Headlight Restoration Guide
What Causes Oxidation on Car Headlights?
By Clearified Headlights · 3 min read · Last updated 2026-08-01
Oxidation happens when UV light breaks down the protective coating on a polycarbonate headlight lens, exposing the plastic underneath to air and sunlight. The exposed surface degrades and turns yellow, then chalky.
The chemistry, briefly
Polycarbonate is durable but UV-sensitive. Ultraviolet energy breaks molecular bonds at the surface; oxygen then reacts with the exposed material. The result is a discolored, microscopically rough layer that scatters light instead of transmitting it.
What makes it worse
Every accelerant adds to the same underlying process.
- Sustained outdoor UV exposure
- Heat cycling from headlight operation and engine bay warmth
- Abrasion from road grit and winter treatments
- Chemical exposure from harsh cleaners
Why it's fixable
Because oxidation is a surface condition, removing the degraded layer and refinishing the lens addresses the actual cause of the cloudiness rather than covering it up.