8b 
 
 NH 
 
 595 
 
 B94 
 
 1890 
 
 THE 
 
 
 i 
 
 ) E 
 
 v li L; 
 
 OP MEET 
 
 
 
 
 
 
 OF 
 
 
 n i 
 
 \ 'i' ' 
 
 liLii, 
 
 h 
 
 Mi 
 
 Dry Pi ,y 
 
 1 .*« N 
 1 JQaJ 
 
 3 
 
 1-1 
 
 i; 0 > a 
 
 jpMlA I. A, 
 
 1 S 1 ,3 K. !: s A N M , 
 
FRANKLIN INSTITUTE LIBRARY 
 
 PHILADELPHIA, PA. 
 
 Class 
 
 XZ.4L... Book J&SSLL Accession ...ZXX.XX 
 
 
 
 Given by 
 
B 
 
 
 4 
 
 39 - 
 
 
 
'the: 
 
 DEVELOPMENT 
 
 OF 
 
 Gelatine - Dry - Plates 
 
 a practical flDanual for tbe amateur. 
 
 R;ev.„W. H. lilJ.R BANK, . 
 
 j j J J J J J > ' ) - ^ J 
 
 j J J J J J J J ) ) J J 
 
 Author of “ 'Pkpto^radJric Priutjng b T ethoa y, ” ‘ The 
 Photographic Negative," Etc. 
 
 BRUNSWICK, MAINE : 
 
 W. IT . BURBANK!, 
 i 8 90. 
 
THE GETTY CENTER 
 LIBRARY 
 
PREFACE. 
 
 Of making books photographic there is seemingly no end, 
 and he who is rash enough to add still another to the long 
 list may well be asked his reasons for so doing. 
 
 In the present case it is hoped that a satisfactory answer 
 will be found in the fact that there is at present no exhaus- 
 tive treatment of the important question of development 
 readily accessible to American amateurs. 
 
 The foundation of a good print is a good negative, and 
 this is largely a matter of skillful development, the leading 
 principles of which, as they have been taught me in my own 
 practice, I have endeavored to explain in plain language in 
 the following pages. 
 
 So far as possible I have aimed to give a reason for the 
 formulas and methods recommended, and I have entered 
 somewhat at length into the theory of development, in 
 order that the amateur may be in a position to compound 
 his developer intelligently and with reference to his special 
 needs. 
 
 I have not sought to multiply formulas in the body of the 
 book ; I have merely taken a typical formula under each 
 class and endeavored to make its method of action and its 
 possible modifications so plain that he who runs may read. 
 
 To the great army of amateur photographers, many of 
 whom are known to me personally, all of whom I would be 
 glad to know, this attempt to make smooth the somewhat 
 difficult path of development is most heartily dedicated by 
 
 The Author. 
 
 79 3 - 5 ¥- 
 
SPECIAL LITERATURE ON DEVELOPMENT. 
 
 Outside of current periodical literature, which is full of 
 articles on the subject, the following special works have 
 been consulted : 
 
 “ Le Developpement de L’lmage Latente.” By A. De 
 La Baume Pluvinel : Paris, 1889. Gauthier-Villars et Fils. 
 
 “Traite Pratique du Developpement.'’ By Albert 
 Londe : Paris, 1889. Gauthier-Villars et Fils. 
 
 “ Development.” By Lyonel Clark : London, 1890. 
 
 Hazell, Watson & Viney. 
 
 “The Chemistry of Photography.” By Raphael Mel- 
 dola : New York and London, 1889. Macmillan & Co. 
 
 To the first and last of these, special obligations are due 
 foj information regarding the chemical reactions of 
 development. 
 
CHAPTER I. 
 
 general principles. 
 
 HE Latent Image. — The sensitive surfaces which we 
 
 have to consider in the following pages are formed by 
 coating glass, paper, or other suitable substance with a 
 viscous solution of gelatine, holding in suspension bromide 
 of silver in a more or less finely divided state, according to 
 the degree of rapidity of the emulsion. When such sur- 
 faces are exposed to light, either in the camera or under a 
 negative, the sensitive compound undergoes a change of 
 some kind, the exact nature of which is not definitely 
 known, and which is invisible until the application of cer- 
 tain reagents, called developers, which possess the property 
 of making the image visible. The bromide of silver is 
 decomposed wherever it has been affected by the action of 
 light, and a dark deposit of silver is formed on those parts, 
 in exact proportion to the intensity of the light-action. 
 
 This action of light is called latent or actinic, and the 
 invisible image is a latent image, since it can be made visible 
 by the application of suitable reagents. 
 
 The Nature of the Latent Image. — Photographic 
 scientists are by no means in agreement respecting the 
 exact nature of the image formed by the action of light on 
 these gelatino-bromide surfaces. Two theories have been 
 advanced in explanation of the change thus produced — the 
 one chemical, and the other physical. According to the 
 chemical theory the image produced by a short exposure t c 
 
 5 
 
6 
 
 Development of Dry Plates. 
 
 light is of precisely the same nature as that produced by a 
 prolonged exposure, that is, it is a partial or complete 
 decomposition of the bromide of silver, which is reduced 
 to a sub-bromide. If the action of light has been suffi- 
 ciently energetic the number of molecules thus reduced is 
 numerous enough to produce a visible image. In the case 
 of exposures of brief duration the reduced molecules are 
 too few in number to produce a visible image, and a latent 
 image is the result. 
 
 According to the dynamic or physical theory, the luminous 
 rays produce a change of molecular condition, destroying 
 the equilibrium previously existing, thus producing a new 
 molecular arrangement, which is amenable to the action of 
 the developer. The reduced or changed molecules are still 
 molecules of bromide of silver, only in a modified condition. 
 
 Owing to the fact that the direct demonstration of the 
 nature-of the change is at present quite beyond the reach of 
 even the most refined chemical methods, it is impossible to 
 give an authoritative statement regarding the correctness of 
 either of the above theories, but inability to determine the 
 exact nature of the latent image does not, fortunately, 
 seriously affect the conditions of development. We know 
 that a change of some kind is produced, and that the effects 
 of this change may be made visible and permanent by the 
 use of suitable reagents. How best to do this is the sole 
 object of the following pages. 
 
 The Possibility and Theory of Development. — Here, 
 again, positive statement is not permitted. If the dynamic 
 theory be accepted, it seems probable that the tendency of 
 the action of light upon the molecules of silver bromide is 
 to separate them and thus weaken the bonds of union 
 between them. The molecules thus separated may. be 
 
Development of Dry Plates. 
 
 7 
 
 regarded as possessed of a certain degree of potential 
 energy, by which they are enabled to exercise a greater 
 attraction over surrounding bodies than is exercised by 
 those molecules which are more intimately combined. If an 
 exposed plate is covered with a reagent containing silver in 
 a condition of easy precipitation, the metal is attracted by 
 the molecules of the film, which have been acted on by 
 light, and is deposited only on those parts of the film which 
 have received a light impression, and in exact proportion to 
 the intensity of that impression. The image is thus built 
 up by accretion, and the developers which act in this way 
 are known as physical developers. This is the usual 
 method of development for collodion plates. 
 
 Instead, however, of precipitating the stiver on the sur- 
 face of the exposed film, it can be subjected to the action 
 of a reagent which has a reducing power over the modified 
 molecules of silver bromide. In this case the molecules of the 
 reagent are attracted only by the modified molecules of the 
 film, and the decomposition of the latter takes place only in 
 those parts which have been impressed by light. In this 
 case the coloration of the film is more in the nature of a 
 stain than a deposit, as in the former case. Developers 
 which act in this way are called chemical developers, and 
 the method is that employed in the development of gelatino- 
 bromide plates, and is, therefore, the subject of this book. 
 
 Before leaving this preliminary treatment of the subject, 
 it should be said that the modified bromide of silver can be 
 completely reduced only by reagents which are able to con- 
 tinue the separation of the bromine from the silver begun 
 by the action of light. In other words, the developer must 
 be a reducing substance. Such substances are found among 
 those bodies which have a strong oxidizing power. But all 
 
8 
 
 Development of Dry Plates. 
 
 easily oxidizable substances are not equally well adapted 
 to the development of the latent image. Many are too 
 powerful to be used for this purpose, even when well 
 restrained. When the action of the developing agent is 
 too powerful, we have a general reduction of silver over the 
 entire surface of the plate, producing the phenomenon 
 familiarly known as fog. 
 
CHAPTER II. 
 
 the DEVELOPING ROOM. 
 
 A LTHOUGH the discussion of the construction and 
 arrangement of the developing room is not entirely 
 germane to the subject-matter of the present book, a brief 
 discussion of the subject does not seem wholly out of place 
 in view of the important part which the developing room 
 plays in development. I have purposely discarded the use 
 of the time-honored expression, “ Dark Room,” as being a 
 misnomer. We do not want dark rooms when we develop 
 our plates. We want rooms abundantly lighted with light 
 of a safe quality. I am not a believer in the charms of an 
 imperfectly lighted developing room in which the chances 
 of success are appreciably diminished by inability to deter- 
 mine the condition of things in the developing tray at a 
 glance. I prefer to have an abundance of light and .to 
 provide my trays with covers of stout cardboard or wood, 
 removing them at brief intervals to examine the plate. 
 
 It is obviously impossible to give any hard and fast de- 
 tails for the construction of the developing room. Indi- 
 vidual needs and tastes differ so much that what would 
 suit one would be of no value for another. In general it 
 may be said that the room should be of fair size. Ten by 
 fourteen feet is none too large if much serious work is to 
 be done in the room. If possible, it is well to have another 
 room connected with the developing room by double doors, 
 for such photographic operations as do not require seclu- 
 
 9 
 
io Development of Dry Plates. 
 
 sion from daylight. If this room be fitted up with the 
 usual appliances of a laboratory, including a sink and run- 
 ning water, the amateur is well equipped for serious experi- 
 mental work, which should form a oart of the education of 
 every lover of the science. 
 
 The developing room proper should be provided with 
 double doors in order that one may go in and out without 
 fear of injury to the sensitive surface. 
 
 The Lighting. — I very much prefer artificial light to 
 daylight, for the reason that it is more constant and more 
 easily controlled. Whenever possible the source of light 
 should be placed outside the room, to avoid heat and the 
 products of combustion. In this case a large opening is cut 
 in the wall immediately over the sink. At least three sliding 
 frames should be fitted to the opening, one glazed with plain 
 ground glass, another with ruby glass, and the third with 
 yellow glass. If orthochromatic work is to be attempted, 
 a fourth frame, covered with stout brown paper, should 
 be added. With this arrangement the operator has perfect 
 control over the quality and intensity of the light, both of 
 which may instantly be adapted to suit the work in hand. 
 
 The Sink. — A lead-lined wooden sink is preferable to 
 one of iron or earthen ware, as there is less danger of 
 breaking a plate or graduate which may be carelessly 
 dropped. It will be found advantageous to provide two 
 swinging water-taps, one fitted with a fine rose and the 
 other with a plain open nozzle. The sink should be of 
 good size and preferably provided with a bottom sloping 
 from the sides to the lowest point in the middle. It should 
 be fitted with a sliding rack on which to place the develop- 
 ing tray. At the right should be placed the hypo tank or 
 tray in a position to be free from all chance of contaminat- 
 
Development of Dry Plates. 
 
 i 
 
 in g other chemicals. Shelves may be arranged on either 
 side of the window over the sink to suit individual tastes. 
 Beneath the sink suitable racks for trays should be 
 arranged. Fig. i gives a suggestion for the construction 
 of a very convenient and serviceable sink. 
 
 The other fittings of the room, such as shelves, drawers, 
 tables, etc., are best left to the fancy of each worker. 
 Efficient and light-tight means of ventilation should be 
 provided and the question of heating must not be neg- 
 
12 Development of Dry Plates. 
 
 lected. Fig. 2, which is reproduced from M. Londe’s book 
 on Development, shows a very effective arrangement of 
 developmental accessories. On the right of the sink is 
 seen a very simple rocking arrangement, which will be 
 found a great convenience in cases of prolonged develop- 
 ment. 
 
 Of course, it is understood that successful development 
 is not conditioned by the possession of such elaborate facili- 
 ties as are described. Good work is possible in any 
 darkened room with a water jug and a waste-water pail for 
 accessories, but these are only make-shifts, and have no 
 place in this discussion. 
 
 ' A Portable Developing Room. — Figures 3 to 6 show the 
 details of construction of an easily constructed developing 
 room which combines the advantages of convenience and 
 portability. It can be taken down or put together in a 
 short time, and it is recommended to those amateurs to 
 whom the first of May brings new quarters, or who do not 
 care to go to the trouble or expense of building a perma- 
 nent abiding place for the Lares and Penates of develop- 
 ment. The cuts are taken and the description is abridged 
 from the pages of Der Amateur Photograph. 
 
 Fig. 3 is a perspective view of the room showing the 
 method of construction. A number of light frames of 
 wood covered with stout pasteboard or sheathing paper, 
 forms the sides, ends and top of the structure, which may 
 be placed in a convenient corner of any available room. 
 One of the frames contains a smaller frame mounted on 
 hinges to form the door. As to size, a room 6 feet long, 
 4/4 feet wide and 7 feet high, is as small as will afford the 
 necessary working space. The width is governed by the 
 width of the work table and the space to be left between 
 
DEVELOPING ROOM. Fig. 
 
i4 
 
 Development of Dry Plates. 
 
 Fig. 3. 
 
 it and the side of the room. In joining the frames the 
 following precautions must be taken to insure light-tight 
 
 joints : All joints 
 
 must be reinforced 
 by strips of thin 
 wood screwed on 
 both sides. Fig. 4 
 shows the method 
 of protecting the 
 joints on the two 
 sides. Fig. 5 shows 
 the method of pro- 
 tecting the corners, 
 and Fig. 6, the same 
 principle applied to 
 the top or roof. The 
 door must fit snugly against battens fastened to the inside 
 of the frame. Any places where white light creeps in are 
 easily made safe by pasting black paper over them. In 
 order to prevent the light from coming around 
 the bottom edge, it is well to screw half-inch 
 cleats to the floor where this is admissible, 
 and to screw the bottoms of the frames 
 tightly against these. f<g. 5. 
 
 Fig. 7 shows a very con- 
 venient work table for such 
 a room as this. Its con- fig. 4. 
 
 struction is so plainly shown that extended description 
 is unnecessary. The dimensions should be about 
 three feet high, three feet long and eighteen inches 
 wide. That portion where development is carried 
 may be covered with sheet lead with the edges turned 
 
 on 
 
Development of Dry Plates. 15 
 
 up about half an inch and provided with a waste-pipe lead- 
 ing to a pail underneath, as shown. The fixing bath is 
 kept in a tray on the shelf under 
 the top of the table. This shelf 
 also holds the washing tray. 
 
 Other conveniences may be 
 added as need may arise, and 
 the room will be found a very 
 decided improvement over the 
 out - of - the - way, inconvenient 
 closets which serve so many 
 for developing rooms. 
 
 I have intentionally omitted 
 all mention of trays, graduates, 
 bottles, and the other impedi- 
 menta of the well-stocked de- 
 veloping room. Individual 
 needs and circumstances vary 
 so that no exhaustive list can be given. All these things 
 have a way of accumulating of themselves as one’s photo- 
 graphic horizon broadens, and their acquisition may be left 
 to the purse and necessities of the worker, aided by the 
 few hints which I have aimed to give in this chapter. 
 
CHAPTER III. 
 
 tHe principles of development — tH e tentative 
 
 METHOD. 
 
 OEFORE entering upon the more practical part of the 
 subject, it will be well to give what I conceive to be the 
 underlying principles which govern all good development, 
 and since in doing so I shall run counter to the advice of some 
 good authorities, I desire to state that I believe the princi- 
 ples which I shall advance to be susceptible of proof by 
 actual experience in the developing room. They are given 
 as the result of careful study of the conditions which seem 
 to me to govern all successful development of the latent 
 image. 
 
 My experience has taught me that something more is 
 required for the proper development of the latent image 
 than the possession of a good formula and the ability to 
 compound it; that there are laws of development which 
 must be known and followed before the operator can hope 
 to approach development intelligently. These laws con- 
 stitute what we may term the philosophy of development. 
 As the end of development is the production of a negative 
 which will yield a print of a desired quality, the first step 
 is the knowledge and appreciation of the qualities which 
 the various printing processes, now commonly employed, 
 demand in a negative. There is no question here of sharp- 
 ness of outline or artistic quality. These are taken for 
 granted. 
 
 Detail and intensity must be placed first among the neces- 
 
 16 
 
Development of Dry Plates. 
 
 T 7 
 
 sary qualities of a good negative. There must be no large 
 patches of blank shadow, and the density must be propor- 
 tioned to the printing process likely to be used in making 
 the final print. 
 
