Seattle Scott

Well, I did my "Glass Cleaner Abrasion" test this weekend.

I'll explain why I did it first. My car was sold at auction and then I bought it. After several months writing appeared on the windshield that you could only see in the morning dew. Stuff like "97 A6 Quattro" "VIN 40545..." etc. I tried Windex, alcohol, acetone and Goof Off to remove the left over crayon or whatever the substance was to no avail. I need to replace the windshield on my 85 pickup truck so I have a place to test and play. So I decided to do this experiment.

I applied each substance with a wet paper towel and rubbed the glass (the windshield on my pickup truck) in one orientation, back and forth 200 times. To determine if the glass was scratched I looked from inside and out at different angles. The experiment was pretty boring. I tried the following things :

Bon Ami
Comet
Soft Scrub
Glass Polish (comes in a hot pink can, bought at Ace hardware)
Copper pot scrubber
Steel pot scrubber
SOS pad
00 Steel Wool
GOJO Orange hand cleaner (Pumice)
Lan Lin hand cleaner
Toothpaste
Course (NAPA heavy duty) and Fine (Turtle Wax heavy duty) rubbing compound
(Course and fine determined by polishing my chrome truck wheels)

Turtle Wax One Step Car Wax
400 grit sandpaper
150 grit sandpaper

The only thing that visibly scratched the glass were both grits of sandpaper.

I may re-run the experiment with some "soft glass" or plexiglass to get a better feel for how abrasive these things are. A person on the forum mentioned some windshields will haze or get scratched with Comet. A local glass shop recommended 000 steel wool, dishwashing soap and great care. All I know is my truck must have a hard windshield. I though a steel pot scrubber or rubbing compound would leave a mark. Perhaps if I used a microscope. Humm, glass sample slides are usally pretty cheap glass too.

I used the glass polish on my 97 Audi windshield to remove the writing on the windshield. I tried the Bon Ami too but the glass polish seemed to "cut" better and faster. I also felt more comfortable using it. If I really believed my test results I would have gone after the windshield with a pot scrubber. ;-) I polished the entire windshield and it looks nice and smooth and beautiful. Also found some little tiny tiny rock hits maybe Novus can take out.

Bollinger

Try a scotchbrite pad, both the real 3M "non scratching" kind and the cheap imitations which will scratch stainless steel sinks and can even put scrapes in an enamel/porcelain one (try that with steel!).

Also try a razor blade.

If xylene (Goof Off) won't remove it, I have strong doubts that any chemical will. Perhaps a very strong degreaser, as the sticks they use are kind of wax/grease pencils. I'm really drawing at straws here chemically, since I've never found anything xylene couldn't remove before. In fact most often my biggest concern is whether xylene or acetone will dissolve the surface I am removing the marks from.

I assume that you've investigated the possibility that there is a coating on all your windshield except for the place where the writing was. Now I know it sounds odd, but once you've exhausted every other possibilty it could be your only choice.

Seattle Scott

I looked at the Scotch Brite pads,next to the steel scrubber they looked mild but who knows without a test.

I was scared to rub Goof Off on the windshield. I know it is glass but Goof Off is "nasty".

I pondered the coating theory. What are you going to do? The car is five years old and the glass is insured, much as I hate to think that way. I can see putting a brand new clean windshield in a vacum depostion chamber but trying to patch a coating doesn't sound good. If the coating is hard enough to withstand wipers it must be chrome based I'd guess. I'll see if the writing reappears in few months. I did really see a differant "spot" with a lot of diffraction (color rainbows) where I started using the polish but letting the polish dry and then buffing as instructed seemed to cure that.

Also, since we had the earthquake all the computer monitors at work have big "OK" marks on the CRT face. I'm going to try the Glass Polish on a few tomorrow. Most computer monitors have an AR coating which can be soft. Problem is once you polish an area it's differant but if I just gently apply the polish in area that might be an OK test.

wwbecker

Well, I've never tried it, but it might be worth a shot since you're experimenting anyway. Try "Oxi-Clean". You know that stuff advertised on info-mercials. I saw the other day you can now buy it in Bed, Bath & Beyond. I'm assuming you can also get it in Wal-Mart, K-Mart, etc.

Oh, one other trick I learned when detailing cars over the summer in college. Try vinegar. Wipe the windshield with newspaper. We used this technique to get the cleanest windshields you've ever seen. Although, we never ran across you're porblem.

w-

DrHandball

xylene will probably damage any finish that it contacts.

Xylene while noxius is not really all that nasty. Toluene and Benzene are two solvents that you really have to be careful around.

Delaware_Tom

I tried the TSB (see link) procedure for cleaning glass on a 3 yr. old Ford Taurus. The car had streaking wipers that no amount of cleaning or new blades seemed to help. I had tried ammonia & newspaper, paint thinner, lacquer thinner, etc. after failing with windex, dish soap, etc.

I ordered the 3M Gloss enhancer from the 3M online store and got some cleaner clay locally. I did the drivers side in about 5 minutes last night. Seems to have solved the wiper problem, definitely feels a lot smoother than the other side cleaned with glass cleaner. It is supposed to rain tomorrow, will leave the windshield 50/50 and find out then.

- Tom (waiting for a 2.7T in April)<ul><li><a href="http://tech.vw.com/audipdf/a640004.pdf">http://tech.vw.com/audipdf/a640004.pdf</a</li></ul>