How long does hypo last

[ColinRH]

I know, of course, that mixed hypo will deteriorate with use AND that it will deteriorate over time if left in a dish, but how long can it be mixed and not used before it needs to be discarded?
I ask as I sometimes only make a couple of 5x4 salt prints in 3 - 4 hours. Should it be discarded after x - hours?

 

[wildbill]

not all hypo is the same.
also depends on usage.
the kind I mix lasts for months

 

[Sirius Glass]

Until it goes out. That is why there is hypo test. Or it takes twice as long to clear film as it should.

 

[Gerald C Koch]

It depends on whether the fixer is acidic or not. Hardening fixers which are acid have a shorter life span than neutral or alkaline ones. If you are using a "plain" hypo bath it depends on whether it contains sodium sulfite as a preservative or not.

 

[RalphLambrecht]

I know, of course, that mixed hypo will deteriorate with use AND that it will deteriorate over time if left in a dish, but how long can it be mixed and not used before it needs to be discarded?
I ask as I sometimes only make a couple of 5x4 salt prints in 3 - 4 hours. Should it be discarded after x - hours?

Tetenal sells hypo test strips,which indicate how saturated the fixer is with silver salts.after 1-3g/l, it's time to mix fresh.unused fixer should be good;see the hypo test above.time to clear a film striptimes 2 is a good starting point;so are the manufacturer's recommendations.

 

[ColinRH]

Thanks all for the information.
I am using straight hypo for salt prints and for fixing PMK negs. Easy to check the negs hypo but for the prints it seems a visit to Tetenal is required.

 

[M Carter]

I use straight hypo for prints - just sodium thiosulphate and water - often. Nothin' else in the mix. Supposed to die fairly quickly, I've found it keeps for a very long time.

At the beginning of a printing session, I test the fix. Under safelights, I bend a strip of paper into sort of an "A" and hang it in a tray or small graduate of hypo, and fix for 3 minutes. Then I turn the room lights on (which exposes the paper), and put the whole strip in a graduate of developer.

If the fix is good, the fixed portion of the paper will be pure white - if the dev. is good, the unfixed portion will be dead black. For long print sessions, I'll do the same test several times to be safe.

I do test every keeper print for residual silver and for residual hypo - I leave enough margin for the drop tests so it can be trimmed off (even on properly fixed and washed prints, the droplets of tester will turn yellow or brown eventually).