OaKST Ly 1 JU l\. * OF THE U N 1VER.S1TY or ILLINOIS 771 T254 Return this book on or before the Latest Date stamped below. University of Illinois Library 24 FEB 2 k 1972 MAR i 8 m/id 24 issj : E-O r^pR -9 iB? 0 AUG l-’81972 1 Iv, ? i 23 mi ' ,01] 1 3 19H3J ilAR b 19; 9 DEC 10 1954 HA- Jui p ms JM2S «72 L161— H41 Digitized by the Internet Archive in 2017 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/darkroomworkpracOOtenn If DARK ROOM WORK A PRACTICAL DARK ROOM MANUAL, WITH SUGGESTIONS AS TO EQUIPMENT; WORKING CONVENIENCES; SHORT CUTS AND HANDY METHODS OF DARK ROOM WORK TENNANT AND WARD NEW YORK Copyright 1912 by TENNANT AND WARD, NEW YORK CONTENTS V7 / TZSd Chapter I WORKING SPACE; VENTILATION AND CLEANLINESS Chapter II THE ILLUMINATION OF THE DARK ROOM Chapter III WORK TABLES; TRAY CUPBOARD; PLATE CARRIERS s n Chapter IV WATER SUPPLY; TAP FITTINGS; TUBES AND RODS; LABELS Chapter V FILTERING SOLUTIONS; FILTER PAPERS AND STANDS Chapter VI CORKS AND BOTTLES Chapter VII A TRAY ROCKER; PLATE LIFTERS; WEIGHING AND MEASURING Chapter VIII METHODS OF MAKING SOLUTIONS Chapter IX FACTS ABOUT CHEMICALS Chapter X WASHING AND DRYING PLATES AND PAPERS Chapter I WORKING SPACE; VENTILATION AND CLEANLINESS J UST as surely as necessity is the mother of in- vention and inconvenience the progenitor of expediency, so, sooner or later, do we all — who pursue elusive sunbeams and fantastic shadows under the ruby lamp — become prolific inventors or artful dodgers. It could not be otherwise; photography confronts us with so many necessities to be provided for — or dodged! No matter how simply the novice begins, or how fore-thoughtful the expert be, they meet at last in the inevitable resort, dodging and con- triving in ways innumerable to make means fit their ends. Probably this is true of all craftsmen, but certainly in photography the individual worker speedily becomes a law unto himself, devising expedients and modifying methods to suit his own peculiar needs. And every man’s necessities are slightly different from those of his neighbor! Out of these spontaneous and temporary expedients come, now and again, the happy dodges which enable us to make sport of necessity. Then one day a friend comes along, who, seeing the dodge in practical operation, exclaims: “Splendid idea! Just the thing for its purpose. Why do you not patent it — or publish it.^” A thousand dodges of this 5 DARK-ROOM WORK sort are recalled as I write: the pointed thimble serv- ing as a plate lifter, the corrugated finger-tip which grips, the plug of cotton-wool pulled halfway into a bit of glass tubing to form “Buckle’s brush,” and a host of similar trifles which, like a drop of oil, make the wheels go round more easily and without friction. Here we have the purpose of this little book; to gather together a ready reference cyclopedia for the dark-room worker; short cuts, methods and ways of doing things and home-made contrivances or “tips” which may serve in an emergency to take the place of more elaborate conveniences. For the most part a few pence, a little leisure and such handy tools as may be found in the home will suflSce for their making. And this is worth noting, they are all practical dodges, being largely contrived by an artful dodger for his own use; or “lifted” from the notebooks of other worthy dodgers; or seen in the rose-red light of other dark-rooms. It is needless to add that all dodges should be taken as they are given, in the indicative rather than in the imperative mood. In constructing a convenient dark-room we require size suflScient to allow the various operations to be conducted without overlapping, and no more. A room which will give space for a worker without cramping him, after a sixteen-inch shelf has been run around three sides of it, is suflficiently large, and except for ventilation, no advantage is to be gained by increas- ing its size. We require a good sink and water supply, a safe light, adequate ventilation, heat in winter, working benches, and racks and shelves for holding bottles and trays. As for actual size, if the room is 6 DARK-ROOM WORK never occupied by more than one worker at a time, about seven by five feet would not be too small — though one larger would be preferable; this would give a working space of about five and a half by two and a half feet; or four and a half by three and a half according to whether the double row of benches ran the long or the short way of the room. Often the dark-room is partitioned off from some other room, and is long and narrow, with the sink and shelves running along one side only. This is a convenient arrangement. In speaking of a room of small size it must be remembered that we are speaking only of a dark-room, not of a work or store room. The dark-room should not be used as a general store- room, for chemical fumes or heat may have a dele- terious action on stock. Much of the writer’s dark- room work has been done in a closet measuring about five feet by thirty-three inches, but possessing the great advantage of a porcelain bowl with running water; and many workers will, like him, be bound by actual rather than by ideal conditions. It is not possible to give any actual dimensions for a room. Many photographers never handle larger sizes than 8 x 10, while the- greater proportion of their work is smaller. Where sizes up to 17 x 22 are handled, the minimum size suggested above would be quite inade- quate. The door needs some consideration. In a small dark-room such as we refer to, the photographer would probably close and bolt his door after him, and if he needed to leave during development would cover his tray and leave his plate in darkness; but with a room which is regularly used, and in and out 7 DARK-ROOM WORK of which people may require to pass, some other ar- rangement is needed, such as two doors with a suffi- cient space between them, so that a man may close one behind him before opening the other. Another way, preferable, where people are constantly passing in and out, is to have no door at all, but a short pas- sage constructed with light traps. Wings are run about two-thirds of the way across the passage, alter- nately from the left and the right; these are colored dead black, and four of them will prove as efficient a light trap as is needed. That the dark-room should be kept free from dust is a precept which needs no emphasis here. In these days of dry-plates and films the problem of keeping dust out of the dark-room and, at the same time, securing abundant ventilation, has brought forth many inventions. The plan I adopted in my base- ment dark-room years ago has proved as efficient as it was simple. Procuring, from a neighboring plumber, twelve pieces of IJ^-inch lead piping, each piece seven inches in length, I bent these to form a right-angled tube similar to B in Fig. 8, except that the bend was about two inches from one end. These tubes I lined with coarse felt or flannel, LePage’s glue serving as the adhesive. Next, this felt lining was saturated with linseed oil. Six of these tubes were snugly fitted into holes bored through the dark-room door, about five inches from the floor, the long arm of each tube hanging free within an inch or so of the floor inside the room. On the outside of the door I fixed a strip of wire-net, to cover the circular apertures, admitting air from the passageway. The other six tubes were 8 DARK-ROOM WORK similarly fixed into a wood panel above the dark- room window, thus communicating with the free air out-of-doors. In this case, however, the long arm of each tube was turned to the ceiling. By this simple dodge, which occupied a spare afternoon, I secured abundant ventilation, freedom from that musty dampness peculiar to basement dark-rooms, and a minimum of dust, the air passing through tubes lined with oiled felt. The tubes should be removed three or four times yearly, and the felt re-oiled; but beyond this slight trouble the system has given perfect satis- faction. The walls and shelves of the dark-room should be coated with a waterproof paint, such as Probus. Keeping a dark-room clean is an elementary detail, but is often an unsuspected source of trouble. I have often wondered to see otherwise intelligent workers dust down their shelves and tables, and then begin to change their plates or develop a batch of exposures. This is beginning at the wrong end. Dusting the dark- room should be done at night just before closing, or at least a few hours before any photographic work is attempted. When any dark-room work is on hand, take time by the forelock. Early in the morning take a slightly damp cloth or mop and gather up the dust from shelves, table and floor. Follow this with a dry cloth, and then let the room be closed for an hour or two at least. With this simple precaution, the reader may at all times be confident that dust will not trouble him in the operations of changing or developing his plates. It has been my practice for a long time to dust my plates in the holder. This I do by drawing out the 9 DARK-ROOM WORK slide and then slowly and lightly passing a dry, broad and soft camel’s-hair brush over the film. In the wooden handle of the brush is a hole, and through this a loop of elastic. This loop conveniently goes over the top button of my coat, so that I do not need to put down the brush on a dirty table or wet shelf during the operation. The loop also serves to hang up the brush on a nail at the end of a shelf opposite the dark- room lamp, so that it can readily be seen in a dim light. For large plates I prefer a home-made brush, as shown in Fig. 1. This consists of an old film bent over to bring edge to edge, covered with silk velvet, the two ends being fixed to a bit of cigar-box for a handle. One point to remember when dusting plates is that if you quickly rub the film with the duster you charge the surface with electricity, and this tends to attract particles of dust. This point can be demon- strated by briskly rubbing a bit of clean glass with a bit of silk and then holding it half an inch away from some tiny particles of paper. Plate-holders, dark slides, or whatever you please to call them, require cleaning out