 By far the larger portion of the subjects which are sought 
 to be reproduced by means of photography are those in 
 which there is an infinite gradation of tone from high light 
 to intense shadow. Theoretically, the perfect negative is 
 obtainable only under the condition of giving to each por- 
 tion of the subject an exposure proportionate to the rapidity 
 of its action on the sensitive film. But this is evidently an 
 impossibility. What the photographer actually does in 
 practice is to give an equal exposure to objects unequally 
 lighted, thus introducing special difficulties in the later 
 operation of development. 
 
 Those parts of the subject which are most strongly illu- 
 minated act with greater energy on the sensitive film than 
 those less strongly lighted, and do so, probably, in direct 
 proportion to the degree of the illumination. Hence, when 
 the developer is applied, the high lights, as they are called, 
 that is, those portions of the view which were most strongly 
 illuminated, appear first, and are followed by the less 
 intensely lighted portions, and these, in turn, by the darker 
 parts, thus giving the tone gradation which is so marked a 
 characteristic of a good negative. 
 
 If a proper exposure be had the details are obtained by 
 continuing the development until these are well out in the 
 deepest shadows. Save in exceptional cases, no part of the 
 negative should be devoid of a certain amount of detail. 
 From this we may deduce the first general rule or principle 
 governing development : 
 
 The development must be continued until all the detail is visible 
 
i8 
 
 Development of Dry Plates. 
 
 in the clear or white portions of the negative , which correspond 
 to the shadows of the subject. 
 
 We may best study the question of intensity by distin- 
 guishing between local and general intensity. The former 
 being the direct result of the unequal lighting of the sub- 
 ject, it reproduces the difference of tone gradation. It is 
 determined by the intensity of the rays of light reflected 
 from the different parts of the view, and it is generally 
 independent of the operator, who, however, has it in his 
 power to modify slightly the final result. 
 
 General intensity is the degree of density which must be 
 given a negative in order to obtain good positives from it. 
 There must be a certain degree of obstruction to the free 
 passage of light through different portions of the negative. 
 
 It is quite possible for a negative to have detail and local 
 intensity without being a good printer, for the reason that 
 it lacks general or printing density. This maybe too weak, 
 in which case the print will be monotonous and tame, or 
 it may be too strong, giving only harsh prints. The remedy 
 in the first case is intensification, in the second reduction, 
 neither of which, if properly conducted, affects the local 
 or artistic intensity, for if it did, successful intensification 
 and reduction would be impossible. 
 
 In addition to the rendering of detail, then, the operator 
 must seek to give his negatives the degree of printing den- 
 sity best suited to his favorite printing process, since the 
 different printing methods require negatives of varying 
 density — the carbon process requiring thin and harmonious 
 negatives, the albumen process those of medium density, 
 and the platinum process those of greater strength. 
 
 Nothing is more detrimental to successful development 
 than the belief that detail and density can be secured simul- 
 
Development of Dry Plates. 
 
 19 
 
 taneously. This is the weakness of all one-solution devel- 
 opers, that they are based on the false assumption that detail 
 and density go hand in hand. Only in the case of negatives 
 of feeble contrasts and proper exposure do the rendering 
 of detail and the acquirement of printing density hold an 
 equal place. But how often are these conditions realized ? 
 Not once in a hundred exposures. When the negatives 
 present strong contrasts, and the time of exposure has been 
 more or less wrong, as it usually is, the application of the 
 developer reveals the difficulty of obtaining detail and 
 printing density at one and the same time. The high lights, 
 which are the first to appear, continue steadily to gain in 
 intensity, and long before the details in the shadows are 
 well out, the density of the high lights has passed the 
 proper degree. Such a negative will give harsh prints in 
 which the contrasts are exaggerated. The proper method 
 of development in such cases is to hold back the density 
 until the details are well out, by developing for detail 
 first. 
 
 In the opposite case, where we have to deal with exposures 
 on subjects feebly lighted and devoid of contrasts, the devel- 
 opment must be for density first, if we would avoid foggy 
 and weak negatives. This gives us our second rule or prin- 
 ciple of development. 
 
 If these principles are well founded, it follows that a 
 knowledge of the best methods of obtaining both density 
 and detail is essential to anything like true development. 
 These methods will be discussed later on. As a step in 
 this direction, I propose now to discuss briefly the condi- 
 tions outside of the developing room, which have much to 
 do in determining both detail and density. 
 
 First on the list I place the influence of the plate itself. 
 
20 
 
 Development of Dry Plates. 
 
 It is far from being a matter of indifference whether we 
 use slow or rapid plates. No manufacturer of sensitive 
 plates will care to dispute the assertion that the quality and 
 speed of the plate affect, even if they do not determine, 
 the finished result. 
 
 With the slower grade of plates printing density is a mat- 
 ter of comparative ease. It is in the rendering of detail 
 that the difficulty begins. With rapid plates the conditions 
 are reversed. Detail is easily rendered, but printing den- 
 sity does not always accompany this rendering. 
 
 Slow plates have a tendency to increase contrasts unless 
 the time of exposure is purposely prolonged to avoid this 
 difficulty. Rapid plates tend to diminish contrast and so 
 to produce more evenly lighted prints. 
 
 For the beginner there is nothing better than plates of 
 medium density, since they have not the same tendency to 
 fogging which is noticeable in rapid plates, always remem- 
 bering that with slow plates the time of exposure should be 
 lengthened to avoid excessive contrast, while with rapid 
 plates the time of exposure should be made as short as 
 possible, to avoid fog. 
 
 Another important element in the character of the nega- 
 tive and consequently of the print, is the nature of the 
 objects to be reproduced. Careful study of the view to be 
 photographed is essential to success. 
 
 M. Londe’s division of the different photographic sub- 
 jects is so true and helpful that I make no apology for 
 reproducing it. The division is threefold : 
 
 First — Subjects which have a perfect harmony of tone 
 gradation. 
 
 Secondly — Subjects which present strong contrasts and 
 oppositions. 
 
Development of Dry Plates. 
 
 21 
 
 Thirdly — Subjects which have not enough of contrast 
 and opposition, and are, consequently, weak. 
 
 Now, it is very evident that the same method of exposure 
 and development cannot be adopted in all these cases, that 
 some modifications are necessary in order to bring out the 
 very best of which the view is capable. 
 
 It is a fact established by observation that if light is 
 allowed to act upon a sensitive surface the effects of the 
 light-action increase up to a certain point, and that beyond 
 this point the intensity gradually diminishes, the light 
 seeming to destroy the effects of its own work. 
 
 The law of reduction is this : The intensity of reduc- 
 
 tion is directly proportional to the length of time during 
 which the addition of light has been continued, up to a 
 certain point, which for any given plate may be called its 
 fogging point. Beyond this point the effect is inversely as 
 the action of light. 
 
 In practice, then, we obtain an increasing degree of in- 
 tensity by lengthening the time of exposure, so long as we 
 keep within the limit where the inverse action begins. 
 
 It is easy to see the importance of this principle, since 
 the knowledge of it practically applied enables us to 
 modify at will the results of an exposure. 
 
 With subjects of the first class the time of exposure 
 should be as nearly correct as it is possible to make it. 
 Subjects of the second class should be somewhat over 
 exposed, both in order to secure the detail in the dimly 
 lighted portions and to reduce the density of the high lights. 
 Subjects of the third class require a brief exposure in order 
 to increase the contrasts. 
 
 The reader who has followed me intelligently thus far is 
 prepared to profit by the succeeding remarks on the general 
 
22 
 
 Development of Dry Plates. 
 
 principles of development, which are here given only after 
 a thorough test of their value in the developing and print- 
 ing rooms. 
 
 As the pyro developer is more flexible than any other in 
 common use I have taken it as the standard of judgment, 
 but the principles are equally applicable to all forms of 
 developers. 
 
 In the development of an exposed plate either of two 
 methods, the automatic and the tentative, may be adopted. 
 I use the expression automatic development with reference 
 to that method in which the plate is left in a ready mixed 
 solution without any modifications being made to suit the 
 seeming exigencies of the case. All one solution develop- 
 ers, as well as those in which a given formula is blindly 
 followed, come under this head. I have a well-founded 
 distrust and lack of confidence in the method of automatic 
 development, which is rapidly becoming popular with 
 amateurs of a certain class, whose one aim seems to be to 
 reduce photography to a mere mechanical routine. 
 
 The tentative method of development, which I believe to 
 be the only rational and philosophical method, is based 
 upon the wise and intelligent adaptation of means to ends. 
 
 Starting with a thorough knowledge of the leading 
 features of the view on the plate, and a perfect under- 
 standing of the effects to be produced, the various ingredi- 
 ents of the developer are to be so proportioned as to lead 
 up to the desired result. From time to time as need arises 
 various modifications are made. “Festina lente ” is the 
 motto of this method. A wise caution is exercised at the 
 outset, constant vigilance is maintained till the end of the 
 development, and a wise intelligence recognizes and meets 
 all the exigences of the case as they present themselves. 
 
Development of Dry Plates. 
 
 2 3 
 
 I would lay it down as an axiom seldom to be deviated 
 from that all development should begin slowly with a 
 developer relatively weak in both accelerator and reducer. 
 In this way the image will not surprise one by a sudden 
 appearance and an equally sudden disappearance in a veil of 
 fog. So far from beginning with a bath of maximum or even 
 normal energy I would advise a bath of minimum strength 
 save in those special cases, to be mentioned later, where a 
 different method is absolutely necessary. . In this way the 
 operator remains an easy master of the development. 
 
 Several methods of reducing the strength of the de- 
 veloper are open to the operator. He may either diminish 
 the quantity of the components of the solution, or dilute it 
 with water, or finally add a trace of bromide. It is by no 
 means a matter of indifference which of these methods is 
 adopted, since each modification produces a different effect. 
 
 The diminution of the quantity of the accelerator and 
 reducer is valuable chiefly because it allows a wider range 
 of subsequent modification to suit special needs. 
 
 The addition of bromide retards the development and 
 tends to increase contrast. Hence, its use is indicated for 
 negatives of evenly lighted subjects where all possible con- 
 trast is sought. When the developer is diluted with water 
 the development proceeds slowly, because the constituents 
 of the solution are not present in sufficient quantities to 
 produce a rapid reduction. The tendency of a diluted 
 bath is to produce softness, and it should be employed in 
 cases of known over-exposure when softness is desired. 
 
 If the development was begun with a bath weak in alkali 
 and reducer, and it is desired to bring out the details 
 before giving printing density, as is usually the case, suc- 
 cessive small additions of the alkali are made until the 
 
24 
 
 Development of Dry Plates. 
 
 detail in the shadows is well out, then a final addition of 
 pyro confers printing density. 
 
 As an example, let us take the case of a subject of strong 
 contrasts which was intentionally over-exposed to diminish 
 the contrasts. The proper method of development would 
 be to begin with a small percentage of pyro and carbonate, 
 in the developer, adding the carbonate gradually in small 
 quantities until the details are well out in the shadows. If 
 the development were stopped at this point we should have 
 a negative full of detail and of good local density, but 
 lacking in general or printing density. This is gained by 
 adding pyro until the general density is judged to be 
 sufficient. 
 
 If the whole amount of pyro ultimately employed had 
 been present in the solution from the start, the result would 
 have been a negative in which density had been reached 
 before the details were all out, the contrasts would be too 
 strong, and it would present the appearance of -an under- 
 exposed plate. 
 
 If the view belongs to the third class, that is, if it lacks 
 contrast and opposition, density must be given before the 
 details are entirely brought out, by the addition of the 
 carbonate in smaller quantities and the use of pyro to 
 confer density. 
 
 This is the only rational method of development, and the 
 fact that it requires intelligence on the part of the operator 
 should be an argument in its favor with those who regard 
 photography as something more than a press-the-button, one- 
 solution sort of business. It is the only method which gives 
 the operator an easy mastery of his negative and enables 
 him to produce effects of various kinds. It is, I have reason 
 to believe, the method of the masters in photography. 
 
CHAPTER IV. 
 
 THE automatic method— tHe Use of bromide 
 over-exposUre. 
 
 A UTOMATISM in photography has followed the ad- 
 vent of the dry plate and the discovery of methods of 
 combining the elements of a developer in one solution of 
 good keeping qualities. To make automatic photography 
 more easy, ingenious cameras have been devised which do 
 away with focussing, time exposures and most of the rou- 
 tine of the older school. I am as ready as any one to recog- 
 nize the value of the new photography for many purposes, 
 but I must protest against its being taken for all there is to 
 photography. 
 
 Similarly, I do not deny that one solution developers 
 have a certain value, but I maintain that they cannot pro- 
 duce the highest results. 
 
 The reign of automatic developers may be said to have 
 begun with the general introduction of hydrochinon as a 
 developing agent. It was found to be much easier to make a 
 stable solution with hydrochinon than with pyro, and as it 
 unquestionably simplified the process of development, much 
 enthusiasm was manifested by its advocates. In another 
 chapter I have tried to state the hydrochinon case as 
 fairly as possible. Here I wish to say a few words about 
 automatic development, meaning by this expression the 
 development of a negative without any of the modifica- 
 tions mentioned in Chapter III. Theoretically the time of 
 exposure is not an element of importance with this method. 
 
 25 
 
26 
 
 Development of Dry Plates. 
 
 All the operator is required to do is to place the exposed 
 plate in this magical one-solution developer, take an occa- 
 sional look at it and remove it when it is done, just as the 
 cook removes the Thanksgiving turkey from the oven. 
 
 For every subject there is a time of exposure which we 
 may call normal, the time that is required for all the de- 
 tails to impress themselves on the plate. Corresponding to 
 this normal exposure there is, we may suppose, a normal 
 developer, that is a developer which in a certain time will 
 produce a negative rich in detail and of the proper general 
 density. Now, if it were possible to determine the exact 
 normal exposure for every subject, automatic development 
 would become a possibility. In other words, it would be 
 possible to develop every negative in a developer of the 
 same constitution and in the same time. The exposure 
 having been normal, the development would be normal as 
 well. 
 
 But the moment the normal time of exposure is exceeded 
 or not reached that moment the normal developer beomes 
 practically useless. For every length of exposure there is 
 a developer which will give the best results. What this 
 developer is, can only be determined by adopting the ten- 
 tative method of development. The negative may belong 
 to any one of the three classes mentioned in the last chap- 
 ter, requiring special treatment which cannot be applied in 
 the automatic method. 
 
 I have no hesitation in saying that it is almost an impos- 
 sibility to produce two negatives of precisely the same 
 quality in any one-solution developer. Although no visible 
 change may take place in the solution, either through use 
 or age a change is produced nevertheless, which affects the 
 result. ' 
 
Development of Dry Plates. 
 
 27 
 
 If any one doubts this assertion, he has only to make, 
 say, three exposures on*the same subject under similar 
 conditions of light, exposure and plate. Let one of these 
 exposures be developed for a given time in any one-solu- 
 tion developer. Let the other exposures be put away in a 
 safe place, and at the end of two varying periods of time 
 let them be developed in the same solution for the same 
 length of time. Unless my experience is greatly at £ault, 
 a marked difference will be noticeable in the three nega- 
 tives — a difference which can come from no other cause than 
 a chemical change in the developer, the possibility of which 
 is sufficient to condemn the one-solution developer for the 
 highest grade of work. One other reason is sufficient to 
 condemn the use of single solution developers. Most of 
 these solutions are purchased from dealers and the buyer 
 has no knowledge of their composition. He cannot there- 
 fore modify them intelligently and he thus places himself 
 at the mercy of his developer. 
 
 The use of Bromide. — As bromide is naturally a retarder 
 of development, at first sight it might seem that the proper 
 corrective of over-exposure would be the addition of brom- 
 ide in a quantity proportionate to the degree of the over- 
 exposure. A more philosophical way of stating the prin- 
 ciple governing the use of bromide, would be to say that 
 the amount of bromide must be proportional to the inten- 
 sity of the action produced by light. 
 
 This is the general law, but, like most other laws, it has 
 its exceptions. In negatives of harsh contrasts where the 
 time of exposure has been purposely exaggerated, the use 
 of bromide is interdicted, since it would produce the very 
 effect we are seeking to avoid. We then use a minimum 
 of bromide and a diluted solution. 
 
28 
 
 Development of Dry Plates , 
 
 The use of bromide is recommended for negatives of 
 poorly lighted subjects in order t& heighten the contrasts. 
 
 There seems to be very little choice among the two brom- 
 ides commonly used. The bromide of potassium is a more 
 stable compound than the corresponding ammonium salt, 
 and its use is therefore advised. Bromide of sodium is also 
 a good restrainer. The bromides of zinc and copper seem 
 to work best with the eikonogen developer. 
 
 Intentional Over-Exposure. — There are occasions when 
 a judicious lengthening of the exposure will improve the 
 quality of the negative, but the method is hardly to be 
 recommended to the beginner, and in any event it is to be 
 used with extreme caution, and preferably with slow plates. 
 In spite of frequent statements to the contrary, I maintain, 
 and am prepared to prove the statement, that with intelli- 
 gently-conducted development, the time of exposure within 
 reasonable limits, is not the all-important matter it is said 
 to be. The statement which I make is, that the proper 
 time of exposure may be increased without producing in- 
 jurious results. 
 
