Cycle for a dishwasher to reduce filming

Abstract

A method for operating an automatic dishwasher in a manner to minimize the deposition of contaminants or filming on the dishes is provided. The present invention contemplates that objectionable filming on washed dishes or dishware items may occur if residual water left on the dishes at the end of the final drain step is not given a chance to drip off or drain from the dishware. The present invention provides for a drip period following the final drain step in the dishwashing cycle. The drip period provides an opportunity for gravity assisted draining or 'drip-off' of residual water from the dishware items prior to evaporation such that the minute particles which are suspended in the residual water are not deposited onto the dishes. During the drip period, rapid evaporation of residual liquid from the dishware items is prevented. This is accomplished, in part, by keeping a vent aperture in the dishwasher door closed for a predetermined time after the final rinse such that the relative humidity remains high in the dishwasher tub and by delaying the energization of the heater such that evaporation is not promoted by the introduction of heat into the dishwasher tub. The present invention further contemplates the use of a purge operation prior to the rinse step wherein a small amount of liquid is supplied into the dishwasher, briefly recirculated and then discharged to drain. The combination of the purge operation with a drip period after the final drain minimizes filming on the dishware items within the dishwasher.