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.
Developing. We will suppose that you have made your prints and are ready to develop. Decant a portion of the bath into a rubber tray, which has not been used for any other purpose. We would advise that you never use this tray for other purposes than to hold the platinum developer. Use sufficient developer to cover the bottom of the tray, at least one-half inch deep.
544. Develop the print by sliding under the developer face side up with a steady motion, watching for any air-bells which may appear, and expelling them at once. It should require from thirty to sixty seconds to develop a properly exposed print. A longer time in the developer will do no harm. In fact, prints from contrasty or hard negatives are much improved in the half-tones by prolonging the development, and warm developer will also assist in overcoming harshness.
546. As before stated, the developer may be used over and over again, by adding a little new to the old bath from time to time. If the bath becomes over-charged with chemicals from the paper, the resulting tones will be poor the highlights will bleach. You should therefore watch the developer carefully when using old developer, and just as soon as you notice a change in the quality of the print, make up an entirely new bath. If the developer is too cold you are likely to produce granular prints. The same effects will be produced if the developer is too weak. Rock the trays frequently to prevent markings caused by scum, which is apt to form on the surface of the solution, if the latter is allowed to stand idle for any length of time.
547. It is also advisable to filter the developer before using, so as to remove all particles of dirt, as these particles of dirt settling on the print when first placed in the developer are apt to cause white spots. If the developer is too warm the resulting tone will be brown black. A slightly under-exposed print may be often coaxed up by raising the temperature of the bath and leaving such prints longer in the developer. However, a print that flashes up black will be of no use, as it has been over-printed and even if developed by only a dip would give coarse, mealy, clogged shadows and no half-tones.
Using Two Baths. Too cold a bath will give you muddy, harsh shadows and very contrasty results, without detail in the half-tones. When using a warm bath beware of over-printing, as the developing must be carried farther. A good plan is to have two baths, one cold and the other warm. A print that is slightly over-printed, place in the cold bath first and then transfer to the warm bath, or vice versa. You will find this will produce a great improvement.
549. During the hot summer days it is not advisable to unduly delay the development of prints; if possible, develop within one hour after printing. Extra heavy papers require much longer development than the thinner ones. They may be developed as long as two minutes in the developing bath, without injury. All papers produce better prints from a full development. Use good size dishes and plenty of solution, and should the prints appear gray and granular, one of the following reasons will be found to be the cause: 1 - Under-development; 2 - Granular or weak negatives; 3 - Developer too weak or possibly too cold.
550. When you have finished developing pour this old developer into a separate bottle and label this bottle "Old Developer." The next time you develop decant the clear solution, being careful not to disturb the sediment which settles to the bottom of the bottle and add a little of the fresh stock solution, enough to make up the usual quantity of bath.