the manner of a long pocket-book. The partition must separate the plates over all their surface, and may conveniently be hinged on the slide. When it is desired to use in the dark slide a plate of a size less than the full size of the slide, we use what is known in England as a " carrier," in America as a " kit," merely a frame fitting internally the small plate, externally the dark slide rebate. In America the " shutter " of the dark slide the part re- moved from the front of the plate during exposure is so made as to pull right out of the slide, having a "cut-off" to prevent light entering as the shutter comes out and is re- placed. In England the shutter has usually a " stop," which prevents it from coming right out, and hinges which allow it to be folded out of the way and out of the wind during ex- posure. We do not venture to decide between these two sys- tems ; each has its merits. 20 THE PROCESSES OF PURE PHOTOGRAPH Y. "Koller slides" or "roll-holders" for carrying paper films shall be noticed later. The considerations that regulate the choice of supports or stands for the camera are pretty much the same as those regu- FIG. 3. lating the choice of the camera itself. The studio stand must have every motion, irrespective of weight, and two good sam- FIG. pies are shown at Figs. 3 and 3a. A stand for outdoor pur- THE PROCESSES OF PUKE PHOTOGRAPHY. 21 poses must be as rigid as possible, consistent with portability ; should have sliding legs to meet contingencies of very uneven ground, but should, withal, pack into as small bulk as possible. The point upon which rigidity chiefly depends is the breadth and force of grip with which the tripod head is grasped by the tops of the legs. Fig. 4 shows a good tripod stand. FIG. 4. Photographic lenses are of a few different types, and made of many different focal lengths. The focal length of a lens is really the paramount consideration, provided, of course, the manufacture is good. Each type of lens is made with a view to meet certain special requirements, to a special degree, and a good lens for any special purpose is really a pure compromise between a number of qualities, special attention being given to the special quality required for the special purpose. Thus the portrait lens, the triumph of photographic optical compromises, is so made as, with the least possible sacrifice of other qualities, to give the greatest possible rapidity of action. The portrait lens was the outcome of the struggle for rapidity at any price, in the days of slow plates ; it is now gradually falling into disuse, and its place is being taken by the rectilinear, or symmetrical 22 THE PROCESSES OF PURE PHOTOGRAPHY. lens. The rectilinear lens is formed of two combinations, sometimes alike, sometimes dissimilar. Its uses are at least two-fold, it secures rectilinearity of lines in the camera image, and it enables us, under certain conditions, to work rapidly ; hence we have the term " rapid rectilinear," or '-rapid sym- metrical." We have other " symmetrical " lenses, which, by reason of their special uses, cannot be used at all times for rapid work. The term "wide-angle" is so frequently used, without comprehension of its true signification, that we explain. The "covering power" of a lens depends mainly upon its focal length, and if we use a lens to cover a plate large in pro- portion to the focal length of the lens, we are using that lens at a " wide-angle " ; so it has come about that lenses made with a view to cover a plate large in proportion to their focal length are called " wide-angle lenses." A lens is used as a nar- row, or wide, or medium angle lens according to the size of the plate upon which it is used, in proportion to its focal length. A complete treatise on these subjects would require a vast amount of space, more than we can give the subject here. The so-called " single " lens has certain qualities which place it, in our estimation, higher than any other kind of lens. The number of reflections inside the lens is reduced to a minimum, and the result is a quality, especially in the shadows, not given by doublet or triplet lenses. Until lately the single lens had to be so " stopped down " as to make its action very slow, but this defect has, to a great extent, been rectified ; the other defect is that when a single lens is made to embrace too wide an angle, straight lines in the subject are distorted in the photograph. This defect has been greatly exaggerated, and we believe that the cases where the use of a " single " lens, used at moderate angle, is not permissible, are much more rare than is generally known by operators, or admitted by opticians. For por- traiture the writers have found the "single" lens inferior to no other type of lens, but it is advisable that the single lens, for this purpose, be made to work with as wide an aperture, and be used at as narrow an angle, as possible. "Group lenses," so called, are compromises between the portrait and the rectilinear types. "Wide-angle rectilinears " THE PROCESSES OF PURE PHOTOGRAPHY. 23 are made so as to give non-distorted lines while working at wide angles. Perhaps the type of lens that will most com- pletely meet every class of requirement is the rapid rectilinear, and lenses of this type go under many different names in dif- ferent countries. The focal length of lens necessary to cover a plate may be calculated from the diagonal of the plate. In cases of neces- sity, lenses may be used of focal length less than the diagonal of the plate, but, as a general rule, the focal length ought to be at least 50 per cent, over the length of the plate. The exposure required depends, so far as the lens is con- cerned, entirely on the proportion of the area of aperture to the focal length at which the lens is being used. If a lens is focused on a very distant object, as the sun, when the sun- image is in focus on the ground-glass of the camera, the sun is in the position known as the anterior conjugate focus of the lens, and the ground-glass is at the posterior conjugate focus, or, briefly, the solar focus. The focus of a lens is usually measured from the "stop," in case of a combination lens, from the lens itself in the case of a single lens, to the ground- glass. This is not strictly scientific. But if we focus a closer object, say ten feet off, with a lens of about four inches focus, principal focus, the ground-glass will be found further from the leus than it was when the sun was focused with the same lens ; the ground-glass is still at a focus of the lens, but it is not the solar focus, and, in calculating our exposure by means of the proportion of aperture to focus, it is not the sun focus we have to deal with, but the focus of the object which we are focusing ; a very different matter in the case of close objects. From inat- tention to this point persons are often greatly deceived in their exposures when working upon near objects. The proportion of aperture to focal length is usually called the " intensity ratio," and expressed as a fraction thus : - or -j , x being the focal length in inches, and the numerator of the fraction being the measure of the aperture. "Stops" or "diaphragms" are always sold with lenses for photography ; these stops may be separated from the lens and used by being placed in a slot made for the purpose in the lens tube, or they may be fixed 24 THE PROCESSES OF PURE PHOTOGRAPHY. to the lens and rotated so that any of the apertures may be used. The stops are usually so cut as to give, with the lenses to which they belong, intensity ratios as follows : {, (these two usually confined to portrait lenses) ; |, yf . T , T ^-, ^.-g-, ^-, T y> beyond which it is not usual nor, indeed, advisable to go, except in special cases, when -/ T may be used. These terms simply express that the solar focal length of the lens is 4, 6, 8, 11.3, etc., times the diameter of the aperture. Exposures are calculated by comparing the squares of the denominators of these fractions. If at ^ the proper exposure is found to be ten seconds, the exposure at /? will be not twenty seconds but forty seconds. As 16 2 : 32 2 : : 10 : 40. In calculating exposures for close objects, the caution above given as to real focal length must not be neglected. Some op- ticians number their stops according to an arbitrary table drawn up by a committee of the Photographic Society of Great Britain. A table will be found at the end of this book show- ing the connection between the so-called " Uniform System" of numbering stops and what is really the crucial point the intensity ratios. For the special province called instantaneous photography, mechanical "shutters" are required. The simplest and the oldest is the "Drop" or Guillotine shutter, figured No. 5, FIG. 5. wherein a loose piece with an aperture falls across the THE PROCESSES OF PURE PHOTOGRAPHY. 25 axis of the lens, the shutter being placed sometimes on the hood or front of the lens, sometimes at the back of it. As, usually, it is desirable to expose the foreground of a subject more than the upper part, this form of shutter is preferably- placed behind the lens ; for if it is in front, the increasing velocity of the f ailing plaque of wood, metal, or other material allows the foreground less exposure than the upper part. Shutters of this type should have their aperture by no means less than the working aperture of the lens. An aperture longer than the lens diameter is recommended, and the action may be quickened by an elastic spring. Many shutters are used in the centre of the lens, and, in cer- tain ways, these shutters have great merits. As a rule, the apertures of these shutters are of square or diamond-shape, and cross each other in the act of exposure. When a shutter act- ing in this way is placed either in front or in rear of the lens, the inequality of lighting inherent in certain types of lenses is exaggerated ; when the shutter is placed in the centre of the lens, not only is this defect not exaggerated, but the result FIG. 6. is better, in this respect, than if the lens were used with the same stop and the lens-cap. There is an advantage to be found in shutters opening from the centre, viz., that the loss of time occupied in opening and shutting is made up for by the fact 26 THE PROCESSES OF PUKE PHOTOGRAPHY. that the shutter acts during part of the exposure as a stop. The advantage of using a stop is that, thereby, greater sharp- ness is obtained over the plate, and planes of the subject at various distances from the lens are brought more evenly into focus on the plate. The markets teem with shutters for instantaneous exposures. If the purchaser can procure one which will work without jar during the exposure, which will, at will, give an exposure as short as one-hundredth of a second, or as long as half a second ; if it give either even illumination all over the plate, or extra exposure to the foreground; if it allows the full amount of light to act on the plate during the greater part of the duration of its working ( co-efficient of light ") ; and if, in addition, it can be made to give an exposure regulated by the THE PROCESSES OF PURE PHOTOGRAPHY. 27 hand of the worker, that purchaser will not regret his pur- chase. It would be invidious, from such a number of good shutters, to single out any one as the best, but we give figures (6 and 7) of two good shutters, one well known in America, the other in Great Britain. With the ordinary lens-cap, by hand, an exposure can be, with a little practice, made not exceeding one-fourth or one- fifth of a second, but the performance is, in some hands, risky. It will be noticed that as yet we have not written a word of suggestion as to size, nor do we propose to more than allude to the matter. The photographer must choose the size for himself, according to his bank account, his bodily rigour, his available leisure, and his object. Expense, exertion, and at- tention required, all increase, at an enormous rate, as size of work increases. The smallest size commonly used is known as " quarter-plate," the size of plate being 4Jx3^ inches. The impedimenta for work of this size are not worth mention, and the expense moderate. By an easy process lantern slides can be produced from quarter-plate negatives, and we doubt whether we could name a nobler finale to a set of photographic operations than a good lantern-slide, for which we shall give very careful instructions in this book. " Half-plate," 6x4f (in England), 6x4^ (in America), is, perhaps, the smallest size from which a direct print can be made that will not look trivial. " Whole-plate," 8x6^ inches, is a very convenient, and in our opinion, elegant size. The largest size we can recommend for amateurs, in a general way, is 10x8 inches, which most persons will find auite enough to carry into the field. For portraiture, where weight is a matter of no consideration, we recommend the largest size the would-be 'purchaser can afford. We confess ourselves sick of the everlasting " cabinet " portrait, and its little brother, the " carte." If the amateur must trespass on the domain of the professional, let him do so en grand seigneur." Besides such necessaries as we have touched upon, there are 28 THE PROCESSES OF PUBE PHOTOGRAPHY. a number of smaller articles which will be required. These we shall merely advert to. A cloth, known, too often, as the "black cloth," or "black rag," is used to cover the camera while focusing is being done. This cloth looks much better when dark-colored, but not black, and waterproof cloth is far superior to velvet, because it is FIG. 8. waterproof, and often useful in that capacity ; because it has a better appearance, and because it does not cling to the cap, or air, when the head is being withdrawn from under it. The THE PROCESSES OF PURE PHOTOGRAPHY. 