Ferrous Oxalate.—This developer is the traditional one for bromide papers, but we do not recommend it unless a very large amount of work of this kind is done. It involves a good deal of trouble, but gives bright, sparkling pictures and grey half-tones.
A. Potassium Oxalate (neutral) . . . . . 5 oz.
Ammonium Bromide . . . . . 6 gr.
Water . . . . . . . . . 20 oz.
B. Ferrous Sulphate . . . . . . . i oz.
Sulphuric Acid . . . . . . 5 minims Water . . . . . . . . 3 oz.
At time of using pour i oz. of B into 6 oz. of A. The oxalate must not be poured into the iron solution, or a thick yellow precipitate of ferrous oxalate will form. After development wash the print in two changes of a solution of citric acid, 3o gr. to every pint of water, and then in three changes of pure water before fixing. Otherwise the iron salts will become insoluble and stain the print a pinkish yellow colour. Prints from an Unfixed Negative.—The bromide printing process has this convenience over any other, that, if a proof is wanted in a hurry, it may be taken from a negative within a minute after development. Wash the negative well, lay it face upwards in a dish of clean water, and bring in contact with it a piece of bromide paper of the same size. The two are squeegeed together, and then exposed in the printing frame ; the exposure being about four times as long as would be the case with a dry, properly fixed negative. Bromide prints may be reduced and intensified in just the same way as ordinary negatives, except that the solutions are rendered more dilute for the former. Local reduction or intensification is easily accomplished by means of a brush dipped in a solution of copper bromide with glycerine. Blisters may be cured by the alum or formaline baths given under develop ment of plates.
Belitski's Reducer.—If the ferric salt can be conveniently obtained, this reducer surpasses all others for bromide prints. No stains are likely to result from its use—in fact it will often remove developer stains—and it does not alter the original colour of the print. One feult is that it must not be exposed to daylight, but keeps for a long time in the dark.
Potassium Ferric Oxalate . . • . . 5o gr.
Sodium Sulphite . . . . . . 4o „
. . . . . . . 5 oz.
Add to gr. of oxalic acid when the above are dissolved, stir well, and decant off the green solution, to which must then be added about 25o gr. of Hypo.
Toning Bromides.—Bromides may be toned with uranium, copper, iron, and other methods, most of them rendering the permanence of the print subjected to them very question able. The sulphide toning process, converting the silver image into the practically unalterable silver sulphide, bears at present a good reputation. A hot bath, which will serve for several kinds of paper, is made up as follows : Hypo . t oz.
Alum . . . . So gr.
Water . . . . . 10 oz The bath is made up with hot water, and 5 mm. of nitrate of silver solution are an improvement, serving as a restrainer. The solution should be allowed to cool and then warmed again to 120° use. If any precipitate settles on the prints it must be wiped off with cotton wool. Warm brown tones are given.
In the Kodak formula for sepia tones, i oz. hypo is dissolved in 7 oz. water at Fahr., and 13o gr. alum added by degrees while still at the same temperature. The liquid will be milky, but must not be filtered. After the prints have been fixed and washed, they should be placed in a saturated solution of alum for ten minutes and allowed to dry. The actual toning is carried on by immersing the prints in an iron dish containing the cold hypo-alum solution, which is then raised to 120' or 125°, and kept at that heat for twenty minutes, or until the desired tone is obtained. The fumes of these hot alum hypo baths are very injurious both to dry plates and papers, and this toning process should not be carried on in any apartment where they are stored.
Bleaching Process.—Bleach the print in Potassium Bichromate . • . . . . . ro gr.
Hydrochloric Acid . . . . . . 5 min.
Water . . . . . . . . I oz.
Wash with several changes of water until yellow stain is discharged ; a little alum will hasten the effect. Then either leave to print in the sun or redevelop with either rodinal or amidol. The brown image may then be toned in any ordinary gold toning solution, after which the print may be reduced in the fixing bath if necessary.