occasionally. This is best done in daylight. At the same time see that the slides draw in and out easily. If not, ease them with a little dry black lead or soft graphite. A fairly soft pencil is convenient for this purpose, and enables one to get into the corners and grooves. On no account use oil, grease, or anything of that kind. The dark-room lamp is an item of considerable im- 10 ov^xunmnifiintfirf, V" ’ll', '(A it i DARK-ROOM WORK portance, and a few words about the form which I have worked up to may be suggestive. There are innumerable patterns buyable at all prices, yet I found it cheapest to have made for me the one I have now had in satisfactory use for some years. It consists of a tin box roughly 12 inches high, 12 inches wide, and 6 inches from back to front. The parts are fixed together by over-lapping joints, strengthened by rivets in case of the solder giving way. Light is trapped in the usual way. The front contains two grooves, the outer one wide enough to easily hold three sheets of ordinary glass loosely. The inner groove is about half this width. A glance at Fig. 2 (not drawn to scale) will show how these two grooves may be used to hold sheets of colored glass. I find a gas fiame the most convenient light, inside the box, which is fixed to the wall to my left, over the sink. Inside the box and behind the flame is a sheet of white pot or flashed opal glass. This acts as a reflector; and a sponge and soap will clean it in a minute. Next comes a sheet of fine ground glass (dotted in the diagram) in the inner groove; and in the outer groove one or more sheets of colored glass, according to my needs. For bromide paper and lantern plates I find a sheet of orange glass 11 U. OF III. 1-‘B DARK-ROOM WORK quite safe with ordinary care, For ordinary plates I replace this by a sheet of ruby glass. For more sensi- tive plates the orange and ruby glass are used together, or any other combination of “safe lights” required for the manipulation of the particular plates in use. 12 Chapter II ILLUMINATION OF THE DARK-ROOM M uch depends upon the correct lighting of the dark-room. There are two main factors to be considered — the safety of the light as towards sensitive films, and the worker’s comfort. This latter factor has too often been over- looked. To obtain “safety” photographers have been content to work with the dimmest of dull lights. A glimmer through a deep ruby glass is one of the com- monest mistakes; for it is quite possible to combine safety with a fair volume of light; and light of a tint which does not affect the eyes unpleasantly. The light may be either day or artificial. One disad- vantage urged against the former, by those who can do their work during daylight, is that it is variable in intensity, but this argument is valid only with those who closely examine their negatives from time to time during development, to judge density, a custom which is largely dying out. In regard to a “safe” light, it is much a question of how close and for how long a time the plate is held to it. A light that illumines the dark-room so that every bottle and package can be seen, would probably be safe, if the plate to be developed were taken from its holder and at once placed in the developer and covered over; but the same plate might fog if the developing tray were held 13 DARK-ROOM WORK close to a much weaker light, in an endeavor to see the first indication of any image. For orthochromatic plates I use a triple screen of aurantia, naphthol yellow and methyl violet 6B. The easiest plan to prepare these is to fix and wash three unexposed ordinary plates, so as to obtain glasses coated with clear gelatine, and then soak them in aqueous solutions of these dyes. It is not every amateur, however, who finds it convenient to buy a box of 12 X 15 plates in order to get three sheets of glass a foot square coated with gelatine. I tried this plan, but found the gelatine coating so thin that it did not hold a sufficient quantity of dye. My next plan was to obtain three pieces of ordinary clear glass 12 X 12 inches. These were thoroughly cleaned. A fiat drawing board was carefully leveled with the aid of three wedges underneath. A glass ball about the size of a hen’s egg (costing a few cents at the toy shop) soon helps one to get the board level, as it always rolls toward the lower side of the board. I now take 15 to 20 grains of shredded gelatine (Nelson’s) and soak this in one ounce of a cold saturated aqueous solution of aurantia. When the gelatine is quite swelled, the containing vessel is put into a pan of warm water and the gelatinous mass gently heated. Meanwhile the glass plate to be coated is slightly warmed. Then the aurantia-gelatine solution is poured on the warmed glass plate laid on a sheet of paper on the level drawing board. A glass rod enables us to guide the liquid. The plate being warmed keeps the mixture fiuid for some little time, and so gives plenty of time to slowly add the coating and lead it to the edges of the plate. 14 DARK-ROOM WORK It is then allowed to set and dry in this horizontal position. In the same way we use gelatine and a cold saturated solution of naphthol yellow for our second plate. For the third plate we do not need a saturated solution of methyl violet 6B, but one which is so strong that one drop seen by transmitted light on a glass plate is a fairly deep violet. In this way I found I got much more of the two yellow dyes. If the violet screen dries too dark it can be lightened by washing in cold water. If not dark enough it can be darkened after drying by pouring over its surface a stronger solution and allowing it to soak in. These three plates, when put together, permit only a narrow band in the far red end of the spectrum to pass. In this light the most sensitive orthochromatic plate may be developed. This set of dyes has been published before, but they are so very important and of such great value that their repetition here may be helpful. A window may be utilized by glazing it with colored glass, or by covering the clear glass with colored paper or fabric. The fabric may be pasted on the glass, or, preferably, mounted on a frame to fit the window. This frame should be made of light, flat laths, and just large enough to fit snugly over the window sash, close to the panes. With a couple of staples at the top of the window for the edge of the frame to be slipped under, and a turn button at the bottom to hold it lightly in place, it can be put up in a moment. A strip of thick felt tacked along the edges of the frame will provide against shrinkage and ensure a snug fit in the window casing. A common mistake is made of entirely blocking the greater portion of a window, 15 DARK-ROOM WORK leaving a small opening of perhaps a foot square; it would be more comfortable to have the opening two or even three feet square, and this is quite feasible if a suitable medium is used. In my present dark-room I have a rather large window, e. g., about 4 feet by 6 feet. And as I use the same room for other purposes, I wish to have a daylight-room or dark-room at will. A light wooden framework was made to fit the recess of the window. The frame is very ^ similar to that used for “stretchers” for canvas for oil paint- ing. So that if the reader is not very handy with his fingers, for a quite small cost he can order to be made a canvas stretcher at any shop where artists’ materials are sold. In my case this frame was first covered over with cotton sheeting, folded over the edge and fixed by tacks, as suggested in Fig. 3. The sheeting was then covered by a couple of thicknesses of somewhat thin, yet tough, opaque parcel brown paper. I find this quite opaque to day- light. Two smalt blocks, A and A, were screwed on the window-frame so that the shutter, as we may now call it, just rested on them. Two other side blocks at B and B kept it in position. To each of the four blocks I put a flat wooden “turn button.” In the lower corner of Fig. 3 is shown a diagram section of the 16 DARK-ROOM WORK turn button and block. It should be noticed that the lower side of the tongue of the turn button is slightly chamfered away. If this is not done, you will find your turn buttons constantly catching and tearing the sheeting or getting jammed with the nails holding down the sheeting. It may be useful to know how to test the safety of the dark-room lamp or window, lest our plates fog with overmuch light, for there is ruby glass and ruby glass. The eye fails to tell us which is safe and which is unsafe. Moreover, plates vary in their sensi- tiveness. And, again, it may be safe to expose a certain plate to a light, for say, one minute and yet unsafe to expose it to the same light for ten minutes. To test this the “strip test” method is useful and easily made. Take a strip of card the same length as that of the plate to be used in testing. Cut this into a stepshaped piece like Fig. 4, having as many equal steps as you wish your test plate to register (in this case five steps). Put the plate into an ordinary plate-holder in the usual way, but do this well away from the dark-room lamp and under cover of the focusing cloth. Have a friend at hand to time the minutes with a watch. Now go up to the developing table. Draw out the shutter and expose the plate to the lamp as though developing it for one minute. Then push in the shutter just the length of one step (marked 1). 