Originally Posted by rj45

Removing hard-water spots can be difficult, especially if they dried on a hot surface. A chemical based paint cleaner may not remove the spots, but it's best to try the least aggressive option first. If the paint cleaner doesn't work, you'll need an abrasive polish. I use Meguiar's Ultimate Compound, it's a good OTC polish. It can be used safely by hand or machine. You could also try clay, but I doubt it'll remove the spots.

Just make sure you work on a cool surface and keep the polish wet to increase its work time...a little spritz of water is plenty (I use distilled water in a spray bottle). You may need a few applications. Hopefully, the spots will come out or at least be reduced significantly. Then, follow-up with your favorite wax or sealant.

Good luck!

Originally Posted by kenchan

Claybar is your friend. Use Griot's yellow super soft clay though.