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.
Development Of Normal Exposures. If you want a steady quality of negatives you must be able to reproduce identical conditions in your dark room every day, if you cannot, you will not reap the reward you desire if even exposures were made in the field or skylight room. Buy only the best chemicals, keep fresh solutions made with pure water, always test the temperature of the developer by means of a thermometer, using it at a temperature of between sixty-five and seventy degrees Fahr., and maintain this temperature during the whole period of development. Keep your trays, graduates, bottles and dark room clean, provide a proper fixing box and keep it filled with a fresh acid-fixing bath.
562. Accustom yourself to working far away from your dark room light, and to exposing plates during development as little as possible to its influence. Use sufficient solution to keep the plate well covered, and continue the development until the lights are sufficiently intense, and no longer. As soon as a plate shows under-exposure, add to the developer an equal quantity of water which may be somewhat warmer, so that there may be time for all possible detail to develop before the lights become too dense, your object being to get as soft a printing negative as you can. Continued action of normal developer will unduly emphasize the contrasts by giving abnormal density in the lights before all the shadow detail is out.
563. If the plate is over-exposed, the lights and shadows will appear simultaneously, and the negative will develop flat without contrast, unless a sufficient quantity of a one to ten solution of bromide of potassium is added to the developer, either in the beginning or as soon as over-exposure is noticed, the quantity of bromide solution to be added depending on the degree of over-exposure.
564. A few years ago the G. Cramer Dry Plate Co. put on the market their liquid acetone, and during this time it has earned a well deserved place on the dark room shelf. Acetone is a neutral liquid which replaces the alkali in developing solutions. Combined with sulphite of soda and a developing agent it makes a far more regular working developer than any form of alkaline developer can. As no alkali is used there is less danger of the film softening in warm weather, the false densities common with an alkaline developer are avoided and chemical fog from a developer which is too warm or too strong in alkali entirely absent. Liquid acetone should not be confounded with acetone-sulphite (a dry acid powder), which will not answer the purpose.
565. With the pyro-acetone formula, any temperature between sixty-five and eighty degrees Fahrenheit can be used with perfect safety. For tank development it is ideal, as the temperature need not be watched, though of course the higher temperatures naturally cause more rapid development.
566. With normally exposed plates, and any of our standard normal developers at seventy degrees, development should be completed in from five to eight minutes, depending on the factor of the developing agent used. If it is necessary to develop longer than eight minutes, investigate the quality of the chemicals used, the temperature of your developer and dark room, suspecting especially the quality of your carbonate of soda if using an alkaline developer, and of the quality of your sulphite of soda if using acetone.