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.
Blisters. Blisters are generally caused (if they do not appear until the prints reach the hypo) by too strong a hypo bath, or too much acid in the hypo; uneven temperature of developer, fixing bath and washing waters; final wash waters may be too warm. Prints may have been creased or broken while washing. Do not allow water directly from the tap to fall upon the prints.
Blisters On Sepia Prints. Blisters showing on sepia prints doubtless come from the insufficient use of hardener in the fixing bath, when making the black and white print. Too strong a solution of developer, or too long immersion in this solution will also cause blisters. A salt bath after bleaching may be used if blistering is excessive.
Round White Spots. These are generally caused by air-bells gathering on the surface of the paper when the print is first placed in the developer. Always slide the print under the developer, and if air-bells have gathered, break them with the tip of the finger.
Milky Deposit On Surface Of Prints. This is caused by using a hypo bath which is milky. The bath is either too warm, or too much acid was used; or, the bath was not allowed to settle before using. The deposit will do no harm if you remove it when placing in the wash waters. If there is any trace of milkiness on the dry print it can be removed with a wet sponge. Great care, however, should be taken to have this sediment removed while in the wash water.
Prints Developing Irregular And Freaky, And In Streaks. This will occur at times on all makes of paper. It is sometimes caused by using impure sulphite of soda, which contains sulphate, or by too much dilution of the developer. This difficulty usually occurs during warm weather, when the humidity is great. Keep your developers cool, and if this does not overcome the difficulty wet the prints thoroughly in clear water before developing. Usually a fresh developer used in hot weather will overcome these difficulties.
Edges Of Prints Discolored. All developing papers are more or less affected when exposed to gas fumes, such as illuminating gas, coal gas, sewer gas and ammonia vapors. It is also caused by using an insufficient amount of developer to spread evenly over entire print. Always keep the package of paper tightly closed when not in use.
Fine Black Lines On Surface Of Prints. These are generally found on the surface of glossy paper, but at times occur on the matte surface. They are caused by friction before developing and are commonly called " abrasion marks." This friction causes the silver in the emulsion to rise to the surface of the paper, therefore developing black. Oftentimes they can be removed during development by rubbing carefully with the tips of the fingers; or when the print is dry, with a tuft of cotton which has been dipped in alcohol. With matte surface papers these lines can be removed with a soft erasing rubber. Abrasion marks may be avoided entirely by the addition of 5 grains of commercial iodide of potassium to each ounce of developer used.
Round Or Irregular Dark Spots. These are caused by air-bells forming on the print when placed face down in the fixing bath and by failing to keep prints in motion. It is advisable to turn each print over several times after entering the hypo bath, to insure even immersion.
White Spots Irregular In Shape And Size. If a drop of water or saliva touches the surface of the print before printing, it will always leave one or more of these white spots. Extreme care should be taken to avoid the splashing of water from the sink. Never try to blow dust from a negative or sensitized paper, as there is danger of saliva coming in contact with either. Always use a camel's-hair duster for such purposes.
White Spots With Heavy Fine Lines. Are usually caused by finger marks. Perspiration from the fingers will leave a mark, on which the grain of the flesh will show. Avoid touching the surface of the paper with the fingers before printing and developing.
Difficulties - Manipulating Velox Papers. 231
Canary Yellow Tones, When The Non-Abrasion Bath Has Been Used, Or The Iodide Of Potassium Has Been Added To The Regular Developing Bath. This is a sure sign that the print has not been fixed sufficiently. The canary color should disappear entirely when properly fixed in a correctly prepared acid hypo bath. The entire disappearance of this color insures correct fixing.
Greenish Yellow Tones Where The Non-Abrasion Developer Has Been Used. This is caused from under-exposure and forcing in development. It will fix out if left long enough in a fresh acid hypo bath.