Glassware washed in an automatic dishwasher occasionally develops a cloudy film, which may be one of two different problems.

Hard water film is caused by very hard water or not enough detergent to soften the water. A failure of a home or municipal water softening system may temporarily make the water too hard. If vinegar applied to the film spot for a minute or so removes it, this is a hard water film. You can reduce this problem by using the maximum recommended amount of detergent, or stop it by installing a water softener. Also check to be sure the detergent cup fits tight and works all right so detergent is released at proper time in wash cycles.

Silica film is caused by high phosphate detergents in very hot (above 140 F.) water that has been softened. Insufficient rinsing also increases this, since detergent is not removed. This begins as a colored film (like oil in water) which can be removed by scratching with a pin. Later on it become cloudy and cannot be removed by scratching. You cannot remove it with vinegar or other acids; it is permanent. The glass is permanently etched. Some glass is more resistant to this than others. You can slow the buildup by using no more detergent than needed for soil removal, using water no hotter than 140 F., and loading so all detergent is rinsed off.

This article was written by Anne Field, Extension Specialist, Emeritus, with reference from the Soap and Detergent Association.



MSU 2003