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.
Plate Developed Too Far Before Restraining. In case the development has been carried too far in the normal developer before restraining, and you have clogged the shadows, then it will require further development in the restraining bath. In other words, allow it to remain in the restraining bath considerable longer so as to build up the required contrast which must be obtained before the plate is fixed. A plate of this kind may appear extremely dense, so dense that it is almost impossible to see through it when holding it up to the light. This, however, must not alarm you because you cannot injure the plate no matter how dense it may be, as after fixing you reduce the entire plate to where you want it, and you will have obtained a negative of good printing quality.
Treatment Of A Plate Which You Know Before Developing To Be Over-Timed. If you are aware in advance that a plate is over - timed, then in place of starting to develop it in normal developer start it in old developer first. If you have no old developer on hand, add a few drops of bromide solution to fresh developer. This will answer the same purpose.
208. Always have on hand a ten per cent, solution of bromide of potassium. Have it ready in case of over-exposure. A few drops added to the developer will add much to your restraining. If you have started a plate in normal developer, and you find it slightly over-timed, and needs restraining, do not add bromide while the plate is in the solution, but remove the plate, holding it under a tap of running water. While adding the bromide to your bath, rock the tray thoroughly, thus mixing the chemicals. Then return the plate to the bath. This must be done rapidly, because even though your plate is removed from the bath it will keep on developing.
Treatment Of Plates Slightly Over - Exposed. In case the plate is slightly over-timed, and needs only a little restraining, we would advise using only half old and half new developer. The old developer will have sufficient bromide in it to restrain the shadows while developing until the highlights are carried to their proper strength. Sometimes a plate that has been only slightly over-timed may be restrained too much, and the consequence would be that you would produce a contrasty negative with no detail in the shadows. As soon as a plate during development shows signs of too much contrast, immediately rinse in plain water, then place it in a normal developer, in which conclude the developing. This may also be the case with very much over-timed plates, where a too strong restrainer is used. If you find the plate building up with too much contrast, immediately rinse the plate in clear water, and transfer to normal bath.
Practice Work. In preparing this instruction, you make two exposures of the same subject under the same conditions, over-exposing both. Develop one in normal developer, and the other treat according to instructions given in this instruction for over-timed plates. Dry the negatives, and make good proof prints. Carefully note on back of prints which method of developing was employed, and any data relating to the manipulation, such as time required for complete development, first appearance of image indicating over-exposure, how restrained. Each print must bear the exposure given; this is important.