 Every one is aware that there exists for each class of 
 subjects, with a plate of a given rapidity, a time of expos- 
 ure which we may call the time of normal exposure, since 
 it is the time the plate must be exposed in order to render 
 all the detail combined with good general density. 
 
 Now, if this normal time is diminished, some of the de- 
 tails will be lacking. If it is exceeded, the details will be 
 all impressed, but there will be danger of fog through 
 over-exposure. It is plain that what light has not ef- 
 fected, no developer, however powerful, can make visible. 
 Hence, an under-exposed plate cannot be developed into a 
 satisfactory negative. 
 
Development of Dry Plates . 
 
 29 
 
 It has already been shown that an over-exposed plate 
 can be satisfactorily developed, either by the use of brom- 
 ide or by a diluted or weak developer. Hence, it would 
 seem to follow that the safest plan would be to over-ex- 
 pose and to modify the developer- accordingly, and this is 
 what I commonly do in my own practice, and what I recom- 
 mend to others; only one must know his subject and his 
 plate. 
 
 By adopting the tenative method of development, I find 
 no difficulty in making good negatives on plates which 
 have received at least double the normal exposure, and as 
 this increase in exposure makes me sure of the details, I 
 have long used it, except in special cases where for reasons 
 already given a short exposure is called for. 
 
CHAPTER V. 
 
 THE components OF THE' developer 
 ANd tHeir adjustment. 
 
 'T'HE method of alkaline development is undoubtedly the 
 A one which admits of the widest range of modification to 
 suit the ever-varying conditions which present themselves 
 in the developing room. In all alkaline developers there 
 are three elements : i, pyrogallol, or its equivalent ; 2, an 
 alkali ; 3, a bromide. 
 
 The solution of the problem of development will be ma- 
 terially aided by a consideration of the function which each 
 of these elements is called upon to fulfil and their relation 
 to each other. 
 
 Pyrogallol, or its equivalent, is a powerful absorbent of 
 oxygen and a reducer of the modified bromide of silver. 
 Hence, it is the reducing or developing agent. The inten- 
 sity or density of the deposit is largely conditioned by the 
 quantity of the reducing agent present in the developer. 
 Hence, additional density is conferred by an increased amount 
 of pyrogallol or its equivalent. By judiciously proportion- 
 ing the amount of the oxidizing agent, almost any degree 
 of density may be given to a negative. To some extent 
 the same effect is produced by increasing the affinity of the 
 reducer for oxygen by increasing the quantity of alkali, or 
 by decreasing it by the addition of a soluble bromide. It 
 is not, however, a matter of indifference which of these 
 methods of controlling density is adopted. An increase in 
 the quantity of alkali increases the danger of fog by pro- 
 
 30 
 
Development of Dry Plates. 
 
 3i 
 
 ducirig an undue rapidity in the reduction process. An 
 excess of bromide so diminishes the action of the reducer 
 as to make the bringing out of fine detail difficult, if not 
 impossible. It will be seen, therefore, that the developer 
 must be compounded with a modicum of brains in order to 
 obtain the best results. 
 
 There must be a proper balance between the ingredients of 
 the developer, or partial or total failure will be the only result. 
 
 The problem which has to be solved with every plate is 
 to bring out all the detail possible and at the same time to 
 obtain good general or printing density, and this without 
 the slightest trace of veil or fog. 
 
 The alkali aids in the attainment of detail by increasing 
 the affinity of the reducer for oxygen, and the bromide has a 
 strong tendency to diminish the chance of fog by slowing the 
 reducing action. It is probable that the restraining power 
 of the bromide is due to its tendency to form a double salt 
 with bromide of silver, this double salt being more stable 
 than the silver bromide and therefore less easily reducible. 
 
 If the reducing agent were always used in a dry state, 
 that is, if for purposes of convenience it were not desirable 
 to make up a stock solution to be drawn from as need arose, 
 no other elements would be needed than those just men- 
 tioned. Since, however, a stock solution is often a neces- 
 sity, it has been found necessary to add various substances 
 to the solution of pyrogallol to prevent its rapid deteriora- 
 tion by oxidization. Of these substances the sulphite and 
 meta-bisulphite of soda, meta-bisulphite of ammonium, for- 
 mic, citric and other acids have been used with good re- 
 sults. The best of these is probably the meta-bisulphite of 
 soda or ammonium, either of which will preserve a solution 
 of pyrogallol for a moderate length of time. 
 
3 2 
 
 Development of Dry Plates. 
 
 The objection to the use of sulphite of soda is its tend- 
 ency to pass over into sulphate of soda, which is a powerful 
 restrainer. 
 
 My own custom is not to employ a stock solution, but to 
 add the reducing agent in a dry state to the developer, 
 thus dispensing entirely with the use of a preservative, 
 which seems to me to be a needless if not an injurious 
 complication. The simpler we keep our formulas the 
 greater our chances of success. 
 
 Modifications. — With alkaline developers containing 
 pyrogallol a very wide range of modification to suit vary- 
 ing needs is possible. The normal proportions of the com- 
 ponents of the developer may be taken to be nearly as fol- 
 lows: Pyrogallol, 0.5 parts ; alkali, 2 to 6 pa'rts ; sulphite, 3 
 parts; bromide, 0.5 parts; water, 100 parts ; or for each 
 ounce of developer, 3 grains of pyrogallol ; alkali, 10 to 30 
 grains ; sulphite, 14 grains ; bromide, 3 grains. 
 
 These proportions, however, may be changed to suit 
 special circumstances. It is time now to speak of some of 
 the more important of these modifications, and I shall treat 
 the subject with reference to the pyrogallol developer, since 
 this is the one most commonly employed. 
 
 As I have already said, I am an advocate of a moderately 
 slow development, and strongly deprecate the use of a bath 
 at its maximum of energy to begin development with. It 
 is much safer in every way, especially in all cases where 
 one is in doubt whether the exposure has been correct or 
 not, to begin with a solution at its minimum energy. 
 
 Several methods of reducing the energy of the developer 
 are possible. The quantity of the elements of the solution 
 may be diminished, the bath itself may be diluted with 
 water, or bromide may be added. Which of these methods 
 
Development of Dry Plates. 
 
 33 
 
 is to be employed in each case of known over-exposure 
 will depend upon the character of the subject and the 
 effect which it is desired to produce. 
 
 The addition of bromide retards the action, but at the 
 same time tends to increase contrast and give density. 
 The dilution of the bath equally retards the action but has no 
 tendency to increase contrast or produce excessive density. 
 
 The use of bromide is indicated for the development of 
 subjects uniformly lighted and presenting no strong con- 
 trasts, in order to heighten the contrasts. On the other hand, 
 if the view was strongly lighted and presented great opposi- 
 tion, which it is desired to diminish as far as possible, the 
 normal bath should be diluted with water. If the subject 
 was well illuminated and the contrasts well balanced and 
 harmonious, the development should be begun in a bath 
 weak in pyro and alkali, developing first for detail and lastly 
 for density. This result is obtained by adding successive 
 small doses of the alkali at intervals until the details in 
 the shadows are well out and then obtaining the density by 
 a final addition of the necessary amount of pyrogallol. 
 
 With subjects of feeble contrast the method should be 
 reversed. Here the aim should be to retard as much as 
 possible the appearance of the details by a wise caution in 
 the addition of the alkali, and to gain the greatest possible 
 density by adding sufficient pyrogallol to accentuate as 
 much as possible the feeble values of the subject. 
 
 Density. — One of the greatest difficulties connected with 
 development for the beginner is to know the exact moment 
 when the process of development should be stopped, that is, 
 when sufficient printing density has been obtained. Of the 
 many negatives which I have examined, including many of 
 my own, there have been few which were removed from the 
 
34 
 
 Development of Dry Plates. 
 
 developer at just the right moment. Either they were taken 
 from the bath too soon and lack printing density, or they 
 were allowed to remain too long in the developer, and are 
 over-dense to give the best results in the printing frame. 
 
 It is not an easy matter, even for the most expert, to 
 determine in the light of the developing room the exact 
 moment when the proper degree of density has been 
 reached. Indeed, I am not certain that it is not largely a 
 matter of intuition, gained only by long practice and not 
 to be learned from written words. Still some hints may be 
 given which may help a stumbling brother along the diffi- 
 cult road of development. 
 
 In general terms, it is best to allow the developer to act 
 until those parts of the plate which have been feebly im- 
 pressed, that is, those which remain white longest, begin 
 to darken. With certain brands of plates, which lose 
 strength in the fixing bath, it is safe to prolong the 
 development until the edges of the plate which were pro- 
 tected from the action of light by the ledges of the slides 
 show a slight veiling. If a plate be examined at this stage 
 by reflected light, it will show a uniform dark tint. Ex- 
 amined by transmitted light the image will appear over- 
 vigorous and the finer details somewhat clogged up. 
 With some plates it is even necessary to allow the 
 developer to act until the image seems to have disap- 
 peared entirely. A properly developed plate should show 
 the image feebly on the back. A generally safe rule is to 
 develop until the blacks and the strongest half-tones are 
 plainly visible at the back of the plate, but much depends 
 on the character of the plate and the method by which the 
 prints are to be made. A properly exposed and normally 
 developed plate should be finished within five minutes. 
 
CHAPTER VI. 
 
 THE FERROUS-OXALATE developer. 
 
 /^HEMICAL Reactions. — When a sensitive surface 
 which has been exposed to light is placed in a solu- 
 tion of ferrous-oxalate, the following reactions take place : 
 
 The ferrous-oxalate decomposes the water, changes into 
 ferric-oxalate and ferric-oxide, while the hydrogen of the 
 water is set at liberty. 
 
 6(C 2 0 4 Fe) + 3H 2 0 = 2 [(C 2 0 4 ) 3 Fe 2 ] + Fe 2 0*6H. 
 6(Fe0,C 2 0 3 ) 4- 3 HO = 2 (Fe 2 0 3 , 3 C 2 0 3 ) + Fe 2 Q 3 -f 3 H. 
 
 The hydrogen, thus set at liberty, acts upon the modified 
 bromide which it reduces : 
 
 AgBr + H = Ag+HBr. 
 
 The hydrobromic acid, formed by this reaction, acts upon 
 the ferric-oxide of the previous reaction and produces fer- 
 ric-bromide and water : 
 
 6 HBr + Fe 2 O s = Fe 2 Br 6 + 3H 2 0. 
 
 3 HBr + Fe 2 0 3 - Fe 2 Br 3 4 - 3 HO. 
 
 Adding these three equalities, we have as the final chem- 
 ical expression of the reaction : 
 
 6(C 2 0 4 Fe) + 6 AgBr - 2 [(C 2 0 4 ) 3 Fe 2 ] 4- 6Ag + Fe 2 Br 3 , 
 6(Fe0,C 2 0 3 ) + 3 AgBr = 2(Fe 2 0 3 ,3C 2 0 3 ) 4- 3 Ag-|- Fe 2 Br 2 . 
 
 The modified bromide of silver is decomposed by the 
 ferrous-oxalate, the reduced silver forms the lights of the 
 
 35 
 
36 Develop 7 ?ient of Dry Plates . 
 
 image, and there remain in the bath ferric-oxalate and fer- 
 ric-bromide. 
 
 Preparation of the Developer. — The developer con- 
 sists of a solution of ferrous-oxalate. This salt is formed 
 when a ferrous salt is added to a solution containing 
 an oxalate or oxalic acid. If a solution of neutral 
 potassic oxalate is added to a solution of ferrous sulphate 
 the liquid becomes red, grows muddy, and deposits yellow 
 crystals of ferrous-oxalate, which is nearly insoluble in 
 water, but readily soluble in warm solutions of the neutral 
 oxalates of potassium or sodium. It is in combination with 
 solutions of these salts that the ferrous-oxalate is employed 
 as a developing reagent. Its best solvent is a saturated 
 solution of neutral potassic oxalate. 100 parts of this 
 solution dissolve 12 parts of ferrous oxalate. A saturated 
 solution of potassic oxalate contains 1 part of the salt to 3 
 of water. In order to prepare 100 parts of the developer, 
 33 parts of neutral potassic oxalate are dissolved in 100 
 parts of water, and 12 parts of ferrous oxalate are added 
 to the warm solution. 
 
 The more usual method of preparing the developer is to 
 form the ferrous salt and dissolve it at the same time. 
 This is easily done by adding one part of a saturated solu- 
 tion of sulphate of iron to three parts of a saturated solu- 
 tion of neutral potassic oxalate. In this case the potassic 
 salt plays a double part : One part forms the ferrous oxa- 
 
 late, while the other part acts as the solvent. 
 
 As the proportions of oxalate and sulphate are deter- 
 mined by the solubility of the salts, they cannot be in- 
 creased in order to strengthen the developing action. If 
 an excess of the sulphate is added, a precipitate of ferrous 
 oxalate is thrown down and the bath loses its reducing 
 
Development of Dry Plates. 37 
 
 power. It is important also that the potassic oxalate be 
 neutral. An acid sample will not give clear images. 
 
 If the water employed to dissolve the potassic salt con- 
 tains sulphate of chalk, a slight trace of oxalate of chalk is 
 formed and the solution is not clear. As soon as the solu- 
 tion cools, however, the chalk will deposit and the clear 
 liquid may then be decanted off for use in compounding 
 the developer. To avoid the precipitate, distilled rain or 
 melted ice water should be used. 
 
 The - mixed developer does not keep well without the ad- 
 edition of some substance capable of reconverting the 
 ferric sulphate to the corresponding ferrous salt. Tartaric 
 acid has this property, and old solutions may be restored to 
 activity by adding a trace of the acid and standing the bot- 
 tle in the sun. The tartaric acid is oxidized at the expense 
 of the ferric sulphate, which returns to the ferrous state. 
 
 We are now prepared to give a definite formula for the 
 preparation of the developer, and the following has given 
 me uniformly good results : 
 
 A. Neutral oxalate of potash, 30 parts. 
 
 Water, 100 parts. 
 
 B. Sulphate of iron, 30 parts. 
 
 Tartaric acid, o. 5 parts. 
 
 Water, 100 parts. 
 
 This solution will keep indefinitely if placed in the sun- 
 light when not in use : 
 
 C. Bromide of potassium, 1 part. 
 
 Water, 10 parts. 
 
 This is the restrainer, and is to be used only in case of 
 over-exposure, or with very rapid plates to diminish the 
 danger of veiling. 
 
3 « 
 
 Development of Dry Plates. 
 
 Development of Plates Normally Exposed. — When 
 the exposure has been correctly timed, the percentage of 
 one to three should be diminished. My own practice is 
 to add one part of solution B to ten parts of A. If the 
 high lights begin to appear in one or two minutes, the 
 exposure has been about correct, and the plate is trans- 
 ferred to a tray containing one part of A to four of B, and 
 the development is completed in this stronger developer. 
 If for any reason exceptional density is desired, a few 
 drops of C should be added. In any case the action of the 
 developer is to be continued until the image seems to have- 
 disappeared and is quite plainly visible at the back of the 
 plate. 
 
 Development of Under-exposed Plates. — If a three 
 or four minutes’ treatment with the one to ten solution 
 produces no visible effects, the plate should be treated 
 for under-exposure. For this purpose it is transferred 
 to a tray containing the strong one to three solution. If 
 this does not produce the desired effect within a few mo- 
 ments, the plate was probably too slightly acted upon by 
 light to make successful development possible, there being 
 too slight an amount of modified bromide present in the 
 film for the developer to act upon. Something may 
 possibly be effected by the addition of a drop or two of a 
 i to 2.000 solution of hyposulphite of soda, itself a power- 
 ful reducer. This addition is always attended with danger, 
 owing to its strong tendency to produce fog. 
 
 Development of Over-exposed Plates. — If the image 
 comes up quickly and evenly in the one to ten solution, 
 the plate must be treated for over-exposure by removing 
 it at once to a dish containing one part of solution 
 C to ten parts of water. A few drops of C are then 
 
Development of Dry Plates. 
 
 39 
 
 added to the developer and the plate returned to it. Un- 
 less the time of exposure was greatly exaggerated, the 
 image will develop gradually and strongly in this modified 
 developer. It is always best, however, to have a quantity 
 of old developer at hand for use with over-exposed plates. 
 Many skillful operators recommend the addition of one 
 part of old developer to three of freshly mixed for the 
 development of landscape views, and the method has its 
 advantages. 
 
CHAPTER VII. 
 
 THE pYROGALLoL developer. 
 
 HEMICAL Reactions. — Pyrogallol, or pyrogallic acid, 
 
 (C 6 H 6 0 3 ,C 1 2 H 6 0 6 ) is a white powder extracted from 
 gall nuts or by treating gallic acid. It dissolves in 2.5 its 
 weight of water, and is readily soluble in alcohol and ether. 
 