17 DARK-ROOM WORK Expose for one more minute and push in as far as the second step (marked also 1). Then expose for two minutes and push in again as far as the third step. Similarly give the four- and eight-minute exposures, according to the times marked on the step. A mo- ment’s thought will show that the plate has had five different exposures — of one, two, four, eight and six- teen minutes. Develop as usual, but keep the dish covered all the time; fix, wash and dry. Now lay the plate, film side down, on a sheet of white paper. You can then easily see the strip first to show a difference between the edge of the plate protected by the rebate of the plate-holder (hence the reason for changing the slide in the dark). Such a test will tell you, perhaps, that a two-minute exposure to the dark-room lamp just begins to show signs of light fog and that four minutes is serious. You will, therefore, conclude that during development your developing dish should be kept covered over most of the time, and that the total time of uncovering the plate for examination of the progress of development should not exceed the time your test plate indicates as the practical safe time limit. I lay some stress on this strip-testing method, both for plates and bromide papers and slides. Two points should be noted. If we are working with a rapid bromide paper, e. g., enlarging, the light may be just sufficiently unsafe to give a very slight fog which is not noticeable in the yellow light, and especially when the paper is wet, but is seen when the paper is dry. Similarly, when making slides a very slight fog veil may not be seen until the slide is examined against a white background. 18 DARK-ROOM WORK Three kinds of tray-covers are useful, according to circumstances. First, thin pieces of wood about half an inch or an inch larger than the top of the dish. I have several of suitable sizes standing on edge by the sink side. These are cut from the ordinary backing boards used to back picture-frames. They are used simply to cover the dish as an extra precaution when developing. But if I want to turn up the naked gas flame to And a bottle or graduate during development, these flat wooden lids are not safe. In that case I use a stout cardboard lid, e. g., the lid of a half-plate box for a quarter-plate developing tray. This card- lid has a coat of black enamel paint inside and out, to make it proof against light and to protect it from the effects of splashing liquids. A third form of pro- tection when the light is to be turned up for any length of time is needed. In that case I put the tray into a cardboard box with a lid. It is a good plan to number every plate used. This may be easily done on the dry film by the aid of a fine- pointed, rather hard pencil. If this number is written in the right-hand lower corner, as the plate is film facing you in the plate-holder, with the shutter drawn out to your right for dusting, it will always come in the foreground (not sky), whether the plate be ex- posed for a horizontal or vertical view. In that case the pencil number never shows when the plate is printed. Do not attempt to number a plate when the film is wet; a torn film is the probable result. This pencil number is not very readily seen, however, and if the plate gets much rubbing it may get rubbed out. Hence, as soon as the plate is developed and dried it 19 DARK-ROOM WORK should be re-numbered with water-proof ink, written with a fine-point steel pen. It can then be reduced, intensified, etc., without any harm, as the ink is not affected by most of the aqueous solutions we use for such purposes. If, however, we wish to remove the water-proof ink at any time, it can easily be done with a little methylated spirit, applied with a bit of clean rag. Higgins’ water-proof India ink is excellent for this purpose. Where such an ink is not handy the dry negative can be numbered at the extreme edge with a sharp-pointed tool, which will cut the number clean through the film to the glass. Usually the nega- tive has a rebate strip which offers place for this method of numbering. Dust on the film may arise from the grinding of the sharp edge of the glass plate against the wood of the plate-holder. This is liable to arise when the apparatus has been well shaken on an auto or train trip. In such cases the following dodge should be applied before exposure, otherwise the negative will show dust pin- holes after development. Hold the plate-holder by one hand in a vertical position and give it two or three sharp raps on its lower edge upon the palm of the other hand. This will probably dislodge the fine particles adhering to the film surface and cause them to fall to the lower edge of the plate. Of course, this lower edge will be the long or short side, according as you are about to take a horizontal or vertical picture. 20 Chapter III WORK TABLES AND TRAY CUP- BOARD; PLATE CARRIERS T he work-table used in the dark-room is liable to become soiled and unsightly by the constant action of chemical solutions. To avoid this, it is well to prepare the top of the table in such a way as to render it impervious to the action of acids and alkalies. A writer in the Journal of Applied Micro- scopy tells how to accomplish this, and I quote from his paper as follows: “Prepare the following solutions: 1. Iron sulphate, 4 parts; copper sulphate, 4 parts; potassium perman- ganate, 8 parts; water, q. s., 100 parts. 2. Aniline, parts; hydrochloric acid, 18 parts; water, q. s., 100 parts, or aniline hydrochlorate, 15 parts; water, q. s., 100 parts. By the use of a brush, two coats of solution No. 1 are applied while hot, the second coat as soon as the first is dry. After solution No. 1 has dried, the excess of solution which has dried upon the surface of the wood is thoroughly rubbed off before the application of solution No. 2. Then two coats of solution No. 2, and the wood allowed to dry thoroughly. The black color does not appear at once, but usually requires a few hours before becoming ebony black. Later a 21 DARK-ROOM WORK coat of raw linseed oil is to be applied, using a cloth instead of a brush, in order to get a thinner coat of the oil. The linseed oil may be diluted with turpentine without disadvantage, and after a few applieations the surface will take on a dull, and not displeasing, polish. The table-tops are easily cleaned by washing with water or suds after a course of work is completed, and the application of another coat of oil puts them in excellent order for another eourse of work. Strong acids or alkalies when spilled, if soon wiped off, have scarcely a percepti- ble effect. The writer used this method on some old laboratory tables which had been finished in the usual way, the wood having been filled, oiled and varnished. After scraping off the varnish down to the wood, the solutions were applied, and the result was very satis- factory. My next bit of home-made apparatus is known among my friends as my ‘‘family four-poster.” A glance at Fig. 5 will show at once its very simple nature. It consists of four stout posts of wood about inches square and perhaps 43^ feet long. These form legs or pillars of a table about S}/2 feet by 3 feet top. Below the top, at convenient distances, I have in my own case put four shelves (three only shown in 22 DARK-ROOM WORK sketch). The four legs are on casters, for convenience of moving. I find this a most convenient thing for holding several large trays, or washing dishes, when enlarging. And, as will be seen, it is a great saver of space; for one does not often find an amateur’s dark- room with table space for, say, three dishes to hold 20 X 16 prints, as well as the usual developing and fixing baths. A friend who saw my ‘‘four-poster” adopted and adapted the idea for his own cupboard dark-room, and employs it to hold nearly everything he uses, except what goes on the small housemaid’s sink and small shelf over the sink. The contrivance is useful for drying purposes. All apparatus is removed and a sheet of clean blotting paper put upon each of the shelves, and on the paper is laid the plates or prints to dry where they are reasonably safe from falling dust. When I am preparing for a trip from home all the shelves are cleaned, and then I here collect all the odds and ends which I think I may want when away from home. Other uses will suggest themselves to other workers according to their needs. The top of this table should be prepared or protected as dealt with in the preceding paragraph. In Fig. 6 is shown another very homely bit of ap- paratus which has stood under my sink for some years, and holds dishes and trays of all shapes, sorts and sizes. The apparatus was one morning quickly knocked together, using a packing case which had just come to hand. This was done by way of a trial, with the intention of making something more tidy and elaborate. But this rough box has so well filled my wants that I am content to let well enough alone. N. B. — Porce- 23 DARK-ROOM WORK lain and glass dishes should not be stored flat down, one inside or resting on the other. Experience long ago taught me that this was the most breakable way of doing things. Under my sink I fix a shelf, after the manner shown in Fig. 5. On this shelf stands my fixing-bath for all plates of 10 x 12. This dish-holding rack just easily goes under the fixing-bath shelf. Thus no room is wasted. The fixing-shelf is large enough for two fixing-baths, side by side. It is, I think, as well to give a plate likely to be of more than momentary interest a second bath. The plate remains in bath No. 1 until all milky appearance is gone, and then goes into bath No. 2 for about an equal length of time. Bath No. 2 is always kept as clean as possible; and at fairly frequent intervals No. 1 is emptied out and the contents of No. 2 put in No. 1, and a new lot of hypo solution put into tray No. 2. The experimental photographer very soon finds that he wants a lot of odd size carriers. For example, he may wish to cut up a half-plate into three equal pieces and use these strips in a half-plate camera. He soon finds that it takes too much time and money to be having these carriers made. Fortunately it is a very easy matter to make quite efficient carriers out of stiff card for all small sizes, up to whole plates, and of thin wood for large sizes. For example, suppose we 24 DARK-ROOM WORK wish to make a carrier to hold a 2 x 3 plate in an ordinary half-plate-size holder. First, cut a piece of card the size of the holder, viz., 4i^ x 63^. Out of its center (found by drawing diagonal lines) cut out an opening just taking easily the 2x3 plate. Next cut a second piece of card, ’j/^-inch all the way round less the first, viz., 434 X 6, and from its center cut an opening just 3^-inch less all the way round than the plate it is to sup- port. In this case the plate is 2 X 3 and the opening is, therefore, 1% X 2^. With fish- glue we fix these two cards together so that their openings are concentric. The result as seen from above is shown in Fig. 7, A, and as seen from below is shown in Fig. 7, C, while a section is shown in Fig. 7, B. In the diagrams the reader will rightly surmise that for clearness’ sake we have drawn the thickness of the card out of proportion. Naturally, we shall select card of suitable thickness to agree with the rebate of the plate-holder in which it is to be used, so that the slide will close easily. Fig. 7. 