Wet density readings (widely used in the Graphic Arts industry for checking continuous tone color separation negatives, positives and masks) are often misleading because of density changes which take place when the films are dried. These density changes appear to be complex phenomena, the basic causes of which are not fully understood. The influence of many individual factors has been studied. Chemical composition of the fixing bath and temperature and humidity of the drying air have been identified as the principal factors in Graphic Arts applications. It is shown that adjustment of the fixer formula to reduce the extent and rate of emulsion hardening can substantially reduce the magnitude of wet-to-dry density change, thus increasing the reliability of wet densitometry. A practical fixer formulation is presented which can be conveniently prepared in most shops. The use of controlled drying has been shown to improve the reproducibility of results.