Chemical sanding method that will remove discolored ABS plastic

[JimNY]

Thanks for the quick reply and thanks for the excellent info you provided on this topic. I've used your technique for soft plastic as well. Both results far surpassed anything I was able to get prior.

[TelePlay]

Parts of this method or process can also be used on sun affected automotive clear ABS headlight housings. Over a few years, the clear, white surface plastic yellows, oxidizes, to the point that only limited light gets through the yellowed, oxidized surface.

I've seen older cars where one could not make out the lamps and reflectors through the yellowed housing, and most of the light was being stopped.

I opted for paper sanding. I mask off the housing in place and sand off the surface crud with 2000 grit wet sandpaper (you can feel the sandpaper being grabbed by the crud but as the crud is sanded off, the wet paper begins to glide over the plastic indicating it's time to stop sanding). I use a wet rag to remove the sanding residue. This left the clear plastic quite dull.

I then applied Novus 3 three times using a cotton patch backed by a cotton ball wet with a 25%/75% acetone/isopropyl alcohol mixture. Each application is removed using an orbital buffer with a cotton bonnet. This got rid of almost all sanding scratches.

I repeat that step with Novus 2 to shine the plastic.

The final step is to apply Novus 2 without the acetone mixture and using a clean cotton bonnet to remove the Novus 2.

I then cleaned off the surface with a soft, damp cotton cloth and when dry use 2 coats of Renaissance Wax on the surface to slow down future oxidation. Other surface protective coatings could also be used.

Takes about 30 minutes per housing.

They sell headlight plastic restoration kits in hardware store and Walmart but anyone who restores phone plastics can use what they have on hand.

Here are the before and after images. I do this to both headlights every 3 years or so, as needed

[TelePlay]

While at the local Wal-Mart a few days ago, I parked in a spot facing these two cars. Both not mine. One is very new and the other some 8 to 10 years old. This gave me the chance to take a comparison photo of both headlight housings from the same angle under the same light.

The yellowed housing is probably letting about half the light by the lamp generated to get through.

The yellowed housing is a driving hazard at highway speed.

[countryman]

The yellowed housing is a driving hazard at highway speed.

Wouldn't pass inspection. It must be a function of local UV intensity, but manufacturing quality also is a factor.

[MMikeJBenN27]

Doesn't that leave it thinner?

[TelePlay]

Doesn't that leave it thinner?

About 0.0015"