25 Chapter IV WATER SUPPLY; TAP FITTINGS; TUBES AND RODS A GOOD supply of water is essential in the dark- room. There should be two taps over the sink, and one of them should be sufBciently high to allow of filling the largest bottles under it. The water, when running into the sink, may cause splash- ing; to prevent this, a short length of rubber piping may be slipped over the end of the tap, or a piece of thin cloth a couple of feet long and a few inches wide may be thoroughly wetted and then wound tightly round the tap so that the projecting cloth forms a tunnel through which the water will fall. This cloth may cling to the tap if tightly wound, but it is safer to hold it in position by slipping a strong rubber band over it, or using a piece of string, to ensure its not slipping from the metal pipe. This cloth will tend to make the water fall in a soft even column instead of a splashing stream. Filters which scarcely affect the flow of water may be purchased at a nominal price. The filter itself is a piece of fine wire gauze in a brass socket which attaches to the tap by means of a rubber washer; and it not only checks splashing but also arrests any solid particles in the water. The second tap should be fitted with a fine rose jet. These are to 26 DARK-ROOM WORK be bought mounted on a swivel tap by which the rose may be swung against the wall when not in use. When pushed against the wall the water is automatically turned off; when drawn forward over the sink it gives a fine spray which will evenly rinse a plate without at all damaging the film. The tap fittings needed, roughly, are three. First, a short piece of rubber tubing which easily can be slipped over the nozzle of the tap. In the other end of the first piece of 7\ tubing is a short bit A VL -1/ of stout glass tube. This is filled with bits of charcoal, and over its end three thick- nesses of clean fine flannel are fixed. This is a handy filter for use when I want water free from any organic impurity or suspended (n c Fig. 8. matter, as in making or washing color screens. In a simi- lar way, to my second bit of tube is fixed a rose or spray. which I had bought of a hardware dealer for ten cents. This is of brass, and in shape is but a small edition of the rose or sprinkling end of a greenhouse watering-can. My third bit of tube is longer, long enough to reach from the tap to the bottom of the sink, or nearly so. Into the free end I can slip various shaped pieces of glass tubing according to my needs. One of these I may as well now describe, as it is the one by far the most often used. This I call my current-producer. 27 DARK-ROOM WORK A piece of soft glass tube is selected, of such a size as to hold firmly when slipped inside the rubber tubing. This is softened in a batwing gas flame and gently drawn to such a shape as shown in Fig. 8, A. Next applying the flame edgeways, we again soften locally and get a bend such as is shown in Fig. 8, B. When cool a file scratch at C enables us to part the tube at this point. The ori- fice at C should be 1-6 or 1-8 inch in- ternal diameter. If slightly larger it can easily be contracted by gently heating again at the edge of the flame. This also softens off the rough edges. This simple bit of apparatus is very useful when one wants to quickly wash a few prints. Fig. 9 shows how it is used in conjunction with a shallow tray. The outlet of the tube is arranged so that a fine stream rushes along the side from A toward B, thence out to C and out at D, as indicated by the curved arrow. An ordinary gummed label soon comes off in the frequently damp atmosphere of the dark-room. Sized and varnished it will last as long as the bottle, prac- tically. The writer has had such labels in use for years in the acid-laden atmosphere of a chemical laboratory without their showing signs of leaving their supports. Use a thin paper, make the bottle dry and rub the gummed and moistened label down. Then apply a coating of size (1 part of glue in 10 parts 28 DARK-ROOM WORK of hot water), and, when quite dry, varnish with an “oak” or “church” varnish, i. e., a varnish containing linseed oil. Spirituous varnishes (as used for nega- tives) do not last so well. For attaching the labels a mixture of glue and gum is better than gum alone. Here is a good formula which is easily made up: Soak 1 part of the best glue in water until thoroughly swollen, add a little sugar candy, 1 part of gum-arabic and 6 parts of water. Boil with constant stirring over a spirit lamp until the whole gets thin. The moisture does not keep; coat sheets of paper with it, let dry and cut up into convenient sizes. To prevent written labels getting “smudged,” use water-proof ink when writing on the paper. Let this dry very n thoroughly. Then coat your label with the following varnish : Cut up into fine shreds an old celluloid negative film, from which you have previously removed all traces of the gelatine coating. Put these shreds in a Fig. 10. sniall bottle. Half-fill with amyl acetate and then add wood alcohol or methylated spirit. The celluloid will become dissolved. Then inside the cork of your bottle fix a trimmed stiff feather, as in Fig. 10. This forms a. convenient brush with which to coat the labels. Two or three coatings should be given. A few odds and ends which any handy person can make for himself may now be described. All we need are as follows: a gas (or spirit lamp) flame, a small three-cornered file which need not cost more than a 29 DARK-ROOM WORK few cents, and some pieces of glass tubing and rods (obtainable at any chemical apparatus store). First learn to cut a tube. Lightly and sharply draw one edge of the file across a bit of tube. You may see that you have made a tiny scratch. Now seize the tube with one hand on each side of this crack and pull, rather than bend it apart. One or two trials will quickly show the way. Next bear in mind to slowly heat glass and slowly cool it. Do not thrust the tube straight into the flame, but first warm it a little by holding it a few inches above the flame. Stirring rods are gen- erally made from solid rod, cut, and the sharp edges round- ed off by heating in the flame. But I prefer a bit of small tube with each end closed by drawing out in the flame. A tube is far less likely to smash a delicate glass vessel than is a solid rod if one lets it slip. One end of a closed tube is shown in Fig. 11, A. Knob-ended rods, however, are very useful at times. If you heat the end of a rod in the flame until it is quite soft and then press it down upon a bit of metal, such as a knife-blade, or face of a hammer, you get an end something like that shown in Fig. 11, B. Sup- 30 DARK-ROOM WORK pose you find a slight fog veil on a negative. Take an ordinary cylinder-shaped graduate. Throw into it a crystal of potassium ferricyanide, add a teaspoonful of water, give the glass a swish and pour off the water. Then with your knob-ended rod crush and grind the red crystal to powder. The wet bottom of the grad- uate prevents the particles flying about. Then add an ounce or two of hypo from your hypo jug, and you have a fog reducer at hand in a moment. From the sketch it will be seen that the knob is more conven- iently flat, rather than round. This shape is much better for crushing purposes. A spade-shaped rod end is very useful for loosening the contents of bottles, which have become more or less obstinate, such as often happens with small crystals of soda sulphite, alum, borax, etc. This shape is shown in Fig. 11, C. Soften the end of the rod and then, when quite pliant, seize it suddenly with a pair of flat-ended pliers, or seize between two flat-irons. A hook-shaped end is also useful. See Fig. 11, B. First heat and slightly draw out the rod, then curve and cut when cold. We now require a short length of tube, wide enough to admit the hook and a trifle to spare over that. A bit of absorbent cotton is shaped something like a small sausage. It is then caught in the middle by the glass hook and pulled up into the mouth of the tube, as in Fig. 11, D. This forms a very useful brush when it is needed to apply delicate solutions to paper, as, for instance, local toning in platinum or velox printing. It is also useful for local applications of acids and, being entirely of glass, i. e., no metal parts, is not affected by the usual acids. 31 Chapter V FILTERING SOLUTIONS; FILTER PAPERS AND STAND O RDINARY solutions, like developers, fixing and toning baths, ought to be so made up and with chemicals of such purity that no filtering is necessary, but when one gets a little off the beaten track, then filtering often becomes necessary. Filter papers are of various qualities — Rhenish, French and English. French and English are much coarser papers than Rhenish. The ideal paper is that which is strong enough to support large volumes of liquid, without holes through which suspended water can pass, and permitting the liquid itself to pass rapidly. One of the best papers for a photographer’s dark-room is Schleicher & Schiill’s No. 597, Rhenish, which costs, per 100 5-inch papers, about thirty cents. The funnel makes a lot of dif- ference to the filtering. A ribbed funnel is best, and ribs which wander spirally around the funnel better than those which are vertical. The deeper the ribs the quicker the filtration. There is a funnel sold — Hehner & Richmond’s — with specially deep ribs. Small funnels ought to have a fine stem. Such filter quicker. For large funnels, diameter of stem does not matter much, although width is preferable. 