Bromide Printing and Enlarging / A Practical Guide to the Making of Bromide Prints by Contact and Bromide Enlarging by Daylight and Artificial Light, With the Toning of Bromide Prints and Enlargements

by John A. Tennant

There are many different formulas for the uranium toning of bromide prints, and I suppose that most of them have given good results with the workers who published their methods. Of those which I have tried, however, none has yielded the results which I have been enabled to obtain from my own formula—my own in that I arrived at it by patient experimenting. It may be that this formula is not wholly original with myself. At any rate, I do not claim anything for it except that it works, with me, better than others I have tried.

The requirements for toning bromide prints with uranium are: 1 ounce of uranium nitrate; 1 ounce of potassium ferricyanide (the red crystals); ½ pound bottle of acetic acid—c. p. glacial preferred; water; a supply of blotting paper, to be kept exclusively for this purpose, and a few absolutely and chemically clean trays.

The expense attached to these toning processes is slight. Uranium nitrate costs from forty to sixty cents per ounce, and an ounce will last a long time. Potassium ferricyanide costs about twenty cents per pound, and a pound is ample for a lifetime. Glacial acetic acid is a little more costly, but a half-pound bottle will prove a good investment. It is used also, as the reader will recall, in making acid hypo for acid fixing.

To prepare the toning baths, dissolve the ounce of uranium nitrate in 10 ounces of water. The water should be distilled if this is easily obtainable, and the solution should be kept in an orange-glass bottle or an ordinary bottle protected from light by a non-actinic paper wrapping. Dissolve the ounce of potassium ferricyanide in 10 ounces of water. Keep this also in an orange-glass bottle, well corked. There are many cautions about this particular salt, and it has been said that it will not keep in solution. In my practice I find no difficulty whatever in the use of a solution six months old, despite the difficulties mentioned in the text-books.

To tone the bromide prints, first note that the prints should have been developed and fixed and washed just as usual. It is necessary that prints to be toned shall contain no trace of hypo. To secure this, the prints should be specially prepared for toning by being again thoroughly washed, as any hypo remaining in the print will cause spots and streakiness. With care at this stage the toning will give clean and bright prints, which should be as permanent as the original bromide print.

I cannot give the reason why, but, as a general rule, bromide prints tone better if the print has been dried after washing and rewet just before toning. There may be a chemical reason for this, but I am inclined to think that it is a physical one, viz., that the emulsion is softer after its first washing than after having been dried and wet, so that it allows toning solution to get into the film more quickly. This naturally results in more rapid toning, and quick toning does not yield as good prints as a slower and more gradual building up of the color image.

Having the print ready for toning as here outlined, take 1 dram of the uranium solution, add ½ dram of acetic acid and then 5 ounces of water. In a separate graduate put 1 dram of ferricyanide solution and 5 ounces of water. Just before toning, pour these two solutions together into the third graduate and use immediately. To proceed, lay the rewetted print face up in a clean tray and flow the freshly made toning bath (the two solutions combined) over the print. The print and tray must be kept in motion by gentle rocking during the toning operation. The toning solution tends to throw a red precipitate as it works. This precipitate should not be permitted to settle on the face of the print. Some workers tone their prints face down, but I do not advocate this, as it is important to take the print from the toning bath at just the right moment, and, as the toning process is short (six or seven minutes is usually sufficient even for the deepest red) you need to watch the print all the time. In the toning operation note that a constant quiet motion of the tray, to keep the solution moving over the print, is essential to success.

I have already given, in an earlier paragraph, the order in which the colors come. But that order was for a normal print. Some prints behave differently, and it is in the control of these unavoidable variations with different prints that skill and success come. A print of a half-tone subject against a jet-black background, a portrait, for instance, will hardly follow the normal order in the appearance of colors. This because the half-tones will be brown and even red-brown before the toning solution has changed the dense black deposit of the background at all. If the toning was stopped at this stage, some very pretty effects in double toning might result.

From this explanation of the toning process, the discerning reader will perceive the need for caution in selecting the best kind of a print for uranium toning. Thus a print which has a bald-headed sky will tone only in the body of the print, but if there is any tint at all to the sky, it also will tone, giving an effect not much to be desired except for sunset or sunrise pictures. If white high-lights are desired in the toned print, they must be white originally and not the least bit fogged. As double-toned effects in a print are not usually desirable, those prints having deep black shadows or dark masses will be avoided. The best kind of print for this method of toning is one fully exposed and slightly under-developed, since, when the uranium does take hold of the shadows, it makes for an increase of contrast.

Experience is the best teacher, and I could not begin to describe in detail what the reader can himself ascertain from a few experiments. Some prints needing contrast should be carried far in the toning solution; others, not needing contrast, will give better results if they are toned only through the browns, and so on. The reader who can spend a Saturday afternoon with a few bromide prints, varying in character, will learn more from his experimenting than I could tell him in many pages. For these experiments waste or imperfect black prints can be used with practical economy, the chief object being to watch the progress of toning and chemical changes.