What is the most effective way to clean windows? The answer depends upon how soiled the windows are. Professional window cleaners use a sponge to apply liquid cleaner to the glass then they use a squeegee. If you use paper towels to dry the glass, be aware that some towels leave a film on the glass. Water by itself can be sufficient when cleaning lightly soiled glass. We recommend using an anomia based glass cleaner for heavier soiled glass. To make the job easier, avoid cleaning glass that is exposed to direct sunlight.