32 DARK-ROOM WORK Don’t filter if you can do anything else. It is better to let any deposit settle (if it will) and pour off the clear liquid above it. You should never filter solu- tions containing pyro, hydroquinone or other de- velopers which oxidize readily, because filtration exposes the solution so freely to the air. If it is neces- sary to filter it should be done before the pyro, etc., is added. Do not filter when decanting will do as well. Or perhaps you can decant three-fourths or so of a mix- ture which has been set aside in a bottle for a few hours, and need only filter the last and bottom fourth part. In any case, let the tube of the funnel just touch the inside of the bottle. This will hasten matters a little, and also it is better for the fluid to run down the in- side of the bottle in a fine stream than go down by splashing drops. The usual way of folding and placing a filter paper in a funnel is that best calculated to try the patience of the user. One-half of the funnel is covered by one thickness of paper, the other half by three thicknesses. While exercising patience on this account some time ago, I filled up time by trying various fold- ings, and so hit on one which gives only one thickness of paper all the way round. As this does not seem generally known, though doubtless it has been dis- covered by other impatient people, I give it here. 33 DARK-ROOM WORK Fig. 13. See Fig. 12. First bring the point of A of the paper over to its opposite C, and make the diagonal crease B D. Open out the paper again. Now bring the point B over to D and make the crease A C. Open out again. Turn the paper over and make the crease M N, about midway be- tween B C and A D. This last crease is, of course, the opposite way to the first two creases. Turn over again and bring the folds M and N toward each other, obtaining a result shown in Fig. 13. This now fills any angle of funnel and has but one thickness of paper between the contained liquid and the walls of the funnel. A filter stand is a handy contrivance. Take a block of wood, say 6 inches square and an inch thick. Toward one corner bore a hole exactly to fit a 12- or 15-inch length of broomstick. See Fig. 14. In the upper half of the broomstick drive half-way home three or four brass-head nails, at a distance of about \}/2 inches apart. Take a stout piece of copper wire. At one end make a loop large enough to hold the fun- nel to be used. At the other Fig. 14. 34 DARK-ROOM WORK end make another loop a little larger than the broom- stick, i. e., just large enough to pass the heads of the nails, when the loop is horizontal, but not in any other position. A glance at the figure will show that we can readily adjust the height of the holder to suit any bottle or graduate. 35 Chapter VI CORKS AND BOTTLES C ORKS that are kept dry are apt to get hard and lose some of their eleetricity. This may, to a great extent, be restored by soaking in warm water. But if one is in a hurry, just wrap up the cork in a bit of clean paper and put it under the foot and roll it about. At first only the most gentle pressure must be used or the cork will break. Corks soaked in hot melted paraffin wax are rendered less porous and so more nearly air-tight. Corks for bottles con- taining volatile fluids such as alcohol, ether, etc., should be coated with sealing-wax. Put the cork in the bottle, then warm a bit of good wax and rub on the cork. Now take an old knife, make it warm enough to melt the wax, and with it spread the wax all around that part of the cork which is now outside the bottle. As sealing-wax is soluble in various fluids, alcohol for instance, care must be taken to keep the fluid from touching the cork. Any vapors of these fluids which may, however, find their way through the pores of the cork, do not seem to have any effect on the wax. Developer bottles with corks that are in frequent use are apt to jump out of one’s fingers (the corks, not the bottles) and then roll to the most inaccessible part of the dark-room floor. It is easy to prevent this. 36 DARK-ROOM WORK See Fig. 15. Borrow a crochet hook. Thrust this through the upper part of the cork, as in 15 A, then hitch over the hook a bit of string, thin string, pull back the hook and the string with it, and tie the string in a loose loop. The other end of your string is tied around the neck of the bottle, and the lengths are so adjusted that when the cork is out of the bottle and not in your fingers it is hanging to the bottle, and yet not touching the shelf on which the bottle may be standing. This will be ex- plained by a moment’s glance at 15 B. This brings us to ask whether stoppers are better than corks for the photogra- pher’s solutions. In most cases they are not; in many, they are not so suitable as corks (e. g., for all alkali solutions), for they are liable to stick. The only instances where a stoppered bottle is really necessary are for solu- tions of gold chloride and potassium chloro-platinite (which are decomposed and reduced to the metallic state by contact with organic matter like cork), and for strong acids such as hydrochloric and sulphuric, which speedily destroy cork or rubber. For all other solutions corks are just as good as stoppers, bearing in mind that the cork is porous and absorbs the solution which it isolates from the air; the photographer must not there- 37 DARK-ROOM WORK fore indiscriminately transfer corks from one bottle to another without an hour or so soaking in clean water. It might be thought that nothing could be said on such an every-day subject as bottles, but there are a few points which conduce to comfort in one’s dark- room. The type of bottle selected should be one with a thin lip projecting a good way round the rim — not one with a thick, square lip. The former allows the liquid to be poured out without wasting a drop; with the latter it is impossible to deliver small quantities without some of the solution dribbling down the side and into the coat sleeve of the victim. The bottles for one’s set of solutions, e. g., pyro, bromide and alkali, may very fitly be selected of dis- tinctly different size and shape, so that they cannot be mistaken in the rosy gloom of the dark-room. As suggested some time ago, the bottle proposed for poisons and in shape like a fashion-plate young lady, i. e., nipped in at the middle, might be adopted for pyro were it not to be feared that by a natural associa- tion of ideas the photographer might pass from clasp- ing of the waist to pressing to the lips — with disastrous results. Two hints ought to be so borne in mind that the practice of them becomes habitual. Always keep the label uppermost when pouring from a bottle, so that if any liquid trickles down the side the label misses it. Result — your labels keep clean and legible for much longer. Secondly, if you want to deliver drops (or a very small quantity) of liquid, just moisten the lip of the bottle with the finger. The fiuid then trickles 38 DARK-ROOM WORK out without having to overcome the resistance of a dry patch. I could easily fill pages with directions for cleaning bottles which have contained this or that chemical. But it doesn’t pay to spend time over such business. If water does not clean the bottle right away try shaking a little hydrochloric acid in it; if this is of no use, shake up (still with the hydrochloric acid) with shot, or small coal, or coarse sand or something which will scrape the impurity of the side. If this fails, cast the bottle aside as useless. Commercial hydrochloric acid is a solvent of many precipitates, sediments, deposits, which are not re- moved by water, and it is pretty safe to say that what is not removed by it must be rubbed off by friction. Keep the spirit mixed with an equal volume of water, and see that you do not splash any of it (neat or diluted) on clothes or upholstery, for it leaves a rotten and stained patch as a memento of its visit. Dishes, measures, etc., if rinsed out once or twice with this liquid are easily made quite clean, as a general rule. If the acid will not remove any stain, brisk rubbing with a tuft of any kind of paper will almost al- ways do so. I know of no better way of cleaning right into the cor- ners of bottles and dishes than this. If you wish to have a ten per cent solution of bromide, it is convenient to^have it in a dropping bottle. A 39 DARK-ROOM WORK dropping bottle can, of course, be made by cutting a couple of nicks down opposite sides of the cork, but the drops are very apt to trickle down the sides of the bottle, and make both it and the shelf it stands on unsightly. Take a bit of rather narrow glass tube, soften it in the flame and gently bend it and then cut to suitable length and insert into the cork of your bottle, taking care that it goes just a trifle below the inside surface of the cork. Fig. 16 will make this quite clear. By suitably selecting the size of the glass tube you will And that you can deliver about five separate drops, parting with each with just the sus- picion of a slight shake of the hand, without inverting the bottle to let in air. That is to say, with a one-in-ten solution of potass, bromide we can very conveniently add half a grain of bromide as fast as we can say “one, two, three, four, five.” 40 Chapter VII A TRAY ROCKER; PLATE LIFTERS; WEIGHING AND MEASURING F rom dropping bottles we naturally pass to aids to development. One of the most useful and simplest things is just a strip of wood to put under the middle of the dish as it rests on the table, so that with one finger one can rock a whole- plate dish. For quarter and half-plate an octagonal cedar-wood lead pencil is just the right size and length. For whole-plate, up to 10 x 12, dishes we want a round O piece about twelve inches long and say %-inch in diameter. With a plane we remove a little of this, so as to make it rest firmly on the table and not roll about. To make this quite clear I give in Fig. 17 a section of the rod of wood, and below we see this rod resting with its flat side on the table and a de- veloping dish resting on the rod. One need hardly say that the dish must not be allowed to stand with all the developer at one end and part of the plate 41 Fig. 17. DARK-ROOM WORK uncovered, as shown in the figure. A few handy plate- lifters should find a place on every dark-room