*This product is available for in store pick up only. Edwal Hypo Check - 3/4 oz. 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. If the addition of Hypo-Chek produces a cloudy precipitate, the bath is exhausted and the fixer should be discarded. A 3/4 oz. bottle provides about 800 tests.