How steep is fixer exhaustion curve?

[Duggbug]

I had a liter of Ilford Rapid Fixer working solution from a few weeks ago. Tested ok. I printed about ten 8x10 sheets, and afterwards tested it again and it showed cloudy: exhausted.

Are the last prints toast? Or is there some leeway with the definition of “exhausted”?

 

[randyB]

They should be ok. You can always mix up some fresh fixer and re-fix the prints. I have not had much luck with the Ilford rapid fixer, it works ok for a few weeks and then starts to sulfur-out, Of course I don't know how long the concentrate sat on the dealer's shelf. I have also had Kodak rapid fix concentrate and working solution go bad--sulfur-out-- but it was rather old--1.5 years old. I now mix powder fix for film and prints..

 

[halfaman]

Precipitates on hypo check does not indicate explicitely fixer exhaustion, but it is not far away. You can perform a silver retention test on your prints with sodium sulfide (Kodak ST-1) to check if they are properly fixed.

 

[Doremus Scudder]

Hypo Check is not really sensitive enough for determining fixer exhaustion for fiber-base prints if you desire "archival" or "optimum" permanence. It's okay for film and RC prints.

If in doubt, simply mix new fix and refix whatever prints your need to from the session in which the fixer tested bad.

For film, the clearing test is a more reliable measure of fixer exhaustion. For prints, using throughput recommendations from the manufacturer and then testing for residual silver (ST-1 or KRST tests) is a good idea. This works for both RC and FB papers.

Best,

Doremus