Resuing Fixer?

[rxmd]

The instructions on fixer about "exhaustion" are misleading. I have never seen instructions, which, when tested, really meant that the fixer was "exhausted". Under average use, they have you throw the fixer out when it gets to about 6 g/L silver, the limit for fixer to still produce negs that store well long term. Fixer will keep dissolving the silver out of your negs for a LONG time after it gets to 6 g/L but they are not long-term stable. If you really want proper fixation and good storage for your negs, use a two-bath approach, testing regularly and throwing bath 1 out after it gets to 6 g/L silver.

If you want long term stability of the negs or prints, use FRESH fixer.

As Marty suggested, you can get both the efficiency of reusing fixer, and the archival stability of fresh fixer, by using a two-bath approach.

Keep two bottles of fixer, labeled A and B. Pour your somewhat-used fixer into A, and your fresh fixer into B.

When fixing your negatives, fix using somewhat-used fixer A first; the somewhat-used fixer will still have enough dissolution power to get most of the unwanted silver out of your negatives. Then, fix the same film using B. The fresh fixer will do a good job of getting the remaining silver out of it. After a while, pour out the spent fixer A (for silver reprocessing or whatever you do with your spent fixer). Pour the formerly-fresh fixer B into bottle A and keep reusing it. Pour some new fixer into bottle B. Start over.

The reason this works is because the dissolution of unexposed silver out of negatives is a result of the gradient of silver concentration. The unexposed silver goes wherever there is less of it. So whenever you fix a film, you get the unexposed silver content in your negative down to whatever silver content you have in your fixer. So when you keep using your fixer for a long time in one-bath fixing, all the negatives you process will have a little residual silver left, because the concentration gradient is not strong enough.

On the contrary, in two-bath fixing, you have a first solution of fixer (bottle A) that has already some silver in it, but still gets most of the silver out of the negatives - as Marty has pointed out, spent fixer works for a long time, just not perfectly well. After this, you have a negative with a little silver left in it for. Now you use a second solution of rather fresh fixer (with a low silver content, bottle B). Because this is fresher, the concentration gradient is strong enough to get the remaining silver out of the negatives, resulting in very good archival stability. And because there is only a little bit of silver left in the negatives when you move over to bottle B, the fixer in bottle B will remain fresh for a much longer time than in one-bath fixing. After a while, your bottle B fixer will become a little bit spent, at which point you pour it over into bottle A and start over.

That way, using two-bath fixing you can easily use your fixer several times as long without sacrificing archival stability, or, in fact, while enhancing it.

 

[Ljós]

Two-bath fixing

Two-bath fixing

Hat off to rxmd for the thorough description of the two-bath-method!
I have been using this method for years now, too, and I can only see advantages.
For archival fixing of FB-paper this is also a good idea, just keep in mind to have separate fixer for your film and your paper-fixing.

My films never spend more than 4-5 minutes in the fixer (Ilford Rapid 1+4), and I can always be sure that they are archivally fixed because the last two or so minutes are in "fresh" fixer.

Greetings, Ljós

Edit: Also the Ilford fact sheet linked above recommends the two-bath method.