What happens to outdated fixer?

[Cluster]

I am nearly out of fixer for my film developing. I had an old stock of unopened 1ltr bottles of Agfa ag-fix, maybe 10 yrs old.
A couple had been thrown out, but I thought that I would test if the fixer would clear some leader off-cuts of film that I developed today.
To my surprise, it cleared the small pieces in under a couple of minutes. Is it likely to clear all developed and undeveloped emulsion on an exposed film?

 

[ChrisR]

If it clears test strips it should clear a film, IMHO. Time to test it out!

I think one bottle of Ilford Rapid Fixer "went off" with little flaky bits in it, but they were easy to see when I diluted it.

 

[Cluster]

I tried it on a 36 exposure test roll (camera test that is..). It's fine, just like the stuff I was using before.

 

[VirtualAdept]

As an aside, what sort of time do you guys feel is acceptable in terms of clearing and fixing?

 

[Terrywoodenpic]

As an aside, what sort of time do you guys feel is acceptable in terms of clearing and fixing?

The rule used to be twice the clearing time.
However it does no harm to pop it back and give it more time.
Fixer exhausts from use not age.

 

[dmb]

As an aside, what sort of time do you guys feel is acceptable in terms of clearing and fixing?

Used to measure clearing time for freshly mixed fixer and note it on bottle. Tested clearing time again before each use if it went above 2x the fresh time then make a fresh mix as residual silver content had built up. Fixing time was then always twice clearing time.

 

[VirtualAdept]

Sorry, I wasn't clear with what I was asking.

When doing a clearing test, how long would you say is too long for it to be worth doing? For example, if its taking 4 minutes just to clear, thats an 8 minute fix. Is that the point you start thinking about mixing fresh, or would you be willing to go to 10/15 mins to fully fix film?

 

[Terrywoodenpic]

Sorry, I wasn't clear with what I was asking.

When doing a clearing test, how long would you say is too long for it to be worth doing? For example, if its taking 4 minutes just to clear, thats an 8 minute fix. Is that the point you start thinking about mixing fresh, or would you be willing to go to 10/15 mins to fully fix film?

Providing it is fully clearing it is still working. How long depends on your patience.
If it started to smell of ammonia. It is certainly time for fresh. Or if there is a deposit of sludge, which is a deposit of silver, and this can badly mark the film and can not be easily removed.
Fixer lasts longer if you use a stop bath, not just a rinse.

 

[john.margetts]

What happens to old fixer is that the sodium thiosulphate degrades to a mixture of sodium sulphate and elemental sulphur. My last bottle of fixer had a thick crust of yellow sulphur floating on top of the liquid. Clearing the film was very slow.

 

[dmb]

@VirtualAdept clearing time and hence fixing time does depend on both the working concentration and composition of the fixer as well as the film being fixed, Tabular grain films like Tmax and most colour films take a bit longer than cubic grain films. In the days I used to mix my own fixer from scratch I aimed for a start clearing time of 2 mins on cubic grain films, so 4 mins fixing time increasing eventually to 8 mins. These days I make sure I read the data sheets for the fixer and film to find base times that might alert me to problems.

 

[Terrywoodenpic]

Prepared fixer can be either sodium thiosulfate or ammonium thiosulfate or a mixture of the two and often an acidic buffering/ hardening component.
The higher the proportion of the ammonium thiosulphate the more rapid the fixing. Is is more often used for films but less often for papers, because if left in too long it can bleach them.