29 cloth should be tied, or buttoned, on to the camera front, and should be of ample size. Dishes for development of ordinary dry-plates should be black, and papier-mache is perhaps the best material. To save extra quantity of solution the bottom should be flat, but in order to avoid staining the fingers in lifting the plate up for examination, either a hook must be used, or the dish made with ridges at bottom. For other operations, as " toning," porcelain dishes are to be preferred. For the smaller sizes, glass dishes are found very elegant, but they have the defects of weight and brittleness. Graduated measures of different sizes, scales and weights, filter-funnels, and other laboratory requisites are necessary in small quantities, but need no remark. FIG. 9. Plate boxes for storing sensitive plates must be made care- fully light-tight, and of such wood or other material as will not affect the most sensitive plates (Fig. 9). FIG. 10. A rack for drying plates is preferable to leaning the plates against a wall, or other object to dry (Fig. 10). Other apparatus will be described, as the need for it turns up, in our future chapters. CHAPTER IV. THE DARK-ROOM. THE above is the name technically, but not accurately, given to the apartment wherein are conducted such operations as would be hurt or impossible in actinic light, by reason of its action upon our sensitive salts, as described briefly in Chapter II. The requirements of an operating-room are of the sim- plest, but it may not be amiss to give a few hints as to the easiest and best way to arrange an apartment for the purposes with which we propose next to deal. Many amateurs find it impossible or highly inconvenient to secure an apartment of any kind for their work, and for such a " dark-tent " may be the most convenient way out of the diffi- culty. But it is probable that each of our readers will be able either to adapt, or to find, or to build an apartment for his photographic requirements. If a room is to be used only occasionally or temporarily as an operating-room, the most required will be to stop out all white light by whatever means appear most handy. .A window may either be blocked up entirely by opaque material, such as thick brown paper, or brown paper in several layers, or it may be preferable to block out the light only partially with opaque material, and allow some light into the room through some medium, such as ruby glass or orange or yellow paper. The color and thickness of .these light-filtering media depend on the sensitiveness of the photographic substances we propose to use. For wet collodion, dry collodion, or gelatine-chloride plates, yellow glass or lemon- colored paper will be sufficient pro- tection, even from daylight. For processes wherein we use gela- tine-bromide of silver in a moderate state of sensitiveness, as for "lantern-slides,"- bromide prints," or "slow gelatine-bromide THE PROCESSES OF PURE PHOTOGRAPHY. 31 plates," an orange-colored filtering medium, a single ruby glass, or " canary medium " may be used. With very rapid gelatine- bromide plates we must use several thicknesses of orange or canary paper, or we must add to the ruby glass a thickness of yellow glass. If we are going to expose our sensitive mate- rial to the light for a prolonged period, as in emulsion-making, we must redouble our precautions in this line, and for ortho- chromatic work (see Chapter XVIII), we must not only restrict ourselves to ruby light, but we must, as far as possible, restrict the quantity of that. If there be any doubt as to the " safety " of our light, we should expose a sample of the material with which we are working under a " sensitometer screen," or under a negative, to the suspected light, and ascertain by develop- ment whether any light-action takes place. We may place one FIG. 11. of our plates in a book, so that part is protected by the book and part exposed to the suspected light for (say) five minutes. If, on development, any action is observed on the exposed part it is evident that further precaution must be taken with regard to the light. Alternatively, and perhaps preferably, the light may be en- tirely, blocked out of the room, and a " non-actinic lamp " used. The variety of these in the market is infinite. We figure one only, Fig 11. If gas is laid on, we recommend the principle of building a lantern around a jet, so that (1) the heated air and combustion- 32 THE PROCESSES OF PUKE PHOTOGRAPHY. products are carried right out of the apartment, if possible ; (2) the gas can be raised or lowered from the outside of the lantern. In the case of a room temporarily used as an operating- room, it is well to cover the tables with waterproof or " American " cloth. A basin or foot-pail may serve as a sink, and any vessel of suitable size and shape may be " annexed " for water. We have, in a hotel bedroom in Italy, made rapid gelatine emulsion, coated, dried and developed plates, with some little exercise of ingenuity, but without accident or failure. But we venture to say that success will most likely at- tend operations conducted in apartments made or adapted solely for the purpose of these operations. The apart- ment chosen or built must be thoroughly ventilated as well as thoroughly light-proof, otherwise the accruing vapors will damage both the health and the success of the operator. A north aspect should, if possible, be chosen for the win- dow. A window should exist in the room, whether that window is to be used for the photographic operations or whether it is to be blocked up during operations. The system of dark-room lighting, which we find most satisfactory, is to have our window glazed with perfectly safe light, but to have, also, our gas lantern lighted and worked from the outside. We commence developing operations by daylight filtered through our " safe " window, and when we come to the point where critical examination is required, we turn up our non-actinic gas lantern, which is provided with various filtering media viz., clear ruby glass at one side, canary medium paper at another, and ruby glass, ground on one side, at another. Ruby glass ground on one side is one of the most perfect media we know. Of " ruby glasses," the safest sample we have ever seen was ordinary "metal-flashed ruby " on one side and " stained yellow" on the other side. Some persons cannot tolerate ruby color ; others dislike yellow-greens. The ruby tints are used clear, and often combined with clear yellows. The yellow media require the light to be more or less diffused, either by paper or ground-glass, or semi-obscured glass in some form or other. Of THE PROCESSES OF PUKE PHOTOGRAPHY. 33 course, a medium that may be " safe " with artificial light might be disastrous if used with daylight ; and, moreover, a medium safe with daylight in mid winter may be fatal in spring or summer. The test recommended above is equally useful here. The sink for an operating-room is often made of stoneware, often of iron. We greatly prefer wood lined with sheet-lead, which does not, perhaps, look so pretty, but does not fracture a measure knocked over or laid too briskly down on it. The tap should be of the " arm " kind, but the turning of the arm must not regulate the water-flow ; there should be a cock to turn the water on and off. On one side, at least, of the sink, and projecting slightly over the sink, should be a table, lead-lined, and sloping down towards the sink. This is to receive dripping measures, dishes, plates, etc., and to carry the drip into the sink. A slightly- raised ledge, or "beading," round the table, will prevent liquids reaching the floor. Shelves, cupboards, tables, etc., are evident requirements of an operating-room. Hot water supply is an immense boon. A fixed syphon trough for washing negatives is a great con- venience. The nozzle of the tap should end in a thread, to which, by means of a gas coupling, can be attached a variety of small apparatus, as a rose tap an invaluable article a rubber tube, etc. Drying presses and other matters shall be described as their uses are treated. The dark-room should be kept, as far as possible, at an even and moderate temperature. Whatever be the fuel used the products of combustion must be carried right out of the room. Gas, in particular, has a noxious effect on many of our products. CHAPTER V. "NEGATIVE" AND "POSITIVE." THE result of every set of photographic operations is either a positive or a negative. A " positive " shows the light colors in nature as whites, the shadows as dark, while a "negative" shows the high lights of nature as dark, the shadows as light. A positive may be looked either at or through, a negative is not intended for looking at, but is merely intended to be printed through, so as to produce what is always our ultimate object a positive. Positives are very seldom now produced direct from nature, they are almost always produced through the intervention of negatives. A negative is of no value or merit irrespective of the value or merit of the positives which may be produced from it. We have to deal with " positives " as prints on paper, on opal, or on other opaque or semi-opaque supports ; and with ' transparent positives," as " lantern-slides," window transpar- encies, etc. "VEHICLE" AND "SUPPORT." We require for our sensitive salts (1) a substance wherein they may be suspended, because we cannot, in practice, spread or use them on a hard, repelling surface, such as glass. The suspending substance is called the u vehicle," and may be col- lodion, albumen, gelatine, paper, or other substances. (2) Some " support," to hold our suspended sensitive substances in such a layer and condition, that we may expose a consider- able surface of our sensitive substances to light-action, and be able, thereafter, to manipulate them. Glass is the commonest " support " now in use, but we have, also, acting as supports, paper, gelatine films, metal plates, etc., etc. THE PROCESSES OF PUKE PHOTOGRAPHY. 35 The support may be " temporary," as in cases where, after operations are complete, we strip our vehicle, with its sus- pended substances, from the temporary support ; or the sup- port may be " permanent," as in the cases of the glass of our ordinary negatives, or the paper of our ordinary prints. Paper, among other substances, may be at once vehicle and support, temporary support and permanent support. We propose first to deal with the wet collodion process, which may be ifsed as (1) a negative process, (2) a transparent positive process, as in the case of lantern-slides, (3) an opaque (or simply) positive process. As the use of wet collodion, under Ko. 3, is now rare and confined to the production of positives not remarkable for excellence at the best, we shall not do more than allude to it under this heading. We cannot do the wet collodion process full justice, as we are well aware, in our limited space, but the process is so inter- esting, so educative, and so beautiful in many of its results, that, though of late years it has fallen into comparative disuse, we feel impelled by our own wish, as well as for the good of our readers, to devote some space, however unworthy of its merits, to the process. CHAPTER VI. THE WET COLLODION PROCESS. IN this process collodion forms the vehicle, glass the sup- port, and silver haloids the sensitive salts. The latter salts are formed in the vehicle by the chemical action known as " double decomposition." The vehicle at first holds in suspen- sion an iodide (as of potassium), or a bromide, or a chloride, or all three ; these halogens, coming in contact with silver nitrate in solution, combine with the silver to form the silver haloids in the vehicular film of collodion, and these haloids are the salts that receive the light-action, and determine another action known as development, which is really a reduction of the silver to the metallic state. It is utterly impossible, in a few words, to explain, even in outline, a series of chemical actions such as this; the safer way, for all parties, will be not to attempt desultory and partial theory. Collodion is a solution of gun-cotton in ether and alcohol, and is sold ready for our purpose either "iodized" or with a separate bottle of " iodizer," to be mixed with the plain collo- dion, according to instructions. As a rule there is, along with the iodide, a certain proportion of bromide, and for landscape work a good proportion of bromide is desirable. A plate of glass, being thoroughly cleaned, is " coated " with iodized collodion, and is thereafter immersed in a solution of silver nitrate. The now sensitized plate is exposed in the camera, brought back to the operating-room, where it was sensitized in non-actinic light, flooded with a developer, con- sisting of a salt of iron in solution, washed, * fixed," and washed again, when it is supposed to be a finished negative. To take these operations in detail : Cleaning the Glass Plate is usually performed with a mix- THE PROCESSES OF PURE PHOTOGRAPHY. 37 ture of alcohol and ammonia, containing a little rouge powder or tripoli. If the plate has been used previously, the cleaning must be performed with all the more care, and a preliminary bath of nitric acid and water is desirable ; in any case, the plate, back and front, must be scrupulously clean and free from the slightest trace of grease or organic matter of any kind. Sometimes the plate is flowed twice with albumen thinned with water and alkalized with ammonia, and, of course, most carefully filtered ; this is preferable to having a dirty plate, but is apt to disorder the silver-bath. After the plate is cleaned, it must be "polished" with a scrupulously clean chamois leather. The plate must not be rubbed with silk immediately before coating. Coating the Plate with Collodion. This is an operation which requires both care and practice. In no process of pho- tography is more attention to apparently trivial details re- FIG. 12. quired than in the wet collodion process ; absolute cleanliness, freedom from dust, and method are required at every step. The first crucial operation is that of " coating the plate." The collodion containing the " iodizing " agents must be kept clear of dust, free from solid particles of collodion, in a bottle of such form as to permit of neat and even pouring, and to prevent solid or semi-solid particles 'from settling on the 38 THE PROCESSES OF PUKE PHOTOGRAPHY. plate. A suitable bottle is shown in Fig. 12. The collodion must run evenly over the whole of the face of the plate, must run over no part twice, nor stop for any considerable time on any part. The operation is performed in the following way, and those uninitiated, yet unwilling to waste collodion, may try their " prentice hands " with milk or thin cream. The polished plate is taken by one extreme corner, or, much preferably, on a pneumatic-holder scrupulously clean (Fig. 13). FIG. 13. The face and back are quickly dusted with a camel's-hair brush, and the plate held in the left hand in the position shown in the figure, A E being next the operator's body. FIG. 14. A pool of collodion is poured about the point A in sufficient quantity to more than cover the whole plate, the pool as it widens is guided by tilting the plate slowly but steadily towards B, then around towards C, then towards A; the now broad wave is directed towards D, at which corner it is poured ie plate into a second bottle, through a filter if convenient THE PROCESSES OF PUKE PHOTOGRAPHY. 