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.
Action Of Developer On Over - Exposed Plates. A plate that is over-exposed will flash up quickly, as soon as the developer is flowed over it. The quicker an image appears or flashes up the more it is over-exposed. The image on a plate or film, normally exposed, should appear in not less than one-half minute, much depending upon the strength and temperature of the developing solution. Warm developer will develop more quickly than cold. Strong developer will also develop more rapidly than normal or weak developer. The entire outline of the image on a normally exposed plate will generally appear in from thirty to fifty seconds, and the image on the plate will gradually continue to grow, until the entire image is developed. The image flashing up in from five to eight seconds is over-exposed and must be restrained immediately, and the amount of restrainer must be judged by the rapidity of the appearance of the image. The quicker the image appears the stronger must be the restrainer. The following suggestions may be of service to those whose practical experience in the handling of overexposures has been limited. These suggestions are based on the presumption that only pure chemicals are used in preparing the developer, and that they are mixed according to the formula and, of course, the plate must be started developing in normal developer.
First. If the image appears in thirty to forty seconds, the exposure is normal and should be developed to completion in the normal developer.
Second. If the entire image appears in eighteen to twenty seconds, the plate or film has been over-timed beyond the latitude for development in a normal bath, and the plate should be restrained at once, either by adding one-half old bath to the normal developer, or by transferring the plate to a tray containing old or once used developer, allowing it to remain in this bath for two minutes. If then it shows too much contrast, rinse it in clear water. Then return the plate to the tray of normal developer and conclude the development in this tray.
Third. If the image appears in fifteen seconds, the plate or film is considerably over - timed, and about ten drops of a ten per cent, solution of bromide should be added to the old developer, and the plate transferred at once from the normal bath to the restraining bath. The tray must be agitated continually and the plate examined occasionally, and if the bath is not too much restrained, the development may be concluded in this bath.
Fourth. Should the plate flash up in eight to ten seconds, the plate is very much over-timed, and should be placed in a bromide restraining bath, made up as follows: To three ounces of water add one and a half drams of ten per cent, solution of bromide. Immerse the plate in this bath for one minute. Then transfer to a tray containing old developer, and conclude the development in this bath. Should the plate, or film, show signs of over-restraining and develop too contrasty, then return the plate to the normal developer.