Soap can be one of the hardest substances to clean off of glass, which seems cosmically unfair. Whether your car windows were washed by kids who are more enthusiastic than skilled, or someone left you a well-intentioned birthday message, safe driving demands visibility; so the soap's got to go. It can be frustrating to clean soap off car windows, but it can be done. There isn't one tried-and-true method to get soap off glass---it depends on the kind of soap, the kind of glass and how long it's been sitting. Try the steps below until you find one that works for you.
Scrape off thick dried soap with a hard plastic scraper like the ones you use when making a cake. This won't remove it entirely, but it prepares the windows for the steps that follow.
Mix 1 cup white vinegar with 1 cup water and heat it for 45 seconds in the microwave on high. Transfer the hot liquid to a spray bottle and spray it on the soap marks. Let it sit for 10 minutes. Wipe it off with crumpled newspaper.
Spray window cleaner onto the soap marks and let it sit for a few seconds. Use a plastic scouring pad to break up the soap marks. Wipe them away with newspaper or a clean shop cloth.
Dampen a Mr. Clean Eraser with warm water and use it to scrub away the soap marks. Make sure you have more than one on hand, because they clean wonderfully but they also fall apart very quickly.
Pour a little ammonia onto a damp sponge and scrub the soap marks. Do this outside or in a well-ventilated area because ammonia has very strong fumes.