39 The plate, while the collodion is running off, must be gently and slowly rocked by depressing alternately corners E and B, and the corner E may be gently touched by the neck of the second bottle, or the filter, but must on no account be ground against any hard substance. When the collodion is " tacky," or takes the impression of the skin of the finger at corner D, the plate must without delay be placed in the " nitrate bath." Many operators hold the plate, while coating it, with the narrow end next the body, pouring the pool of collodion near the right top corner ; some pour it on near the left side next the body, but we, after considerable experience, prefer the method we have given. The "Silver Bath" or "Sensitizing Bath" is as simple to make as it is difficult to keep in order. Therefore, it should be made in two batches at once, one solution to replace the other when the first used goes wrong : Silver nitrate (crystallized) 35 grains Pure water 1 ounce in sufficient quantities, of course, to cover the plate thor- oughly in the bath. This is the most generally useful strength, and the limits of variation are but small. Very cold weather may indicate a bath five grains per ounce stronger. A trace of iodine must be added to this bath, either by adding for every ten ounces of " bath solution " about a grain of potas- sic iodide direct, or by coating a plate with iodized collo- dion and leaving in the bath for some hours. If the addi- tion of iodide be neglected, pinholes (tiny transparent spots) will surely affect all the plates first sensitized in the bath. The water must be absolutely free from organic matter ; water distilled in a glass or clean metal " still " will answer, or rain water caught direct from the clouds in a clean not metal or wood vessel. Even rain water is not entirely to be trusted. A crystal of silver nitrate should be placed in about a pint of rain water, the vessel containing it allowed to stand some days in bright light, and the water carefully filtered through pure filter paper. To prepare the bath : Dissolve the full quantity of silver nitrate in about one-half the full quantity 40 THE PROCESSES OF PURE PHOTOGRAPHY. of water, add the iodide if the addition is to be made directly ; then make up with water to full bulk, and filter. The "bath" is at all times, after long use, liable to become supersaturated with either (1) iodine, or (2) collodion solvents ether and alcohol. No. 1 is indicated by " pinholes " in the negatives ; to cure this, dilute the bath to half its strength, make up to original strength with silver nitrate, and filter care- fully. If No. 2 be indicated by unequal sensitizing and streaky development, the application of heat will drive, off the offending solvents. A third adulteration, that of organic mat- ter, is more difficult to get rid of ; it will be indicated by fog, " veil," dirty negatives, etc. To remove organic matters which get into the bath from the fingers, the clothes, the at- mosphere, or dirty plates, make the solution distinctly alkaline with sodic carbonate, and place the solution in a strong light for some days, after which filter out the black deposit, re- acidify with nitric or acetic acid, and filter again. The sensitizing bath must never be used alkaline ; it must be tested for acidity with blue litmus paper. If the paper does not turn red, acid nitric or acetic must be added to the bath till the paper shows distinct redness. For negative work, acetic" acid is, perhaps, preferable ; for positives, nitric acid. When the collodion has " set " on the plate, as described the time requisite for setting depending chiefly on the temperature, and varying from twenty seconds upwards the plate is to be immersed in the " bath." Two kinds of receptacles are used for the bath solution. In some countries we find the dipping bath almost in universal use ; in other countries an ordinary flat porcelain or glass dish is used. The dipping bath, figured at No. 15, requires a "dipper" of silver, porcelain, or varnished wood (the last not strongly recommended), and it also necessitates a much larger quantity of solution than the flat dish, but it has the advantage of better protecting the plate and the solution from dust and other impurities. We leave the choice to our readers, saying only that, having used both, we prefer, on the whole, the flat dish, keeping it carefully covered and the solution fre- quently filtered. The plate is to be immersed in the solution THE PROCESSES OF PUKE PHOTOGRAPHY. 41 steadily, without either a sudden plunge or a hesitating stop- page, and the lower end of the plate, where the collodion is probably thicker, is to be immersed h'rst. In a few seconds a change will be seen on the plate, a kind of gray or bluish-gray film appearing, due to the formation, by "double decompo- sition," of the silver haloids. After the plate has been in the bath about forty -five seconds, the thick collodion end, if in a flat dish, the whole plate on the dipper, if in a dipping bath, should be gently and only slightly raised. The sensitization is complete when there is no longer any appearance of " greasi- ness" on the plate, that appearance being due to the collodion FIG. 15. solvents. The plate should now be covered with a perfectly even film of gray or bluish-gray (according to the salts in the collodion) color. Of course, the sensitizing -of the plate must be done in non-actinic light in the present case yellow glass, or even a candle shaded by yellow paper will afford sufficiently safe illumination. The plate, now sensitive, is raised from the bath slowly, the drops at the lower . end blotted off on clean filter or blotting paper, the back wiped with similar paper, and the plate is placed in the dark-slide, propped up in the position it will occupy in the camera. The plate being placed in position, film to the front and against the silver or glass corners in the slide, a piece of red blotting paper, which may with advantage be damped, is placed behind the plate, and the slide is closed. 42 THE PROCESSES OF PUKE PHOTOGRAPHY. As a rule, the thicker part of the collodion film should be placed at the upper part of the dark-slide which will receive the foreground of the picture. The slide once charged in its proper position must never be waved about nor reversed so as to cause the silver solution to run back over the plate ; it must be carried steadily, and if laid down must preserve the position in which it was charged. We then proceed to make an exposure (see Chapter XIII.)^ and after exposure, return to the dark-room with the slide, which we again prop up in its former position, till we are ready to develop the plate. Development. An average iron developer may be formu- lated thus: Iron protosulphate .............................. 12 grains Acetic acid (glacial) ........................ ---- 30 minims Water ........................................... 1 ounce Alcohol ........................................ q. s. For the acetic acid we may substitute nitric acid, 1 minim. The quantity of alcohol is regulated by the amount of alcohol in the bath, a new bath necessitates almost no alcohol in the developer ; as the bath ages, so the alcohol in .the developer must be increased, otherwise streaks will appear. The iron protosulphate must be fresh, and of a fine green color; the yellow crust, often seen, is due to oxidation, and does mischief acting as a restrainer (Abney). The propor- tions of iron may vary greatly ; as little as five grains, and as much as forty grains, to each ounce, may be used under certain conditions. One of the writers used with great satisfaction, in Italy, the following : Ammonia sulphate of iron ........................ 77 grains Aceticacid .................. . .................. 70 minims Alcohol q s 3 ounces The acid is in each case used as a "restrainer " or "retarder." Without it the image would flash out, fog, and be not only uncontrolable, but useless. The plate is taken out of the slide by " safe " light, prefer- THE PROCESSES OF PUKE PHOTOGRAPHY. 43 ably with the pneumatic holder (vide supra\ is held over the sink with the thicker end of the collodion film next the oper- ator. Sufficient of the developer, amply to cover the plate, is taken in a cup, and swept over the plate in one wave, not vio- lently, but without hesitation ; if possible, no solution should be spilled. This is allowed to move over the plate for half a minute, more or less, and is then poured off into the sink, or into a residue jar. If the image flashes up gray, the exposure has been too great ; if it comes up reluctantly, or black and white, or not at all, the exposure has been too short, in each case supposing the " bath " and the developer in proper order. In place of acid, certain viscous substances are some- times used as "retarders" of development, making the de- veloping solution more " syrupy," and so offering more resist- ance to the solid particles traveling through it. Among sub- stances recommended for this purpose are sugar, glycerine, gelatine, and the " collocine " of Mr. Carey Lea. He-development. It is probable, especially if the wave of developer carries any solution over the edge of the plate, that the image, after development, will not be dense enough for printing purposes, and possible that there may be a lack of de- tail, as well as of density. In this case the plate is washed under the tap, and a further dose of developer is applied, with the addition, this time, of some silver nitrate. To each ounce of the fresh developer, in the cup, we may add ten or twelve drops of a ten per-cent. solution of silver nitrate. (Silver nitrate forty-eight grains, water up to one ounce, acidified with nitric acid.) This is applied to the plate, and allowed to move over it as before, density and detail will both increase. If, after development, the image is weak, and wants detail, re- development is wanted ; if weak, and full of detail, it is contra- indicated. In the latter case intensification (see p. 44) is in- dicated as necessary. Fixing. The plate, after re-development, is again washed and fixed (i. e., the unaltered-by-light silver salts are dissolved) by pouring on either : Potassic cyanide 25 grains Water. . . .1 ounce 44 THE PROCESSES OF PURE PHOTOGRAPHY. Or, Sodic hyposulphite 100 grains Water 1 ounce till the yellow veil disappears from the plate entirely. The potassic cyanide is highly poisonous, even by absorp- tion, its fumes are noxious to some persons ; the sodic salt is harmless. After the plate is perfectly " fixed " or " cleared " it must be carefully washed, especially after " hypo." Intensification is resorted to for plates that are wanting in density, and consists of an operation very similar to re-devel- opment ; the same solution may be applied as for re-develop- ment, or the iron, this time, may be replaced by three grains of pyrogallic acid. The silver nitrate is to be added as before in re-development. The plate is finally washed and allowed to dry. Drying before a fire will slightly increase the density. These processes are practically the same for a transparent positive (as a lantern slide) as for a negative. The wave of developer may be allowed to carry a little solution over the edge of the plate, and any increase of density must be admin- istered with caution. The collodion film is very delicate, and requires to be pro- tected by a varnish usually composed of gums dissolved in spirits. Varnish is sold by every dealer, but may at need be made thus : Seed lac 1 pound Methylated spirit 1 quart Keep some days in a warm place, shaking occasionally. After four days decant and filter. To apply varnish : Heat the plate to blood heat, apply the varnish after the manner of collodion, drain well, removing the last drip by resting lower part of the plate on bibulous (filter or blotting) paper. Then heat again till the back of hand cannot bear it. The varnish must not be allowed to dry cold. For certain purposes negatives in black and white are re- THE PROCESSES OF PUKE PHOTOGRAPHY. 45 quired. For such purposes copies of plans, line engravings, etc the negative may be intensified thus : Mercuric chloride 1 part Water.. 20 parts Acidified with hydrochloric acid. Immerse in this till the image is almost, or quite, white. Then plunge, after thorough washing, into : Liquor ammonia, fort 1 part Water 20 parts The image will now turn densely black. Wash thoroughly. Dry, and varnish as before. CHAPTER VII. A DRY COLLODION PROCESS. DRY collodion plates are very rarely, if ever, now used for making negatives, but, as the process naturally follows the wet collodion process, we propose to insert here a dry collodion process, which we have used extensively and successfully for lantern-slides, and which may be used, if desired, for negative- making. The formula is mainly due to Mr. "W. B. Bolton. Dry collodion emulsion is called "washed" or " unwashed," according to the stage at which it is washed, for washed it always is, at one stage or another. Instead of using a bath of silver nitrate solution, and immersing a coated plate therein, we add the silver nitrate to the liquid salted collodion, thereby producing an " emulsion " of silver haloids in collodion, and that emulsion, sensitive to light, we pour on plates which we thereafter dry. But in the process of "double decomposition," by which the sensitive salts are formed, there are formed other compounds, or " bye-products," which, if left to dry on the emulsion, or on the film, would crystallize, and spoil all our plates. In the " washed " emulsion process these bye-products are washed out of the bulk of emulsion before the plates are coated. In the " unwashed " emulsion process the bye-products are washed out of the film of each plate after it is coated. UNWASHED COLLODION EMULSION PROCESS. The zinc bromide must be dry, or dried by heat on a clean surface'. The pyroxylin e is that made at, and known as, " high temperature." Sulphuric ether, .720 ..................... 