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Are you positive they look as good as new? I used Mothers Mag & Aluminum Polish on a yellowed headlamp and I thought it was great, and I was ready to say that it was as good as new. Then, I looked over at another headlight I had that really was brand new, and only then did I really notice that the polish helped but wasn't a cure.

okay ya got me there maybe theyre not as good as new but they sure look darn good for being almost ten year years old

Yeah, I'll agree with you that it helps a lot. Anyone who has yellowed plastic headlight lenses, just go buy some of this polish, rub it on, and wipe it off. It'll cost you a few bucks and about 10 minutes of work and it'll help a lot. Could save your life.

my method really does make them almost like new

I'd say your method, Josh, makes them better than new, since you definitely sand away all the yellow and the clear coat helps prevent it from returning.

My lens were slightly glazed over on the edges so I tried some plastic window cleaner. (Mfg. by McKay part number 321) I was using the stuff on my motorcycle helmet shield but it works on my headlight lens too.

Josh and Morgie, I have a couple questions.

1) About how long did you spend hand-sanding with each of the different grits? How much paper did you use up?

2) Is the clear coat required to fill in all the tiny cracks? Like, after the final sanding, was the lens still cloudy?

It depends how badly the lenses are yellowed, and/or pitted. The acetone eats through the plastic. This was the only way to fully get rid of all the yellowing on the lights. It however left the surface of the lense extremely cloudy and rough.

I sanded with each grit until it was as smooth as I could get with that grit. I then kept bumping up to the finer grits. There's really not a set time unfortunately....just have to go by feel.

The lens was still slightly cloudy when I was done sanding. You could possibly buff out the fine scratches, but then you'd be right back to where you started from and the lense would yellow over time. The clear coat does help fill in the tiny scratches.

Stick the light in the fridge/freezer before you clear coat them. It helps with reducing orange peel.

Also, I applied a light coat to the lense. The lense still wasn't perfectly clear. On the second or third coat I put down a pretty thick coat, and that seemed to sink in and clear things up.

I've got my old set of lights that are pretty nasty. I'll probably sand them up over the winter and paint them. It'll be a good before and after project. I'll probably sell those.

Cool... I have a spare pair of lights that I need to do this to, since I hit a bat (:!:) and it spread a nice pattern of cracks all over my driver side lens. Just have to find the time...

Okay, so the lens isn't actually crystal clear until the clear coat fills in all the tiny scratches created during the sanding process. Makes sense.

The lense still isn't "super dooper crystal clear" but it's as good as your going to get a plastic lense of this type...however that's me being super nit-picky. For all intents and purposes....it's clear

Cool. Maybe periodically applying a little bit of wax would get it a tiny bit further?

The slight bit of cloudiness is in the plastic lense and/or in between the plastic lense and clear coat interface. That's why putting a heavy coat of clear coat on helps fill in all the little crevasis.

Also, that's why getting the lights as good as you can with the wet sanding is important. I suppose you could try some polishing compound afterwards. I may play around with that when I do the ones I have.

Ah, okay.

Well, I'll let you guys know how my attempt goes. Probably this weekend.

Cool....take pics

I'll see if I can borrow a digital camera.

just curious vikash.....how'd this project turn out?

Oh yeah, I meant to post it...

I didn't end up having a lot of time, so I didn't do the job completely.

I spent a few minutes wiping each lens with my girlfriend's nail polish remover and some cotton rags, and then wet-sanded with 220, 320, 400, 600, 1000 and 1500 grit sandpaper. I only spent a couple minutes on each grit, and used maybe a 2"x2" piece of 3M wet-or-dry paper of each grit. I just sanded them in a kitchen sink with the faucet dribbling water onto where I was working.

I finished up by rubbing them with Blue Magic Plastic and Plexiglass Cleaner (just about 30 seconds of rubbing with a cotton rag), and then with Mothers Mag & Aluminum Polish (same process). I rinsed the lights off and then rubbed in some carnauba wax.

At each stage (after the acetone) I could see the surface clearing up, but I had a very hard time telling if I was continuing to smooth the surface or not. I guess I'm just not used to sanding things other than wood. Does it matter whether you use small circular motions or back-and-forth motions? I used circular ones but my arm started to get tired.

Anyway, the lights look pretty good now, but I'm wary of putting them on the car without more protection. I think I might next try to wash the wax off with dishwashing soap or something and then put rattle-can clear coat in place of the wax. Or maybe I'll just see if a local body shop guy's willing to spray them with clear coat for me for not too much money.

definately put the clear coat on it

would you buy a car with just a layer of wax and no clear?

Right. I agree with you. It's just that I didn't have time to go out and buy some clear coat and then apply it. I'm not going to install the lights in their current state.

I don't think it really matters whether you used circular or back and forth. The main thing when sanding is you get as smooth as you can with that grit....and the surface should get slightly "clearer" with each step to a finer grit.

The process is not really something I'd suggest rushing.

How clear are the lenses right now with just polishing them?

It did get slightly clearer after each step, but I couldn't tell for sure whether I'd accomplished everything that grit could do or not. Probably not, since I spent so little time and used such a small amount of paper.

Anyhow, now, they're very clear, considering that they're plastic lenses. In fact, if I knew they were well-protected I'd be happy with them.

I agree with your advice about not rushing it... This time around was kind of just to familiarize myself with the process. I'll wash off the wax and then do the whole thing again more carefully.

also you should put the clear on first then wax it. Just like paint

Yeah, may as well.

Actually, I just thought of something... I wonder if it's possible to find out the index of refraction of polycarbonate, car wax, and clear coat paint. If wax is a lot closer than clear coat, I might actually try seeing how it goes with just wax.

I had this question in my mind that I may as well throw out to see what you guys think:

Does it matter if the clear coat is matte finish or glossy? I think glossy would look better but I was wondering if a matte or flat finish would technically or visibly let more light through the lenses. . . something like anti-reflective coating on eye glasses--the flat coating allows about 12% (IIRC) more light through.

btw, I was surprised to find this thread here rather than in the Electrical section. But I guess it's like doing body work to the car, huh?