Just mixed up some Sprint Rapid Fixer concentrate at 1:4 and added the listed amount of alum to make a hardening fix for film. The solution came out slightly milky in apperance. There was some white precipitate in the concentrate that I filtered before mixing. The Sprint is about 6 years old and is in an airless cubetainer (kind of like 'box-o-wine' comes in). But I have noticed some air has come into the container. Every other time I've mixed film strength fixer I remember it being clear. I tried it out on 2 rolls of 35mm and it cleared the film in a normal fashion but I was just wondering if anyone else had come across this sort of thing.