3J4 fluid ounces. Alcohol, .820 ........................... . 2 fluid ounces. Pyroxyline, (H.T.) ...................... 36 grains. Zinc bromide ............................ 59 grains. Mix in this order, and let stand one day, at least, to settle. THE PROCESSES OF PUKE PHOTOGRAPHY. 47 After the above are fully dissolved and any precipitate settled, dissolve ninety grains silver nitrate in a test-tube, with forty-five minims of distilled water, boiling. Boil, in another test-tube, six drams of alcohol .820, and while both test-tubes are at the boil, pour about four drams of the alcohol into the silver solution, reserving two drams for future use. Now take the two test-tubes and the bromized collodion into the dark- room (yellow light will do) and little by little pour the hot alcoholic-aqueous silver solution into the collodion, shaking the latter violently after each addition of silver. After all the silver solution is into the collodion, use the two drams of alco- hol in reserve to rinse out the silver which will be crystallized, probably, in the test-tube, and add that to the collodion. Shake vigorously for a minute or two. We have now formed a collodio emulsion of silver bromide, which is left to " ripen" for- several days. When fully " ripened," the emulsion is filtered through pure cotton wool, glass wool, or swan's-down calico, and plates are coated with it. For this process, the plates should be carefully cleaned, and they should have a sub- stratum of albumen, or an "edging" of india-rubber dissolved in pure benzole. The albumen solution is made by switching the white of an egg with forty ounces of water, adding liquor ammonia till the smell of ammonia is distinctly perceptible, letting stand, and filtering most carefully. This improves by keeping, but the ammonia smell must be kept up. The clean but wet glass plate is flowed twice with the albumen, then dried. The plate coated with collodion emulsion is left till the col- lodion sets, when it is plunged into distilled water, after which it may be washed in ordinarily pure water till greasiness dis- appears ; after this it is placed for about a minute in one of the following solutions : 1. Coffee (ground) 2 ounces Boiling water 10 ounces carefully filtered. 2. Bitter beer 10 ounces Pyrogallol 10 grains filtered. 48 THE PROCESSES OF PUKE PHOTOGRAPHY. After No. 2 the plate is to be washed before drying, but not after iNo. 1. Drying may be accelerated by gentle heat. Washed Collodion Emulsion. Process of sensitizing is very similar to that given for unwashed emulsion. Ether, .720 3 ounces Alcohol, .820 2 ounces Pyroxyline 48 grains Zinc bromide 72 grains To sensitize use, this time, silver nitrate 1 20 grains. The ripening is allowed to proceed as before, and thereafter the emulsion is poured out into a large, flat, clean dish in the dark- room, and allowed to set thoroughly. As a skin forms on the top, it is broken with a clean bone, horn, ivory or silver instru- ment, so that it may " set," by evaporation of the solvents, to the very bottom. The emulsion is then cut or broken or torn into very small shreds, and washed in running water for several hours. The " pellicle," or dry emulsion, after being broken up, may be put into a tea-pot, a piece of muslin tied over the top, and a stream of water directed down the spout for a night. The pellicle is next thoroughly dried, first, by squeezing, next, by submersion under alcohol for an hour or two. It is then dissolved in ether and alcohol, thus : Pellicle 20 grains Ether 4 drams Alcohol 4 drams The plates are coated with this, and require only to be dried. Development. For lantern-slides the developers we prefer will be found under the heading appropriate, page 176. We here briefly state a method suitable for plates made by this process, and exposed upon landscape subjects. The required exposure, we may say, is very long compared with other nega- tive processes in common use. Flow the film with Methylated spirit 1 part Water I part for half a minute. Wash under the tap. THE PROCESSES OF PURE PHOTOGRAPHY. 49 COL. STUART WORTLEY'S DEVELOPER. 1. Pyrogallol 96 grains Alcohol 1 ounce 2. Potassic bromide 120 grains Water 1 ounce 3. Liquor ammonia 6 minims Water 1 ounce Developer consists of No. 1 6 minims No. 2 3 minims No. 3 . . 3 drams mixed. This is poured upon the plate, or into a flat dish in which the plate is placed, and after a short time the image will begin slowly to appear and gradually to gain strength, Develop- ment does not progress nearly so quickly as with wet collo- dion. Re-development, fixing, intensification, and varnishing may be conducted exactly as in the wet process; '"pyro" being preferable to iron for " strengthening " processes. As a rule, a dry collodion plate for landscape work, the film being very thin and transparent, requires " backing." This is done by painting the back of the plate with a pigment of the following nature (Abney): Powdered sienna, burnt 1 ounce Gum arabic 1 ounce Glycerine 2 drams Water 10 ounces. This is to be removed before development, a sponge being used. The ferrous oxalate developer gives fine results with dry collodion plates (see page 91.) CHAPTER VIII. GELATINE EMULSION PROCESSES PRELIMINARY. WE cheerfully acknowledge, and proudly assert, that in the markets of every civilized country, plates prepared for photo- graphic purposes, with gelatine emulsion, are found, excellent in their qualities, and suitable for every purpose for which they may be intended. We do not expect that any person mak- ing emulsion on a small scale, or with limited appliances, will produce plates of such even perfection as those of professional plate-makers; and we are pretty confident that the amateur plate-maker will not save any money by his plate-making. But we urge upon every one who wishes to work with intelligent comprehension of what he is doing, and every one who has the ambition to further photographic knowledge, by his own efforts to acquire a perfect knowledge of, and facility in, the produc- tion of gelatine emulsion, and the preparation of plates, or paper, therewith. No treatise on modern photography would, in our opinion, be worthy the name, unless it showed evidence of an attempt, at least, to initiate its readers into this, the most important photographic process of the present day. Our modest directions shall be given, to the best of our ability, in such a way that any intelligent person following them, shall be able to produce a good emulsion, and with a little practice, to prepare good plates ; at any rate, so that any person reading them with moderate attention shall grasp the facts guiding our practice,.and the conditions necessary to ensure success. The change of " vehicle " from collodion to gelatine carries in its train more important considerations than might, at first sight, be expected. In a collodion emulsion the collodion is practi- cally a purely mechanical menstruum, in a gelatine emulsion the part played by the gelatine is more, by far, than mechani- THE PROCESSES OF PUKE PHOTOGRAPHY. 51 cal. Many of our most mysterious and aggravating failures arise from this fact. Again, one property of gelatine is, that it permits of a silver haloid being formed in it in a state of very fine division, and of that fine st.ite of division being car- ried through various stages to a much coarser state ; as a num- ber of " marbles " lying together expose to light a much larger amount of surface than a much larger number of " shot drops," so a coarse-grained deposit of silver haloid is more affected by light than a fine-grained one. Moreover, the gelatine is a more powerful halogen absorbent than collodion, and so conduces to greater sensitiveness; and lastly, the gelatine, apparently pro- tecting more strongly the silver haloid molecules, permits of a much more vigorous reducing agent being applied in de- velopment. The haloid chiefly used in gelatine emulsions, for negative work, is silver bromide, and as its general sensitiveness, as well las its special sensitiveness to the less refrangible rays, is greater than that of iodide, we have to take greater precautions as to safety of our light with gelatine bromide emulsion than with either collodio-bromide or the iodide of the wet collodion process. In fact, if we propose to make gelatine bromide emulsion of any suitable degree of sensitiveness, we should use for illumination either ruby and yellow glasses, or several layers of orange paper, or other fabric. Certain apparatus must be provided before any other step should be taken towards emulsion making. A drying-press will be required for drying the plates after they are coated, and it must be noted that aqueous solution of gelatine is by no means easily or speedily dried. The press must, of course, be absolutely light-tight, and the drying must depend on a constant current of cool, dry air rather than on any system depending on heat. We illustrate by a cut, Fig. 1 6, a press, the principle of which may serve to guide others who wish to construct a drying-press. Drying-closet, designed by one of the writers (see Pho- tographic Times, 1888, pp. 133-135), 6x6 feet by 9 feet high ; cross section of air-passage one square foot area. The air is drawn from a veranda and heated by an oil stove. No 52 THE PROCESSES OF PURE PHOTOGRAPHY. burnt air comes in contact with the plates, the heat being used solely to create draught. (For full description, see article cit. sup.) FIG 16. Receptacles, too small to be called "presses," are sometimes used on a small scale ; these are described and figured in many THE PROCESSES OF PURE PHOTOGRAPHY. 53 journals and books ; one designed by Mr. "W. England is, per- haps, as good as any. A drying-room will be found far superior to smaller recep- tacles. If any apartment provided with thorough ventilation and means for entirely excluding every speck of light can be found, plates will dry in such a room, even if it be only ten or twelve feet square, much more quickly than in any box, or even cupboard. Dry air, in a constant and vigorous current, is the required agent for desiccation. Heated air may be used to create a draught, but products of combustion, as from burnt gas, oil, or coal, must on no account be allowed to enter the drying receptacle. While drying, the plates are usually placed on drying-racks, or they may be made to lean against upright spars, with the film turned away from any direction whence dust might come. Plenty of room, as well as plenty of air- current, is required. Leveling Slab. As the plates are coated with a warm ^nd liquid solution of gelatine, which sets in a firmer jelly when cold, and as the plates must have an even film of the emulsion, it is necessary to have a level table whereon to lay the plates after they are coated until the gelatine sets. And as it is ad- vantageous to cause the gelatine to set as rapidly as possible, this level table should be cold. A slab of thick plate glass, slate, or marble is generally used, and it is necessary to have means of leveling the slab. One of the writers uses the large, thick, marble slab of a wash-hand-stand, leveled with screws from below. As emulsion usually gets accidentally upon the back of the plate, and causes the plate not only to be unlevel, but to stick to the slab, it is well to stretch strings or piano wires tightly across the top of the slab. Apparatus for Mixing, Cooking, and Washing the Emul- sion. For mixing the emulsion any vessel may be used that will stand heat and will not in any way chemically affect the emulsion. Glass beakers must be very carefully handled, and vitrified stoneware jars are preferable ; glazed earthen- ware must be avoided. We figure an article, known as a " shut-over jar," which we find admirably suited for emulsion operations ; the price is trifling, and the jars are practically 54 THE PROCESSES OF PUKE PHOTOGRAPHY. light-tight, though we do not unnecessarily expose them to light. Flasks or bottles should be of glass, so that we can tell whether they are clean or not. FIG. 17. Some appliance is needed in order, at a certain stage, to break up the emulsion which lias set into a jelly, and this appliance must, if metal, be of " noble " metal silver, gold, platinum, etc.; or it may be of ivory, ebonite, etc. Frequently the* jelly is forced through a piece of coarse canvas, which must be thoroughly clean. Sometimes the jelly is forced through a silver wire mesh by means of a plunger working in a cylinder. For washing the emulsion a hair sieve will be handy, as described later, or a tea-pot may be utilized, as also mentioned later. Mr. Henderson, of London, provides the most satisfac- tory emulsion washer we have seen, but we have not space to describe or illustrate it here. An operation superior, in our estimation, to washing is that of "centrifugal separation," remarks on which we must also reserve. CHAPTER IX. GELATINE-BROMIDE EMULSION. PART I. To Make a Slow Gelatino-Chloro-Bromide Emulsion, suit- able for subjects with which shortness of exposure is no object. The exposure for this emulsion will be about the same as that for an ordinary " wet-plate." a. Gelatine Nelson's No. 1 60 grains Soak in Water 6 ounces for a few minutes. Add Potassic bromide 275 grains Potassic chloride 40 grains Ten per cent, dilution of strong hydrochloric acid i n water 25 minims b. Silver nitrate 400 grains Water 6 ounces Remarks on the above, which will apply throughout our chapters on emulsion-making. Potassic bromide is frequently found alkaline. Such must at once be rejected. Slighf acidity no harm. The same applies to potassic chloride, The amount of argentic chloride resulting from the above quantity of potassic chloride is very small, but the color of the image seems to be improved by the presence of the chloride. Hence we recommend this emulsion for lantern-slides (see Chapter XXX.) Kelson's No. 1 gelatine is generally used for the emulsifica- tion on account of its purity, but it is not, on account of its softness, so well adapted for forming the bulk of the gelatine in the finished emulsion, (vide " . Shake vigorously, and go on, little by little, pouring I into a, shaking vigorously each time, till the whole of b is mixed into a, and a is in a complete state of froth. Kinse out b with a small quantity of water ; pour into a, and shake for two or three minutes, a will now be a creamy emulsion of gelatine and silver chloro-bromide. A