I had some very old and very hard water spots on my windows that I finally got rid of by using Mothers power polish by hand with mf pad. I tried the usual clay, vinegar, steel wool but nothing worked until this. The steel wool actually scratched the glass even though I was assured that it wouldn't, so I had scratched up water spots on one window. I did scrub very hard on that one spot with my finger on the steel wool and that is probably why it scratched. Anyway, Mothers power polish did it for me, so you may want to give it a try if nothing else works for you.