This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
291. Undoubtedly many negatives are made in which it is desirable that certain portions of the plate be made a trifle thinner, yet it would not do to sacrifice the whole plate for a few minor improvements. By careful application of the reducing solutions, whether it be the red prussiate or persulphate of ammonia, the portions of the plate which print too harsh can be subdued.
Class Of Negatives That Can Be Improved By Doctoring. In landscape, cloud effects, and interior work, this doctoring is invaluable, for in this way all halation and objectionable highlights can be subdued, or entirely elimi nated. In portraiture, for instance, where you have a red or tan faced subject gowned in white, there is apt to be great contrast, unless care has been taken in the lighting; even then, one when developing, in their endeavor to build up the face as strong as possible so it will not print black, is very apt to over-develop the drapery. Then, again, a white bow in the hair, a blue ribbon, etc., may develop very strong, and give chalky results. It also happens very often that the plate is under-exposed, and in forcing the detail in the shadows, the highlights become too dense. All these objections can be removed, and the negative very much improved by local reduction.
Doctoring White Drapery. Great care must be exercised, else you overdo, or spoil the plate; still these methods are successfully employed every day, and practice will make you perfect. Sometimes in large groups there may be but one or two subjects in white drapery, and the rest are all in dark; usually the white gown is developed a trifle stronger than you would like, and, consequently, the white drapery prints chalky, compared to the others. In such cases it is necessary that only these white draperies be reduced. By careful application of the reducing solution one can improve many faults in any negative, even with entire groups of subjects all gowned in white, such as bridal parties, graduating classes, or even single subjects dressed in white. Where the delicate trimming of lace, etc., is sometimes lost, and there is little or no detail in any part of the drapery, one can by careful application reduce the harshness and supply detail. Where the dress is arranged in folds one can accent the shadows more or less by applying the reducer to these parts.
294. In Part First, of Negative Reducing, we described, in paragraph 260, the class of plates that should be reduced with red prussiate of potash. In preparing this Instruction, reducing portions of the plate only where it will do no harm to reduce the shadows a trifle also, it is advisable to use the red prussiate, and your first experiments should be with such a negative. After soaking the negative in the hypo bath for ten minutes, apply with a soft camel's - hair brush the diluted solution of red prussiate of potash to all parts that need reducing.