sink shelf. We often enough want to be attending to two or three plates in as many different solutions. One or two plate-lifters enable us to lift the plate up and see how matters are going without contaminating one’s fingers with the solution. In Fig. 18 two equally convenient forms are shown. That marked A is easily made from the bone handle of a worn-out tooth-brush. All one needs is a file and a little patience. Do not make the likely mistake of making the finger-nail-like end too sharp and thin at its edges, or you will find your plate- lifter become a plate-scratcher. All sharp edges should be well rounded off with glass paper, or by rubbing on a stone. The above caution, of course, equally applies to form B, Fig. 18 . In this case our plate-lifter is of somewhat larger size, and made out of a bit of broken vulcanite tray. A piece was roughly shaped with a saw, then softened by immers- ing in hot water and bent to shape. When cold it was finished up with a file and glasspaper. The handiest measures for the dark-room are the tumbler-shaped ones. They are less liable to break than those running down to a point and standing on a flat glass foot. But they are of no use for measuring very small quantities of solution, and so one or two small-sized conical ones should be kept at hand, preferably the sort fitted with hard rubber bases. Dishes, at any rate in small sizes, are of poreclain, 42 Fig. 18. DARK-ROOM WORK glass, papier-mache, compressed fiber, hard rubber and tin. Porcelain is the most desirable despite its cost; it has the advantage of showing any dirt or stain, and thus conducing to cleanliness. Glass trays are, if anything, less liable to breakage than porcelain. Composition and metal trays are light and practically unbreakable; when they begin to look worn, or rust and leak, they should be thoroughly scrubbed in soap and hot water, and then coated inside and out with varnish or Probus. There is such a thing as needless accuracy in weighing and measuring. It is no good weighing chemicals more accurately than the solutions contain- ing them can be measured. From tests which I got some careful photographic friends to do in conjunction with personal tests some time ago I found that in broad daylight their measurements of solutions (1 or ^ ounces) varied about 1 per cent (1 in 100) on either side of the truth, i. e., total error of 2 per cent. Hence weights can be safely just as inaccurate — but not more so. This means that an “ounce” of say, potassium bromide, may be 4.37 (1-100 of an ounce) more or less than an ounce without “cutting any figure.” In other words, it may be 441.8 or 433.1 grains. This means that the trouble of finally adjusting the weight to one-half a grain is simply wasted. When small quantities, 20 grains and less, are being weighed the greatest accuracy must be observed. Every dark-room ought to have two balances — one for weighing small quantities up to, say, a quarter of an ounce, and another from this latter quantity up to a pound or so. The first is for chemicals required 43 DARK-ROOM WORK in small amounts, but with approximate exactness; the second for substances such as hypo or potassium oxalate, which need not be weighed with special accuracy. For the former, the ordinary beam balance of the dealers, preferably with glass pans, is the best, for the latter a spring balance with a good-sized pan, 6 inches or more in diameter and detachable from its setting. To those who care to go to the expense, the most convenient plan of any is to combine these two scales in one and to use a Beranger balance. An instrument of this pattern carrying two pounds is delicate enough for the smaller quantities a photog- rapher requires, but it is expensive. When very small quantities of chemicals have to be weighed out it is best to make instead a stock solution (10 per cent or 1 per cent), and to measure of this the quantity re- quired to give the weight of salt. Thus, instead of weighing 2 grains of sodium sulphite (for a toning bath) I would dissolve 44 grains in 10 ounces of water (i. e., make a 1 per cent solution) and use 200 minims. It is of the utmost importance to keep the pans of the balance scrupulously clean. That is why glass is best; practically no chemical attacks it. But there is no need to place the salt on the bare pan. In fact, this should never be done. Cut out circular discs of paper and keep a stock handy, placing one on each pan. Or a better way is to get a little aluminum bowl or dish which will stand on the pan and to cut a counter- poise for it out of sheet lead. It is quite easy to clean a separate vessel, but not so in the case of the pans. When liquids have to be weighed a glass vessel must be counterpoised. The best for the purpose is the 44 DARK-ROOM WORK beaker (of the analytical chemist) of the low and wide type. It is very light, stands steadily on the pan and pours cleanly; but it must be most carefully handled, for it is very thin and broken at once if squeezed or set down hurriedly on a hard place. Generally it is most convenient to measure liquids rather than weigh them. Measuring solutions requires separate treatment. If you look closely at some water standing in a measure you will see that the sur- Ct face is convex on the under side. Measures are gradu- ated — or are supposed to be graduated — so that they hold the given amount when the lowest point of this curve coincides with the line of the graduation. In measuring volumes of liquid of an ounce and upwards this is a refinement which can be entirely ignored. Fig. 19. but when measuring out a few minims it is well to bear in mind that a (Fig. 19) is the correct reading for 10 minims, and not h. Remember, also, when measuring out small volumes such as these (a few minims only) that a large propor- tion of the liquid clings to the sides of the measure, and unless the latter is rinsed out with a little water you don’t get all the indicated solution. The difference is appreciable in measuring out bromide solutions into 45 DARK-ROOM WORK small lots of developer, gold into toning bath, or platinum chloro-platinite into a platinotype sen- sitizing solution. A very handy fitment for measuring small volumes of liquids quickly is a glass tube drawn out to a fine point at one end and fitted with a rubber teat or bulb at the other, i. e., a fountain pen “filler.” It is graduated by scratching with a file at various points, which are best found by trial and error. Stick a scrap of sharp edging at the point where you think the 30-minim mark should be, and, pressing the bulb, draw up some water; expel the water until the level stands at the top of the edging and then discharge the tube into a minim measure, or, more ac- curately, into a little dish which has been balanced on a balance. If the guess is right scratch a mark with a file; if not, try again. A tube of this kind is very easily made and serves to measure solu- tions, such as bromide, very rapidly and accurately. A good plan is to keep it thrust through the cork of the bottle in which the stock solution is kept. This will necessitate a goodly number of graduated tubes, but will repay the trouble. (See Fig. 20). 30 25 20 10 5 Fig. 20. 4G Chapter VIII MAKING SOLUTIONS HERE are several factors which contribute to the rapid compounding of a solution — the quality and fineness of division of the chemicals, the temperature of the water and the way the two are mixed. By looking after these points much time and labor can often be saved. Let us consider them in the above order. Some chemical substances are very soluble in water and some are not. It is their nature and nothing will alter it. But, nevertheless, there are various devices which the photographer can practice by which he can get over some diflficulties nature puts in his way. Let him not forget that the remedies are also nature’s. An “anhydrous” salt, i. e., one deprived of water crystallization, dissolves much more quickly than the crystallized substance. Anhydrous sodium carbonate and sodium sulphite (see elsewhere) are two of the best known instances, and are obtainable commercially. Do not suppose that because a salt is anhydrous, it is therefore soluble. The fact is that the anhydrous salt does not lower the temperature of the water in which it dissolves as does the crystallized salt. A second method of aiding the solution of a salt is to add some second substance which has no effect 47 DARK-ROOM WORK on the action of the first. A most useful example is that of mercuric chloride. If powdered and mixed with an equal weight of ammonium chloride it dissolves very readily. A wedgewood pestle and mortar is the best thing for powdering chemicals. In purchasing one see that you get a pestle with a fairly fiat end. A too rounded end is less efficient for the purposes of the photographer, who does not want exceptional fineness, and is apt to throw the crystals out when used with sudden vigor. Make a point of cleaning the mortar directly after use. In the absence of a mortar a piece of stout brown paper and a wooden roller or mallet does the work almost as well. The hotter the water the more freely salts dissolve in it, as a general rule. I divide here the common photographic chemicals into 2 classes. I. Chemicals dissolving much more quickly if hot water is used: Oxalic acid, hydroquinone, alum, borax, lead nitrate, mercuric chloride, potassium ferricyanide, potassium ferrocyanide, potassium oxalate, sodium sulphite, sodium thiosulphate (hypo). For these it is worth while to use hot water. II. Chemicals dissolving very quickly in cold water: Ammonium sulphocyanide, ammonium bromide, citric acid, potassium bromide, potassium carbonate, potas- sium cyanide, potassium bichromate, potassium hy- droxide (caustic potash), sodium acetate, sodium car- bonate, sodium hydroxide (caustic soda), sodium chloride (common salt), uranium nitrate. For these it is of no advantage to use hot water. I must add that some salts must not be dissolved 48 DARK-ROOM WORK in hot water if they are to be obtained unaltered in the solution. The chief of these are: Potassium metabisulphite, sodium bicarbonate, sodium sulphanti- monate (Schlippe’s salt). To get hot water quickly in the dark-room I prefer a small gas or alcohol stove. Petroleum is not so clean. A small alcohol stove can be had at hardware stores which will boil a pint of water in five or six minutes. It is one of the most handy things you can have in a dark-room or mounting-room. The every-day method of dissolving salts, viz., putting them in a bottle and shaking till all have dis- appeared, is bad, because it needs constant attention. The concentrated solution collects at the bottom of the liquid and protects the solid from the action of the still unsaturated liquid above. Hence the neces- sity of frequent shaking. The proper method of solu- tion is to suspend the solid at the top of the liquid, by suspending the chemicals from the top of the con- tainer in a porous bag which hangs in the water. 