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.
Not washing the hands often enough when handling the different trays. Wiping the hands on dirty towels. Toning the prints too near the fixing tray. Careless handling of the hypo. These are some of the many causes for hypo stains.
No Strength Or Brightness To Prints After Fixing. Extremely slow toning in the gold bath; gold bath being too alkaline; extremely slow toning in the platinum bath; using too much alkali in the wash waters would cause the prints to become weak and lose all brilliancy after fixing.
Prints Bleaching. All prints will grow somewhat lighter in the hypo, but this is not bleaching. A print that bleaches loses all detail in the highlights and the shadows become weak. If the hypo bath is acid the prints are sure to bleach. Always test your hypo bath and neutralize it, or make it slightly alkaline if necessary.
Bleached Prints. Prints will bleach if a poor quality of borax is used. Powdered borax frequently contains impurities, and it is for this reason we recommend the use of crystal borax. Always aim to have the borax solution a saturated one. If you use a hypo bath too strong it is apt to cause bleaching. In preparing hypo by hydrometer test, carefully test the hydrometer from time to time, as the paper scale inside of the tube designating the strength is liable to slip down. If this happens it would register the strength of the solution incorrectly, probably causing it to be three or four times too strong. To test your hydrometer place it in plain water. If it is correct, it will test zero.
Red Spots. Red spots on paper may come from a number of causes. The most common are unclean trays, finger marks, bubbles, and preservative chemicals still in the paper. When from finger marks they can be easily recognized.
294. When the spots are round, or oblong, and have defined edges, they are from bubbles and can be avoided by sliding prints under the water in the first washing. If the red spots are uneven and scattered over the paper, or if the prints act as if they were greasy when they are in the washing water, the trouble comes from oil or grease, which may come from the hands, trays or water.
295. This trouble can be overcome by adding one ounce saturated solution of carbonate of soda to each gallon of the first wash water, handling prints over in this water for five minutes.
296. This alkali cuts off all oil or grease on the prints and neutralizes the acid preservative chemicals in the paper. The six changes of clear water afterward wash out all trace of the alkali, and bring the prints up to the gold bath in a perfectly neutral condition.
297. Red spots which appear on the paper after gold toning can be removed by putting the prints in the gold bath face down and keeping them under the bath for four or five minutes before turning them face up, when the red spots will have disappeared. Should they not do so, put a drop of the platinum stock solution on the spot, which darkens the spot, and the rest of print tones up to it.