 When exposed to atmospheric influences its solutions 
 rapidly oxidize, absorbing oxygen from the air with the 
 formation of certain obscure brown products and such acids 
 as oxalic, acetic and carbonic, according to the following 
 formula : 
 
 C 6 H 6 0 3 -f-70 = C 2 H 3 0 4 -|-C 2 H 4 0 3 -f-2CO s , 
 
 C 12 H 6 0 6 14O = C 4 H 2 0 8 -}- C 4 H 4 0 4 + 4CO 2 . 
 
 The addition of an alkali to a solution of pyrogallol 
 greatly increases its avidity for oxygen, and in consequence 
 its reducing power on the salts of silver. A plain solution 
 of pyrogallol Will develop an exposed plate but only with 
 great slowness. Its action is hastened by the addition of 
 an alkali which quickens the development by acting upon 
 the acids arising from the oxidation of the pyrogallol, and 
 by combining with the hydrobromic acid produced by the 
 decomposition of water. A bromide of the alkali is thus 
 formed in the developer. 
 
 The following formula expresses the complex reaction : 
 
 C 6 H 6 0 3 +2AgBr+2AzH 3 +H 2 0 = (C 6 H 6 0 3 +0)+2Ag-|-2AzH 4 Br, 
 C 1 2 H « O « q- AgBr+ AzH 3 +HO = (C 4 2 H 6 O 6 +0)-l- Ag+ AzH 4 Br. 
 
 40 
 
Development of Dry Plates. 
 
 4i 
 
 This formula expresses the reactions which take place 
 when an exposed plate is developed in a solution of pyro- 
 gallol with ammonia as the alkali. 
 
 Preparation of the Bath. — The pyrogallol developer 
 must consist of the acid and an alkali. This alkali may be 
 either ammonia, potash, or soda either as carbonates or 
 sulphites. In England, ammonia has been the alkali most 
 commonly used. In America, soda or potash, or both com- 
 bined, are usually preferred. 
 
 The action of these alkalis is not the same. Ammonia 
 is probably stronger in detail giving power, and produces 
 better modeled negatives, but its use is attended with 
 greater danger of fog. Carbonate of potash seems to have 
 more power over the rendering of detail than the corre- 
 sponding salt of soda, while the latter is a better density 
 giver. With either of these salts there is less danger of 
 fog than with ammonia, but they have a more decided 
 tendency to frill the plate. On the whole, however, my 
 personal preference is for a developer containing both the 
 carbonates of potash and soda, with sufficient sulphite of 
 soda added to insure a clean development. 
 
 A normal developer with ammonia is compounded as fol- 
 lows : 
 
 Water, 100 parts. 
 
 Pyrogallol, 0.3 parts. 
 
 Ammonia, o. 5 parts. 
 
 Bromide of potassium, 0.5 parts. 
 
 The proportion of ammonia may safely be increased to 
 three parts, but it should not exceed this. The amount of 
 pyro may be doubled or trebled if necessary to obtain 
 density. 
 
42 
 
 Development of Dry Plates. 
 
 The following may be taken as a normal potassic car- 
 
 bonate developer : 
 
 Water, ioo parts. 
 
 Pyrogallol, 0.5 parts. 
 
 Carbonate of potassium, o. 5 parts. 
 
 The amount of carbonate may safely be increased to five 
 parts, if necessary, and the amount of pyrogallol to two or 
 three parts. 
 
 A normal soda developer is given in the following formula: 
 
 Water, 100 parts. 
 
 Carbonate of sodium, 1 to 5 parts. 
 
 Pyrogallol, 0.4 parts. 
 
 A good combined soda and potash formula is as follows: 
 
 Water, 100 parts. 
 
 Pyrogallol, 0.5 parts. 
 
 Carbonate of soda, . 2 parts. 
 
 Carbonate of potash, 1 part. 
 
 Preservatives. — The baths prepared as above discolor 
 rapidly during development, and the plate becomes more 
 or less tinged with yellow. In the case of thin negatives 
 this yellowishness is an advantage, since it has a tendency to 
 increase contrast, but most operators prefer to avoid it so 
 far as possible, or to remove it after fixing. The latter is 
 attained by placing the negative in a bath of dilute 
 sulphuric acid containing a little alum to counteract the 
 frilling effect of the acid. 
 
 The discoloring of the bath is due to oxidation, which is, 
 in turn, caused by the reduction of the silver salt and by 
 the absorption of oxygen from the air. This process of 
 oxidation may be greatly retarded by the addition of some 
 
Development of Dry Plates . 
 
 43 
 
 substance which has greater affinity for oxygen than the 
 pyrogallol. Such substances are sulphite of soda, the 
 meta-bisulphites of soda and ammonium and many others 
 of similar nature. Either of these three salts will produce 
 the desired result by absorbing oxygen from the air and 
 leaving the pyrogallol free to deal with the modified silver 
 salt. Until recently sulphite of soda has been almost exclu- 
 sively employed, but lately the meta-bisulphites have been 
 used with better results. 
 
 The proportion of preservative may vary from three 
 parts to one hundred to much larger quantities. A typical 
 formula of this class is: 
 
 Water, ioo parts. 
 
 Pyrogallol, 0.5 parts. 
 
 Carbonate of potash, 1 part. 
 
 Sulphite of soda, 3 parts. 
 
 If a little sulphuric acid is added to th-e solution it will 
 unite with the sulphite of soda to form sulphurous acid, 
 which is a powerful deoxidizer. 
 
 Sulphite of soda, either in crystals or in solution, easily 
 passes over into sulphate of soda, which is not a preserva- 
 tive, but which has strong restraining qualities. In order 
 to test the purity of a given sample of sulphite, it is treated 
 with hydrochloric acid. The sulphurous acid is set free 
 and chloride of sodium is formed. When the sulphite is 
 entirely decomposed, chloride of barium is added to the 
 solution. If any sulphate is present, a large quantity of a 
 white precipitate is formed. 
 
 Sulphite of Soda as a Developer. — Apart from its 
 preservative action, sulphite of soda has a certain power of 
 development. It can develop the latent image without the 
 
44 
 
 Development of Dry Plates. 
 
 addition of any other alkali. The development is slow, 
 but the image is very pure and bright. For very much 
 over-exposed plates sulphite of soda has a value which is 
 not at present properly recognized. 
 
 For other formulas the reader is referred to the tables at 
 the end of the book. 
 
 The developing solution is conveniently compounded by 
 adding to three ounces of water 6 grains of dry pyrogallol, 
 12 to 30 grains of carbonate of potash and 10 to 20 grains 
 of sulphite of soda, according to the plate and the 
 exposure. 
 
 Development of a Normally Exposed Plate.-— M y 
 own method of development is to make up 1 to 10 solu- 
 tion of the carbonate and sulphite. 
 
 For a 5x8 plate three ounces of water are placed in the 
 tray, six to ten grains of dry pyrogallol and half an ounce 
 of the sulphite solution are added. When the pyrogallol is 
 dissolved, the plate is immersed in the tray, and at the end 
 of half a minute the developer is poured off into a graduate 
 and one dram of the solution of the carbonate is added. 
 This is allowed time to act. If the high lights do not 
 show themselves within one or two minutes, another addi- 
 tion of carbonate is made, the tray being constantly rocked 
 to insure equal action. The image will soon show itself 
 under this treatment and it will probably gain in detail and 
 density until the process is complete. If, however, the 
 details in shadows are slow in appearing, more carbonate 
 is added. If good general density is not obtained more 
 pyrogallol is added, and in some cases a few drops of a 
 one to ten potassic bromide solution. In any case the 
 development is continued until the image is plainly visible 
 at the back of the plate. 
 
Development of Dry Plates. 
 
 45 
 
 Development of Under-Exposed Plates. — If the plate 
 after a prolonged immersion in the above bath shows a 
 general want of vigor and detail, it has been under-ex- 
 posed, and the bath must be modified in order to meet the 
 conditions of the case. In order to understand the nature 
 of these modifications, a thorough knowledge of the action 
 of each of the components of the bath is necessary. This 
 knowledge I now propose to impart to the best of my ability. 
 
 The alkali has a double function ; one portion is used in 
 neutralizing the acids which are formed in the bath and 
 thus accelerates the action. The amount of alkali taken 
 up by this action varies according to the quantity of 
 pyrogallol present. The remaining portion of the alkali 
 remains free in the bath and acts directly upon the plate. 
 The tendency of the alkalis is to transform the bromide of 
 silver into the modified state. Hence, the alkali which is 
 free to act upon the plate modifies that portion of the 
 bromide which has been feebly impressed by light, and 
 tends to bring it into the same molecular state as the 
 bromide which has received a more energetic light-impres- 
 sion. Hence, the alkali acts as an accelerator and dimin- 
 ishes contrast. 
 
 If a large amount of pyrogallol is added the bath 
 becomes more concentrated and the development more 
 rapid. But -at the same time the amount of free alkali is 
 diminished and its action on the bromide of silver is 
 lessened. Hence, the increased addition of pyrogallol to 
 the bath is equivalent to diminishing the amount of alkali, 
 and has the further effect of increasing contrast. 
 
 From this somewhat abstruse reasoning, which seemed 
 to be necessary to a complete understanding of the subject, 
 we may easily deduce the best course to follow in the 
 
4 6 
 
 Development of Dry Plates . 
 
 development of under-exposed plates. If the plate has a 
 tendency to fog, the quantity of alkali must be diminished, 
 otherwise the plate will probably veil over and nothing but 
 a monotonous image be developed. Hence the proportion 
 of alkali to pyrogallol must be diminished. The develop- 
 ment will proceed slowly but the image will acquire the 
 requisite density, which it would not have done had the 
 opposite course been taken. 
 
 . If the plate is a good fog resister, as is the case with 
 most slow plates, and the contrasts are harsh, the alkali 
 must be increased and the pyrogallol diminished. The 
 alkali has a tendency to veil the plate and so to produce 
 soft images. When the details are well out, the develop- 
 ment is completed by the addition of pyrogallol to give 
 sufficient density. 
 
 Contrast may also be diminished by allowing the devel- 
 oper to remain at rest during the development. This is 
 due to the fact that the developer rapidly loses its energy 
 where it is in contact with the heavy shadows which have 
 been most strongly impressed, and retains it longest where 
 it is in contact with the half-tone, since here it does' not so 
 soon become saturated. But this method can be adopted 
 only when the bath has been considerably diluted. A 
 strong bath would in this case produce markings. 
 
 Development of Over-Exposed Plates. — When a plate 
 has been over-exposed the contrasts are diminished and 
 the likelihood of fog increased. For both these reasons 
 it is necessary to begin the development with a small 
 amount of alkali and an excess of pyrogallol. Bromide of 
 potassium may also be added, and should be so added to 
 the normal developer when the image flashes up at once 
 on the application of the bath. 
 
CH APTE R VIII. 
 
 tHe HYdrocHiNoN developer. 
 
 T TYDROCHINON or quinole is an aniline derivative 
 ** prepared by oxidizing aniline sulphate with potassic 
 bichromate. Its chemical symbol is C 6 H 6 0 2 , and owing to 
 its powerful reducing power and its comparative freedom 
 from fog and stain, it has gained many friends and is now 
 quite generally employed. Chief among the many advantages 
 claimed for the quinole developer are : simplicity and ease 
 
 of working ; the great latitude of exposure allowed ; ab- 
 sence .of fog and stain ; clear glass in the shadows ; suita- 
 1 bility for bromide paper work. 
 
 On the other hand the developer has a strong tendency 
 to give harsh negatives, full of excessive contrast. It often 
 produces yellow fog or stain, and it is extremely slow in 
 action. 
 
 On the whole, after careful experiments with quinol, I 
 have found it decidedly inferior to pyrogallol in the major- 
 ity of cases. Still it has some excellent qualities, and I 
 would recommend the amateur to master its method of 
 working as a help to the solution of difficult problems in 
 the developing room. Many a negative which shows lack 
 of general density under the action of the pyrogallol devel- 
 oper may be brought up to the printing point by the applica- 
 tion of an old quinol solution. 
 
 I have been most successful with the formulae and 
 method of preparation recommended by the Paris Photo- 
 
 47 
 
48 
 
 Development of Dry Plates. 
 
 graphic Club, which is as follows : Boil one quart of distilled 
 or ice water and divide equally into two quart bottles ; while 
 still warm, add to one of the bottles 250 grains of sulphite of 
 soda in crystals, to the other add 500 grains of sodic carbon- 
 ate in crystals, both salts having been previously powdered. 
 Shake well until dissolved. To the sulphite solution add 150 
 grains of quinol and shake until dissolved, then add 8 to ro 
 drops of glacial acetic acid. When the two solutions are cold 
 the quinol solution is poured rapidly into the carbonate, and 
 the mixture is then filtered. The mixed solution forms a 
 powerful developer which keeps well and works satisfac- 
 torily. For time exposures, it should be diluted one-half 
 with water, or equal parts of new and old developer may 
 be used to advantage. 
 
 Another good formula is the following: 
 
 Quinol, ......... 15 grains. 
 
 Citric acid, 7 ‘ ‘ 
 
 Sodium sulphite, 60 “ 
 
 Water to make 3^ ounces. 
 
 The caustic alkalis are often used when a more speedy 
 action is desired. The best method of using them seems to 
 be the addition of about 5 <f 0 of a 40$ solution of caustic 
 potash just before development. 
 
 Mr. Henry J. Newton recommends the following for- 
 mula: 
 
 Water, 1 ounce. 
 
 Caustic soda, 4 grains. 
 
 Sulphite of soda, 30 “ 
 
 Hydrochinone, 3 “ 
 
 This forms a good developer for instantaneous expo- 
 
Development of Dry Plates. 
 
 49 
 
 sures : for time exposures, the strength should be reduced 
 from one-half to one-third with water. 
 
 Good results can be obtained on nearly all brands of dry 
 plates with any of the above formulae, but I have found 
 that certain makes of plates do not take kindly to quinol, 
 quickly veiling over. 
 
 As a rule, it will be found advisable to add a trace of 
 bromide of potassium to the bath, and to follow the gen- 
 eral method of development recommended for pyrogallol. 
 Development will be begun with a weak bath and its energy 
 will be gradually increased, if necessary, by the gradual 
 addition of the alkali to bring out detail. 
 
 The bath should be used at its maximum strength only 
 in cases of known under exposure. The best results are 
 obtained by the judicious use of a new and an old bath. 
 The longer the exposure, the greater the proportion of the 
 old bath ; short exposures require a smaller percentage of 
 old bath. Where strong contrasts are desired, an old bath 
 is to be used. For soft, harmonious effects the quantity of 
 new bath should be increased. 
 
 Although the same solution can undoubtedly be used to 
 develop a number of negatives in succession, it must not be 
 forgotten that the bath loses its strength with use. With 
 each plate developed the composition of the bath changes 
 and it works more slowly and with greater contrast. If a 
 number of negatives are to be developed in the same solu- 
 tion, it is best to begin with a weak bath and to develop 
 the negatives in the order of their times of exposure, be- 
 ginning with that which received the shortest exposure. It 
 will also be found necessary, now and then, to strengthen 
 the bath by the addition of more alkali. This same method 
 is also recommended for other forms of developer. 
 
5 ° 
 
 Development of Dry Plates. 
 
 When the development has been unduly prolonged, the 
 negative often shows a yellow stain. This may be removed 
 by the application of Farmer’s ferricyanide and hypo 
 reducer which will be found under the formulae for reduc- 
 ing agents. 
 
 On the whole, I cannot recommend the quinol developer 
 as in any way superior or even equal to pyrogallol. It has 
 all the deficiencies of the latter and is devoid of many of 
 its good qualities. I am convinced that more detail can 
 usually be obtained and better printing negatives made 
 with pyrogallol than with quinol. 
 
 For negatives where great purity in the lines is necessary, 
 as in the case of reproductions and slides, quinol undoubt- 
 edly possesses some advantages, but for landscapes this 
 same excess of transparency produces harshness in the 
 prints. 
 
CHAPTER IX. 
 
 THe eiKoMogeN aNd pYrocatecHiN developers. 
 
 T7 IKONOGEN is an aniline derivative of great reducing 
 power which has recently come into general use as a 
 developing agent, owing as much perhaps to judicious and 
 persistent advertising as to its intrinsic merits, which, though 
 great, are not overwhelmingly superior to those of pyrogallol. 
 About the same claims are made for the new reagent as for 
 quinol. It works rapidly, has no pronounced tendency to 
 produce fog or stain, keeps fairly well in solution, and is 
 strong in power to bring out detail. Its great weakness is 
 a varying degree of solubility with different samples and a 
 tendency to give thin negatives. 
 
 I have not found that a solution of eikonogen keeps 
 appreciably better than a properly prepared pyrogallol solu- 
 tion, but as I always use both reagents dry, I do not con- 
 sider this an important point. Eikonogen certainly does 
 bring out detail more rapidly than other developers, but in 
 the end I have not usually found a greater amount of 
 detail in a negative developed with it and one of the same 
 subject, similarly exposed, developed with pyrogallol. 
 Some operators have claimed that it was not an uncommon 
 experience with them to develop a negative with eikonogen 
 and fix it while another was developing in a pyrogallol bath, 
 but my experience does not bear out this statement. 
 