49 Chapter IX FACTS ABOUT CHEMICALS T he chief things one wants to know about the chemicals used in photography are not their formulae or atomic weights, but their practical qualities, i. e., their solubility, keeping properties, the differences in name and fact between commercial varieties, and such facts as the impurities likely to be found in the chemicals we buy at the stores, how far these impurities are harmful, and how they can be minimized or removed. As a rule, chemicals are more readily soluble in hot than in cold water, so that if more than the quantity soluble in cold water is dissolved by the aid of heat, the excess of the salt will separate when the solution is cooled. Such a solution is said to be "‘saturated” in the cold, and for a given temperature contains always a certain definite quantity of salt. Generally 60° Fahr. (15.5° C.) is the temperature which is presumed when talking about cold saturated solutions. There are two ways of expressing solubility. We can say how much of the solid is contained in a given volume of saturated solution ; or we can say how much of the solid is required to saturate a given volume of water; other things being equal, the latter is always rather more than the former. 50 DARK-ROOM WORK The practical thing to remember about solubility and making solutions is, that if left to themselves at the bottom of a bottle most chemicals do not forthwith form a saturated solution. This point is gone into more fully in the section on making solutions. Note here that as chemicals generally dissolve more freely in hot water than in cold, the straight way to get a saturated solution is to take more of the salt than is necessary (see figures later), dissolve and cool. There should be a deposit at the bottom of the vessel if all is well. Many chemicals do not keep indefinitely. Their failing in this respect is mentioned seriatim below. As a general rule, all chemicals should be kept tightly stoppered and in the dark. In particular are developers (pyro, etc.), sulphites, sulpho-cyanides, ferrous and ferric salts (the former oxidize in the air, some of the latter reduce on exposure to light), silver, gold and platinum salts (get “reduced” in the light). Among others which spoil by absorbing moisture from the air, and which must, therefore, be tightly stoppered are ammonium and potassium sulpho-cyanides, uran- ium nitrate and chloride, calcium chloride, bleaching powder, ferric chloride (iron perchloride), potassium carbonate, caustic potash, potassium cyanide, caustic soda and sodium sulphite. The permanence or otherwise of a chemical solution is a matter of conditions — generally whether the air gets access to the liquid or not. Two methods of preserving solutions from the action of the air are worth bearing in mind. The first is to store the solu- tion in a lot of small bottles, say 4-ounce capacity, 51 DARK-ROOM WORK each filled to the lip and well corked. The second is to store the solution in a bottle with a cork at the bottom such as is described above, and to pour a layer of “heavy” paraflSn oil on the top of the solution. The oil, although designated heavy, is lighter than water, has no action on any ordinary solution and effectually excludes the air. Developers and other solutions must be kept fairly reasonably around 60° Fahr., i. e., from 55° to 65° Fahr. To do this in sum- mer and winter is not always easy. In winter remember that it is not enough that the de- veloper only be at the right temperature. If the room be nearly down to freezing, the developer will be chilled the mo- ment it is poured into the dish. Where it is not possible to keep the room warmed the following simple arrangement is easily made. A large square tank is filled with water at 65° (or other tempera- ture) and a metal frame fitted in the top so that the dish can be immersed to nearly the level of the water (see Fig. 21). Such a large volume of water does not alter in temperature very quickly, and a test every now and then with a thermometer keeps matters right. Those who do not want to go to this trouble should arrange a shelf over their dark-room lamp on which they can place developing dishes or bottles. 52 Fig. 21. DARK-ROOM WORK A little adjustment will enable them to get just the right degree of warmth. In summer the problem of cooling developing and toning solutions is not so easily solved. Ice is generally at hand during the summer months. Where it can be had these diffiulties disappear. One way of getting a supply of cooled water is to wrap up a large bottle of the water to be cooled in rags which are placed somewhere in a draught and kept well wetted. The heat absorbed by the evaporation of the water is sup- plied by the water in the bottle, which thus becomes cooler. It may be added, — though this is getting a little outside the province of this book, — that the less the fingers are placed in the baths used in summer, the better. 53 Chapter X WASHING PLATES AND PRINTS; DRYING T here is a good deal of misconception about the proper amount of washing required for plates and papers. The word “washing” suggests the drastic methods of the laundress, and indeed some writers seem to suggest that the hypo and other salts which we aim to remove are “knocked off” the gelatine film by a stream of water something after the manner of the ash from a cigar. As a matter of fact, the re- moval of hypo from a gelatine depends upon a process of diffusion, not abrasion, the facts about which are, briefly, as follows: Liquids which mix, say pure water and strong hypo solution, do so even though the heavier solution be at the bottom. Thus a layer of strong hypo solution carefully lowered by a funnel to the bottom of some water standing in a tall cylinder will, in course of time, gradually mix as completely as though the whole had been stirred together. The force of diffusion overcomes the attraction of gravity. Had the strong solution been introduced at the top of the water, gravity and diffusion acting together would have brought about this uniform mixture much more rapidly. Now these facts give the key to the common sense 54 . DARK-ROOM WORK of washing both plates and prints. The gelatine film, fresh from the fixing bath, is full of strong hypo solu- tion. If left at the bottom of a dish of water the hypo will gradually diffuse out, but it will do so much more rapidly if the outgoing solution can fall away from the film, because the rate of diffusion is greatest when the difference in strength of the two solutions is greatest. In other words, we want to intermittently replace the solution next the plate by pure water, so that the strong hypo solution in the film may have the greatest in- ducement to pass out. If properly conducted this process is not at all slow. Experiments by Haddon & Grundy and by Gaedicke have shown that a series of 5-minute soaks rapidly reduces the residual hypo in plates or paper to a negligible minimum. The number of soaks need not be more than five or six, which means that half an hour’s washing practically does everything that can be done. The best commercial pattern among negative washers is a siphon or other washer which allows some space, say 2 inches below the plates, and a depth of water above them equal to the height of the plates. The washer should fill slowly and empty as rapidly as possible (in a few seconds) so that the ideal conditions — quiescent soak and complete removal of soak- water — are approximately realized. There is no ad- vantage in the expensive arrangements for squirting jets of water over the negative. With constant change, an hour’s wash at the most is all that is necessary. In the case of prints the surest and simplest way of ensuring the frequency of change is by hand, though it is tedious. Remove each print slowly from the fixing bath. Much of the hypo is thus dragged out of 55 DARK-ROOM WORK the paper by capillary attraction and drains away. Plunge it for an instant into clean water and place in dish (A) of clean water. When all the members of the batch have arrived in A, remove them singly to a second dish (B) of clean water, taking each from the bottom of the pile. In B they are allowed to soak for ten minutes, the bottom one being continuously brought to the top. They are then taken back — singly, as before — to dish A. This ten-minute soak, agitation and transference to a second dish during the course of an hour will completely free them from hypo and ensure permanency. Amongst the enormous variety of print washers, really eflScient machines are rare, especially those capable of dealing with large prints. The efficiency of a washer is to be judged by how far it permits the complete change of the water without endangering the prints by tearing or without allowing them to clot together. The best plan is to confine them in a series of dishes through which a stream of water passes or which is placed in a box which is alternately filled and exhausted by a siphon. Such a washer is easily made, and it is the only kind in which a number of large prints can be satisfactorily washed. To set a negative to dry just as it comes out of the washing tank is not good practice. Many wash waters are hard and leave a white (calcareous) deposit which, though it may do no harm, is untidy and may give rise to patches should the negative be