This is a very quick guide to testing your film fixer. Unless you make fresh fixer every-time you develop your film you might be using your fixer more than you really should. I have in the past pushed mine a little too far and have regretted ending up with poor negatives that required to be re-fixed. So now if I have any concern at all I test my fix or just make a new batch.
1. Retain the leaders that you are cutting from your film.
2. Pour some fixer into a container
3. Put the leader in the fix
4. Agitate the mixture and time how long it takes for the film to go clear
5. This is for how long you should fix your film .
Any more than 3 mins and I discard the fixer and make a fresh batch.
Aware of the Void 
What’s wrong with hypo check?
How can you test your hypo check?
I like the visual confirmation that actually testing the fix gives me. One less variable.
Fair enough!
Good advice. I do this every time, too. In fact, I have a graduated cylinder that I use just for this. I set a timer to count up while I’m prepping everything else. Unlike you, I fix for twice the time it takes to clear. But whatever works!
You teach me something every time I come here!
I have probably developed a couple hundred rolls, and honestly did not know that diluted fixer (1:4) could be reused.
Sad really…I have thrown away a ton of chemicals!
(I think I’m going to try the two bath method…)
Thanks and all the best,
Mark
Thanks Mark – I mix my ilford stuff 1+9 and it seems to last me between 20 and 30 rolls – but unless I just made it fresh I always test it. I have been told if you rinse between stop and fix it will last a bit longer also…..but I don’t always use stop so am kind of out of this habit.