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.
Prints Cracking. Using extremely cold water for washing is apt to cause the prints to crack. If you are careful about properly flattening and handling the prints during the entire manipulation, there should be no trouble. If the paper is exceedingly dry it is likely to crack. Manufacturers of Aristo Platino paper recommend the use of a moistening box. This box is made of galvanized iron, with a close fitting hinged cover. In this is placed a sponge tray. In order to have the moisture circulate beneath the package of paper, a false bottom is used. This is made of slats. If you have very dry paper, it is a good plan to place it in a box of this kind until it has become sufficiently moistened.
Rubbed Places. Rubbed places on face of print which do not show until prints are dried are sometimes caused by rubbing the face of the print on the bottom of tray during washing and toning. When this trouble is experienced examine the bottom of toning trays, also try handling prints face up.
316. Rubbed or marred places on face of print may also be caused by heavy pressure of fingers on back of prints when pouring off wash waters, also by the pressure of fingers on the back of paper when it is being adjusted to the negative.
Blisters. Blisters are caused by a change of temperature in the baths or water, and will usually make their appearance in the hypo, or afterward. Putting prints in cold hypo bath and then into warmer water frequently causes blisters. This can be prevented by throwing prints into salt water after hypo bath; four ounces salt to the gallon of water.
318. Another plan, - after the prints are fixed gradually reduce the hypo bath by pouring off part and adding water; repeating until down to clear water, handling prints over all the time. Finally, transfer to regular washing tray.
320. Too much carbonate of soda in the first wash water will cause blisters. When this is the cause they sometimes appear in the first wash waters before toning. If you experience this trouble, reduce the amount of carbonate of soda in the first wash water, or do not use it at all.
321. Another cause of blisters is gas, or air, in the water. The presence of gas can easily be detected. Fill a glass with water directly from the faucet. Examine it by holding the glass up to the light. The gas will be seen as minute bubbles rising to the surface and clinging to the sides of the glass. In some cases the water is so heavily charged as to produce a slight effervescing noise when the ear is held close to the surface of the water. Water containing gas should be allowed to stand in a barrel, or tub, for from six to eight hours before using, to allow the gas or air to pass off.
322. Extremely old paper, or paper that has been kept in a warm atmosphere and which therefore ages rapidly, is apt to blister. By treating the prints to a strong salt bath after fixing, this can be overcome to a certain extent.