Problems wet sanding a headlamp

[prr]

Mods, not sure where this belongs. Feel free to move this.

This week I tried to restore a headlamp. 2005 Sienna, never done this before, so I used toothpaste, and then after rinsing it off, sprayed on some coats of clear coat. On one side, it worked fine. On the other headlamp, I sprayed too much clear coat and saw it run down. Now this is where things went sour. I decided to use a cotton swab to dab up the runny clear coat. I succeeded in pushing a bunch of white gunk all over the headlight. That was yesterday.

This morning, I've been using 400 grit sandpaper with a very liberal amount of water (on the sandpaper, as well as on the plastic headlamp itself). I do see some white, milky goo in the water that runs off (which I can only imagine must be bits of the clear coat). But I'm not sure its making it any better. In a Chris Fix video I saw him recommend a possible second attempt at the 400, before moving on to higher grit levels. I've now done this at least 3 times (wet down the lamp & paper, and gently, using circular motions, sanding away that top layer on top of the headlight). There appears to be fewer white streaks, like I saw before, but it does appear to be more cloudy all over the light cover.

I'd hate to just do this interminably, and end up putting lots of scratches into the plastic light cover.

Should I move to a higher grit? I also bought a 2000 grit paper. My hesitation to use that, however, is that if a rougher sandpaper can't pick it up, why would a smoother paper do it?

 

[Mantilgh]

Why not just sand to level the runs then respray.

I guess if you used 2K clean the can is only good for one go at it.

 

[prr]

I'm hoping to clear as much of the white gunk off the headlights as possible, before respraying (which is my ultimate goal). I'd like to not make permanent, a lot of gunk that would cover the headlight.

I have a can of Rustoleum clear coat, that feels like there is a lot more paint left in the can, so that won't be a problem.

 

[DaveT435]

If you're using 400 I think the white your seeing is actually the lens, which is fine, I would follow up with 800, 1200, 2000, and 3000. 1200 isn't real popular you may have to use 1500 which will take a little longer to get the 800 marks out. Then compound and polish. You said you used toothpaste on the headlight. I doubt that removed the factory protective coating, which was obviously failing, if you don't get that off I don't know how long your fix is going to last.

What kind of car is it and what spdo you have to use as far as grits of paper, compound, polish? Do you have a polisher??

 

[prr]

I went ahead and did some more toothpaste, and then applied isopropyl alcohol a few times, and then went ahead and re-applied the clear coat. Right now (an hour old), it does not look bad. It actually looks clearer than the other one, that didn't get the sanding (the one that went just fine with toothpaste & clearcoat). I'll see what it looks like tomorrow...

At any rate, I'll know to do more sandpaper treatment if this fix doesn't hold.

 

[Calendyr]

It's been a while since I watched the video where ChrisFix shows how to restore a headlamp. What I do remember is that he only used very rough sand paper to allow the clearcoat to bind to the plastic.

So, first thing, sanding plastic requires a lot of elbow grease. You will have to sand with each grit for several minutes. What you want is have a uniform scratch pattern where the entire headlamp looks the same with no spots being shinier or darker. Once you achieve that clean thoroughly then move to the next finer sand paper grit and repeat. Also, the "gently" part might be your issue. Don't go gentle, apply pressure. You are trying to remove clearcoat, not polish paint. It's normal that it will turn cloudy, 400 grit is very rough. The clearcoat will give the plastic it's transparency back.

Before spraying the clear coat, make sure to clean very well, and use a paint prep product like Grease and Wax remover (Duplicolor) or Isopropyl alchool (50%) to make sure absolutelly no oil is present on the plastic.

This should give you excellent results.