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.
Multi-Colored Gum-Bichromate Prints. A variety of effects can be obtained by the skilled worker, by coating the print with different colors so as to obtain color effects. This is usually done by first printing in the body color, or that color which is to be most predominant in the print. A second coating can be made with a color to enhance the shadows and half-tones, and a third coating of color can be applied for the sky or any other part that is desired. The method of applying the colors to the paper, sensitizing it, registering the paper on the negative, developing and finishing are the same as previously described, but such work should not be attempted except by those who are skilled in the use of colors. Very good effects can be obtained by making a weak print on platinum paper and then coating this paper with any desired color. The surface of platinum paper is such as to give most beautiful results when rooted with gum-bichromate.