cover is now placed on the vessel containing a and b mixed, or, failing a cover, the emulsion is by other means kept warm for about an hour, being well stirred several times during that time. Then Make a fresh solution of sodic hyposulphite, as for the fixing-bath, but omit the alkali. Make also a strong solution of potassic ferricyanide (" red prussiate of potash.") Place the negative in the hypo for some minutes, and put into a cup or measure a few drops of the ferricyanide solution. Pour the hypo into the measure with the ferricyanide, so as to mix the two well, and then pour the mixture on the negative in the dish. Immediately a reducing action will begin, and the first dose may be sufficient; if the action ceases before sufficient reduction has taken place, add a little more ferricyanide, as before. " Local " reduction, i. e. t reduction of parts only of a nega- tive, may be easily performed by rubbing the parts with a rag, dipped in alcohol. The rubbing must be fairly vigorous and prolonged ; but care must be taken not to break the film by over-rubbing, nor by allowing any grit to get between film and rag. CHAPTEE XYI. DEFECTS IN GELATINE-BROMIDE NEGATIVE. THE gelatine-bromide process is, like all other processes involving delicate manipulation (especially in semi-darkness) and accurate chemical calculations, liable to defects, and some- times a worker will produce a defect altogether peculiar to his own manner of working and unintelligible to others. All that can be done in this chapter is to deal with the defects that anyone may fall upon, and that the writers have themselves experienced and seen. Fog may be due to many causes. It is not difficult to recog- nize, and hardly needs description, but we may liken it to a general veil, of more or less pronounced character, all over the plate. There are two kinds of fog, distinct in nature, appear- ance, and rationale. Green fog is, unfortunately, common in commercial plates kept for any considerable time, and is noticed first in the shadows of a negative as seen from the back of the plate. In this shape it does very little harm ; but what we take to be a variety of the same fog shows itself as a bronzing, spotty, metallic-looking stain, which usually begins at the edges of a plate and creeps inward, finally culminating in red fog, which is a hopeless calamity to the plate. We have watched the progress of this fog from the inchoate " shadow-fog," through the " bronze-period " "into the region of eternal night." Ammonia aggravates it, and in our opinion causes it ; and plates showing a tendency to green fog should be developed with carbonates or ferrous oxalate. Plates even above suspicion of this fog, when they are new, often acquire it if kept in an atmosphere where much carburetted hydrogen gas is burned. Sometimes, indeed frequently, the green fog which appears to be on the surface of the film, can be removed by rubbing the film with a rag dipped in spirits. So far as THE PEOCESSES OF PUKE PHOTOGRAPHY. 101 we know, Mr. R. W. Robinson first brought this cure under our notice. Red fog we have never been able to cure or even to mitigate. We believe it is merely an exaggerated form of green fog. In emulsion-making, red fog may be caused by the boiling process in presence of alkali ; such red fog may be " separated " by the action of " centrifugal force " (see page 64), which makes it probable that this fog is due to some gelatine combination. Grey fog may arise from over-exposure the cure is evi- dent, or rather, the means of prevention ; unsafe light in the developing-rooin, camera or dark-room , slide not light-tight; reflections inside camera or lens-tube. All these can be readily discovered and remedied. Fog may be produced by too long a time being employed for the drying of plates after coating with emulsion, the danger or defect being aggravated in pro- portion as the drying atmosphere is damp or contaminated with carburetted hydrogen or sulphurous fumes. To discover for certain whether the light of the operating- room is at fault, one of the plates may be exposed to the light suspected, for five minutes, in contact with a negative or" the screen of a " sensitizer." If no image appear on subsequent development, the light is " safe." We have already given a method for testing the camera, etc., for light-tightness. An- other method is to place a plate in the camera in the dark-slide as usual, and to draw the shutter, leaving the cap on the lens. The whole is allowed to stand in bright light for a few minutes. On development, fog will show if due to leak- age in the camera, or reflections arising therefrom. Fog may be due to development, to overdose of alkali in pyro development, or to alkaline reaction in ferrous oxalate development. Over-density of the negative may be due to over-develop- ment, pure and simple, or to over-forcing in development of an under-exposed plate. In the former case the cure will be found in the method of " reduction " given on page 99. The other defect, where the high lights are dense out of pro- portion with the shadows, is difficult, if not impossible, to remedy. 102 THE PROCESSES OF PUKE PHOTOGRAPHY. Thinness, or want of density, may be due to several causes. Tinder-development ; intensification will be found more easy in this kind of case than in any other. Over-exposure; in- tensification may be resorted to. Light fog, in quantity not sufficient to entirely ruin the plate, will produce a thin image ; thus a very dim reflection in the camera, or a moderately unsafe light in the operating-room, while not sufficient to pro- duce a regular fog, will produce a thin image. Thinness may be due to the emulsion. If the plate is too thinly coated ; if the emulsion does not contain sufficient of the silver haloid ; if the emulsion has an over-acid, or a very alkaline reaction ; if too much chrome alum be used in the emulsion, and under many other less common conditions, a thin image may result. Frilling may be due to dirty plates; plates overheated before coating; an improper quality of gelatine, or want of alum in the gelatine in very warm weather; osmotic action in the hypo, produced usually by a too strong solution of hypo ; action of too strong acids on the film at some stage, as in the alum bath. Sometimes plates will frill in spite of all that can be done to prevent it, but in commercial pro- ducts frilling is now happily very rare. Yellow Stain all over the plate, due to the pyro, and occur- ing especially with the carbonate developers. The alum and acid bath will remove this stain. Spots. Small transparent spots on the negative are usually due to dust. Opaque spots may arise from the quality of the gelatine ; we have known immense crops of them produced by iron rust in the water supply. Circular transparent spots, with sharp outline, are due to air-bubbles forming in develop- ment, or in the emulsion. (See our instructions for applying the developer.) A broad camePs-hair brush may be used to spread the developer over the film in the developing dish im- mediately after the first application of the developing solution. Some workers soak their plates in plain water before develop- ment, there is no harm in, nor need for, this operation with glass plates. Halation (appearance of "halo." ) Found when objects in THE PROCESSES OF PURE PHOTOGRAPHY. 103 high light and objects in deep shadow are close to each other in the picture, the most frequent examples being the windows in interiors, and branches of trees against a brilliant sky. Halation is due to two causes, which must not be confounded. 1st. Reflection from the back of the glass plate, at an angle near to that of " total reflection." This kind of halation may be obviated by using films in place of glass plates, and to a certain extent by "backing" the glass plates with some sub- stances of non-actinic color in optical contact with the glass. Burnt sienna, rubbed into a paste with gum and water, may be applied to the back of the plate before exposure, and removed with a sponge before development, or a piece of black " carbon tissue " may be wetted and squeegeed into con- tact with the back of the plate. A thin film of emulsion, especially in the absence of the yellow stain due to iodide, is very apt to give halation. The defect may, to some extent, be removed by rubbing with a rag dipped in alcohol. (See page 100.) 2d. Halation due to dust in tTie air. This is, of course, not true halation, in the technical acceptation of the word, but it is often mistaken for the true halation. Neither the use of a film nor "backing" will prevent this kind of halation, but the same cure may be tried, viz. : rubbing down the over-dense parts with alcohol on a rag. Various curious markings may be produced by various blun- ders. Scummy marks are over-produced by using too small a quantity of developer, and not keeping the solution in motion during development. Crape-like marks occur frequently with certain brands of plates, and seem due to dirty glass plates. If, during drying of a negative, water is splashed on to the film, a mark will occur which we can neither account for nor efface ; the result is a patch lig liter than the rest of the nega- tive. Sometimes a bronze-like, metallic-looking scum forms on negatives developed with pyro preserved with sodic sulphite. This may be removed with a rag and alcohol. Whether it is identical with one form of green fog we cannot say. CHAPTEE XVII. PAPER NEGATIVES AND STRIPPING FILMS. IN the chemical operations of developing an image in gela- tine emulsion, there is no difference whether the film of gela- tine be on a rigid, permanent support, or a flexible, textile, temporary support, but of necessity the manipulations must be somewhat altered to suit the altered circumstances. The composition of the solutions for developing, fixing, clearing, etc., already given, will answer for paper negatives and films quite as well as for glass plates. Paper Negatives, wherein the paper remains permanently the support, of which, as a type, we may take Eastman's Nega- tive Films. These may be exposed in cut sheets, for experi- ment ; but vastly preferable are the roll-holders known as the Eastman-Walker. In one of these is placed, with every con- venience for exposure, a long band of negative paper, to be unwound for exposure in proper quantity and position, which can be determined by fittings forming essential parts of the apparatus. In Fig. 20 we show the latest pattern of the East- FIG. 20. man-Walker Roll-holder, and as full instructions are given in various places for its use, we need not waste space in repeating THE PROCESSES OF PUKE PHOTOGRAPHY. 105 these instructions. We will, however, give one or two hints, which we think may prove useful, whether " negative films " or " stripping films " are used in this roll-holder. Although the instrument itself registers on the paper the extremities of each exposure, it is well, whenever opportunity offers during a tour, for instance to mark in pencil each end of the film as it presents itself when the shutter is withdrawn. This will form a further safeguard, beyond the small punched holes, against cutting up the film in the wrong places. (The neces- sity for this is much lessened in the new pattern.) When about to develop a spool of exposed films, the inexperienced will do well to cut off one exposure at a time, and develop one before he cuts off another. (The new pattern is vastly im- proved in this respect, also; in fact, the new design is so superior, in almost every essential point, to the pattern origin- ally introduced, that those who bought the original pattern have a distinct grievance, that, so soon after they had pur- chased one pattern, another so greatly superior should be brought under their notice, and should excite their covet- ousness and tempt them to extravagance.) The exposed length of film for development, being cut off, is immersed in water face downwards for a few seconds, being slidden sideways, if possible, into the water; after the few seconds have elapsed it is lifted face up and either brushed over with a broad hair brush under water, or pulled quickly along the face up under w^ater. This is simply to prevent air- bells. Development follows, then fixing, washing, clearing, washing again. Then the film is squeegeed face downwards to a polished sheet of vulcanite, where it is allowed to dry, "and whence, when dry, it ought to strip off with ease, one corner being raised with a knife or other pointed instrument. According to the instructions, the negative should then be rendered translucent by the application of some oily lubricant, such as the " translucine," sold for the purpose. Against this oiling we protest. Printing truly is rendered more rapid, and "grain," possibly, may be slightly eliminated, but with- out special and highly inconvenient means the negatives so treated cannot be preserved for any considerable length of 106 THE PROCESSES OF PUKE PHOTOGRAPHY. time. The best method by far, if the negatives are of any nature, is to leave them as they come from the vulcanite. Stripping films (also "Eastman") are coming into more and more general use by rapid strides. In this case develop- ment, fixing, and washing are precisely as before ; but, for evident reasons, the paper being removed finally, the develop- ment should be carried a little further, apparently (i. , or on the floor in the case of a separate easel, and if the table of enlargements found at the end of this book be consulted, the relative positions of the various parts can be very easily regulated, and the focus almost precisely found without examination. Suppose, for instance, it is desired to enlarge a quarter-plate negative to a whole-plate positive, with a lens of 6 inches focus. Consult- ing the table, we find in the proper square under " 4 times " 7 3 . "We, therefore, at once place the centre of our lens 7 inches from the negative, and our easel 30 inches from the lens. We then arrange our picture suitably on a piece of plain white paper attached to the easel, raising or lowering our camera front or our easel as desired. An even less cos'tly arrangement for enlarging verjr small negatives, as quarter-plates, to moderate sizes, as 10x12 (pro- vided the worker has two cameras, a small one and a large one, with sufficient stretch), is figured 27 on page 173. For enlarg- ing, of course, this arrangement is reversed that is to say, the small camera is placed next the light. With this arrangement good enlargements may be produced without any specially adapted apartment. It is impossible to lay lown rules for exposure, so many different cases have to be met. The light varies, our sensi- tive materials vary, our negatives vary ; but supposing there was no variation in these, and supposing the same lens with the same aperture to be invariably used, we can then give at least one rule which will be of service. 