For the past 50yrs I've driving I used #0000 steelwool and vingar. I
seen it used when I was a kid by this black guy that use to detail and
buffout cars in the town I grew up in L.A. That guy was a Wizard!! By
the time that guy was through with a car the paint looked like glass. I
use to watch him for hours.....Ahh!,  but I digress :-)

Rick

Tom,

There is only one thing needed for removing water spots caused by hard water -
vinegar.  It works equally well and safely on auto paint and is the only smart
way to remove water spots before waxing a vehicle.  FYI - the moderately acidic
content of rain water will also remove water spots over time, but it is a
painfully long process.

White vinegar is preferred, but any vinegar will work.

Extremely fine steel wool can speed up the process but shouldn't be necessary.
A plastic scrubber such as the type used on Teflon pans or the type used to
speed up bug & tar removal on auto finishes is a better option on auto glass.

Soft Scrub is moderately safe and works on problems other than water spots.
But I wouldn't use such an abrasive if vinegar alone solves the problem.  I've
used Soft Scrub on home windows and been happy with the results, but extremely
fine scratching on a car windshield can be much more noticable.  I would
contact the manufacturer or test the Soft Scrub before using it on a
windshield.

(To test the Soft Scrub, try it on a scrap piece of very clean glass.  Use a
power polisher with a very clean buffing bonnet.  Continually re-hydrate the
Soft Scrub while doing a lot of polishing in one spot on the glass.  Wash and
rinse well and observe the glass for fine scratches under a variety of angles
and a variety of lighting.  If no scratches are observed then the Soft Scrub
should be is safe, assuming that the auto glass is equally hard.)

Once again, if vinegar doesn't remove the spots fairly easily, then the spots
are not hard water spots.  And remember to wash and rinse glass well before
rubbing hard to remove anything from the glass.  Glass is commonly scratched
by the abrasive action of the dirt which is being rubbed off.

Gideon

Duragloss (Brothers Research)  makes a glass polish for this exact purpose.

http://www.duragloss.com/product.asp?pid=303

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