Headlight renewer

 "You will do the greatest services to the state, if you shall raise not the roofs of the houses, but the souls of the citizens; for it is better that great souls should dwell in small houses than for mean slaves to lurk in great houses." - Epictetus

Another Thanksgiving day has come and gone.  Once again we managed to get a turkey that wasn't very good.  It didn't seem right to begin with, and after a few hours in the oven, the house smelled very unpleasant.  So we ate side dishes and called it a day.  From now on, we will do pre-cooked turkey rolls, which are a more appropriate size anyway.  Next year, I'll donate the free turkey to charity.  I have a story about that...

Enough about the turkey.  This is about removing haze and discoloration from plastic headlight fixtures.  The new car had some haze and pitting on the lenses, but the lenses did not have noticeable darkening.  Nevertheless, I thought it would be worth attempting to see if the lenses could be improved.  

Modern headlight housings are made with a really tough polycarbonate plastic lens.  Polycarbonate is amazingly strong, and can deal with a lot of impact from road debris.  It has a weakness though, and that is a tendency to darken when exposed to UV light.  The lenses are therefore coated with a UV resistant chemical, which itself darkens and gets hazy over time.  The purpose of renewing headlights, then, is to remove the damaged coating and darkened layer of polycarbonate, refinish the surface once that is done, and re-apply a new UV-resistant coating.

I spent about 30 minutes on each side, on a cold garage floor.  The process goes like this:

• Tape off the adjacent painted areas and pop the hood open to get better access to the headlight fixture
• Wipe off the oxidized coating with a chemically-treated cloth.  (They include several cloth packets for each headlight fixture)
  
• Wet sand using 2000 grit sandpaper to remove rough surface imperfections and remove the remaining UV protective coating.  Wet sanding must be used, or friction will heat and damage the polycarbonate.
  
• Wet sand using 3000 grit sandpaper to finalize the finish on the lens.
• Apply a new UV protective coating on the polycarbonate headlight housing.  This coating also fills in the sanding marks remaining from the final sandpaper stage.

I took a few photos along the way, and other than fixing some haze, can't tell if there has been much improvement.  A little, I guess.  Not much for the effort involved - but on the other hand, they weren't really that rough.

First up, a before/after.  You are looking at the headlights on the center car.  Much of the haze in this image is road grime, like what's on the paint.  You need to clean that off before starting.

Below:  Driver side, before/after, and a comparison with the un-renewed passenger side afterwards.  In the first image, the road grime has already been washed off, so this seems to be an improvement.

Below:  Passenger side, progress through the steps.  I spent a bit more time on this one, and it seems to look a wee bit better.  There is still a bit of pitting, but whatever minor yellowing and haze was there seems to be gone.

And lastly, the finished project.