There is probably a greater volume of photographic legend concerning glycin than any other developing agent. Those who are familiar with it regard it very highly and there are some who speak of it in tones of actual reverence.
Glycin, when compounded with carbonate, is a slow working, though powerful, developing agent that is capable of producing very handsome and exquisitely graded negatives. When compounded with trisodium phosphate it is somewhat faster than with carbonate. When used with sodium hydroxide, it is very active indeed, and will produce negatives on badly underexposed film. Because of its capacity for rendering gradations it is well suited for landscapes and for softly lighted shots such as women’s and children’s portraits, high-key work etc. It is claimed that glycin is almost non oxidizable by air. This is only partly true, but concentrated stock solutions keep their developing power very well even though they acquire a brown color with age.
When fresh, glycin is a white crystalline powder. On storage in air, it gradually becomes cream or fawn-colored. In some cases it will turn black. To prevent this, a preservative is used in the commercial product. The american brands usually are packed in an atmosphere of sulphur dioxide or with a trace of sodium bisulphite, and as a result have a “sour” sulphur-dioxide odor. Foreign brands seem to contain organic substances which often interfere with the production with true black tones when glycine is used in paper developers. The trace of sulphur dioxide or bisulphite found in american brands is harmless, since both of these substances are converted into sodium sulphite by the alkali in the developer and have no undesirable effect.
Note: Photographic glycin should not be confused with the medical “glycine” which is amino-acetic acid or glycocol. To avoid this confusion, some manufacturers market photographic glycin under trade names such as Athenon or Monazol.