 But this is not to say that eikonogen is not a most excel- 
 lent developer. I am now using it largely in preference to 
 
 51 
 
52 
 
 Development of Dry Plates. 
 
 pyrogallol on account of its general freedom from liability 
 to fog or stain the negative. It gives as clear negatives as 
 quinol with much less of harshness and excessive contrast, 
 and it possesses remarkable staying powers. I have devel- 
 oped as many as twenty 5x8 negatives in the same solution 
 with no appreciable lengthening of development or change 
 in the quality of the negatives. 
 
 My favorite formula and method of working are as 
 follows : 
 
 A. Water, 1 ounce. 
 
 Sulphite of Soda, 40 grains. 
 
 Eikonogen, ; 20 “ 
 
 Dissolve in the order given. With some samples of 
 eikonogen it will be found impossible to dissolve the above 
 amount, but this seems to make no appreciable difference. 
 The water should be distilled and hot. 
 
 B. Distilled water, 1 ounce. 
 
 Carbonate of potash, 50 grains. 
 
 Sulphite of sodium, 50 “ 
 
 In both solutions the crystallized sulphate is used. These 
 are strong solutions and are to be mixed in equal parts for 
 short exposures. For time exposures the mixed developer 
 should be judiciously diluted with water, the greater the 
 proportion of water the softer the negative. 
 
 Solution A will retain its good qualities for several weeks 
 if pure chemicals and distilled water are used. 
 
 My own practice is to dissolve the proper amounts of 
 sulphite and eikonogen in distilled water immediately before 
 using. 
 
Development of Dry Plates . 
 
 53 
 
 If the image flashes up immediately on the application 
 of the developer, the negative is quickly transferred to a 
 tray containing 4 grains of bromide of potash, 1 cfram of 
 glycerine and 10 ounces of water, which is allowed to act 
 for two or three minutes, after which the plate is returned 
 to the developer. 
 
 If no trace of an image appears within two or three 
 minutes, two or three drops of a 10-grain solution of caustic 
 soda may be added. 
 
 If the developer as above compounded works too 
 rapidly the amount of water in solutions A and B should 
 be doubled. 
 
 Another equally good formula is that recommended for 
 use with the Cramer plate, but which I have found to work 
 well with most other makes. 
 
 A. Distilled water, 10 ounces. 
 
 Sulphite of soda (crystals), .... 240 grains. 
 
 Eikonogen, 120 “ 
 
 B. Water, 10 ounces. 
 
 Carbonate of potassium, 1 ounce. 
 
 C. Water, 10 ounces. 
 
 Bromide of potassium, ...... 1 ounce. 
 
 NORMAL DEVELOPER. 
 
 Solution A, 3 ounces. 
 
 “ B, I ounce. 
 
 “ C, 6 to 12 drops. 
 
 A mixture of old and new developer is recommended for 
 general work. 
 
 Soft, harmonious negatives are produced by the addition 
 of water. 
 
 To sum up the case in favor of eikonogen, it may be said 
 that while the extravagant claims of the introducers of the 
 
54 
 
 Development of Dry Plates. 
 
 new reagent have not been confirmed by careful experiment, 
 it is a valuable addition to the list of photographic chemi- 
 cals. It is probable also that further experiments may give 
 an increased ability to work the salt to better advantage. 
 As a developer for instantaneous exposures, I regard it as 
 greatly superior to either pyrogallol or hydrochinone, 
 bringing out all possible detail and giving good general 
 density if it is given time to act. The negatives are, as a* 
 rule, perfectly free from fog or stain and of a good printing 
 color. 
 
 The Pyrocatechin Developer. — Pyrocatechin, C 6 H 4 
 (OH 2 ), although recommended as a developer by Dr. Eder 
 as long ago as 1880, has never come into general use, in 
 spite of its many excellent qualities, on account of its high 
 price. 
 
 In conjunction with carbonate of potash it is a quick act- 
 ing and powerful developer, giving clear negatives of a 
 beautiful brown tone. 
 
 The solution quickly turns a 
 
 deep brown and does not 
 
 keep well. The following formula has given good results 
 in my hands : 
 
 A. Water, .... 
 
 
 Sulphite of soda, . 
 
 . . . . 4 parts. 
 
 Pyrocatechin, . . 
 
 
 B. Water, .... 
 
 
 Carbonate of soda, 
 
 . . . . I part. 
 
 Normal developer : Equal parts of A and B. Restiain, 
 
 if necessary, with bromide of potassium. 
 
 If the cost of the salt can be reduced, it will undoubtedly 
 assume a prominent place among the developers of the 
 future. 
 
CHAPTER X. 
 
 development of instantaneous exposures, 
 films aNd Lantern slides. 
 
 T NSTANTANEOUS EXPOSURES.— The problem to be 
 A solved in the development of plates which have been 
 but feebly impressed by light is to obtain all the details that 
 can be forced out without producing an undue degree of 
 density. At the outset it may be stated that no developer 
 will bring out on a plate details which the action of light 
 has not first impressed upon the sensitive surface. The de- 
 tails must be present potentially or they can not be made 
 visible by the action of the developer. 
 
 Authorities are divided on the question as to whether a 
 weak or a strong developer should be used for instantaneous 
 work. M. Londe recommends a concentrated solution, 
 strong in reducer and accelerator, with a trace of bromide 
 added and a smaller quantity of water than is used for the 
 normal developer, and advises a rapid development. I have 
 done good work by this method, but many makes of plates 
 will not stand forcing at the outset. A safer plan is to be- 
 gin with a weakened developer, giving the plate a prelimi- 
 nary soaking for two or three minutes in a dilute alkaline 
 solution made by diluting the usual ten per cent, stock so- 
 lution with twice its bulk of water. 
 
 It is important that the details be obtained before suffi- 
 cient printing density is had, and the preliminary alkaline 
 treatment helps towards this. A very safe method is to 
 
 55 
 
56 
 
 Development of Dry Plates. 
 
 keep the alkaline and reducing solutions in separate trays, 
 changing the plate from one to the other as may be neces- 
 sary. In this way the operator has more control of the 
 process and is better able to treat his subject intelligently. 
 As a general rule it is safe to say that the alkaline treat- 
 ment should predominate at the beginning at least, and that 
 density should be sought for only well towards the end of 
 development. 
 
 Any of the formulae already given will serve the present 
 purpose, bearing in mind the special directions given for the 
 treatment of under-exposed plates. Above all things avoid 
 being in a hurry. It may take an hour to develop a shutter 
 exposure, but I am seldom longer than twenty minutes 
 about it. The development must be carried further than 
 with longer exposures. Quick plates feebly light-impressed 
 lose much of their density in the fixing bath. The image 
 should show strongly on the back. 
 
 The eikonogen developer seems to possess a better capac- 
 ity for rounding out an instantaneous exposure than either 
 pyro or hydrochinon, and there is less likelihood of stain. 
 
 Development of Films.— Very little need be said on the 
 development of the film negatives, which seem likely to play . 
 an important part in the photography of the future. They 
 are coated with the same emulsion used on glass, and the 
 only modifications are those made necessary by the uncom- 
 fortable tendency of the films to curl up in the bath, a diffi- 
 culty more apparent with the thin Eastman film than with 
 those which have a thicker base of celluloid. In the case 
 of the former I have found it a fairly good plan to soak the 
 film for a short time in clean water to which a slight trace 
 of glycerine has been added, or to add a modicum of glyc- 
 erine to the developer. The use of glycerine is not, how- 
 
Development of Dry Plates. 
 
 57 
 
 ever, to be advised indiscriminately. In damp weather it 
 will not be needed, and on the whole it is better to endure 
 the ills of curled films than to make use of a substance 
 likely to complicate the drying. 
 
 Any developer that will work satisfactorily with films on 
 glass will work equally well with celluloid films. After fix- 
 ing and washing, the films should be pinned by the corners 
 to boards in order that the tendency to curl may be dimin- 
 ished. If after drying, they curl badly, they should be 
 wound tightly about a round stick with the films out and 
 left for an hour or two to straighten. 
 
 So far as my experience extends, the greatest difficulty 
 with thin films at least comes in the printing frames, when 
 the heat of the sun is apt to aggravate the tendency to 
 curl. 
 
 Development of Lantern Slides. — The prime essential 
 to a thoroughly good slide is sufficient clearness in the high 
 lights to allow most of the light to pass through, and not 
 sufficient density in the shadows to offer too great an ob- 
 struction to the passage of the light. • Most slides made by 
 amateurs err in both these particulars. They are too dense 
 in the shadows and too transparent in the lights. Abso- 
 lutely clear glass is not what is wanted in the perfect slide, 
 but just the degree of depth of deposit which will give at- 
 mosphere to the projected image. I am speaking now of 
 slides of natural scenery. For buildings, reproductions of 
 drawings, plans, etc., the shadows should be dense and the 
 lights transparent. But the snow effect so often seen in 
 slides with summer foliage, owing to the excessive clearness 
 of the high lights is neither pleasing nor truthful. I do not 
 believe that the perfect slide can be made on the gelatine 
 dry plate, and I would strongly advise all amateurs who 
 
58 
 
 Development of Dry Plates. 
 
 “ go in ” largely for slide making to book themselves up in 
 the wet collodion or tannin processes, either of which are 
 vastly more economical and give better results than the 
 best gelatine lantern slide plates. But as I know that few 
 will take this trouble, I give one or two formulae which 
 I have found to be reliable. But before doing, I wish to 
 say a word about the exposure. Whether made by contact 
 printing or by reduction in the camera, a full exposure 
 should be given if the best results are desired. A lantern 
 slide which has been forced in development to bring out 
 details which should have come out easily, is rarely such 
 as one would care to exhibit. In order to give clean effects 
 it is usually advisable to add a considerable proportion of 
 bromide to the developer, and this addition necessitates a 
 full exposure, which must not, however, be prolonged to 
 the fogging point. 
 
 The ferrous-oxalate developer has long been a favorite 
 with dry-plate slide makers, on account of its simplicity and 
 cleanliness. 
 
 Those who like strong and vigorous blacks will find the 
 
 following formula a good one : 
 
 A. Oxalate of potash, 8 ounces. 
 
 Water, 30 “ 
 
 Citric acid, 60 grains. 
 
 B. Sulphate of iron, 4 ounces. 
 
 Sulphuric acid, 8 drops. 
 
 Water, 32 ounces. 
 
 For the developer add 1 ounce of B to 3 of A, and ^ 
 ounce of water, and 5 to 10 drops of the usual bromide 
 solution. 
 
 Allow development to proceed until the shadows are 
 strong and the image visible on the back. Then wash and 
 
Development of Dry Plates. ♦ 59 
 
 fix. Wash for half an hour and immerse for five minutes in 
 
 Water, 36 ounces, 
 
 Pulverized alum, 3 “ 
 
 Citric acid, \ ounce, 
 
 to harden the film and clear the image. 
 
 Hydrochinon, pyrogallol or eikonogen will give equally 
 as good, if not better results. The following formulae are 
 known to be reliable : 
 
 HYDROCHINON. 
 
 A. Sulphite of Soda (crystals) 400 grains, 
 
 Water, 6 ounces, 
 
 dissolve and filter, and add 
 
 Hydrochinon, 120 grains, 
 
 B. Carbonate of potassium, ...... 240 “ 
 
 Water, 6 ounces, 
 
 dissolve and filter. 
 
 Developer. — 1 ounce each of A and B, and 2 ounces 
 of water. Bromide if needed to produce clean work. 
 
 EIKONOGEN. 
 
 A. Sulphite of soda (crystals), ..... 240 grains, 
 
 Water, 8 ounces, 
 
 dissolve, filter, and add 
 
 Eikonogen, 20 grains, 
 
 B. Carbonate of potash, 32 “ 
 
 Water, 1 ounce. 
 
 Developer. — 2 ounces of A and 1 dram of B. 
 
6o 
 
 Development of Dry Plates. 
 
 PYROGALLOL. 
 
 A. Carbonate of soda (crystals), i ounce. 
 
 Water, 8 “ 
 
 B. Sulphite of soda (crystals), i “ 
 
 Water, .8 “ 
 
 Pyrogallol, 2 drams. 
 
 Developer. — Equal parts of A and B. Restrain with 
 bromide if necessary. 
 
 The development of lantern slides should be continued 
 until the image is clear and distinct and seemingly more 
 dense than is necessary, but for clean work it is essential 
 that the development be stopped as soon as the edges of 
 the plate show signs of darkening, or even before. Other- 
 wise the high lights will be too strongly veiled. Cleanliness 
 is another essential point. It is best to have a separate set 
 of trays for developing slides. The hypo solution should be 
 freshly mixed, and for slides it need not be stronger than 1 
 to 10. The acid fixing bath is to be recommended. 
 
CHAP TER XI. 
 
 fixing aNd Washing. 
 
 T^IXING. — The process of fixing is necessary in order 
 A to dissolve out all the unreduced silver which is still 
 sensitive to light, and therefore a cause of fading or dark- 
 ening if the unfixed plate be exposed to the action of light. 
 
 After development, the film contains both metallic silver 
 and unaltered bromide of silver ; both of these salts must 
 be removed by a suitable solvent in order to render the 
 negative transparent and permanent. The salt most com- 
 monly employed for this purpose is the hyposulphite or 
 thiosulphite of sodium. When a negative is immersed in a 
 solution of this salt a double hyposulphite of silver and 
 sodium is formed. The first is readily soluble both in a 
 solution of hypo and in water, while the second is insoluble 
 in water and only slowly soluble in hypo solutions. Hence, 
 the necessity for a prolonged immersion in the fixing bath 
 to insure the complete solution of the salt, the presence of 
 which in the negative would cause its speedy destruction. 
 The negative should be left in the bath at least five minutes 
 after the whitish color has disappeared. 
 
 The degree of concentration of the hypo solution is not 
 of special importance, except so far as it affects the speed 
 of the solving action. A dilute solution will fix, but only 
 slowly. The proportion of one to five is about right. Until 
 quite recently a plain hypo solution has been most common- 
 ly employed, the addition of alum to harden the film and 
 
 61 
 
62 
 
 Development of Dry Plates. 
 
 prevent frilling not being advisable on account of the dan- 
 ger of the formation of a sulphur compound. But within a 
 short time acid solutions have been recommended, on account 
 of the clearing and hardening action which such a solution 
 has on the gelatine film and the greater permanency thus 
 given to the bath. A solution of hyposulphite undergoes a 
 change even when kept from atmospheric influences. Sul- 
 phur is deposited and sulphite of sodium formed. The 
 presence of the latter salt is not injurious, since it is itself 
 a fixing agent, but tfie presence of sulphur is likely to work 
 injury to the negative. 
 
 One of the latest and best formulae for the fixing bath 
 
 is Cramer’s, as follows : 
 
 Water, . i , quart, 
 
 Sulphite of soda (crystals) . . . . .4 ounces, 
 
 Dissolve, and add 
 
 Sulphuric acid ^ ounce, 
 
 Chrome alum (powdered), 3 ounces, 
 
 Dissolve and pour into a solution of 
 
 Hypo, 2 pounds, 
 
 Water, 3 quarts. 
 
 This bath remains clear even with frequent use; it does 
 not discolor the film, and it has a hardening effect. 
 
 Another equally good bath is made by the addition of 
 one ounce of acid-sulphite of sodium, a new chemical, to 
 each pint of hypo solution. In this bath, which remains 
 clear after long use, fixation is very rapid. The only pre- 
 caution necessary is to keep the bath distinctly acid at all 
 times by the occasional addition of fresh acid-sulphite 
 solution. 
 
Development of Dry Plates. 63 
 
 I would strongly advise the use of a grooved tank or a 
 triangular trough for the fixing bath in place of the time- 
 honored tray, which allows all the impurities present in the 
 bath to settle on the film to its detriment. In a tank the 
 negatives stand up in the bath and the impurities do not at- 
 tach themselves to the films. In a trough they are fixed 
 with the films down. 
 
 Since the formation of the double insoluble hyposulphite 
 is promoted by the action of light, the fixing should be 
 done in the developing room, but extreme care must be 
 taken to keep the fixing solution from the developing trays. 
 
 The number of plates which can safely be fixed in a 
 single solution of hyposulphite has its limits. It is limited 
 by the production of the double salt. Fifteen grains of 
 bromide of silver require about seven grains of hyposul- 
 phite to form the double salt. The average whole plate 
 contains not far ‘from fifteen grains of bromide of silver, 
 and seven grains of hyposulphite are required to form the 
 double salt. If then we have twenty ounces of bath con- 
 taining four ounces of hyposulphite, we can theoretically 
 fix at least 220 whole plates in it. But since an excess of 
 hyposulphite is necessary in order to dissolve the double 
 salt it is not safe to fix more than half that number. The 
 cost of the hyposulphite is low enough to warrant a little 
 prodigality in its use. 
 
