Towler, John. The Silver Sunbeam. Joseph H. Ladd, New York: 1864. Electronic edition prepared from facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson, New York. Second printing, Feb. 1974. ISBN 871000-005-9

Chapter XVI.
THE DEVELOPING SOLUTIONS.

IN the ordinary, or wet-collodion process, there are three Developing Solutions, the Protosulphate of Iron Developer, the Pyrogallic Acid Developer, and the New Developer, with the double salt of the sulphate of the protoxide of iron, and the sulphate of ammonia.

Sulphate of Iron Developer.

Formula No. 1. For Ambrotypes and Melainotypes.

Pulverize the iron salt, if it has not been precipitated in alcohol, and mix it intimately with the rain-water in the mortar; then add the acid and the alcohol, and see that the solution is complete; then filter and use. From a previous observation on the subject of developing, it will be conceived that the quantity of acid must vary according to several circumstances. In summer, that is, when the temperature is high, more acid will be required to keep the reducing agent in check; in like manner, if the time of exposure has been too long, the development or decomposition is more easily accomplished, and on this account more acid is required. On the contrary, in winter, when the temperature is low, as also when the time has been very short, as for example, for instantaneous operations, the proportion of acid may be diminished, until finally the solution of the iron salt may be used without any acid. In such cases it is well to have a bath of the solution, into which the exposed plate can be immersed almost instantaneously, and treated with the ordinary acid solution afterward. Considerable dexterity is required in this twofold operation. Of course diminishing the iron salt, or increasing the acid are correlative expressions, and signify almost the same thing, the slight difference depending upon the influence of the water which remains stationary, or relatively increases sometimes in favor of the iron, and sometimes of the acid.

Formula No. 2. For Negatives.

Pulverize and mix as before. A negative requires a longer exposure than the ambrotype, or the melainotype; the iron, therefore, is diminished whilst the other ingredients remain the same. In the first formula a drop or two of pure nitric acid may be added, because it produces a more reguline reduction of the silver salt, and leaves a very beautifully white metallic-looking film where the light has acted. Too much nitric acid would spoil the picture by producing too intense a reduction, accompanied with irregularity of deposition.

Formula No. 3. For Negatives.

Shake the solution well, and keep in a dark place.

The reduction by this developer is quite appropriate for negatives; its color is grayish, but not metallic in appearance. This developer is very manageable, and very successful. It requires, however, a longer exposure than the iron developer, in the ratio of three to one, from my own experience in out-door photography. It is not so apt to fog a picture as the iron developer.

Formula No. 4. For Negatives.

When required, dissolve a two-grain dose of the preceding in four drachms of distilled water. The amount of citric acid can be modified according to the same circumstances which regulate the treatment with acetic acid.

Disdéri's Developer.

Lieut.- Colonel Stuart Wortley's Developer.

Dissolve.

Dissolve.

Mix the above solutions, and as soon as the precipitate has settled, decant off very carefully. Add

This mixture is the stock solution, from which a portion is taken, when required, and filtered for use.

Meynier's Developer.

Or the preceding formula may stand as follows

Hockin's Developer.

This developer is poured upon the plate, and kept there until the intensity is deep enough. It acts more quickly than the pyrogallic acid containing acetic acid, but less so than the iron developer; but it is less liable to fog than the iron developer, and can consequently be retained longer on the plate.

Waldack's Formulas for Collodion Positives.
Formula No. 1. For Dead-Whites.

Formula No. 2. For Brilliant and Metallic Whites.

In all the preceding formulas, alcohol may or may not be added, according to circumstances. It is used when the developer does not flow easily over the plate, forming, as it were, oily streaks on the surface. It remains, therefore, with the artist to use or reject it, as it may be found necessary.