intensified. Moreover, drops of water cling here and there and make places which are much longer in drying. There- fore, having carefully rinsed the negative under the tap, gently mop the gelatine surface with a soft piece 56 DARK-ROOM WORK of cambric or absorbent cotton until it is surface-dry all over. The rapidity with which a gelatine film dries de- pends on two things: (1) the dryness of the air in contact with it and (2) the temperature of the air. The greatest rapidity is gained by a combination of these two conditions. The atmosphere, remember, always contains moisture, and the warmer the air the more moisture it can contain. What we want is dry, warm air, and by the “dryness” of air is to be under- stood air which contains very little moisture compared with the quantity which it can (at its temperature) take up. Thus the air in a warm room may be drier than the atmosphere out of doors because, though containing exactly the same weight of water per cubic foot, the warm interior air can take up more water than the colder external air. These facts ought to be borne in mind. They will save the amateur from doing some of the absurd things which in ignorance of them he sometimes attempts, such as putting negatives to dry in a damp dark-room simply because it is warm. In a confined space the moisture from a negative will saturate the air with moisture, and so checks drying. Hence the first condition is to get a constant change of air. If this is warm air, all the better. If it is filtered from floating particles of matter, better still. About the worst thing on which to dry negatives are the racks sold for this purpose, i. e., if they are anywhere near being fully loaded. About the best plan, on the other hand, requires no special apparatus. Drive into a convenient wall (or into a large board which can be reared up somewhere) a number of iron nails in pairs, the two nails being driven in at a dis- 57 DARK-ROOM WORK tance apart about equal to the shorter side of the negative. The negative is laid on these nails (see Fig. 22). If it is placed film upwards drying takes place more rapidly; if film downwards, however, there is less chance of dust settling. In order to expedite drying it is a good plan to place these home-made racks some few feet from the floor, and also to arrange an oil stove somewhere near at hand. The current of heated air and products of combus- tion will greatly decrease the time of drying. A more com- pact arrangement (of which there are commercial forms) is one in which the plates are set on a vertical rack, and a current of warm gases caused to ascend over them by means of a row of tiny gas jets in the chamber on which the rack is built. This is easily made, and it is well to cover over the upper rack with a framework of fine wire gauze, the floor being likewise cov- ered with the same material. Floating specks of dirt are thus filtered out. There are one or two ways of drying a negative rapidly — in a minute or two — which deserve to be mentioned. The first is by wood alcohol. If only a single negative is being handled, simply place it for 5 minutes or so in the alcohol, rocking occasionally, and on removal stand it up to dry, which it will do in 68 DARK-ROOM WORK a few seconds. But if a large number of plates are being done, it is necessary (to avoid great waste of alcohol) to use two or three baths, for this reason: The first bath gradually becomes weaker (more watery) owing to the accumulation of the water from the films. In this state it cannot do more than produce a plate which still contains a certain proportion of water, and which, though it becomes apparently dry in a few seconds, remains sticky for a very much longer period. By draining off this first water-diluted spirit, and placing in a second bath, the proportion of water in the film is reduced to a negligible quantity and the films dry at once hard and clean. Tanks in which the plates are held vertically are the bes1; for the purpose, an,d when not in use should be kept covered. As soon as the second bath begins to yield tacky negatives, another should be installed. The first may either be kept in hand until it is useless or at once discarded. The latter is more economical, considering the time and trouble involved. Place the negative in a bath of formalin (1 vol.) and water (9 vols.) for a few minutes and rinse under the tap afterwards. The film is now hard enough to withstand drying at practically any heat which the hand holding the plate can bear. Alum, chrome alum and the other hardening agents can be used, but they require more washing after use and do not act so vigorously as formalin. If the surface moisture be mopped off the negative with a piece of cambric or fiuffless blotting paper, a roller squeegee and gentle pressure being used, it is quite possible to carefully dry the negative over a gas stove or before a fire without the aid of a previous 59 DARK-ROOM WORK hardening solution. Some plates are better than others in this respect; with those containing soft gelatine (i. e., plates which develop quickly) it is often very risky. Frequently, however, it is quite safe, and it will be noticed that the tendency of the operation is to give a ‘‘sparkle” to the negative — an advantage or disadvantage, according to circumstances. Roll films are best dried by suspending the strip of film from a metal clip in a current of cool, dry air. Cut films and film packs are most conveniently dried by hanging them on a line with pins at the two top corners in a current of air. The life of the negative is constantly menaced by breakage, either of the film or its support. Glass is a brittle substance and is consequently liable to break- ages, partial or complete. The breakage, when it occurs, may seem irremediable, but seldom is. First, as to glass negatives. Sometimes, when the negative has been developed and dried, scratches on the glass sides are seen. These, if neglected, will print through and mar the image. The scratches should be stopped out with a transparent substance. This can be done by cleaning the scratches and filling them up with Canada balsam, thinned down with benzole. The Canada balsam is to be had at any drug-store. When the balsam has dried, the negative should print through as usual, without markings. If the negative is broken in several pieces, one way to mend it is by mounting the pieces upon clean glass, fitting them accurately together and exposing for a positive. Retouching the positive will remove the marks; after which a nega- tive can be made from it. Jiut the defect being of common occurrence, some CO DARK-ROOM WORK more effective method of remedying is required. The glass of the plate may have been cracked before exposure and development. To detach the film from the broken support, one plan is to soak the negative for twenty- four hours in a cold saturated solution of washing soda. This will soften the film, which can be peeled off the glass untorn. Then soak for two or three hours in plain water. This expands the film. To reduce to the original size, soak in a bath of alcohol, which will re- duce the film to the original size and toughen it. Then transfer to a clean glass plate to which it should adhere. A fine line in the negative may still exist, due to the glass having been cracked before development; this mark can be touched out on the print. Another plan is to prepare the following solutions: (1) Fluoride of sodium, 1-2 ounce; water, 16 ounces; cork the bottle and shake well. (2) Powdered citric acid, 1 ounce; water, 16 ounces; cork and shake well. Have at hand a clean glass plate larger than the negative, in a tray of clean cold water. If a half-plate negative is being stripped, a 5x7 dish and sheet of glass are necessary. To strip the film take 4 ounces of No. 1 solution in a tray of hard rubber (which is impermeable to compounds of hydro- fluoric acid formed in the mixture) ; then add 4 ounces of No. 2. Rock the mixture, then immerse the nega- tive, film side uppermost, rock the tray endwise and crosswise, allow to stand for half a minute, then rock again. The film will slightly frill at the edges; with the forefinger and thumb of each hand lift the film clean off the cracked support, place in the water above the clean glass plate, lift the plate by the two top corners and adjust the film so as to leave a clean margin all round. Lift the plate and film together and drain. DARK-ROOM WORK Lay the plate in a horizontal position and adjust the film so that there are no air-bubbles. After draining, allow the transferred film to remain in a horizontal position to dry. In place of the sodium fluoride mixture, formalin is used by some workers. Solution A: Caustic soda, ten per cent solution, 1-2 ounce; formalin solution, 1-4 ounce; water, 5 ounces. Solution B: Hydrochloric acid, C. P., 1 drachm; water, 8 ounces. By this method, if the negative is varnished or retouched, the coating should be rubbed off with alcohol or turpentine. Soak the film in plain water to soften it, but before this, with a knife and a safe edge, scratch a line through the film to the glass, around the four sides of the negative, close to the edges. This will facilitate stripping. After soaking in water for half an hour, immerse plate in solution A for five min- utes, rinse and transfer to solution B for five minutes. Rinse well and place on table, face up, ready for strip- ping. Dampen a clean sheet of writing-paper large enough to lap over the plate all around, lay this on the film and cover with a blotter. Take a knife and start a corner of the film by gently lifting it up with the finger. A gelatine-coated plate should be ready. To prepare the coating, soak 1 ounce of gelatine in 16 ounces of water until softened, then dissolve by heat. Then add chrome alum, 20 grains, dissolved in 1 ounce of warm water, add gradually to the gelatine solution, stirring to prevent precipitation. The glass plate should be immersed in this solution while warm and then drained and dried. Lower the film into position on the new sup- port and rub into contact under a blotter. Remove the paj)cr and dal) out any bubbles that may remain between the films.