 In order to make sure of perfect fixation, the negative 
 must be left in the fixing bath for some time after all white- 
 ness has disappeared from the back. It is also advisable to 
 place the plate for a short time in a second fixing bath 
 freshly mixed. 
 
 Washing. — The elimination of the last traces of hypo 
 from the film is a matter of no little difficulty. Unless the 
 
6 4 
 
 Development of Dry Plates. 
 
 fixing agent is entirely removed, the negative will soon be 
 made useless for printing by the formation of the unstable 
 hyposulphurous acid, which rapidly decomposes into sulphur 
 and sulphurous acid, a decomposition which produces the 
 yellowing of the film which is so frequently met with in 
 negatives which have been printed from a few times. For 
 rapid and thorough washing nothing is better than a 
 grooved washing box and an abundance of running water. 
 Two or three hours of this treatment will effectually remove 
 the hypo. Where running water cannot be had the plates 
 may be washed in a tray by frequently changing the water. 
 Better than this is a wooden trough in which the negatives 
 can be placed with the films down. The water must be fre- 
 quently changed. Still another good method is to mount a 
 wooden tank at the end of a slanting board of suitable 
 length and width. A small short pipe is inserted at the bot- 
 tom of the tank, and another longer piece is soldered at 
 right angles to it. This pipe is closed at the ends and has 
 a number of fine holes pierced along the front. The water 
 is thus delivered in a fine spray. The negatives are placed 
 on the board, the tank is filled with water, and an hour’s 
 washing will leave the films in good condition. 
 
 Hypo Eliminators. — Various compounds act as hypo 
 eliminators by converting it into a salt which is easily 
 washed away, or whose presence in the film is not in- 
 jurious. They should be used, however, only after the 
 larger portion of the hypo has been removed by washing. 
 Alum and the hypochlorites have been recommended as 
 hypo eliminators. The former, while unquestionably a 
 hypo eliminator, produces a reaction by which sulphur is 
 precipitated, and sulphur is nearly as difficult to eliminate 
 as hypo itself. 
 
Development of Dry Plates. 
 
 6 5 
 
 The hypochlorites are free from this objection. Javelle 
 water, a compound of hypochlorite and chloride of potas- 
 sium, is a very good eliminator of hypo. The plate is im- 
 mersed in a bath containing fifteen parts of Javelle water 
 to one hundred parts of water, where it is allowed to re- 
 main for five minutes, after which it is washed for ten or 
 fifteen minutes. The theory of the reaction is that the 
 chlorine of the hypochlorite decomposes the water, forming 
 hydrochloric acid and oxygen. The oxygen oxidizes the 
 hyposulphite and converts it into bisulphate of potassium, 
 a salt which, being readily soluble in water, is easily washed 
 out. 
 
 Belitzsky’s hypochlorite of zinc eliminator is, perhaps, 
 better than Javelle water. This is made by dissolving 300 
 grains of chloride of lime in one quart of water, six hundred 
 grains of zinc dissolved in twice its weight of water. The 
 mixture is shaken and allowed to settle. The clear portion 
 is decanted for use, one part being added to sixty parts of 
 water to form the eliminator. 
 
 Test for Hypo. — If the operator wishes to make sure 
 that the last traces of hypo have been removed, he must 
 test the last wash water for traces of the salt. Iodide of 
 starch forms a very delicate test for hypo. 
 
 This is prepared by dissolving a small quantity of starch 
 in ten times its weight of water, and boiling until the 
 solution .be clear. A few drops of a saturated alcoholic 
 solution of iodine are then added, which forms the blue 
 iodide of starch. Two drops of this are sufficient to impart 
 a bluish tinge to distilled water. But if any traces of hypo 
 are present the blue will not appear. 
 
 On the Use of Alum. — Alum, owing to its hardening 
 action on films of gelatine, has often been recommended as 
 
66 
 
 Development of Dry Plates. 
 
 a useful addition to the fixing bath to prevent frilling, but 
 this addition is to be deprecated as of little value and liable 
 to injure the film. The sulphate of aluminium contained 
 in the alum forms with hypo a precipitate of alumnium and 
 sulphur which is insoluble and detracts from the clearness 
 of the negative. For this reason, I cannot advise the use of 
 alum in connection with the fixing bath. 
 
 Another purpose for which alum has been recommended 
 is to remove the yellow color sometimes produced by pyro- 
 gallol. This practice is not free from danger unless a ver- 
 tical tank is used. 
 
 Most water contains carbonate of chalk, a substance which 
 in connection with sulphate of aluminium forms carbonic 
 acid, sulphate of chalk and the insoluble sub-sulphate of 
 aluminium, which is precipitated on the film, bearing with 
 it any impurities in suspension in the bath. In order to 
 avoid this precipitation on the film, a vertical tank should 
 be used. 
 
 The alum bath, properly used, has undoubtedly great 
 value in promoting the preservation of the negative, by 
 rendering the gelatine inert to the action of moisture. 
 After a thorough removal of the hypo it is always well to 
 immerse the plate for a short time in a saturated solution 
 of alum and then to wash for a few moments. 
 
 Clearing Solution. — The yellow color due to the use of 
 pyrogallol may be removed by immersing the plate, after 
 fixing and washing, in the following solution: 
 
 Saturated solution of alum, . . • . . .32 ounces. 
 
 Sulphuric acid, ^ ounce. 
 
CHAPTER XII. 
 
 intensification ANd reduction. 
 
 T NTENSIFICATION. — Occasionally, either by reason of 
 ^ under- or over-exposure, or from insufficient develop- 
 ment, the negative lacks the necessary printing strength. 
 The contrasts are too feeble to give strong prints. 
 
 This weakness may be overcome by the process known as 
 intensification, which consists in substituting a more opaque 
 deposit for the deposit of silver. By this means the high 
 lights become more intense and the negative more vigorous. 
 The possibility of successful intensification depends upon 
 the fact that the intensifying solutions act upon the different 
 parts of the negative in proportion to the amount of silver 
 contained in them. The high lights, having a denser de- 
 posit of silver, are more strongly acted upon than the shad- 
 ows where the silver deposit is less dense. In this way the 
 contrasts are heightened. 
 
 Intensification may be partial or complete, local or gen- 
 eral. Partial, when only a part of the reduced silver is 
 acted upon; complete, when the intensifier is allowed to act 
 until it has penetrated through the film; local, when only a. 
 part of the film is intensified; general, when the whole sur- 
 face is acted on. Partial intensification is to be resorted to 
 when the negative lacks only a slight degree of density; its 
 effect is to increase the contrast between the half-tones 
 without appreciably increasing the general contrast between 
 the half-tones and the high lights. -Complete intensification 
 
 67 
 
68 Development of Dry Plates. 
 
 is necessary for thin, monotonous negatives. The essential 
 difference between partial and complete intensification is 
 simply one of the length of time the intensifier is allowed to 
 act. 
 
 It must be remembered that intensification does not pro- 
 duce detail ; it simply heightens contrast and increases 
 density. There is no more detail in a negative after inten- 
 sification than before. The detail may be more distinctly 
 visible owing to the greater strength imparted to it, but the 
 detail must be in the negative before intensification. 
 
 Another point in connection with intensification is the 
 necessity of a thorough elimination of the hypo before any 
 attempt is made to strengthen the negative. If this point 
 is not attended to the film will inevitably be stained. 
 
 One of the most common methods of intensification is a 
 preliminary treatment with bichloride of mercury, followed 
 by copious washing and a subsequent treatment of the mod- 
 ified silver with ammonia or sulphite of soda. In this case 
 the mercuric chloride is converted into mercurous chloride 
 by the loss of half its chloride which acts upon the silver of 
 the. film and converts it into chloride of silver. Both mer- 
 curous and argentic chlorids are colorless, hence the action 
 of the bath whitens the film. After a thorough washing, 
 the film is treated with a dilute solution of ammonia. 
 
 In this bath a double reaction takes place. The ammonia 
 dissolves the chloride of silver and forms an ammonia-mer- 
 curic compound with the chloride of mercury. This com- 
 pound is an intense black, and taking the place of the silver 
 in the film, it acts as an intensifier. 
 
 The bichloride of mercury bath should be made by dis- 
 solving one part of the mercury in twenty parts of hot 
 water. 
 
Development of Dry Plates. 69 
 
 The well washed plate is placed in a tray and covered 
 with the solution. If partial intensification is all that is de- 
 sired, the action of the bath is stopped before the film is 
 whitened through to the glass. Where complete intensifica- 
 tion is necessary, the film must be whitened through its en- 
 tire thickness. After washing for fifteen minutes in running 
 water, the plate is placed in a solution of ammonia diluted 
 with twenty times its* bulk of water. The film quickly 
 blackens, and when the whiteness has entirely disappeared, 
 it only remains to wash the plate thoroughly. The tray 
 should be rocked to insure an even action. 
 
 If the negatives are thoroughly washed after fixing and 
 after the mercury treatment, there is no reason to suspect 
 the permanency of the intensified film. 
 
 A ten per cent, solution of sulphite of sodium may be 
 substituted for the ammonia solution of the preceding for- 
 mula, and in this, case the washing after the mercury treat- 
 ment need not be so thorough. The reaction is similar 
 to the preceding, the sulphite dissolves the chloride of 
 silver and reduces the mercurous chloride to the metallic 
 state. 
 
 A modification of the above method is to treat the plate 
 after whitening with mercury with the ferrous-oxalate de- 
 veloper. In this case both the chlorides of silver and mer- 
 cury are reduced to the metallic state. If the negative is 
 not sufficiently intense after this treatment, the film may be 
 again whitened and the developer applied as before. Other 
 methods of intensification will be found in the tables of 
 formulae. 
 
 Local Intensification. — It often happens that certain 
 portions only of the negative are too thin to print well. 
 This is most common with negatives containing deep 
 
70 
 
 Development of Dry Plates. 
 
 shadows when the time of exposure was not sufficient to 
 bring out detail with the proper degree of density. 
 
 In this case, local intensification may be resorted to. The 
 only absolutely certain method,' in my experience, is the 
 application, with a soft brush, of Hall’s Intensifier to the 
 parts to be intensified. This will strengthen the detail. To 
 lighten up deep shadows and prevent them from printing 
 too deeply, indigo blue moistened with gum water may be 
 applied to the back of the negative with the finger. 
 
 In inexperienced hands intensification is rarely success- 
 ful, in most cases producing spots and stains which ruin the 
 negative. It is always better to make a new negative, if 
 possible, or to over-develop and then reduce. 
 
 Reduction of Negatives. — There are two distinct cases 
 in which it is advisable to reduce the density of a negative: 
 i, those cases in which the general density is so great as to 
 make the negatives abnormally slow printers ; and, 2, those 
 cases in which by reason of insufficient exposure, and con- 
 sequent prolonged development to bring out detail, the 
 contrasts are too strong and the density of the high lights 
 too great. 
 
 In the first case it is necessary to dissolve a portion of 
 the reduced silver without altering the tone gradation. In 
 the second case only the high lights should be reduced, 
 leaving the shadows unaffected. This may be called the 
 method of local reduction, and is best effected by applying 
 the reducer given below to the parts which it is desired to 
 reduce with a soft brush. 
 
 Farmer’s ferricyanide and hypo reducer is one of the most 
 reliable. The negative is immersed for a few moments in a 
 one to two hypo solution. A few drops of a one to ten so- 
 lution of ferricyanide of potassium solution are added, and 
 
Development of Dry Plates. 
 
 7i 
 
 the progress of the reduction carefully watched. If the ac- 
 tion is not sufficiently rapid more of the ferricyanide may 
 *be added. When the negative has been sufficiently reduced, 
 it must be thoroughly washed to reduce the hypo. 
 
 For local reduction, the mixed reducer is applied with a 
 soft brush, but the operation demands great delicacy of 
 touch. 
 
 Dr. Eder recommends a reduction method, which consists 
 in converting the reduced silver into chloride of silver, and 
 then reducing or reconverting the chloride into the metallic 
 state. By this method the half tones may be brought into 
 better balance with the high lights. The method is as 
 follows : 
 
 The plate is immersed for a few moments in 
 
 Water, 1 ounce. N 
 
 Bichloride of potassium, .... 5 grains. 
 
 Hydrochloric acid, 5 drops. 
 
 After washing, the image is redeveloped with ferrous-ox- 
 
 alate, then fixed and washed as usual. 
 
 In order to reduce a negative which has been made too 
 intense by the mercury intensification, a dilute solution of 
 cyanide of potassium may be used, but as this is a virulent 
 poison the greatest care must be taken in its use. 
 
CHAPTER XIII. 
 
 supplementary Notes. 
 
 CO MUCH of the quality of the negative depends upon 
 ^ its proper development, that I am not willing to leave 
 the subject without a few additional remarks, which I 
 trust may still further clarify the matter and help to make 
 the development of a negative less a matter of chance and 
 luck and more of scientific accuracy. 
 
 This also affords an opportunity of calling attention to a 
 new ingredient of the developer which has been introduced 
 into this country from Germany, and which my experiments 
 have conclusively proven to be a valuable addition to Mate- 
 ria Photographica. This substance is a strong solution of 
 the acid-sulphite of sodium which, formed in the solution 
 when sulphite and an acid were added, acted as a preserver. 
 But the quantity of acid-sulphite thus formed was exceed- 
 ingly small as compared with the amount of sulphite present. 
 The new solution contains fifty per cent, of acid-sulphite in 
 solution, and twice the amount of the preserving element, 
 sulphurous oxide, contained in ordinary sulphite of soda 
 crystals. It comes in the form of a pale, yellowish liquid, 
 with a strong smell of sulphurous oxide gas, with which it is 
 saturated. The effect of its addition to the fixing bath is 
 to hasten the action of the bath and to prevent its dis- 
 coloration. Negatives fixed in this modified bath are 
 remarkably clear and free from stain. Added to the devel- 
 oper the new reagent acts as a powerful preserver and 
 diminishes the likelihood of stain or fog. 
 
 72 
 
Development of Dry Plates. 
 
 73 
 
 The proper proportions for the fixing bath are about one 
 ounce of the acid-sulphite solution to every pint of bath, 
 adding more as the bath loses its acid reaction. 
 
 For the pyro developer one drop of acid sulphite should 
 
 be used for each grain of pyro; a trifle less is necessary for 
 eikonogen. It does not seem to give good results with 
 
 hydrochinone. 
 
 
 The following formulae were recommended in Anthony’s 
 Bulletin, and have given me remarkably good results: 
 
 A. — Pyrogallol, 
 
 . . 1 ounce. 
 
 Acid-sulphite, 
 
 
 Water, 
 
 
 B — Carbonate of soda (crystals), 
 
 . . 5 ounces. 
 
 Water, to make 
 
 
 Developei : — Water, i ounce ; A, j to 
 
 1 dram ; B, i| to 2 drams. 
 
 A. — Eikonogen (finely powdered), 
 
 . . 1 dram. 
 
 Acid- sulphite, 
 
 . . 1 dram. 
 
 Water, to make 
 
 
 Dissolve the eikonogen before adding the acid-sulphite. 
 
 B. — Carbonate of potassium (dry), 
 
 . . 3 ounces. 
 
 Water, 
 
 . . 10 ounces. 
 
 Developer : — A, i ounce ; B, i to 2 drams. 
 
 Lambert’s Ammonia Developer.— 
 
 -In the British Journal 
 
 Year Book for 1890, the Rev. F. C. Lambert gives a form- 
 ula for an ammonia developer, with tabulated directions for 
 its use, which is well worth reproducing here: 
 
 P. — Sulphite of soda, 
 
 . . ig- ounces. 
 
 Pyro, 
 
 . . 1 ounce 
 
 Citric acid, 
 
 
 Water, to make 
 
 . . 6 ounces. 
 
 B. — Bromide of potassium, . . . 
 
 . . ^ ounce. 
 
 Water, 
 
 . . 4 ounces. 
 
 A. — Ammonia (.880) .... 
 
 . . 1 ounce. 
 
 Water, to make ..... 
 
 . . 4 ounces. 
 
74 
 
 Development of Dry Plates. 
 
 The table gives the approximate relative proportions of 
 P. B. & A. in drops for four ounces of developer. The table 
 is suggestive only, and must be modified to suit the plate, 
 subject and conditions of exposure. 
 
 EXPOSURE. 
 
 SUBJECT. 
 
 P. 
 
 B. 
 
 A. 
 
 ( 
 
 Strong in contrast 
 
 10-20 
 
 10-20 
 
 IO-30 
 
 Under < 
 
 Normal “ “ 
 
 *0-40 
 
 10-20 
 
 30-40 
 
 ( 
 
 Weak “ “ 
 
 J T 
 
 40-50 
 
 10-20 
 
 40-60 
 
 ( 
 
 Strong in contrast 
 
 30-60 
 
 30-60 
 
 30-60 
 
 Medium -1 
 
 Normal “ “ 
 
 60 
 
 60 
 
 60 
 
 
 Weak “ “ 
 
 60-90 
 
 6O-9O 
 
 30-60 
 
 ( 
 
 Strong in contrast 
 
 60 
 
 60 
 
 10-20 
 
 Over 
 
 Normal “ ‘ ( 
 
 60-90 
 
 60-QO 
 
 20-30 
 
 ( 
 
 i Weak “ “ 
 
 90-120 
 
 90-120 
 
 1 20-30 
 
 The careful study of this and the following tables will 
 teach the thoughtful experimenter many valuable lessons 
 in development. 
 
