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DRY PLATES, FILMS AND PAPERS 191
to withdraw the negative from the solution when the intensification has proceeded far enough, otherwise the deposit will most probably form on parts of the film where its presence is not desired — in fact, this action may take place at the beginning unless the plate has been most carefully washed, and this represents the great difficulty to be met with in this process.
Should the intensification be carried slightly too far a thorough washing in hard water will be found to reduce it somewhat, and to remove any slight traces of stain. There are several other methods of intensification in general use, but the one which, on account of its simplicity, will appeal most strongly to the beginner is that in which the Chromium Tabloid Intensifier is used.
By the action of this intensifier, chromium is added to the original silver image, and the process can be repeated until the desired degree of opacity has been obtained.
All that is necessary is to immerse the plate in a solution obtained by dissolving one of the tabloids in two ounces of Avater, and to leave it in this solution until it has assumed a general buff tint. Next, the plate must be thoroughly washed (if running water is used fifteen minutes will usually be found sufficient), and then redeveloped with any ordinary developer.
All these processes may be carried out in daylight, and the result will be found quite satisfactory as compared with those obtained with other more difficult and expensive means.
Reduction of Negatives. — Should a negative be found to be over-dense it can to a certain extent be reduced, but there is always more risk attached to this process than to the preceding, for a negative which has been overreduced must be considered as spoilt, since if it be intensified again it will be found that a negative having quite false gradations has been produced.
However, judicially used, reducing processes may be of