Clay bars are NEVER intended for removing scratches. They are only made to remove surface contaminants. Only thing they will do is clean the glass. Compound and polish will NOT work on glass either. A windshield is too hard for any compound or polish to see any results. The science of how polish and compound remove scratches is that your not actually removing the scratch when your polishing. All your doing is leveling the surface around a scratch to make it appear less visible. This applies to paint polishing, glass polishing, or anything involving polishing. So in order for a scratch to be removed from glass you would need to level the area around the scratch to make the scratch not stand out. And like I said that's impossible for some paint compound or polish because their not strong enough to remove the surface of the glass to get results.
For glass your going to need to go with a glass polish that has cerium oxide in it and a quality orbital or rotary buffer such as the PorterCable orbital or Makita rotary. Only problem with even using a glass polish on a windshield is that you run the risk of screwing up the optical clarity of the windshield. I've seen people attempt this on other detailing forums and they ruined the windshield and it distorted the glass leading to them having to replace the entire windshield. Everyone knows windshields have a laminate coating on the outside and you could run the risk of ruining it.
Your best safe bet would be to replaced the windshield if it's bothering you that much. Otherwise you'll have to live with it like that.
Corrections:
- compounds and polishes do work on glass, they just need to be made for use on glass. Compounds and polishes for PAINT will not work on glass as effectively, but they will absolutely work.
- An orbital or rotary is a professional tool. Dual Action polishers (Porter Cable 7424) are much more safe for the non-pro/enthusiasts. You will have a very difficult time generating enough heat to distort the glass. Dual action polishers are known to be the safest machine tool for paint - they are even less risk to glass.
- windshields do NOT have laminate on the outside. They have a laminate coating inside - between the two pieces of glass that make up the windshield. There is no surface coating you need to worry about removing. If there is any kind of a water repellant like Aquapel or Rain-X on the surface, polishing will remove it.
- your best bet is to start with a glass polish you can use by hand. If that doesn't give you results, then you could move to a DA machine polisher. If that doesn't work, ask a pro to correct your glass.
hiey good Idea Stephen, do you notice it on there or is it pretty well invisible, and how would that stand up to the ice scraper in the winter..if starting with a new windshield i recumbent to get clearplex installed. it has been keeping the G and the FX windshields great.
-When I say compounds and polishes don't work on glass I'm referring to paint polishes and compounds. I did say a type of polish made specifically for glass would work.
-I know what buffers are which and what they do. I did weeks and weeks of research before I tackled my car with the porter cable I bought back over the summer.
-Laminate coating on the inside, outside, or in between doesn't matter. You still run the risk of distorting the glass. It's not about the type of buffer being used, it's the cerium oxide in the polish that does it. And I didn't say it would definately do it. I just said you run the risk of doing it to the glass. People complaining that the glass wasn't as optically clear as it was before on other detailing websites like autogeek. And if you do some more research you'll see that 90% of the time no one recommends to even polish the glass, but than to just replace the entire windshield.
-While trying out a glass polish by hand would be the first place to start, you probably won't see any results because your hand doesn't move fast enough like a buffer to generate enough heat to level the surface around the scratches. That's why alot of the glass polishing kits come with buffing pads made specifically to go on a machine.