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.
Developing Of Plates. Having carefully prepared your developer, according to the formula, place the exposed plate in the tray, and flow with a sufficient quantity solution to thoroughly cover it with one sweep. Use plenty of developer. Avoid rocking the tray more than is absolutely necessary. Carefully watch the plate, and within a reasonable time the image should appear. If after the image appears it continues to grow right along, you will know the exposure is all right for the developer you are using. If within a few minutes after the image appears the action of the developer is slow and lagging, you will know that the plate was extremely under-exposed. You should then add enough water to make double the quantity of solution, and cover the tray, excluding all light, and continue the developing, and if the developing appears still to lag, every five or ten minutes add two drops of ammonia for every ounce of developer that you are using. This additional ammonia is to take the place of the ammonia which has naturally evaporated. When you have obtained sufficient density in the highlights, then your plate is sufficiently developed, and you should wash and fix the plate in the usual way. The temperature of the developer should be between sixty-five and seventy degrees. The colder the developer the slower the action. If the developer is too warm the action would be rapid, and the plate would have a tendency to soften, frill and fog in the shadows. If you find after fixing the negative it is extremely yellow, you can remove this color, or part of it at least, by clearing with the alum clearing solution according to the formula given in lesson on Reducing. Before clearing, however, unless the shadows appear with good strength, it is advisable to dry the negative, and make a proof before removing the color, as oftentimes the yellow color in a negative is the salvation of an extremely under-exposed plate with weak shadows, for it slows the printing and permits the light to penetrate deeper into the shadows, resulting in a much more solid print.
Caution. Do not add more ammonia to the developer until you require it; that is, when the developing appears to have ceased, and the plate is very thin and lacks strength, then add more ammonia, and add it cautiously. Remove the plate from the developer while adding the ammonia, and rock the tray to thoroughly mix the ammonia with the developer, then return the plate to the developer. Too much ammonia will cause a fog, so work cautiously, and after a few experiments you will be able to judge to the drop how much ammonia to add, and by the proper care and pains you can produce negatives with fair detail in the deepest shadows from plates that if developed with soda developer would render almost clear glass. This formula and method of development is only recommended to those who have carefully worked all the previous developers and formulae given in this volume, for as each different formula is given for a particular purpose it is taken for granted that the reader has had the benefit and experience of all the previous instructions before attempting to apply this method, and for the large majority of exposures any of the former formulae are preferable. Even for instantaneous work usually the metol - hydro developer will, if properly manipulated, render all detail that the given exposure will supply. But those who enjoy experimenting will find some interesting results can be obtained with ammonia developer; yet it is not always reliable, and therefore is not recommended. Proof prints should be made from each experiment, with complete data noted on the back. This data will aid you in your future experiments, and therefore proofs and all data should be carefully filed.