Q:

How do you clean yellowed headlights?

A:

Quick Answer

Clean yellowed headlights by washing, sanding, polishing and buffing the headlight's plastic covering. For seriously yellowed headlights, using a headlight restorer before the polishing step may be necessary to remove all traces of yellowing from the plastic. Prevent yellow discoloration from reoccurring by applying an ultraviolet-resistant barrier to the headlights, either using a rub-on product or a special UV-filtering plastic film.

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Full Answer

When sanding the headlights, start with a medium-grit wet sandpaper, and gradually work up to a 1600 grit paper. Some headlight restoration products come packaged with several different grades of sandpaper to make the process easier. After sanding, the headlights should have a dull appearance, but no traces of yellow should remain.

Polish the sanded headlights using a high-quality buffing compound and a soft cloth. Many manufacturers offer special products for buffing headlights, but in reality any decent automotive buffing compound does the job well.

Headlights yellow because ultraviolet rays interact with the polymer compounds that make up the headlight's protective shell. When these polymer compounds interact with ultraviolet light, they become oxidized, at first clouding the headlight and eventually turning the plastic yellow in some areas. Sanding and polishing the headlight removes the top, oxidized layer of polymer compounds and can restore the headlight's original appearance. Headlight restorer products are essentially just deoxidizing chemicals, which can improve the look of even seriously oxidized plastics.

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