Headlight Restoration: When You Need It and What It Does
Why Headlights Yellow and Fog
The polycarbonate plastic in modern headlight lenses is transparent initially because the UV-protective coating keeps the plastic from oxidizing. As the coating degrades from UV exposure, the bare polycarbonate begins to absorb UV radiation, which chemically changes the plastic — causing the familiar yellow, opaque appearance.
The practical impact is significant: a Transport Canada study found that severely oxidized headlights can reduce the light output reaching the road by 80% or more. You're effectively driving at night with 20% of your intended headlight brightness — a serious safety issue, not just an aesthetic one.
In Canada, the intense UV of summer combined with harsh winters that crack and stress the remaining protective layer accelerate headlight degradation. Headlights typically need restoration between 5–8 years on most vehicles.
What Restoration Involves
Professional headlight restoration uses wet sanding followed by machine polishing to remove the degraded clear coat and oxidized plastic layer, exposing the clear plastic beneath. The headlight is then sealed with a fresh UV-protective coating to prevent immediate re-oxidation.
The sanding starts with relatively coarse grit (800–1000 grit) and progressively refines to 1500, 2000, and 3000 grit before polishing. The result is a headlight that looks new — clear, bright, and glossy. The process takes 30–60 minutes per headlight in a professional shop.
Without the sealant step at the end, the lens will re-yellow within months. This is the most common failure point in DIY kit applications — the sealant that comes with consumer kits is thin and short-lived. A professional application uses a quality UV-cured or two-component sealant that lasts 1–3 years.
Restoration vs Replacement
Professional headlight restoration costs $80–$200 for both headlights, depending on severity and vehicle. Replacement headlight assemblies for most vehicles cost $300–$800 each (some luxury vehicles are significantly more), plus installation labour.
Restoration makes sense when the damage is oxidation on the exterior of the lens. It does not address internal fogging, moisture inside the assembly, physical cracks, or damage to the internal optics or LED arrays. A detailer or shop can tell you on inspection whether your headlights are candidates for restoration or whether replacement is the better call.
Key Takeaways
- ✓Yellowed headlights can reduce light output by up to 80% — a real safety issue, not just cosmetic
- ✓Restoration uses wet sanding and polishing to remove oxidized plastic, plus a UV sealant to prevent re-yellowing
- ✓Professional restoration costs $80–$200 vs $600–$1,600+ for replacement
- ✓Without UV sealant after restoration, headlights will re-yellow within months
- ✓Restoration works for exterior oxidation — not for internal moisture, cracks, or internal damage