 M. Londe has compiled the following useful tables on the 
 modification of the developer : 
 
 MODIFICATIONS IN DEVELOPMENT 
 
 ACCORDING TO THE RESULT DESIRED. 
 
 Result Desired. 
 
 Exposure. 
 
 Modification*?. 
 
 Method of 
 Development. 
 
 Negative with strong 
 contrasts. 
 
 Short. 
 
 Concentrated 
 
 Bath. 
 
 Bromide. Rapid 
 Development. 
 
 Density, 
 then Detail. 
 
 Soft, harmonious negative. 
 
 Prolonged. 
 
 Dilute Bath. 
 
 Trace of Bromide. 
 Slow Development. 
 Detail, 
 
 then Density. 
 
MODIFICATION OF THE DEVELOPER 
 
 Development of D?y Plates . 
 
 £ 
 
 x 
 
 H . 
 
 n ^ 
 
 O a 
 
 <3 
 
 £ 
 
 H w g 
 y h o 
 g 5 h 
 o u 
 
 § Q 
 
 o 
 
 J I 
 O o 
 
 a.'o 
 
 2 ^ 
 
 _ O t/J I 
 
 l 5 O' I 
 
 £ ,j 
 
 U a 
 
 O 
 
 £ 
 
 ~ c/) 
 
 £■3 
 
 .3 'c 
 
 pj fl 
 
 bJD 
 
 O 
 
 H 
 
 • 3 4-T 
 
 <U <U t/i 
 
 £ ^ 
 c 
 
 j_ pS 
 ^ « 
 <1-1 
 O 
 
 o> .£ 
 
 "2 
 
 ‘Si 
 
 pj 
 
 1« 
 
 <U •£ g 
 
 3 S J 
 
 T3 -O 
 
 g S C 
 
 II 
 
 o 
 
 £ £^ 
 § §V 
 
 o g « 
 is 0.-5 
 ^ jj* 
 
 
 V 
 
 '-t- ’qj 
 
 o > £ 
 
 
 rC (U - 
 
 •*-’ nd ^ 
 
 <L> « <£3 
 o TJ _ 
 
 'd 
 
 U 
 
 
 <u 
 
 4) ,J3 
 
 ^.£ fcji * 
 
 “!i 1 
 
 g 2 • 
 
 2 £^-2 
 
 J- C w 
 
 t/5 qj pi ! 
 
 -£ rG t/5 <D 
 
 i?S £ 2.2 
 
 Ill 
 
 •X W-“ | 
 
 Q.S | 
 
 S pj C rt 
 
 Concen 
 bath. ] 
 ish the 
 Increas 
 ingred 
 
 O X> *3 £ 
 C3 £ > 
 
 6 a 
 
 E c 
 3 o 
 
 2 c 3 
 
 O 13 
 
 a, o fci a 
 
 >< CL pS pj 
 
 ‘V 2 <U O 
 
 S 0 . 5 ^ 
 
 0 -S 2 ° 
 
 a I 
 
7 6 
 
 Development of Dry Plates. 
 
 Development with Ammonia Vapors. — Dry plates may 
 be developed by means of the vapor of ammonia. The plates 
 are soaked for some time in a normal pyrogallol solution 
 and then exposed to the ammonia vapor. This is best 
 effected by pouring a dilute solution of ammonia into a tray 
 and holding the plate, film down, a few inches above the 
 tray. Care must be taken to avoid too strong a solution of 
 ammonia, as it is liable to produce red and green fog. The 
 greatest advantage of this method is its adaptability to the 
 local development of those parts of the plate which show a 
 lack of detail when developed by the usual method. For 
 this purpose the ammonia should be kept in a bottle provi- 
 ded with a small tube. Those parts of the plate which it 
 is desired to develop further are held over the tube until 
 the details are out. In this way it is often possible to bring 
 out detail in the shadows, but there is more or less of un- 
 certainty about the process. 
 
 Development in Two Solutions. — Some operators ad- 
 vise the use of two solutions, one of the developer proper 
 and the other of the alkali. If the plate has been over-ex- 
 posed it is soaked for a short time in a solution of pyrogal- 
 lol or other reducing agent, and afterwards transferred to 
 a tray containing the alkali. This will bring out the details. 
 If density is lacking the plate is again placed in the first 
 tray. For under-exposures the process is reversed and the 
 plate is placed in the alkali solution first. 
 
 Intentional Over-Exposure. — One of the safest rules 
 for exposure is to give the plate as long an exposure as it 
 will bear without fogging. By this means one is sure of 
 detail, and in general a better balanced negative. Even 
 with extremely rapid plates of good make considerable lati- 
 tude of exposure is possible, if the necessary conditions of 
 
Development of Dry Plates , 
 
 77 
 
 development are understood and met. With a given de- 
 velopment there is for each class of subjects a time of ex- 
 posure which may be called normal by which is meant an 
 exposure which will give the best results with the given de- 
 veloper. But even with long practice it is far from easy to 
 determine the exact time of this normal exposure. If the 
 exposure has been too short, there will be a lack of detail 
 in the finished negative. If an over-exposure has been 
 given, there will be plenty of detail, but a lack of density, 
 and perhaps fog. 
 
 There is no method by which details are brought out on 
 a plate which has not received sufficient exposure to im- 
 press them on the sensitive surface, but it is possible, as 
 has been shown, to modify the developer in such a way as 
 to overcome the effects of over-exposure. For this reason 
 it is always best to give as long an exposure as the plate 
 will bear without fogging, and to modify the developer ac- 
 cordingly. In this way one is sure of the details in the 
 shadows, and a little practice will give the necessary knowl- 
 edge of the amount of over-exposure allowable with any 
 special plate. , 
 
 Local Development by Brushing. — A ve^ effective 
 method of local development is to apply strong solutions 
 to the portions which it is desired to force by means of small 
 camels-hair brushes. The brush dipped in the alkali so- 
 lution and applied to the plate will assist in bringing out 
 detail which would otherwise be lacking. The reducing 
 solution may be applied in the same way to confer density 
 on parts which develop too thin. 
 
 The Influence of Temperature on Development. — 
 Heat is a great promoter of chemical action. A cold de- 
 veloper will develop slowly and a warm one quickly, often 
 
7 » 
 
 Development of Dry Plates. 
 
 with lack .of density. The proper temperature for the de- 
 veloper is between 60 and 70 degrees. This temperature 
 should be maintained by the use of warm water in winter 
 and ice in summer. 
 
 If a plate develops poorly in a solution at the above tem- 
 perature, the addition of a little warm water will often help 
 matters. 
 
 Saturated Solutions. — The use of saturated solutions 
 is to be deprecated on account of the difficulty of obtaining a 
 solution of standard strength. If a salt is dissolved to sat- 
 uration in hot water a certain proportion of it will crystallize 
 out when the water cools. In winter the strength of a 
 saturated solution is less than in summer. The better plan 
 is to dissolve a certain number of parts in a sufficient num- 
 ber of parts of water to keep the solution well within the 
 saturation point. In this way one is always sure of having 
 a solution of standard strength at any temperature. 
 
FORMULAS 
 
 DEVELOPERS. 
 
 beach’s. 
 
 A. Warm distilled water, 2 ounces. 
 
 Sulphite of soda (crystals), 2 ounces. 
 
 dissolve, and when cold add 
 
 Sulphurous acid, 2 ounces. 
 
 Pyrogallol, ^ ounce. 
 
 B. 1 Water, 4 ounces. 
 
 Carbonate of potash, 3 ounces. 
 
 2 Water, 3 ounces. 
 
 Sulphite of soda (crystals) 2 ounces. 
 
 i and 2 are combined. For shutter exposures take 3 
 ounces of water, ounce of A and 3 drams of B, increasing 
 the latter to 5 drams if the image hangs back. 
 
 For over-exposures take 3 ounces of water, 3 drams of A 
 and i dram of B, adding more if necessary. Bromide may 
 be used to restrain. 
 
 PHOTO TIMES SODA DEVELOPER. 
 
 A. Pyrogallol 1 ounce. 
 
 Sulphite of soda (crystals), 4 ounces. 
 
 Sulphurous acid, 4 ounces. 
 
 Water, 10 ounces. 
 
 B. Carbonate of soda (crystals), . . . . 1 ounce. 
 
 Sulphite of soda (crystals), i£ drams. 
 
 Water, 16 ounces. 
 
 Developer : 1 dram of A to 1 ounce of B. For under- 
 exposures, increase the quantity of B ; for over-exposures 
 restrain with bromide of potassium 1 to 10. 
 
 79 
 
8o 
 
 Development of Dry Plates. 
 
 PHOTO TIMES POTASH DEVELOPER. 
 
 A. Pyrogallol, i ounce. 
 
 Sulphite of soda (crystals), 4 ounces. 
 
 Sulphurous acid, 4 ounces. 
 
 Water, 10 ounces. 
 
 B. Carbonate of potash, 3 ounces. 
 
 Carbonate of soda (granular) . . . . 1 dram. 
 
 Water, 10 ounces. 
 
 Developer : 1 ounce of water, 1 dram each of A and B. 
 Accelerate with B. Restrain with bromide of potash 1 
 to 10. 
 
 Cramer’s carbonate of soda developer. 
 
 A. Sulphite of sodium, 6 ounces. 
 
 Carbonate of soda (crystals), .... 1^ ounces. 
 
 Water, 64 ounces. 
 
 B. Distilled water, 6 ounces. 
 
 Sulphuric acid, - 15 drops. 
 
 Sulphite of soda (crystals) ..... 1 dram. 
 
 Pyrogallol, 1 ounce. 
 
 Developer: In cold weather take 8 ounces of A, and 2 
 to 5 drams of B. Keep at 70 degrees. 
 
 In summer take 6 ounces of water. 4 ounces of A and 2 
 to 4 drams of B. Keep at 60 degrees. 
 
 HARVARD PYRO DEVELOPER. 
 
 A. Distilled water, 12 ounces. 
 
 Sulphite of soda (crystals), ..... 2 ounces. 
 
 Citric acid, 60 grains. 
 
 Bromide of ammonium, . . . - • .25 grains. 
 
 Pyrogallol, 1 ounce. 
 
 Dissolve separately, mix in order given and filter. 
 
 B. Distilled water, . .12 ounces. 
 
 Sulphite of soda, 2 ounces. 
 
 Carbonate of potash, .... 4 ounces. 
 
Development of Dry Plates. 81 
 
 Developer : A, i dram ; B, i dram ; water, 2 ounces. 
 For detail, add more water ; for contrast, increase the 
 amount of A ; for density use more of A and B. For in- 
 stantaneous exposures use double the quantity of water to 
 begin with. When development is partly completed, pour 
 off the solution and finish with the normal developer. 
 
 eder’s one solution pyro developer. 
 
 Sulphite of soda (crystals), 5 drams. 
 
 Carbonate of soda (crystals), .... 2^ drams. 
 
 Dissolve in 2 ounces of boiled distilled water, and when 
 cool add forty-six grains of pyrogallol. Keep in well stop- 
 pered bottles, and dilute with five times the bulk of water 
 for use. 
 
 cramer’s hydrochinon developer. 
 
 A. Sulphite of soda (crystals), .... 480 grains. 
 
 Phosphate of soda, 160 grains. 
 
 Water, 8 ounces. 
 
 Dissolve, filter, and add 
 
 Hydrochinon, 100 grains. 
 
 B. Carbonate of soda (crystals), . . . 480 grains. 
 
 Phosphate of soda, 160 grains. 
 
 Water, 8 ounces. 
 
 Developer. — Equal parts of A. and B. 
 
 CHAUTAUQUA HYDROCHINON DEVELOPER. 
 
 A. Hydrochinon, ^ ounce. 
 
 Sulphite of soda (granular), 1 ounce. 
 
 Meta-bisulphite of potassium, . . 30 grains. 
 
 Water, 16 ounces. 
 
 B. Carbonate of potash, lj? ounces. 
 
 Water, 16 ounces. 
 
 Developer. — Equal parts of A and B. 
 
82 
 
 Development of Dry Plates . 
 
 EIKONOGEN DEVELOPER. 
 
 A. Sulphite of soda (crystals), .... 4 ounces. 
 
 Distilled water, 60 ounces. 
 
 Dissolve and add 
 
 Eikonogen, 1 ounce. 
 
 B. Carbonate of soda (crystals), ... 3 ounces. 
 
 Distilled water, . 20 ounces. 
 
 Developer. — 3 parts of A and 1 part of B. 
 
 ONE SOLUTION EIKONOGEN DEVELOPER. 
 Sulphite of soda (crystals), .... 8 ounces. 
 
 Carbonate of soda (crystals), .... 3 ounces. 
 
 Distilled water, 80 ounces. 
 
 Eikonogen, 1 ounce. 
 
 seed’s eikonogen developer. 
 
 A. Sulphite of soda (crystals), ... 6 ounces. 
 
 (If granular sulphite of soda is used take only 3 ounces.) 
 
 Water (ice or distilled), .... 45 ounces. 
 First dissolve the above and then add 
 
 Eikonogen, 1 ounce. 
 
 B. Carbonate of potash, 1^ ounces. 
 
 Water (ice or distilled), 15 ounces. 
 
 Developer.^ — 3 ounces of A and 1 ounce of B. 
 
 If more contrast is required, use more of A ; if less, more 
 of B. 
 
 The developer can be used repeatedly by adding each 
 time a little of each of fresh solutions A and B. 
 
 Notice the temperature of the room, as a slight variation 
 in this respect causes a difference in the time it takes to de- 
 velop. Temperature should be from 70 to 75 degrees, 
 Fahr. 
 
 The developer may be used repeatedly, but will work 
 slower when old (where no addition of fresh has been 
 made). Fresh developer is better for short exposure, and 
 the old, if the plate has been fully timed. 
 
Development of Dry Plates. 83 
 
 The quantity of eikonogen (A) must be according to the 
 density of the negative wanted. 
 
 If the negative is too strong, use less. If not strong 
 enough, more. 
 
 Wuestner’s Eikonogen Developers. 
 
 FOR PORTRAITS AND LANDSCAPES. 
 
 No. I. — Dissolve in 32 ounces distilled or ice water, 
 
 Sulphite of soda, C. P. (crystals), . 1 ounce. 
 
 Eikonogen, ^ ounce. 
 
 No. 2. — Dissolve in 32 ounces distilled or ice water, 
 
 Carbonate of potash, 3 ounces. 
 
 Developer. —Take equal parts of No. 1 and No. 2. 
 
 This developer may be used repeatedly, and will keep for 
 months if preserved in tightly closed bottles. It is of great 
 importance to use only chemically pure sulphite of soda (crys- 
 tals). In order to dissolve the eikonogen quickly it is ad- 
 visable to pulverize the same in a porcelain mortar. 
 
 FOR INSTANTANEOUS EXPOSURES. 
 
 Dissolve in 300 c. c. m. (or 10 ounces) distilled or ice water, 
 
 Sulphite of soda crystals, C. P. , . 20 grammes (or § ounce). 
 
 Carbonate of potash, 10 grammes (or 3- ounce. ) 
 
 And then add Eikonogen, . . . ,10 grammes (or ^ ounce). 
 
 Cramer’s Eikonogen Developers. 
 
 no. 1. 
 
 Distilled water, 40 ounces. 
 
 Sulphite of sodium crystals, .... 2 ounces. 
 
 Eikonogen, finely powdered, 1 ounce. 
 
 Keep the solution in a well stoppered bottle. 
 
 no. 2. 
 
 Water, 10 ounces. 
 
 Carbonate of potassium, 1 ounce. 
 
8 4 
 
 Development of Dry Plates. 
 no. 3. 
 
 Water, 10 ounces. 
 
 Bromide of potassium, ..... 1 ounce. 
 
 FOR USE. 
 
 Solution No. 1, 3 ounces. 
 
 Solution No. 2, 1 ounce. 
 
 Solution No. 3, 6 to 12 minims (or drops). 
 
 When the developer is quite new, it will be found neces- 
 sary to add a little bromide solution (No. 3) in order to 
 make it perfectly clear. The addition of old developer will 
 answer the same purpose. The developer can be used re- 
 peatedly by occasionally adding more of solutions Nos. 1 
 and 2, omitting the bromide. It produces plenty of inten- 
 sity by simply leaving the plate in it long enough. Any de- 
 gree of softness can be obtained by diluting with more or 
 less water, which is also recommended during hot weather 
 and for under-exposures. 
 
 Over-exposed plates restrain by adding more solution 
 No. 3. 
 
