I have a dealership here that has a car wash built in. They have standard garage bay doors (like 4 columns by 5 rows) with a build-up of soap scum/hard water.
Would a hard water restoration product be effective on these windows? I think I have “bio-clean”.
I am guessing that most of the hydrophobic sealants should work well. The most inexpensive and easiest to get is Rain-X from the auto parts store. Sealants are degraded by the suns uv radiation. But glass filters out some of it. So sealants that are applied to the inside of a window should last much longer. This has been my experience anyhow.