168 THE PROCESSES OF PURE PHOTOGRAPHY. Exposure varies directly as "times" of enlargement. Example : To enlarge a quarter-plate negative to whole plate (4 areas) the required exposure is found to be ten minutes. To enlarge the same negative under the same conditions of light, lens, sensitive surface, etc., to 13x17 inches (16 areas), the ex- posure required would be forty minutes : 4 : 16 : : 10 : 40. During exposure no actinic light must enter the apartment, and during focusing it is well to allow no light to enter the room at all, actinic or otherwise, except what passes through the negative and the projection lens. While the sensi- tive material is being put in position after focusing, the lens is to be capped, and the room may be illuminated by non-actinic light, for which provision was made. While the exposure is going on a great deal can be done in the way of " dodging." Vignettes of any shape can be produced by cutting an aperture of the required shape in a piece of cardboard or wood, and holding the mask so made between the lens and the sensitive surface, moving the mask constantly to and from the sensitive material. As the image is plainly seen projected on the sensi- tive surface, this operation is one of perfect simplicity. In like manner any part of the image that prints too dark can be shaded during part of the exposure. But in any case the mask should be kept on the move, else hard lines will result on the print. Whatever be the sensitive surface used, bromide paper, wet collodion, etc., development is conducted as already laid down under the several headings. When large sheets of paper are used special developing dishes may be required ; dishes for larger sheets may be made with plate glass bottoms and var- nished wooden sides. Enlarging by the Optical Lantern with (1) an oil lamp (2) oxyhydrogen lime light. This is perhaps the favorite process with amateurs, and it is certainly a convenient and simple process for enlarging small originals. But the condenser must be of diameter equal to, and ought to be of diameter slightly greater, than the diagonal of the part to be enlarged. In the next place the lantern nozzle should be so constructed as to allow the objective to be racked to at least twice its own THE PROCESSES OF PUKE PHOTOGRAPHY. 169 focal length from the negative. The sensitive material is fixed in front of the objective, which may be a portrait lens, and the whole system from light to sensitive material should be axially centered, and the paper or glass parallel with the negative. No light must stray from the lantern so as to affect the sensi- tive material, so it is usual to inclose the ordinary optical lan- tern in a larger box, the nozzle only protruding thro ugh a hole for the purpose. Lanterns are, however, made specially for the purpose of enlarging, and usually are well adapted for that purpose. When the oxyhydrogen light is used the area of incandes- cence of the lime, being but small, is easily placed in the focus of the condenser, but where a lamp with several wicks is used there is apt to be a considerable loss of light. To obviate this loss of light Mr. J. Traill Taylor suggests the use of a simple supplementary lens placed between the light and the conden- ser, and, like most of that gentleman's optical suggestions, this one is very valuable. The same rules hold good for this process of enlarging, with regard to exposure, as for the daylight process. The effect of the condenser in shortening the exposure may seem astonish- ing to the beginner, who is ignorant of the optics of the mat- ter. Vignetting and other " dodging " are quite as easy with artificial light as daylight. We have seen and used an arrangement for enlarging still more simple and less costly than 'those described above. No condenser was used, but the artificial light was diffused over the original by means of a sheet of finely ground-glass placed be- tween the light and the negati ve,and about one and one-half inch behind the original. By this process a much larger negative may be enlarged by artificial light, but the exposure is very long, and the rules for choice of projection lens are the same as for daylight enlarging with a reflector, that is to say the pro- jecting lens must be of long focus. If the original be un- usually large, as 8x10 or 10x12 inches, several lights will be re- quired to illuminate the original evenly, the only alternative removing the light to a considerable distance from the ground- glass entailing an inconvenient duration of exposure. 170 THE PROCESSES OF PUKE PHOTOGRAPHY. Collodion Transfers are produced by coating a talced sheet of glass with iodized collodion, sensitizing, developing, fixing and washing in the usual way, provision being made for secur- ing pleasing tones. The film is then placed in contact with a sheet of paper such as " Carbon Double Transfer " (see page 162), squeegeeing the paper to the film, drying, and stripping from' the glass. These transfers are usually enlargements, which is our reason for mentioning them here. CHAPTEE XXX. LANTERN SLIDES. PHOTOGRAPHY, perhaps, reaches its climax of beauty and utility in a good lantern-slide shown on a good screen with a good light. The size of the view so shown is not per se the chief advantage, but it enables a number of people to see in company which is always pleasing to the majority of people. The optical lantern is valuable both to art and science, for while pictures may be shown on a scale more dignified and more worthy of their merits, scientific facts may be demon- strated in a manner precluding mistake, and with a weight of evidence precluding unbelief. But while a good lantern- slide is a thing of beauty and of utility, a bad one is a horror which we too often see in public exhibitions, not to mention private ones. The worker must first learn the characteristics of a good slide, and they are not learned without considerable study. A slide may be a very pretty, little, positive transparency, and yet totally useless as a lantern-slide. A slide must have, first, absolute clearness in the highest lights ; second, transparent shadows. If either of these points is transgressed the slide is useless, to start with. But besides the highest lights no other part must be absolutely clear. The midsummer snow scenes, so frequently seen and frequently applauded by an ignorant public are the results of neglect of this rule. These " hard " slides are usually the result of either hard negatives or under- exposure of the slides, necessitating forced development. A slide must have plenty of half tone, but not too much. The commonest type, perhaps, of bad slides, is that where we see nothing but half tone, to put it mildly, or nothing but incipi- ent fog, to put it plainly. Beginners with gelatine bromide 172 THE PROCESSES OF PURE PHOTOGRAPHY. for lantern-slides are very apt to produce these foggy lides ; nothing can be uglier, unless it is the snow scenes already alluded to. A slide must have : 1. Clear highest lights. 2. Half-tone in secondary lights. 3. Detail in the shadows. -4. A pleasing " tone " or color. The processes commonly used for producing lantern- slides are : Wet collodion, dry collodion, gelatine chloride, gelatine bromide. In point of exposure the gelatine bromide is by far the quickest of these processes, gelatine chloride is so insensi- tive that practically it is only used for making " slides by con- tact." When the negative is just about the size required for a lantern-slide (three and a quarter inches square), contact printing is resorted to, a sensitive plate taking the place of a piece of paper used for ordinary printing in a frame ; care must be taken not to scratch the negative nor the sensitive plate when bringing the two together. When the negative is larger than the standard slide size, the slide has to be made by " redaction in the camera." The process of reduction is simply making a copy on glass of the negative by transmitted light ; the copy will, of course, be a positive. Mechanical Arrangements for Reducing. As a matter of practice any means whereby a copy may be made of the nega- tive as above, the copy being of the proper size, will answer for making a slide by reduction, but it is found better to take precautions to prevent any light, other than what passes through the negative, from reaching the copying lens. Many costly and intricate arrangements have been devised for the mechan- ical part of the process, but we shall confine ourselves to the description of one apparatus which everyone is likely to have, or can at least get with very little trouble. The first requisite is the camera in which the original negative was taken, a wet- plate slide fitting that camera, or a double slide with the inter- nal partition removed. The other requisite is also a camera, this time a quarter plate camera of the simplest description, no motion but a rack and pinion for focusing being required, fitted with a short focus lens, such as a rectilinear stereo lens. THE PROCESSES OF PURE PHOTOGRAPHY. 173 The front, or part of the front of the larger camera is removed, and the small camera is fitted to the front of the larger cam- era, with the small lens protruding into the larger camera. We figure (Fig. 27) our own arrangement, as fitted up by our- FIG. 27. selves, and we have never yet found circumstances which this did not suit. The lens should be of very short focus, not over four inches or four and a half inches focus, and must be recti- linear. The negative to be copied goes into the dark-slide of the larger camera, the sensitive plate goes into the dark-slide of the small camera. The back of the larger camera may be pointed towards the sky, and a sheet of finely-ground glass placed about one or two inches behind the negative ; i. e., between the negative and the light ; or a sheet of white paper 174 THE PROCESSES OF PUKE PHOTOGRAPHY. large enough to illuminate by reflection, the whole negative may be inclined at 45 deg. between the light and the negative. The amount of reduction is regulated by the focusing arrange- ment of the larger camera, different parts of the negative may be selected for copying by the front motions of the larger camera, and focusing is performed on the ground-glass of the small camera, preferably with a Ramsden eyepiece. The exposure with ground-glass behind the negative may vary at -jC- : With Gelatine Bromide lantern plates, from five to one hundred and twenty seconds. With Wet Collodion, from thirty seconds to ten minutes. With Dry Collodion, from three minutes to two hours. We have, of course, gone beyond these limits in both direc- tions ; the table is given merely suggestively. Even gelatine chloride plates may be used for reduction in the camera, the exposure being very long if the negatives are of average density. Gelatine chloride emulsion may be made more sensitive by cooking, but, as a rule, there is great danger of fogginess from this proceeding. Gelatine chloride emulsion for lantern-slides and transparent positives. Plates prepared with this emulsion are usually ex- posed in contact with the negative, for a few seconds, to day- light. The negative is placed in a printing frame face up- wards, and the chloride plate carefully laid on the negative film to film. Mr. A. Cowan, of London, has favored the pub- lic with some very fine developing formulae for such plates, and by the use of his varied proportions and ingredients he produced a large range of tones on his plates. Iron protosulphate 140 grains Sulphuric acid 1 minim Water 1 ounce Add one part of this to three parts of any of the following, No. 1 giving cold tones, No. 3 almost crimson. No. 3 requires much more exposure than No. 2, and No. 2 more than No. 1. 1. Potassic citrate 136 grains Potassic oxalate 44 grains Hot water 1 ounce THE PROCESSES OF PURE PHOTOGRAPHY. 175 2. Citric Acid 120 grains Ammonia carbonate 88 grains Cold water 1 ounce 3. Citric acid 180 grains Ammonia carbonate 60 grains Water 1 ounce The following, due to Mr. B. J. Edwards, gives good tones. a. Neutral potassic oxalate 2 ounces Ammonium chloride 40 grains Distilled water 20 ounces b. Iron protosulphate , . 4 drams Citric acid 2 drams Potash alum 2 drams Water 20 ounces Mix a and & in equal proportions. Chloride plates should develop pretty rapidly ; if the image appears to develop too rapidly add a few drops of a ten per cent, solution of common salt. Fix in hypo, and after washing clear with a saturated solution of potash alum, acidulated with sulphuric acid. Glass and opal plates coated with this emulsion yield beau- tiful positives, when printed in contact and treated as above. Lantern-Slides ly Dry Collodion Processes. Supposing plates to be coated with collodio-bromide emulsion prepared as given on page 46, et seq., we proceed to give instructions how these plates may best be used for lantern-slides, and we may say that it is extremely doubtful whether for really good lantern-slides with clear lights, transparent shadows, and, above all, warm tones, this process can be surpassed. To insure the warm tones on which we so much insist, the use of ammonia is contraindicated, and the carbonates coupled with a long exposure will be found best. The formulae we give are due mostly to Mr. W. Brooks, of Keigate, who pre- pares emulsion, and with it slides not easily equaled. PYRO SOLUTION. Pyrogallol 96 grains Alcohol 1 ounce 176 THE PROCESSES OF PUEE PHOTOGRAPHY. ALKALINE SOLUTIONS. 