Wipers are for wiping off the rainwater droplets that get onto the screen. CLEANING the screen is done by hand with a sponge, water and a detergent, unless you're driving and getting a splash from the pothole of course. Some take it for granted that wipers are meant to keep the front and rear screen clean - at least that is what it looks like when judging mud covered cars. Any cleaning of the screens with the aid of wipers to get off sand and other particles works like using sandpaper on the rubber wipers-they certainly get damaged and won't last long.