My plastic headlight lenses were badly oxidized. I've buffed them before, and it seems like they clouded up again really quickly this time. So I wet-sanded and re-polished them again w/ pretty good results. It's a bit time-consuming to do though (had to work by hand because all my tools are in storage due to a move).
Can I hit them with a coat of clear to harden the finish some? Will that help "hold" the buff job or will it do something undesirable, like yellow quickly? Ultimately, I want to retrofit glass lenses from an earlier model year.
Yes, that's how we do it at the body shop. Sand all the yellowed crap layers off with 3-400, sand it with 600, clear.
It looks perfect, and lasts as long as a car's clearcoat.
Is the yellowing / fogging due to oxidation (clear coat would seal it and prevent this) or UV exposure? (in this case the clear would not really help unless it has UV blocking stuff in it.)
I just used one of those pre-packaged headlight restoring kits sold by the Boys of Pep. It includes some foam pads that have some kind of grit in them. The pads are attached to the end of a drill with a little adaptor thingie. (I know, it's late.) Wow, worked well on Mrs. Editor's Civic. We'll see how long it lasts, but the entire process only took a few minutes. Color me impressed.
I know some detailer dudes and the HID retrofit crowd uses Helmsman Spar Urethane(Indoor/Outdoor)Clear Gloss mixed with Mineral Spirits(1part urethane to 1 part mineral spirits.
reference; http://www.autogeekonline.net/forum/show-n-shine/19021-headlight-restoration-new-uv-sealant-idea.html
Clean real well and hit with several coats of clear acrylic spray paint. It evens out the surface of the lens. The fogging is caused by oxidation and porosity, which makes the once flat surface of the lens refract the light in many different directions. The cool thing about the acrylic is that it will ever so slightly dissolve the surface of the lens allowing it to bond with the new layer. Kind of like glue and primer for PVC plumbing fittings. It forms a chemical bond that won't flake off later. Make sure you hit both sides!!