1. Saturated solution of ammonia carbonate 4 ounces Potassic bromide 60 grains Sodic acetate 120 grains Water 8 ounces 2. Potassic carbonate 360 grains Potassic bromide 60 grains Sodic acetate 120 grains Water 12 ounces 3. Potassic carbonate 300 grains Potassic bicarbonate 150 grains Potassic bromide 60 grains Sodic acetate 120 grains Water 12 ounces No. 1 requires the longest exposure, and gives the warmest tones ; the ammonium' carbonate must be fresh and pure, and for saturation should be left several days in water, getting an occasional shaking. After this some of the crystals must be left at the bottom of the bottle. No. 2 is a more powerful alka- line solution than No. 1, and requires much less exposure. The tones given by No. 2 are not so good as those of No. 1. Nos. 1 and 3, mixed in equal quantities, give a grand chestnut tone with a moderate exposure. After exposure the plate is flowed in yellow light with a mixture of methylated spirits and water in equal parts. This is allowed to act on the film for about a minute, and is then washed off. The plate may either be immersed in the developer in a dish or held in the hand by a pneumatic holder, and the developer flowed over it. Development is not so quick as with a gelatine plate ; the image appears faint at first, with details, perhaps, all over, and density is gained very gradually. The developer consists of Pyro solution, as above 20 minims One of the alkaline solutions, or a mixture of two of them 2 drams Water 2 drams The developer must not be poured off and on at first, but as details and density increase pouring off and on may be resorted THE PROCESSES OF PURE PHOTOGRAPHY. 177 to as a local intensification. Development to full density may occupy five or six minutes, and the plate is then to be washed and fixed with hypo, or, preferably, potassic cyanide, 20 grains ; water, 1 ounce. Ee-development may be resorted to with pyro and silver, as follows, but we do not like it, as the shadows are apt to get blocked up. Ee-developer (which may also be used later as an intensifier): Pyrogallol 30 grains Citric acid 30 grains Alum 30 grains Water 15 ounces Flow a sufficient quantity of this over the plate, then return it to the cup to which meantime have been added, for every two drams of the pyro and acid solution, two or three drops of a twenty-grain solution of silver nitrate. This is to be poured on and off the plate, but the instant any cloudiness appears the solution must be rejected and a fresh quantity made if neces- sary. To get various fine tones more nearly approaching the blues the plate may be toned with : Platinic chloride 1 grain Nitric acid 1 minim Water 3 ounces The plate may be removed when a warm brown tone is arrived at, or at any other desired stage, but to produce a very fine engraving black tone the plate may be left in the platinum solution till the image is almost gone, or very gray ; it is then to be washed and intensified with the pyro intensifier given. Though we do not like re-development, we recommend intensi- fication after fixing by this acid-alum-pyro solution, which is due to Mr. Brooks, and gives very fine tones indeed. Any slight veil or fog on a collodion positive may be removed by flowing over it several times a strong colored solution of iodine made by adding water to the " tincture." Silver iodide is formed, and cyanide solution, as for fixing, will clear the plate at once. Collodion slides and positives for window decoration, which 178 THE PROCESSES OF PURE PHOTOGRAPH r. may be made equally with slides by the above process, should be varnished with a clear white varnish (see formulae at the end). Wet collodion for lantern-slides. We have pointed out in Chapter VI. a suitable method of making slides by this process. The platinum toning bath may be used as above, or the following, due to Mr. T. N. Armstrong, an amateur of Glasgow : Palladium chloride . . : 15 grains Water 15 ounces For each ounce of water required to cover the slide in a dish take one dram of the above. Leave the slide in this till the tone has reached the back of the film, as seen through the glass plate. If any dense parts refuse to tone, pour the solu- tion on to them several times from a slight height. Eight or ten minutes should suffice to tone a plate by this method, and the tone is not only unique but highly pleasing, Gelatine Bromide for Lantern-Slides, In the chapter on slow gelatine-bromide emulsion will be found directions for making an emulsion eminently suitable for the purpose of lantern-slide preparation. We may say that the "slower" the emulsion the more likely it will be to give good slides in the beginner's hands. The gelatine-bromide plates usually put on the market for this purpose are, in our opinion, too rapid and too liable in unskilled hands to give foggy slides, which of all kind of slides are the worst and the commonest. The ex- posure, whether by contact, or in the camera, must be such that no forcing, or abnormal quantity of alkali, is required in develop- ment ; further we need not go. For development the ferrous oxalate may be used, keeping the proportion of iron low, and using a proportion of soluble bromide (say half a grain to each ounce of a developer con- sisting of potassic oxalate solution, as given elsewhere (page 92), six parts, iron solution one part). Mr. Carbutt, U. S. A., gives a formula which will be found to work well with many plates. a. Potassic oxalate 8 ounces Water 30 ounces Citric acid. . . . 60 grains Citrate of ammonia solution. .. . 2 ounces THE PKOCESSES OF PUKE PHOTOGRAPHY. 179 b. Ferrous sulphate 4 ounces Water 32 ounces Sulphuric acid 8 minims The citrate of ammonia solution is : Dissolve citric acid 1 ounce Water 5 ounces Add liquor ammonia till neutral, make up to eight ounces. The developer consists of a 2 ounces b 1 ounce 10 per cent solution of potassic bromide 5 minims Mr. Edward's hydrochinon developer acts well. It will be found quoted on page 145. "Where a warm tone is required, undoubtedly the best de- veloper is alkaline pyrogallol. But sodic sulphite must not form an ingredient of the alkaline pyro developer, we have never liked the tone peculiar to that salt, and we have never yet been able entirely to prevent the peculiar tone given by that salt from appearing in our slides. Very much superior, in our estimation, for this purpose, if for no other, is the potassic bisulphite, which first caught our attention in a formula pro- mulgated by Messrs. Mawsan and Swan, of Newcastle. The salt was, in this formula, called " meta-bisulphite ;" we have never yet met a satisfactory account of this name, and we find ordinary potassic bisulphite precisely the same in action as in appearance and odor. "We shall, however, give Messrs. Maw- san and Swan's own formula, leaving the reader to use the " meta," if he can get it, or omit the " meta," if it is not forth- coming. a. Pyrogallol 40 grains Potassic meta-bisulphite 120 grains Water 20 ounces b. Liquor ammonia fort 2^ drams Ammonium bromide 40 grains Water 10 ounces To develop mix a and b in equal proportions. "With any of these developers the image should begin to appear after the 180 THE PROCESSES OF PUKE PHOTOGRAPHY. plate has been in the solution about forty-five seconds or a minute. There should be no rushing up of details or density. Yery pretty little glass dishes may be obtained for developing slides ; they must be kept scrupulously clean ; a stain that would never be noticed on a negative, may be ruin to so deli- cate a picture as a lantern-slide should be. We give one more pyro developer, which may be called a standard developer ; it works well with every good plate we have yet met. a. Solution of pyro, preserved with citric acid, 20 grains to each ounce 10 per cent b. Ammonia 10 per cent c. Bromide (amm. or pot.) 10 per cent DEVELOPER. a 20 minims b 20 to 25 minims c 20 minims Water 1 ounce Fixing is done with Sodic hyposulphite 1 part Water 5 parts After fixing, a scum is frequently noticed on slides. Strong solution of alum, acidified with sulphuric acid, poured on and off, will almost always remove the scum. Mr. Edwards recommends the addition of ferrous sulphate to the alum and acid. If the plate, after fixing, be not washed, but merely rinsed under the tap, a fine warm tone may be produced by pouring on a solution of the following nature : Alum (potash) concentrated solution, containing citric acid to saturation 1 ounce Iron protosulphate, saturated % ounce The warm tone produced may be suspected of fugitiveness, but we find it permanent. Eastman's transferotype process yields fine slides. (See page 147.) The development is conducted as usual, preferably with ferrous oxalate, and the finished paper film is squeegeed to a piece of glass of the required size, and scrupulously clean. THE PROCESSES OF PURE PHOTOGRAPHY. 181 If the plates are just 3^ inches square, the prints should, before being squeegeed, be trimmed slightly smaller, as the edges of the paper must not overlap the glass. After stripping, which must not be attempted until at least half an hour has elapsed after squeegeeing, the plate is cleared with alum and acid, washed and dried. All slides should be varnished with clear or "crystal " varnish. To Mount Lantern-Slides. Articles required: Masks of variously shaped apertures ; " strips " to gum round edges ; clean and thin glasses 3 inches square. The cover-glasses should be free from imperfections, as bubbles. The shape of the mask apertures is a matter not sufficiently attended to. Mr. J. W. Champney contributed to a New York society some remarks which deserve attention. The masks must be opaque. A very good paper for the purpose is white on one side and black on the other, the white side being utilized for writing the names of the subjects. " Strips " are sold ready-gummed. As a rule, these cannot be trusted to stick long, and the safer plan is to get plain strips of " needle-paper " about 14 inches long, and at the time of use to cover each strip with thin glue, to which is added a small quantity of oil of lavender, a hint for winch we have to thank the illustrious Mr. George Wash- ington Wilson, of Aberdeen. 1 The slide being finally mounted requires some mark, so that the lantern operator may know at a sjlance which way to put it into the lantern. Lay the slide down on the table as the view appeared in nature, and at each of the two top corners place a small disc of gmnmed paper, white on a black mask, and vice versa. CHAPTER XXXI. RESIDUES. AMATEURS, who find their hobby somewhat expensive, and professionals, whose yearly returns are not as large as might be desired, will do well to preserve carefully all material con- taining noble metals in any shape. A very small percentage of the silver originally used in the preparation of sensitive substances is present in the finished negative or print. We have seen it stated that a print on albumenized paper contains only about 3 per cent, of the silver originally present in it. We do not guarantee the accuracy of this estimate, but it is probably not -very far wide of the mark. The following should always be carefully preserved : 1st. All paper containing or bearing silver salts, as trimmings of un- toned albumenized paper, bromide and chloride papers, filter papers used for silver solutions. 2d. Water wherein prints containing free silver nitrate have been washed. 3d. Old toning baths. 4th. Old fixing baths. 5th. Waste emulsions of any kind. 1. Paper Residues. After a considerable quantity of waste paper has been collected, it should be burned completely to fine ashes. An ordinary stove or grate will answer for burn- ing, provided the draught do not carry away the very light ashes. 2. Washing Waters. The first two waters used for washing sensitized albumenized paper should be put into a reservoir with a tap about four to six inches from the bottom. When the vessel is pretty full, hydrochloric acid may be used to acidify the residue, and the silver may be thrown down as chloride by the addition of a quantity of concentrated solution of sodic chloride common salt. Hydrochloric acid may be used to THE PROCESSES OF PURE PHOTOGRAPHY. 183 throw down all the silver, but we prefer the salt. If too much salt be added, the chloride will be re-dissolved. When the chloride is all down, the supernatant liquid is drawn off by the tap, or siphoned off, or even baled off. The chloride is col- lected, washed in water, dried, and added to the paper ashes. 3. Old Toning Baths. In a toning bath the gold may be inert as a toning substance but can be saved. The bottle con- taining a toning bath often becomes encrusted with a deposit of gold ; this may be dissolved by aqua regia and added to the bulk of old baths. The bulk being acidified with sul- phuric acid, a saturated solution of ferrous sulphate is added till no more gold is precipitated. The precipitate is collected, washed, dried, and may either be added to Nos. 1 and 2, or kept separate. 4. Old Fixing Baths are usually the most valuable of all residues. Every plate, whether exposed or gone wrong before? during or after exposure, should be " fixed." The used fixing baths are to be preserved in a vessel similar to that used for No. 2. The solution should be acidified with sulphuric acid, and precipitation of the silver effected by the addition of a strong solution of potassic sulphide, " liver of sulphur." This, however, must not be done in the operating, nor, indeed, in any inhabited room ; but in the open air, for the odor is both unpleasant and unwholesome. As an alternative, strips of zinc or copper may be suspended in the old hypo solution, when the silver will be precipitated on the strips or on the vessel. When the precipitation is complete, the deposit is collected, washed, dried, and kept separate from other residues. 5. Old Emulsions, if of collodion, may be poured out to set in ; a ' flat dish, allowed to desiccate, lifted or scraped from the dish, and added to the paper ashes, or the chlorides. If of gelatine, they should be treated in one of the following ways : Add to the waste emulsion, in a large iron pot, five times its weight of caustic alkali and boil for half an hour. The boiling will be very furious at first, but will subside after a little. Or several times its bulk of sulphuric acid may be added to the emulsion and the whole boiled for a few minutes. In each case the gelatine will be deprived of its setting power 184 THE PROCESSES OF PURE PHOTOGRAPHY. or viscous quality, and the silver in whatever state it is will settle to the bottom and can be separated by decantation from the liquid. It may then be washed and added to the chlorides. Platinum residues are very valuable and may be saved thus : All waste paper should be passed through the developing solution. Old potassic oxalate developing solutions are col- lected and boiled with one-fourth of their volume of ferrous sulphate. The platinum separates and can be collected on a filter. We do not advise the reader to fuse his own residues as a matter of business, for a professional refiner will get much more noble metal out of them than the photographer is likely to do. As an interesting experiment, however, the following may be tried. Take the paper ash and the chlorides, with which may be included the gold, dry all thoroughly and mix with a, flux consisting of four times the weight of the chlorides of a mixture in equal parts of the carbonates of soda and potash. Mix thoroughly and put into a crucible, subjecting it to white heat till the contents of the crucible are perfectly liquid. Then either pour out on to a cold stone floor, or allow to cool and break the crucible. In one case a bar, in the other a button of silver, will be found. If gold is present a refiner will allow for it. THE PROCESSES OF PUKE PHOTOGRAPHY. 