[mikerez]

Throw in my two cents. When I picked up my car from the Kia dealer here in Albuquerque, the glass had hard water (calcium) rings on all of the windows and the sunroof. Bought some "BarTenders Friend" liquid version at Wal mart in the cleaning supplies area, followed the instructions on the bottle and it got rid of all the spots in one application. I now use this stuff on the glass shower doors in the house and it really does the job.