white spots on windshield

Some people will recommend using Bon Ami on automotive glass. I have done so to clean up mineral deposits. There is a caveat that you need to be aware of. The original 1886 formula is still around along with the newer more complex formulation. The 1886 formula is basically Feldspar and soap, while the modern formula has other abrasives and a warning not to use it on glass. I use either one to clean glass or porcelain coffee and tea pots; does a great job, but use plenty of water. The 1886 formula has a hardness of 6 on the Mohs scale. Here is where it gets tricky when you use it on automotive glass. Tempered glass has a surface that usually dials in at about 7, so you can use 1886 Bon Ami, but cautiously. However, windshield safety glass is softer and is about 6 to 6.5 hardness. The idea is to clean the surface and not scratch the glass or haze it. I use the 1886 Bon Ami on windshields after testing on an out of the way corner. Plenty of water, soft clean cloth and plenty of water. There are times when no matter what I do, the windshield wipers just don't seem to sweep the water off. Bon Ami works for me, but I don't make it a regular routine.