Photographers' Formulary Residual Hypo Test - 200ml

Photographer's Formulary Residual Hypo Test is a simple chemical test that can be used to determine if a print or filmstrip has been adequately washed.

The test is based upon the formation of a yellow stain of silver sulfide - silver thiosulfate on the white of a test print (or the clear area of a negative film strip) when the test solution is applied.