 A. p. smith’s eikonogen developer. 
 
 A. Eikonogen (crystals), 120 grains. 
 
 Water, 16 ounces. 
 
 Glycerine, 2 drams. 
 
 Sulphite of soda (crystals), .... 2 drams. 
 
 Alcohol, 2 drams. 
 
 Sulphite of soda (crystals), .... 3) ounces. 
 
 B. Water, 16 ounces. 
 
 Carbonate of soda (crystals), ... 6 drams. 
 
 Carbonate of potash, 3 drams. 
 
 Yellow prussiate of potash, .... 1 dram. 
 
 Developer : A, 2)4 ounces ; B, 1 ounce. Restrain with 
 bromide of potassium. 
 
Development of Dry Plates. 
 
 85 
 
 vansant’s carbonate of lithium developer. 
 
 Distilled water, 1 ounce. 
 
 Tartrate of sodium and potassium, . .25 grains. 
 
 Sulphite of sodium (crystals), .... 25 grains. 
 
 Carbonate of lithium, 1 grain. 
 
 Pyrogallol, 2 grains. 
 
 Dissolve in the order given. When the solution loses its 
 energy after frequent use, it may be renewed by the addi- 
 tion of a few grains of pyro or lithium, as may be required. 
 
 CLEARING SOLUTIONS. 
 
 NO. I. 
 
 Alum, 1 ounce. 
 
 Citric acid, 1 ounce. 
 
 Sulphite of iron, 3 ounces. 
 
 Water, . 20 ounces. 
 
 NO. 2. 
 
 Alum, .1 ounce. 
 
 Citric acid, 3- ounce. 
 
 Water, 15 ounces. 
 
 NO. 3. 
 
 Saturated solution of white alum, . . 32 ounces. 
 
 Sulphuric acid, % ounce. 
 
 INTENSIFIERS. 
 
 No. 1. — Immerse the plate in a saturated solution of 
 chloride of mercury ; wash well and flow with a dilute solu- 
 tion of ammonia. 
 
 No. 2.— Whiten the film in a saturated solution of chlo- 
 ride of mercury ; wash and blacken in a 1 to 5 solution of 
 sulphite of sodium. 
 
 No. 3. — Saturated solution of bichloride of mercury, 10 
 ounces ; iodide of potassium, 10 drams. Dissolve the iodide 
 
86 
 
 Development of Dry Plates. 
 
 in ten ounces of water, and pour gradually into the mercury 
 solution until the precipitate is nearly redissolved. Add i 
 ounce of hyposulphite of soda. 
 
 no. 4. 
 
 Bichloride of mercury, 10 grains. 
 
 Chloride of ammonium, 10 grains. 
 
 Water, ' ; . . . 1 ounce. 
 
 Immerse the well washed negative in this solution until 
 the film is whitened ; then blacken in the following, after 
 
 thorough washing : 
 
 Cyanide of potassium, 2 ounces. 
 
 Distilled water, 48 ounces. 
 
 Nitrate of silver, 1 ounce. 
 
 Distilled water, . . 6 ounces. 
 
 The silver solution is poured gradually into the cyanide, 
 stirring with a glass rod. Allow the mixed solution to stand 
 a few days before using. 
 
 REDUCING SOLUTIONS. 
 
 NO. I. 
 
 Saturated solution of ferri-cyanide of potassium, . 1 ounce. 
 
 Hyposulphite of soda solution, 1 to 5, . . . .10 ounces. 
 NO. 2. 
 
 Potassium ferri-oxalate, 5 grains. 
 
 Hyposulphite of soda solution, 1 to 5, . . . . 1 ounce. 
 
 NO. 3. 
 
 Saturated solution of white alum, 32 ounces. 
 
 Sulphuric acid, . I ounce. 
 
 NO. 4. 
 
 Perchloride of iron, . 30 grains. 
 
 Citric acid, 60 grains. 
 
 Water, 16 ounces. 
 
 Note.- — The negatives should be thoroughly washed, in 
 all cases. 
 
TABLE SHOWING COMPARATIVE VALUE OF ALKALINE CARBONATES IN DEVELOPERS. 
 
 Development of Dry Plates . 
 
 87 
 
 ^!is 
 
 a o 
 
 . <U£! 
 
 ax a 
 
 o . 
 » g 
 
 tj CO 
 
 Id 5 
 
 a 
 
 cd 0 cd ^ co 
 
 1/3 CO O Cd 
 
 . 
 
 o £ o •“ * 
 Oh 
 
 tt co 
 O aj 
 
 l« cd . 
 
 L o o-x> x> 
 
 hOh »h In 
 
 S E cd aJ 
 
 ; o'*# 
 
 iOh 
 
 u 3 
 ' “ rt 
 
 7 cd o c-i 
 U 
 
 ■ ^ oCQ 
 VO 
 
 CO 
 
 ss V. 3 
 
 U1 O o 
 
 O' 
 
 o o cd 
 
 o, in ^ 
 
 -IsS”! 
 
 . 3 cd « 3 3 
 
 cd -H c Vh S -»H 
 co co 3 3 -h co 
 co co 9 £_, 2 co 
 _cd cd -O “ ” cd 
 
 O O cd 75 Id P 
 OhOhU</7C/3 0h 
 
 U CO *H 
 
 c 
 
 g cd c 
 
 S =5 « 
 •S13 0 
 g o -2 
 
 215 2 
 
 a 
 
 r> 
 
 o cd ^ 
 o t 3 cd 
 « o 
 Mi.G 
 cd , 
 
 eo O CD 
 
 5 v s 
 
 s.s 8 | 
 
 g-D°3 . 
 o £.£ o £ 
 x o-S 
 
 b c rn-a 
 
 a _ 
 
 n co u 5 £j 
 cd X rt 0 
 CT co fe X v 
 
 s-sC&s 
 
 o «’2 e 
 
 • 8 gSfj .9 
 
 a a 
 
 Jh-" s « 3 
 
 aS*'o^ 
 
 Gut* 
 
 S §|*3 
 
 o * a 
 
 *o*|-s 
 
 O’” 3d 
 
 •gg-.g 
 
 3 hi 
 
 3 
 
 cd 
 
 U 
 
 CO o ™ OjP 
 
 «di)o DH 
 g.« §00 
 
 s S;.sg 
 H .« § 
 £a ^gx 
 
 s|!S5 
 
 I'PH 
 
 s o . q - a 
 
 X 03 ^ ^ 
 
 9 g 2 <u'a 
 
 £ cu bex Cd 
 
 XI c ~ u 
 
 73 H 2 y. 0 
 
 3 x u . 
 
 ■. o a p» 
 
 ^ • V* . _ 1 ^ 
 
 W «Q 
 
 CO CXI 
 
 5 — O 
 o £ u 
 Oh cd X 
 
IMPURITIES IN PHOTOGRAPHIC CHEMICALS AND TESTS 
 FOR THEM. 
 
 G. M. Jones, in the Photographic Times Annual. 
 
 SUBSTANCE. IMPURITIES POSSIBLY PRESENT. TESTS. 
 
 Ammonia Carbonic Acid Renders lime-water milky. 
 
 Dissolved solid matter 
 
 Residue left on evaporation. 
 
 Chlorides 
 
 .After acidulating with nitric acid, it gives 
 a precipitate with silver nitrate, which, 
 after washing, is readily soluble in 
 ammonia, and re precipitated by nitric 
 acid. 
 
 Sulphates 
 
 .After acidulating with nitric acid, it 
 gives a precipitate with barium ni- 
 trate. 
 
 Lime 
 
 .A white precipitate with oxalate of am- 
 monium. 
 
 Lead is often present, de- 
 rived from the action upon 
 flint glass bottles. 
 
 Nitric Acid Traces of sulphuric acid 
 
 Black precipitate, with sulphuretted 
 hydrogen. 
 
 .After dilution it gives a precipitate with 
 barium nitrate. 
 
 Chlorides 
 
 .After dilution it gives a precipitate with 
 silver nitrate. 
 
 Peroxide of nitrogen 
 
 .The acid is yellow. 
 
 Iodine may be present if the After dilution and cooling it gives a blue 
 acid be prepared from color with starch paste or mucilage. 
 
 sodium nitrate. 
 
 Hydrochloric Acid Free chlorine 
 
 .Liberates iodine from solution of potas- 
 sium iodide. See also chlorides, nitric 
 acid. 
 
 Sulphuric acid 
 
 Perchljride of iron 
 
 .As above for nitric acid. 
 
 .Yellow color. Brown precipitate with 
 ammonia added till it smells slightly. 
 
 Hydrochloric Acid Arsenic 
 
 Some yellow samples contain 
 no iron, but an organic 
 salt, and give an alkaline 
 ash on ignition of the re- 
 sidue after evaporation. 
 
 88 
 
 .Marsh’s test. 
 
 Reinsh’s test ; a small piece of copper 
 foil becomes coated on boiling in dilute 
 acid. 
 
Development of Dry Plates . 
 
 89 
 
 SUBSTANCE. IMPURITIES POSSIBLY PRESENT. TESTS. 
 
 Sulphuric Acid Bisulphate of potassium. . Residue on evaporation. 
 
 Sulphate of lead . .Milkiness on dilution. 
 
 May be completely freed from lead by 
 diluting with three or four times as 
 much water, and allowing to settle. 
 
 No easy test can be given, as the sub- 
 stances are so numerous ; some of 
 them volatile, and most require 
 separation from the acid before de- 
 tection. 
 
 When sold as pure, it inva- 
 riably contains a trace of 
 iron. Common acid is also 
 liable to contain arsenic, 
 selenium, thallium, and 
 many other substances. 
 
 Organic matter, as a piece of 
 straw in a carboy of acid. 
 
 Acetic Acid. . Water 
 
 Gives a brown color to the acid. 
 
 Does not solidify when cooled to 17 0 C, 
 (53° F). 
 
 White precipitate with silver nitrate. 
 
 Blackens in the light after adding silver 
 nitrate. 
 
 Sulphurous and hydrochloric 
 acids. 
 
 Aldehyde, or volatile tarry 
 matter. 
 
 Organic sulphuric acid Smell of garlic. 
 
 Citric Acid. .. . Tartaric acid Strong solution of potassium acetate 
 
 added to a strong solution of the 
 acid will deposit white crystalline 
 bitartrate. 
 
 Pyrogallic Acid Metagallic acid Black residue insoluble in water. 
 
 Silver Nitrate Free nitric acid Reddens litmus paper (neutral silver 
 
 nitrate does not affect litmus). 
 
 Potassium Carbonate. .Chlorides and sulphates. Same as for ammonia. 
 
 Potassium Iodide. Potassium Carbonate A strong solution in alkaline to test 
 
 paper. 
 
 Sulphates and chlorides Same as for ammonia. 
 
 Potassium iodate A pretty strong solution becomes yel- 
 
 low from liberation of iodine on ad- 
 dition of dilute sulphuric acid, or 
 better, a strong solution of citric 
 acid. 
 
 Potassium Bromide Similar to potassium iodide. T .See potassium iodide. 
 
 Sodium Carbonate Chlorides and Sulphates. Same as for ammonia. 
 
 Sodium Chloride Chloride of calcium Oxalate of ammonium (after addition 
 
 Chloride of magnesium of a little acetic acid) gives a milki- 
 
 ness or precipitate, indicating cal- 
 cium; filter this out, and add am- 
 moni, chloride of ammonium, and 
 phosphate of sodium (clear solutions). 
 A precipitate indicates magnesium 
 Both the above cause dampness in wet 
 weather. ^ * i*? 3 * 
 
 Sodium sulphate. . . ?.' J . j. ."^s # ,07 smlphatos ib, ammonia;) -> \ J , 
 
 ' J o » 3 " ’ ' 1 J J J ... 
 
9 o 
 
 Development of Dry Plates . 
 
 SUBSTANCE. IMPURITIES POSSIBLY PRESENT. TESTS. 
 
 Potassium Cyanide. .. .Potassium carbonate nearly Effervescence with dilute acids, giving 
 
 Potassium Hydrate always present. off a gas carbonic anhydride, which 
 
 renders lime water turbid. 
 
 Kaolin Chalk Effervescence with dilute acids. 
 
 Water Sulphates and chlorides Same as for ammonia. 
 
 Calcium carbonate, tempor- Deposited by boiling, 
 ary hardness. 
 
 Ammonia, almost always Test as for calcium chloride, see sodium 
 present in distilled and rain chloride. 
 
 water. Brown coloration, or precipitate with 
 
 Nessler’s re-agent. 
 
 Gelatine Alum Ash, sometimes as much as 10 per cent. 
 
 Fatty matter Separated by precipitation with alcohol. 
 
 Dissolved out by ether or benzine, 
 and left as a residue on evaporation 
 of the solvent. 
 
 Ammonium Bromide.. .Potassium bromide, or other Leaves a residue when heated. 
 
 non-volatile bodies. Same as for chlorides in ammonia. 
 
 Ammonium chloride. 
 
 Pyrogal ic Acid. . Powdered glass Left behind on solution. 
 
 Potassium Iodide Potassium bromide The crystals of bromide are usually 
 
 more transparent than those of iodide, 
 but no reliance can be placed on this. 
 
 Silver Nitrate Potassium nitrate, sometimes Will not yield the full quantity of chlo- 
 
 present in the fused sticks, ride on precipitation with HCI. Gives 
 not in the crystals. a purple color to flame. 
 
 Calcium Chloride Calcium hydrate The clear filtered solution made with 
 
 distilled water is alkaline to test 
 paper, and gives a precipitate on 
 breathing into it through a tube. 
 
 Pure (?) Chemicals Broken glass, bits of straw, These impurities either float or sink on 
 
 generally. wood, paper, etc. the solution, and may easily be seen. 
 
 TABLES FOR THE CONVERSION OF GRAMS (OR CUBIC 
 CENTIMETERS) INTO OUNCES ANI) GRAINS. 
 
 CONVERSION OF GRAMS INTO 
 
 CONVERSION OF GRAINS INTO 
 
 GRAINS. 
 
 Grains, j Grains. 
 
 15-43 
 30.86 
 46.29 
 61.73 
 77.16 
 92.59 
 108.03 
 123.46 
 133.% 
 
 GRAMS. 
 
 Grams. 
 
 1 0648 
 
 2 1296 
 
 3 1944 
 
 4 -2592 
 
 5 3240 
 
 6 3888 
 
 7 4536 
 
 8 5184 
 
 9 •••••; 5832 
 
Development of Dry Plates. 
 
 9 1 
 
 CONVERSION OF GRAMS INTO 
 TROY OUNCES. 
 
 Grams. 
 
 1 
 
 2 
 
 Troy Ounces. 
 
 ... .03215 
 ... . 06430 
 ... .09645 
 ... .12860 
 ... .16075 
 ... .I929O 
 
 ... .22505 
 ... .25720 
 ... .28935 
 
 CONVERSION OF GRAMS INTO 
 AVOIRDUPOIS OUNCES. 
 
 Grams. 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 Avoird’s Ounces. 
 
 03527 
 
 .07054 
 
 IQ58I 
 
 I4IO8 
 
 17635 
 
 ....... .2Il62 
 
 24689 
 
 28216 
 
 31743 
 
 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 ex- 
 ample. Supposing that it is desired 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. 
 
 300. OO 
 
 20. OO 
 
 4.00 
 
 •50 
 
 .OI 
 
 Equivalents in grains. 
 
 4630. 
 
 308.6 
 
 61.73 
 
 7.716 
 
 • I 543 
 
 5008. 2003 
 
 The required quantity is 5008.2 grains. The numbers 
 taken from the table will, in most cases, require a change 
 as regards tne 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 man- 
 ner, by shifting the decimal place of 30.86 one place to the 
 
92 
 
 Development of Dry Plates. 
 
 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. 
 
TABLE OF CONTENTS 
 
 — * : 
 
 CHAPTER I. 
 
 General Principles, 5 
 
 CHAPTER II. 
 
 The Developing Room, 9 
 
 CHAPTER III. 
 
 The Principles of Development — The Tentative Method, . . . .16 
 
 CHAPTER IV. 
 
 The Automatic Method — Use of a Bromide — Over-Exposure, . . 25 
 
 CHAPTER V. 
 
 The Components of the Developer and their Adjustment, .... 30 
 CHAPTER VI. 
 
 The Ferrous-Oxalate Developer, 35 
 
 CHAPTER VII. 
 
 The Pyrogallol Developer, 40 
 
 CHAPTER VIII. 
 
 The Hydrochinon Developer, 47 
 
 CHAPTER IX. 
 
 The Eikonogen and Pyrocatechin Developers, 51 
 
 CHAPTER X. 
 
 Development of Instantaneous Exposures — Films and Lantern Slides, 55 
 CHAPTER XI. 
 
 Fixing and Washing, 61 
 
 CHAPTER XII. 
 
 Intensification and Reduction, 67 
 
 CHAPTER XIII. 
 
 Supplementary Notes, 72 
 
 Formulas and Tables, 79 
 
 93