Testing fixer

[wiseowl]

What's the best way of checking fixer (for prints.)?

For film I use the clearing time as a guide, needless to say that can't be done by watching paper. So how do you do it, based on number of prints, area of paper, do you do a film check, or is there another method?

Regards

Martin

 

[Bruce Osgood]

I use a water-wet test print and blot one corner dry, apply a few drops of KRST (1:9) and wait 2-3 minutes and blot it off.

If there is ANY stain either the fixer is shot or fixing was not complete.

 

[clogz]

Tetenal sell a so-called fixer bath test (test strips)
A tad pricey but they work ok.

 

[Doug Bennett]

I do a film clip test. I know that, for example, the TF-4 fixer that I use will, when fresh, clear a piece of film in about 30 seconds. When that time creeps up to 45-60 seconds, I take no chances and dump the fixer. Does it still have some life left at this point? Probably, but given that fixer is inexpensive, I prefer to play it safe.

 

[fschifano]

If you shoot and process your own 35mm film you can save the clipped leaders and use them as little test strips. See how long it takes for a piece to clear in fresh fixer and when that time gets close to doubling, it's time to dump the fixer. You might even consider it worth your while to sacrifice a roll of the cheapest B&W film you can find just for this purpose. For $2 to $3 US you can have a slew of test strips, since you need a very small piece to perform the test. I've found that if you soak the film in some water prior to the test, you'll get a more accurate result. This has the effect of swelling the gelatin somewhat so that the fixer can penetrate the emulsion more quickly.

 

[Foto Ludens]

I believe you meant "How long should you fix for," right?

I don't have an answer, but though that maybe your question was missunderstood.

these might help:

http://www.digitaltruth.com/store/formulary03.html
look at the "residual silver test" and "residual hypo test"
These should help you determine how long to fix and wash for. I haven't tried them yet, but I might, someday....

If this is not what you meant, and you just need to know how to test for fixer exhaustion, Photog Formulary has a product for that as well, although I use the "Edwal" equivalent (tests for silver content of fixer)

Hope this helps