Early Work In Photography
A Text-book For Beginners

CHAPTER XI. THE AFTER TREATMENT OF NEGATIVES. 30 O matter how carefully a negative has been developed, | / occasions sometimes arise when a little after treat- -LC ment will prove a decided benefit. For instance, let us suppose that a negative has been correctly exposed but not sufficiently developed; it is no uncommon occur- rence, especially when working with a different brand of plates from that generally used. Some plates are deceptive in appearance during development and, after all detail has come up, seem to be sufficiently dense for printing purposes, when in reality they lose mucn of their apparent vigor in the fixing bath. The result is a clear plate full of detail but devoid of density, such a negative as would print in a few minutes, but give a weakly print that would be quite incapable of toning to a pleasant color. A negative of this kind can be readily brought up to full printing density by after treatment called “ intensifying.” Let us consider the principle of the action. We have seen that a silver print on paper is formed by various shades of silver deposited by the action of light, and we know that immersion in a bath of gold causes it to change to a purple color, more or less, according to the depth of the print; this is commonly known as “toning” and, as previously pointed out, is due to the affinity between the gold in solution and the silver in the print. Intensification is somewhat analogous; in the thin negative (full of detail and lacking density) we have an image composed of more or less silver. Now, if we put such a negative in a specially prepared bath, we can cause another metal to become deposited upon the silver in direct proportion to the amount of silver already there. Thus, it stands to reason, we add to the density of the deposit and give to the negative the necessary printing quality. All the extra density that will generally be required can be given by means of mercury and silver cyanide, and in our opinion it is a far better method than the common plan of following the