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.
Blotters. The life and usefulness of blotters is increased by keeping dry. Spread them out to dry when not in use.
Yellowish Stains. 1. Weak or overworked fixing bath.
3. Not quickly and thoroughly immersing prints in the fixing bath.
5. Unclean fingers will cause stains, and the hands should be rinsed often to keep them free from hypo while developing.
6. Unclean trays cause stains.
Brownish Stains. 1. Brown spots or stains are caused by using a fixing bath not properly mixed. (See fixing bath formula, paragraph 977.)
3. Not separating prints thoroughly in running wash water. Prints should be well separated in the wash water to insure the removal of chemicals as quickly as possible.
2. Under-exposure and forced development.
3. Handling paper in unsafe light.
2. Dark spots and streaks are also caused by failing to rinse prints in acid water between developing and fixing. Prints should be quickly and thoroughly rinsed after development and transferred immediately to the fixing bath.
White Spots. White spots are caused by air-bells forming on the surface of the print during development. Rubbing the surface of the print during that manipulation will break any air-bells that may form, and prevent this trouble.
Bluish Tones. Blue tones are caused by under-exposure and forced development; also caused by lack of sufficient bromide of potash in the developer. At least as much bromide as is called for in the formula should be used, and if necessary the amount should be increased. The amount of bromide necessary varies on account of local water conditions, different makes of chemicals used in the developer, etc.