Good Evening Autogeeks,
I was working on a friends headlights this afternoon. She had told me, she had done several things prior to calling me (OTC products and toothpaste) and thought the issue was inside the headlights.
After finishing, I was unsatisfied with the results. I went as low as 600 grit sandpaper and I'm wondering if I should/could have gone lower? Work the 600 grit sandpaper longer?
What could I have done differently?
Thanks!
It looks to me that all of the original coating was not removed. There's two parts to the equation; selection of grit and sanding duration. Many times with BMWs and many SUVs or some Chevys I start with a razor blade. This may seem harsh, but actually works well for me. After the blade I will use a stripper and/or sand with 500 grit.
Technically, you could start with 80 grit, which would quickly remove the old coating, but would also require a lot of sanding disks or paper because it would fill up quickly with the old coating. Then, because of the amount of surface damage you would need to spend a lot of time removing the deep sanding scratches from the 80 grit.
The reason I use a razor blade on some headlights is because it is faster and cheaper than sandpaper. The razor blade doesn't clog up, but will go dull. But at 10 cents apiece, who cares? It also clears easily with 500 grit.
At the other extreme, you could start out with 2000 grit which would also remove the coating, but very very slowly. So, it's a question of selecting the right grit to begin with. It will vary with each headlight.
One suggestion I would propose is regardless of what grit you start with, wet sand with a good lubricant and watch the color of the sanding aid. If it's slightly yellow, it's old coating. If it's white, it's polycarbonate (headlight base). Once it turns white, you have removed the old coating and now your job is to repair the sanding damage.
Another suggestion is to sand/compound until the headlight looks like new or as good as you expect. It is true that some coatings will hide your sins by filling in shallow sanding scratches, it's also true that if the headlight looks great before the coating, it will look even better when coated.
I went through the same scenario early on with BMWs and Jeeps. I wasn't removing all the old coating. I think if you redid the headlights and watch the sanding aid or water/soap if you don't have sanding aid color and sand until all the old coating (and your newly applied coating) you'll get much better results.
P.S.- If you used spar/MS for the final coat, remove it with MS as soon as possible. It fully cures in about 14 days and the sooner you remove it, the better. Hope this helps.
ray6
