Twenty minims of No. 1 solution are introduced into the whole of No. 2, and the Gelatine is left to swell.
In another glass vessel 330 grains of nitrate of silver are dissolved in 3 ounces of distilled water; a small quantity, about two fluid drachms, of the latter is poured into a test tube and diluted with an equal bulk of distilled water.
The solution of the bromo-gelatine is then rendered complete by immersing the bottle in hot water, and the dilute silver nitrate is added all at once.
The bottle is then shaken and the remainder of the strong silver solution added in quantities of half an ounce at a time, shaking the bottle as before after each addition. p41
The emulsion is then boiled for fifty-five (55) minutes, and when cooled down to 90 degrees F., one ounce of gelatine, which has been previously swelled and dissolved in water so as to measure four ounces, is added and put away in a cold place to set.
When set, squeeze through coarse canvas into cold water one half gallon and ¼ lb. salt; let it remain for five minutes, then wash thoroughly.
The addition of two ounces of alcohol and enough water to make up to twenty ounces completes the process.
In the preparation of this or any gelatine emulsion the work may be carried on in daylight as far as the mixing of the bromide and silver, which must be done in a dark room by the aid of a lamp or gas light shaded by orange or ruby glass. Sufficient of this non-actinic light may be admitted to enable the work of washing the emulsion, and afterwards the coating of the plates, to be carried on with ease and comfort, as the emulsion when wet is only half as sensitive as when dry.
GELATINE EMULSION. B.
JARMAN.