Edwal Hypo-Check, Chemical Test for Exhausted Film & Paper Fixers, 3/4 Oz. Edwal Hypo Check tests your fix solution for exhaustion due to silver saturation. One or two drops will test the fixer and, if the fixers still OK, no harm has been done to the bath. A 3/4 oz. bottle provides about 800 tests. If the addition of Hypo-Chek produces a cloudy precipitate, the bath is exhausted and the fixer should be discarded.