I am just wanting to learn how the process works and when each step takes effect. I'm not really in that much of a hurry.
Fixing
The light-sensitive ingredient of photographic paper is insoluble silver halide. During development, previously exposed silver halides are reduced to metallic silver in direct proportion to the print exposure, but the unexposed silver halides remain light sensitive and, therefore, impair the immediate usefulness of the photograph and its permanence. Consequently, all remaining silver halides must be made soluble and removed through fixing.
Fixing Process
For optimum silver-halide removal and maximum fixer capacity, prints are continuously agitated in a first fixing bath for at least 2x the clearing time (typically 1-2 minutes), followed by an optional brief rinse and a second fixing bath for the same amount of time. The clearing time is the least amount of fixing time required to dissolve all silver halides and is determined through a separate test.
During the fixing process, the residual silver halides are dissolved by thiosulfate without any damage to the metallic silver forming the image. The resulting soluble silver thiosulfate and its complexes increasingly contaminate the fixing bath until it no longer dissolves all silver halides.
Eventually, the solution is saturated to a point at which the capacity limit of the fixer is reached. The fresher, second bath ensures that any remaining silver halides and all insoluble silver thiosulfate complexes are rendered soluble.
Fixing Time
By the time it reaches the fixer, each 16x20-inch sheet of FB paper carries 25-35 ml of developer and stop bath. The fixing time must be long enough to overcome dilution by these now unwanted chemicals, penetrate the emulsion layer and convert all remaining silver halides.
Now, you can decide if you want to turn on the lights before the fixing time is up, or if you want to wait until the process is completed.
