The Exhausted Fixer Lesson
Three prints from February have gone yellow in the margins. Not dramatically, but the white borders that were clean when they dried now have a faint straw tint, and the highlights in one of them have a brownish cast under daylight. These are prints I liked enough to put in frames, which is how I noticed. The cause, after some reading and one unpleasant realisation, is exhausted fixer.
Fixer dissolves the unexposed silver halide out of the paper so that it cannot darken later. It has a capacity, measured in prints per litre, and when that capacity is passed the fixer still looks and smells the same but no longer clears the paper completely. The residual silver compounds then slowly react with light and air and turn yellow or brown. In February I was reusing a litre of working-strength fixer across three sessions and perhaps forty resin-coated prints, well past what the bottle said, because it seemed wasteful to pour it away.
There is a simple test that I should have been using all along. A drop of the fixer on a scrap of unexposed, undeveloped paper should clear it to white within about a minute; if it takes much longer than twice the time of fresh fixer, the fixer is done. I tested the remains of the February bottle and it took nearly four minutes. Fresh fixer took fifty seconds.
Changes since then:
- Fresh fixer for every session, mixed one to four from the concentrate, and a litre is poured away after twenty 18 by 24 cm prints or at the end of the evening, whichever comes first.
- The clearing test at the start of every session, with the time written on the bottle.
- Fixing time doubled from one minute to two for resin-coated paper, with the print agitated for the first thirty seconds rather than left to float.
- A hypo clearing bath before the wash, which I had been skipping for resin-coated paper on the grounds that it does not absorb much.
The three yellowed prints cannot be rescued, as far as I can tell. I have reprinted two of them from the negatives and the third negative has a scratch I had forgotten about, so that one stays yellow as a reminder. The negatives, fortunately, were fixed properly in a different bottle, and are fine.