gcthree

My '96 fog lights plastic lenses were hazed from road use.

Using soapy water, I began with 1000 grit wet/dry paper, followed 1500, 2500, 3000 and then 4000 paper. I then polished them with a heavy cut polish and finished with 3M Fine Cut polish. They were back to being clear again and coated them with Meguir's headlight coating. Here's the final result.

WVZR-1

This procedure involved what sort of time? Would you maybe consider being more 'aggressive' with the wet 'grit' if you were doing another few lights? Since you've done the Park/Fog, do you believe that the rear 'Back-Ups' would respond to this treatment? A fellow doubted that in a recent thread when it was suggested.

gcthree

Probably 40 minutes on each light. I never go aggressive with any abrasives as once you go too far there's no coming back. The 1000 paper was a great place to start and it absolutely leveled-out the lens. The rest of the process progressively removed the very fine abrasion that the 1000 created. The coating sealed the final finish.
I believe any plastic lens will respond to this process but you do need a coating to preserve the final polish.

86C4vert

I worked on headlight coatings for some time at a previous job. Forward lighting housings are almost always PC (polycarbonate) (good impact resistance), which yellows due to UV attack and oxidation. Rear lighting is almost always PMMA (polymethylmethacrylate) (not as good of impact resistance as polycarbonate) which does not degrade with UV exposure. A lot of OEM's are trying to move to PMMA forward lighting to eliminate the headlight yellowing problem, but its a difficult path due to regulation of how much abuse the forward lighting is supposed to be able to take.

Both types of lights can be refinished via this type of sand/polish and coat procedure, however you have to be careful because some of the carrier solvents in the coatings can be too aggressive for the PMMA based lights. In fact the best coatings for PC (Momentive AS4700) actually involve using a primer (Momentive SHP 470-FT 2050) which mimics a PMMA surface when applied to the PC. These OEM coatings are expensive and very difficult for the average consumer to get their hands on, but they are both oven cure coatings (the other class of coatings are essentially urethane acrylates that are cured via industrial UV lights).

The issue with all of the consumer grade headlight refinish hits is the lack of a durable protective coating - some simply use a wipe on wax, others use 'plastic restorer' (basically just liquid plasticizers). They tend to lack UV protection, and wash off over time.

The particular Meguiare's product that you most likely used (correct me if I chose the wrong one) is a (probably) siloxane based polymer coating. I've looked up a SDS for the Meguire G178 product as an example (see below picture). Notice that the solids (polymer plus UV absorbers and stabilizers) are less than 3 weight percent. A normal OEM sprayable coating would be closer to 20-30 weight% solids. Such a low solids is going to give a very very thin coating not to mention the fact that since its a room temperature cure its not likely to be very tough. The amount of UV absorbers are very low as well which is another reason why even the best of these restore kits (this is probably one of the best ones you can readily get) don't last.



Now, I might have gone a little deep here - but I thought you might be interested WVZR-1

gcthree

So, should you add multiple coats?

I would love to have taken the units off the car but that involves the front bumper cover removal which I did not want to undertake. I had very good access to the lens in place. The car is garaged and really not exposed to UV much.

ghlkal

Wow, that looks fantastic.

Nice work

86C4vert

I agree your repair looks great and will likely last quite awhile due to limited UV. I don't know about this particular product, but additional coats might wreck the first coat. Some of those solvents are aggressive.

ChumpVette

This is what happens with multiple coats. It does not work like paint with light applications to build up material.

gcthree

I learned of the Meguier's product from a video on restoring headlight lenses. He emphasized that, despite the instructions on the product callilng for 2 coats, his experience indicated that only one coat with multiple passes over the lens yields the best results.

RUU

Faceman89

Not sure if the Meguires you used is the same stuff I did, but if it is it won’t last long unfortunately. Anymore after I’ve sanded everything down, I spray them with 2K Clear.

gcthree

Cannot comment on the longevity of the coating as I've just applied it, but this is what I've used:

Faceman89

Yeah that’s it. I usually get a month or so out of it. I used it to temporarily clear mine up before finally sanding them down and spraying them with 2K.