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.
Fifth. If the plate flashes up in from three to five seconds, or almost immediately after developer is flowed over it, the plate is greatly over-timed and should at once be placed in a tray of old developer and allowed to remain there while preparing a bromide bath of two ounces of a ten per cent, solution of bromide and four ounces of water. Transfer the plate immediately to this bath, allowing it to remain for two minutes. Then return to the tray of old developer for final development, and if necessary in order to obtain strength, finally finish the development in the normal bath.
Developing Plates Of Doubtful Exposure. There are times when one is obliged to make an exposure under circumstances which make it difficult to judge the exact exposure required. Under such conditions it is always advisable to make two exposures, one of which should be according to your judgment of the proper exposure; the other give a longer exposure, or, in other words, over-time it. Mark both slides, and make a memorandum of the exposure given, and when you come to developing, develop first the plate which in your judgment was the normal or proper exposure, starting it in normal developer. If it proves over-timed transfer it at once to the tray containing old developer. If it develops slowly, indicating under-exposure, add more water to the normal developer. The developing of this first plate gives you a key to the second plate. If the former was over-timed then you would start the second plate in old developer, and if the first was considerably over-timed, then you will need to restrain the second one considerably. You should then add to the old developer two drams of the ten per cent, solution of bromide. On the other hand, should the first plate prove under-timed slightly, the second plate should be developed in normal developer. Under all circumstances, your first plate supplies you a key for the treatment of the second one.
Judging During Development How Much The Plate Is Over-Exposed. It often occurs that the photographer, during the course of a day's work, makes a number of exposures, and, in his judgment, correctly times all of them. However, when he comes to developing his first plate he finds that he has erred in his judgment, and the plate is over-exposed, realizing that all plates exposed that day are over-timed. It is a question now as to how badly each plate is over-exposed and how to treat the remainder of the plates so as to produce good results. All will depend upon the first plate developed. This first plate is your key and will indicate how much over-exposed the remainder of the plates are.
219. If they are only slightly over-timed, it is advisable to develop them in the old normal developer from the start. You must bear in mind that this old, or once used normal developer, must not contain any other restraining properties. In other words, this developer has been used as prepared according to the formula and has not been altered in any way. If, for instance, bromide had been added to the normal developer, this would cause the old developer, when used on only slightly over-exposed plates, to develop too contrasty. Therefore, use old developer which was prepared normally and has developed one lot of plates only. Such a developer usually will restrain the plate sufficiently and good crisp negatives will result. However, if the first plate developed appears quite hazy, it may be well to add a few drops of a ten per cent, solution of bromide to the used normal developer. It is well, under such circumstances, to develop each plate separately until you arrive at a developer that is sufficiently restrained to produce good, crisp negatives from the start; then the remainder of the plates should be developed in a developer made accordingly.
220. After a little practice one will be able to judge by the appearance of the first plate developed exactly how much the others are overtimed, and will know exactly how much restraining is required.