I've noticed recently that when mixing up fresh fixer, there is some white precipitate in the concentrated fixer. I've just mixed it with water, put it though a paper coffee filter and used it. It seems to work just fine. Should I be worried? The fixer is Ilford Hypam (5 litres) and I've just seen from Ilfords data sheet that they recommend it be used within 6 months of opening. I've been using it for 2 years and it was given to me already opened by someone who was giving up film photography so goodness knows how long it has been opened. I guess that's why its forming precipitate. Its actually quite expensive for me to buy so I'll probably keep using it until it stops working. I suppose if it fails to clear a film I can just buy some fresh fixer and re-fix the film. Has anyone else come across this problem?