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.
Negative Will Not Fix. Caused by a hypo bath being extremely weak or too cold. A weak hypo bath, of course, is not strong enough to act upon the unused silver salts in the negative; while too cold a bath not being able to hold a great quantity of chemicals in solution, will not fix the negative, because in fixing it is necessary to dissolve the unused silver out of the emulsion and it is obviously necessary that there should be room in the hypo bath to hold this silver. One ounce of crystal hypo to four ounces of water is the correct proportion for the PLAIN hypo bath. The hydrometer test for making a PLAIN hypo bath is 70 degrees. Follow the formula in making the ACID hypo bath.
Fixing Bath Discolors After Slight Use. This is due to your failure to rinse the negative carefully after removing it from the developing solution, as the developer that is carried into the "fixing" bath soon oxidizes and turns the whole bath dark. Ordinarily, with a fresh bath this will not harm, but if it is allowed to become old the negatives will be apt to stain when fixed in such a bath. A PLAIN hypo bath discolors more readily than an ACID bath. The hypo is good as long as it will fix and leave no scum or stain on the plate. If you have no regular fixing box keep your hypo solution in a bottle and in a dark, cool place, and pour it in the tray only when you are ready to use it. Never keep your hypo or developer in a metal pail or can, as the metal would produce a chemical action which would result in the spoiling of your bath. If a scum forms on the surface of the bath, remove it before placing a negative in to fix. If allowed to remain on the bath the scum will adhere to the back of the negative, and when dry is very difficult to remove.
Softening Of Film In Wash Water. This will occur if your developer, hypo or wash water is too warm. Prepare a weak solution of powdered alum, say one-half ounce of alum in 10 ounces of water, and place your plate in this alum solution immediately after fixing, previously rinsing for a few moments. This alum will harden the film.
Negatives Dry Slowly. The room is either too cold or poorly ventilated. Ordinarily it takes a negative from four to six hours to dry. With good ventilation and a temperature of 70 deg. to (not over) 85 deg. Fahr., the ordinary coated plate will dry easily in three hours' time. Do not dry by excessive heat; if the temperature is much over 90 deg. Fahr., the emulsion will become soft and run off the glass or celluloid film, ruining the negative.
Negatives Appear Greasy When Dry. Lack of washing after fixing. This difficulty will not occur if fresh hypo solution is used and the negative is washed for the proper length of time (one hour in running water or in ten changes of water for the same length of time). The scum mentioned under the former DIFFICULTY, "Fixing Bath Discolors After Slight Use," is the cause of the greasy appearance on the dried negative.
Negatives Appear Gritty When Dry (Dirty). Caused by sediment in the wash water. Before placing the negative in the drying rack, wipe both sides of the negative carefully with a tuft of absorbent cotton thoroughly saturated with water. If you are using a washing box, clean it just before you are ready to wash the negatives. Sometimes negatives will collect dust and dirt while drying. This is caused by using dusty drying racks, or, if no racks are used, by placing the negatives on a dusty table or other support. Always lay a clean sheet of paper, or blotter, under the negatives while drying.