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.
62. Plate Slow in Starting to Develop - This difficulty you can overcome by being careful that your developer is not too cold. The temperature should never be under sixty nor above seventy degrees Fahr. Insufficient carbonate of soda or too weak carbonate and poor quality of soda will slow the development. Prepare your sodas by hydrometer test. Always bear in mind that the carbonate of soda opens the pores of the emulsion on the plate and allows the developing agent (pyro) to act; therefore, if there is no carbonate of soda, or if it is extremely weak or of poor quality, the plate would develop very slowly. If the plate refuses to develop at all, you will find you have omitted either the Carbonate or Pyro Stock Solution. If the plate is extremely under-timed it will naturally start slowly. (See Chapter IV (Developing Under-Exposures), Developing Under - Exposures.) Slow developing is not a bad fault, however, as it is better to have your plate start gradually than to have it start fast. Starting slowly will enable you to better judge whether your plate is under or over-exposed, and the slow action of the developer will enable you to treat the plate before it gets beyond your control.
Lack Of Detail In Shadows. If you develop your plate according to its exposure you will be able to overcome this difficulty, providing of course, that the plate is not too badly under or over-exposed. If your plate is under-exposed and you treat it as such, you will produce more detail than if you developed it in the ordinary way; but of course if badly under-exposed you will not be able to get a great deal of detail in the shadows, no matter how you alter the developer. In case of an under-exposure, the first thing to consider is how to prevent the highlights becoming harsh and contrasty, and at the same time producing detail in the shadows. The developing agent (pyro) must, therefore, be weakened. In case of an ordinary under-exposure, simply transferring the plate into fresh water for ten minutes and then returning it to the normal developer will generally produce detail in the shadows.
On the other hand, if the plate is badly under-exposed a new developer should be prepared at once, and this must then be made according to your instructions on Developing Under - Exposures, Chapter IV (Developing Under-Exposures), using only half the quantity of developing agent (pyro), but the same amount of sodas and double the quantity of water. If the plate is overexposed you would naturally think there would be plenty of detail in the shadows. The exposure has provided this detail, but in over-exposing a chemical fog is produced, and if the plate is not treated as overexposed you will produce gray, weak, foggy shadows and there will be no strength to the detail. A plate of this kind must, therefore, be developed in a developer which contains a restrainer. Ordinarily, by transferring a plate from the normal developer to the developer in which plates had previously been developed, will restrain the shadows and prevent them from fogging over; but in case of extreme overexposure the plate must be specially treated with bromide. (See Chapter VII (Instruction In Landscape Photography),Developing Over - Exposures.) In the instructions for developing you are told that old developer contains bromide which has been liberated from the plates which you previously developed; therefore, this old developer makes a splendid restrainer.