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.
Temperature. All wash waters and baths should be exactly the same temperature from the beginning of the washing of the prints until they are ready to mount, the proper degrees being from 65 to 70 Fahr. If the temperature is uniform throughout all operations, the prints will be kept from softening and blistering.
Keeping Qualities Of Sensitized Paper. When buying sensitized paper in quantities, great care should be observed in storing it. Most of these papers are dated by the manufacturer, and the keeping qualities are generally good for about four months from the date stamped on the back. If allowed to become damp the paper will spoil and print poorly, disagreeable tones being the result. If kept in too warm a place the paper will rapidly turn yellow and it will be impossible to make prints with pure whites. The paper should, therefore, be kept in a cool, well ventilated cupboard or drawer.
Action Of Light. Whether the paper has a collodion or a gelatin-chloride coating the action of the light is the same. This coating contains nitrate of silver and is sensitive to the light. When exposed to strong daylight it turns dark. Gas, electric, or lamp light has practically no affect upon it whatever; neither will it be affected by exposure to very subdued daylight for a short period of time. Therefore, all operations in handling the paper when placing it in a printing frame may be conducted in weak daylight, instead of in the dark room.
Printing. The sensitive emulsion of gelatin and chloride glossy paper is only on the surface and does not penetrate through the film. Because of this, the printing will be only on the surface of the emulsion and the wash waters and chemicals used in toning will not penetrate beyond this surface. Therefore, printing for glossy surface papers is carried only a little farther than you desire the finished print; just sufficient to make up for the strength lost in the washing, toning and fixing, which is about one degree.
40. The length of time required for a print to be printed to the proper depth depends not only on the quantity and brilliancy of the light, but also on the density and color of the negative. A negative with a yellow tint will print slower than one of gray. Under any circumstance, without regard to the quality of the negative, print for the highlights - the shadows will take care of themselves.
Printing From Negatives Of Different Strength. Negatives of various kinds require different depths of printing. For instance, a hard negative - or a slow printing one - will require longer printing, in order to tint the highlights. Consequently, you must print deeper into the emulsion than with a soft or weak printing negative. Because a hard negative prints slowly, it gives a more solid print than a thin negative. On account of the great density of the plate, the highlights are restrained from printing until the shadows have received considerable exposure to the strong light. The light, therefore, penetrates the emulsion deeper in the shadow portions than in the highlights. By the time the highlights are properly printed the shadows will be printed sufficiently deep. By printing both highlights and shadows slowly they will not lose any of their strength in the washing. Therefore, a hard negative - contrasty and a slow printer - should not be printed quite as deep as a soft negative. Print until the highlights are but slightly tinted, or about one shade deeper than you would desire the finished picture to be.