Fixing Film and Paper: when long is too long
23/04/21 17:22 Filed in: Fixing
I’ve been reading a couple of threads recently that have covered aspects of fixing. It seems to be a rather difficult part of the process because of some widely spread internet myths.
I’ve been reading a couple of threads recently that have covered aspects of fixing. It seems to be a rather difficult part of the process because of some widely spread internet myths. For instance, it was stated by someone to fix for ten minutes to remove the anti-halation dye! Another statement said that a minimum of 5 minutes was needed to fix a modern films properly. Unfortunately, this advice will damage your precious film.
Fixing has been well researched for decades and so I dug out a couple of books to check on this.
I have the Ilford manual of Photography 1951 and in it it says about fixing with Hypo (Sodium Thiosulphate):
“Hypo itself has a weak solvent action on the silver image and while this action is negligible during the time required for fixation, prolonged immersion in the fixing bath results in considerable reduction in density, and the effect will be very marked where fine grain negative emulsions and printing papers are concerned”. Here it refers specifically to slow to medium speed films and chloro-bromide paper, both of which are fine grained.
Also, from the Gevaert Manual of Photography, 1962
Talking about rapid fixers containing the now common fixing agent Ammonium Thiosulphate:
“Prolonged immersion in a rapid fixing bath will reduce the silver image, paper emulsions may also change colour, and fine grained emulsions are particularly susceptible to their reducing action. If, for convenience, one of these rapid fixers is used the instructions should be followed carefully.”
The instructions are the same for both fixers. Fix for twice the clearing time. A good rule of thumb is that if it takes a rapid fixer more than two minutes to completely fix the film (one minute to clear the film of milkiness plus one minute) it’s time to change your fixer for fresh. This is because the fixer is carrying to much of the dissolved silver by-products and has reduced capacity.
Finally, the most modern tabular grain films may well be affected even more. These films have fine, flat silver halide crystals that present even more surface area to the dissolving powers of thiosulphate.