185 FORMULAE RECOMMENDED. Varnish for gelatine negatives ("British Journal Alma- nac.") Best Orange Shellac \% ounce Methylated alcohol 1 pint Keep in a warm place till dissolved, then add a large tea- spoonful of whiting or prepared chalk ; set aside to clear ; decant. Plate to be heated before and after application. GROUND GLASS OR " MATT" VARNISH. Sandarac 90 grains Mastic 20 grains Ether 2 ounces Benzole ^ to 1)^ ounces More benzole added finer the matt obtained. This varnish to be applied cold. GELATINE BROMIDE PROCESSES DEVELOPERS. EDWARD'S GLYCERINE DEVELOPER. a. Pyro 1 ounce Glycerine 1 ounce Methyl alcohol 6 ounces Mix spirits and glycerine, then add pyro. a. One part of this to fifteen of water. b. Potassic bromide 60 grains Liq. Amm. .880 1 ounce Glycerine 1 ounce Water Bounces b. One part of this to fifteen of water. Developer : Equal parts of the above, a and I. MR. WOLLASTON'S MODIFICATION OF THE EASTMAN DEVELOPER FOR PAPER NEGATIVES a. Sodic sulphite pure 8 ounces Hot distilled water . . 40 ounces 186 THE PROCESSES OF PUKE PHOTOGRAPHY. Cool to 60 deg. Fahr. Make just acid with citric acid. Pour on to one ounce of pyro. b. Sodic carb 4 ounces Potassic carb 1 ounce Distilled water 40 ounces Equal parts of a and b. A SIMPLE DEVELOPER FOR GELATINE BROMIDE. a. Pyro 40 grains Added to, Water 10 ounces In which is dissolved Citric acid 10 grains b, Liq. Amm. .880 1 dram Amm. brom 25 grains Water 10 ounces Equal parts of a and b. HYDROCHINON DEVELOPER. a. Hydrochinon 20 grains Water 10 ounces Sodic sulphite 10 grains Dissolved together first. b. Carbonates according to Wollaston above or to formula in text. CLEARING SOLUTIONS FOR GELATINE BROMIDE PLATES. MR. EDWARDS'. Alum 1 ounce Citric acid 1 ounce Sulphate of iron 3 ounces Water 20 ounces Another : Alum Bounces Hydrochloric acid ^ ounce Water 20 ounces INTENSIFYING SOLUTIONS FOR GELATINE PLATES. a. Mercuric chloride 1 part Ammonic chloride 1 part Water 20 parts THE PROCESSES OF PURE PHOTOGRAPHY. 187 Bleach thoroughly, wash thoroughly, then pour on b. Liquid ammonia 1 part Water 20 parts Or, Sodic hyposulphite 1 part Water lOJparts Or, Sodic sulphite , 1 part Water 5 parts URANIUM INTENSIFIER. a. Uranium nitrate in water 1 per cent. b, Potassic ferricyanide in water 2 per cent. Flood the plate with #, then mix in 5. TONING BATHS. BLACK TONES (MR. SCHOLZIG). Sodic tungstate 30 grains Boiling water 3 ounces Dissolve, then add Gold chloride 1 grain Water to Bounces PHOSPHATE BATH. Sodic phosphate 30 grains Gold chloride 1 grain Water Bounces Does not keep well. 188 THE PROCESSES OF POKE PHOTOGRAPHY. TABLE OF ATOMIC AND MOLECULAR WEIGHTS OF THE ELEMENTS. (Derived from Professor F. W. Clarke's figures.) NAMES AND SYMBOLS. WEIGHTS. wK NAMES AND SYMBOLS. WEIGHTS. wfht* Aluminum, Al. . .. Antimony, Sb. . . . 27.0090 119.9550 74 9180 27. 120. 74 9 Nickel, Ni Niobium, Nb 57.9280 93.8120 14 0210 57.9 93.8 14 Barium, Ba Bismuth, Bi Boron, Bo Bromine, Br Cadmium, Cd. . . . Csesium, Cs 136.7630 207.5230 10.9410 79.7680 111.8350 132.5830 136.8 207.5 10.9 79.8 111.8 132.6 Osmium, Os Oxygen, O Palladium, Pd . . . Phosphorous, P. . . Platinum, Pt Potassium, K 198.4940 15.9633 105.7370 30.9580 194.4150 39.0190 198.5 16. 105.7 31. 194.4 39. Calcium, Ca Carbon, C 39.9900 11.9736 40. 12. Rhodium, Rh Rubidium, Rb 104.0550 85.2510 104.1 85.3 Cerium, Ce 140.4240 140.4 Ruthenium, Ru.. 104.2170 104.2 Chlorine, Cl 35 3700 35 4 43 9800 44. Chromium, Cr. . . . Cobalt, Co Copper Cu 52.0090 58.8870 63 1730 52. 58.9 63 2 Selenium, Se Silicon, Si 78.7970 28.1950 107 6750 78.8 28.2 107.7 Didymium, D. . . . Erbium, E Fluorine, Fl Gallium, Ga Glucinum, G. . . ,. Gold, Au Hydrogen, H Indium, In Iodine, I 144.5730 165.8910 18.9840 68.8540 9.0850 196.1550 1.0000 113.3980 126.5570 144.6 165.9 19. 68.9 9.1 196.2 1- 113.4 126.6 Sodium, Na Strontium, Sr . . . Sulphur, S Tantalum, Ta Tellurium, Te Thallium, Tl Thorium, Th Tin, Sn *Titanium, Ti. . . . 22.9980 87.3740 31.9840 182.1440 127.9600 203.7150 233.4140 117.6980 47.0997 23. 87.4 32. 182.1 128. 203.7 233.4 117.7 48. Iridium, Ir Iron, Fe Lanthanum La. . .. Lead, Pb Lithium Li .. 192.6510 55.9130 138.5260 206.4710 7.0073 192.7 55.9 138.5 206.5 7. Tungsten, W Uranium, U Vanadium, Va. . .. Ytterbium, Yb. . . Yttrium, Y 183.6100 238.4820 51.2560 172.7610 89.8160 183.6 238.5 51.3 172.8 89.8 Magnesium, Mg. . Manganese, Mn. .. Mercury, Hg Molybdenum, Mo 23.9590 53.9060 199.7120 95.5270 24. 53.9 199.7 95.5 Zinc, Zn Zirconium, Zr. . . . 64.9045 89.3670 64.9 89.4 ' Thorpe, T. E., Chemical News, 48 ; 251. THE PROCESSES OF PURE PHOTOGRAPHY. 189 o S^^wc.*.^ "w^w^" 1 : 8 8 " 3 g-0'-' O 00 > O < O^o > ^ o!cn' w M(MK'"tn'Kw' t " t " w " c "'w'M t "M m ' m ' < "wM t ""' t i .E.S ci-S B.S.S.S g.S.S.S iad.S g P '.S S a.S d Q..S.S d.S.S ac c d > 8 8 " ">c. r *. c i'*. e> . "' "' " " " 00 1-.OOCN ^ ^ > ^ ^ . CO M i M rf ; oi M rf BJ rf dg g > d,S > g >.S.S dg.S g.S.S g g g ^.S rf . rf l^id : '1 s "1JS ..111 i*,BsJag8 Rllisl^! ffl III' 190 TBE PROCESSES OF PUKE PHOTOGRAPHY. METRIC SYSTEM OF WEIGHTS AND MEASURES. MEASURES OF LENGTH. DENOMINATIONS AND VALUES. EQUIVALENTS IN USE. Myriameter Kilometer 10,000 meters. 1,000 meters. 100 meters. 10 meters. 1 meter. l-10th of a meter. l-100th of a meter. l-1000th of a meter. 6.2137 miles. .62137 mile, or 3,280 ft. 328. feet and 1 inch. 393 7 inches. 39 37 inches. 3 937 inches. 3937 inch. 0394 inch. 10 ins. r)pkarn>ter, Meter Decimeter Centimeter Millimeter MEASURES OF SURFACE. DENOMINATIONS AND VALUES. EQUIVALENTS IN USE. Hectare '. 10,000 square meters. 100 square meters. 1 square meter. 2.471 acres. 119.6 square yards. 1,550. square inches. Are MEASURES OF VOLUME. DENOMINATIONS AND VALUES. EQUIVALENTS IN USE. NAMES. No. OF LITERS. CUBIC MEASURES. DRY MEASURE. WINB MEASURE. Kiloliter or stere Hectoliter Dekaliter Liter 1,000 100 10 1 1-10 1-100 1-1000 1 cubic meter. l-10th cubic meter. 10 cubic decimeters. 1 cubic decimeter. l-10th cubic decimeter. 10 cubic centimeters. 1 cubic centimeter. 1.308 cubic yards. 2 bu. and 3.35 pecks. 9.08 quarts. .908 quart. 6. 1022 cubic inches. .6102 cubic inch. .061 cubic inch. 264.17 gallons. 26.417 gallons. 2.6417 gallons. 1.0567 quarts. .845 gill. . 338 fluid oz. .27 fl. drm. Deciliter Centiliter Milliliter WEIGHTS. DENOMINATIONS AND VALUES. EQUIVALENTS IN USE. NAMES. NUMBER OF GRAMS. WEIGHT OF VOLUME OF WATER AT ITS MAXIMUM DENSITY. AVOIRDUPOIS WEIGHT. Millier or Tonneau 1,000,000 100,000 10,000 1,000 100 10 1 1-10 1-100 1-1000 1 cubic meter. 1 hectoliter. 10 liters. 1 liter. 1 deciliter. 10 cubic centimeters. 1 cubic centimeter. l-10th of a cubic centimeter. 10 cubic millimeters. 1 cubic millimeter. 2204.6 pounds. 220.46 pounds. 22.046 pounds. 2.2046 pounds. 3.5274 ounces. .3527 ounce. 15.432 grains. 1.5432 grain. .1543 grain. .0154 grain. Myriagram Kilogram or Kilo TVkagrram ... , , , . Gram Decigram Centigram Milligram For measuring surfaces^ the square dekameter is used under the term of ARE ; the hectare, or 100 ares, is equal to about two acres. The unit of capacity is the cubic decime- ter or LITER, and the series of measures is formed in the same way as in the case of the table of lengths. The cubic meter is the unit of measure for solid bodies, and is termed STERE. The unit of weight is the GRAMME, which is the weight of one cubic centi- meter of pure water weighed in a vacuum at the temperature of 4 deg. Cent, or 39.2 deg. Fahr., which is about its temperature of maximum density. In practice, the term cubic centimeter, abbreviated c.c., is used instead of milliliter, and cubic meter instead of kilo- liter. THE PROCESSES OF PURE PHOTOGRAPHY. 191 UNITED STATES WEIGHTS AND MEASURES. ACCORDING TO EXISTING STANDARDS. 12 inches = 1 foot. 3 feet = 1 yard. 5.5 yards = rod. 40 rods = 1 furlong. 8 furlongs = 1 mile. 144 sq. ins. = 1 sq. ft. 9 sq. ft. = 1 sq. yd. 30.25 sq.yds.= lsq. rod. 40 sq.rods.= 1 sq.rood. 4 sq. roods = 1 acre. 640 acres 1 sq. mile. Feet. Yards. Rods. Furlong. LINEAL. Inches. 12 36= 3 198 = 16.5 = 5.5 7,920 = 660 = 220 = 40 63,360 = 5,280 = 1,760 = 320 = 8 Rods. Roods. Acres. SURFACE LAND. Ft. Yds. 9=1 272.25 = 30.25 = 1 10,890 = 1,210 = 40 = 1 43,560 = 4,840 = 160 = 4=1 27,878,400 = 3,097,600 = 102,400 = 2,560 = 640 VOLUME LIQUID. 4 gills = 1 pint. 2 pints = 1 quart. 4 quarts = 1 gallon. Gills. Pints. Cub. In. 8 32 = 8 = 231 Gallon. Pints. 1 = 8 = 1 = Ounces. 128 = 16 = 1 = FLUID. Drams Minims. Cubic Centimetres. 1,024 = 61,440 = 3,785.441 128 s 7,680 = 473.180 8 = 480 = 29.574 1 = 60 = 3.697 16 ounces, or a pint, sometimes called a pound. Pound. 1 Ib. Pound. 1 Ounces. 12 1 TROY WEIGHT. Pennyweights. 240 = = 20 = 1 = Grains. 5,760 480 24 APOTHECARIES' WEIGHT. Ounces. 12 1 3 Drams. 96 8 1 3 gr- Scruples. Grains. 288 = 5,760 24 = 480 3 = 60 1 = 20 1 Grams. 373.25 31.10 1.55 Grams. 373.25 31.10 3.89 1.30 .06 1.00 The pound, ounce, and grain are the same as in Troy weight. AVOIRDUPOIS WEIGHT. Pound. Ounces. Drams. Grains (Troy). Grams. 1 = 16 = 256 = 7,000 ' = 453.60 1 = 16 = 437.5 = 28.35 1 = 27.34 = 1.77 192 THE PROCESSES OF PURE PHOTOGRAPHY. TABLES FOE THE CONVERSION OF GRAMS (OR CUBIC CENTIMETRES) INTO OUNCES AND GRAINS. CONVERSION OF GRAMS INTO GRAINS. Grams. Grains. 15 43 CONVERSION OF GRAINS INTO GRAMS. Grains. Grams. 1 0648 30.86 2 1296 46.29 . . 61 78 3 1944 4 K 2592 . . 8240 77 16 92 59 6 """ 3888 7 . ... 108 08 7 8 9 ::::::::::::::::.::..:::...: ^ 5184 .. .5832 g 123 46 9.... .. 138.89 CONVERSION OF GRAMS INTO TROY OUNCES. Grams. Troy Ounces. 1 03215 CONVERSION OF GRAMS INTO AVOIRDUPOIS OUNCES. Grams. Avoirdupois Ounces. 1 03527 | 06430 2. 8 rmftt 8 09645 10581 4 12860 4 14108 5 16075 5 17635 6 7 . . 19290 . . 22505 6. B! q 21162 24689 2821fi 8 25720 9.... .. .28935 :: :i743 The above tables render the conversion of the weights in question a matter of great ease, the error introduced in the last decimal place being trivial. The use of the tables will be best illustrated by an example. Supposing that it is de- sired to find the equivalent in grains of 324.51 grams, we proceed by breaking up this number into the following series of constituent parts, and finding the grain-equivalent of each part from the table : Portions of original number. 800.00.... 4.00 .50 .01.... Equivalents in grains. 4630. 308.6 61.73 7.716 .1543 5008.2003 The required quantity is 5008.2 grains. The numbers taken from the table will, in most cases, require a change as regards the position of the decimal point ; thus, to find the value of 300 grams, one refers to the table, and finds 46.30 given as the equivalent, and a mere shifting of the decimal point two places towards the right multiplies this by 100, or gives the required number. In a similar manner, by shifting the decimal place of 30.86 one place to the right we obtain the value in grains of 20 grams ; while the number 61.7 is taken from the table without alteration as the equivalent of 4 grams. For .50 the table number must have its point shifted on to the left, making it 7.716 instead of 77.16 ; and finally, the value of .01 is obtained by shifting the point of 15.43 two places to the left. The above operations are, in actual practice, performed with considerable speed, the required equivalents being written down one after the other on a scrap of paper, and then added up. THE PROCESSES OF POKE PHOTOGRAPHY. 193 TABLE SHOWING THE COMPARISON OF THE READINGS OF THERMOMETERS. CELSIUS, OR CENTIGRADE (C). REAUMUR (R). FAHRENHEIT (F). C. R. F. C. R. F. 30 24.0 22.0 23 18.4 73.4 25 20.0 13.0 24 19.2 75.2 20 16.0 4.0 25 20.0 77.0 15 12.0 + 50. 26 20.8 78.8 10 8.0 14.0 27 21.6 80.6 5 4.0 23.0 28 22.4 82.4 4 3.2 24.8 29 23 2 84.2 3 2.4 26.6 30 24.0 86.0 2 1.6 28.4 31 24.8 87.8 i 0.8 30.2 32 25.6 89.6 33 26.4 91.4 Freezing point of water. 34 27.2 93.2 35 28.0 95.0 0.0 32.0 36 28.8 96.8 1 0.8 33.8 37 29.6 98.6 2 1.6 35.6 38 30.4 100.4 3 2.4 37.4 39 31.2 102.2 4 3.2 89.2 40 32.0 104.0 5 4.0 41.0 41 32.8 105.8 6 4.8 42.8 42 33.6 107.6 7 5.6 44.6 43 34.4 109.4 8 6.4 46.4 44 35.2 111.2 : 9 7.2 48.2 45 36.0 113.0 10 8.0 50.0 50 40.0 122.0 11 8.8 51.8 55 44.0 131.0 12 9.6 53.6 60 48.0 140.0 13 10.4 55.4 65 52.0 149.0 14 11.2 57.2 70 56.0 158.0 15 12.0 59.0 75 60.0 167.0 16 12.8 60.8 80 64 176.0 17 13.6 62.6 85 68.0 185.0 18 14.4 64.4 90 72.0 194.0 19 15.2 66.2 95 76.0 203.0 20 16.0 68.0 100 80.0 212.0 21 16.8 69.8 22 17.6 71.6 Boiling point of water. Readings on one scale can be changed into another by the following formulae, in which / indicates degrees of temperature: Reau. to Fahr. Cent, to Fahr. Fahr. to Cent. R J + 32 = t F ?fC + 32 = f F o - [ t F 32 J= / Reau. to Cent. Cent, to Reau. Fahr. to Reau. 5 4 / R = t C 4 F/ C = t R o $(<-^>CO-*OO-*O'OWO-^5DOOOt-Ot- H -rH I -r-l. W 50 > t-^ t~ OO < O' ?? O 35 ~ ? C* B 5 " 2 5- -^i co CO * O * -i-i "O O w OS 00 *> C~ > CO < O oo w jj 5* ^ * w' ^ oJ *-o S r* SI i S ' ^^ 50 00 -. 2| 00 00 O < H rm OO ,rl O eo' TH tJ CO od 1O os *- o ' ~ CJ t-OOOt Q > W 10 t- to > *.' O o i-< a , 1 K o S 2 S 5 & t: B 5 8 5 * s 5 5 ! 5 ^ * S 2 H Q z < IT) CO ** C H ^ ' 10 o => L- - ra 00 , S 1 O t- M a H fc o 3 o S Q ec suaq aq? jo sno -oj juaiBAinb'? looi-oocso^-iojco'* THE PROCESSES OF PUKE PHOTOGRAPHY. 19T GOC5oo? M -'frio^oo^os s^g^SftS'Is'Igia >;=CO;-,CO^CO~^i N O "ioc*oio'<*o^ < in' 1 1-' "3 oo' *^ os o T- 1 1 iScsSc^ScdwcoSSco O'n-^i^OOt-iyjootooooos 00 ' OS 5>j' CO TO C>? ' CO ' 1O o iCO 1 i rp T^O t>o O 1 ^ COO ! w2 SiS wS wo3 WN 2 c^ 1 "- CO CO = Ii 11111! !! 6i sg S" 3 11 .-- ij ^ "S 5-g 5 "? 1 2 "E -si 51 1 ll < i d ii i |p. ; ^^gi 3 UjU llfll 81 S| e -=" e<> 0* -*T1 s a f s^ mil i