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.
Judging Depth Of Printing. No set rules can be given regarding the depth of printing, other than " print until the highest points of light are from one to two shades darker than is desired for the finished print," the depth depending entirely upon the tone desired. Warm tones do not require as much printing as cold tones. Practice and close observation alone will enable you to judge accurately the desired depth of printing from a variety of negatives.
113. Before wetting the prints examine them closely, and remember as nearly as possible their appearance; then after they have gone through the various wash waters, toning and fixing baths, and finally been dried, examine them again. If they are too dark or too light, the error must be corrected in the next printing. After a little practice no difficulty will be experienced in judging the proper depth to print all classes of negatives. The secret of the success of a printer is measured by his ability to print from all kinds of negatives and produce uniform results. Continual practice, carried on in an intelligent and systematic manner, will enable any one to become expert in this work.
Gold Bath Too Acid. If your gold bath tests too acid, simply add more borax until red litmus paper turns blue within two minutes. When adding borax be careful that you stir the bath so that the borax will become mixed with the entire solution.
Gold Bath Too Alkali. If the gold bath tests too alkali, add a little more gold and a little more water. Add the gold, however, without borax; there is enough acid in the gold to neutralize the alkali already in the bath.
Entire Print Weak. This difficulty you generally meet with when making prints from thin, weak negatives, but you will also produce weak prints from a strong, vigorous negative if you tone too slowly and use too weak a toning bath. If your negatives are thin print them in a soft, diffused light, so as to print them slowly, as the slow printing permits deeper printing into the emulsion. If the bath tones too slowly strengthen it by adding more gold and enough borax to neutralize it, so as to increase the speed of the toning. A bath too cold will give weak prints, too warm a bath will give mealy prints.
Highlights And Half-Tones Bleaching. If prints bleach in the highlights and half-tones it is because the bath is acid. To overcome this simply add a little more borax; continue to add borax, a little at a time, until the bleaching ceases, even if the bath tests alkali before adding more borax.
Whites Toning Brown And Muddy. This is a certain sign that your bath is too alkaline. Add a little more water and a little more gold, but add no more borax; do not neutralize the gold. There will be enough acid in the gold to counteract the strong alkali in the bath.