How to Restore Your Yellowed & Dull Plastic Headlights
Updated: Jun 1, 2019
Old opaque plastic headlights can really diminish the look of your pride & joy, but few people know – restoring them permanently can be a simple, inexpensive and satisfying project to complete.
Plastic lenses on headlights were first introduced in the late '80s, in a bid to make cars more pedestrian friendly in the event of accidents.
Manufacturers usually coated the headlights in a layer of clear lacquer. This is the film that tends to turn yellow, dull or peel away, making cars look aged and decayed.
Few people realise that Polycarbonate plastic lenses can be sanded & polished to become as smooth & clear as glass. There are specialists offering a service to restore your headlights, but here we're going to share how to do it yourself, within a couple of hours!
Although not essential, we usually remove both headlights before starting work on them.
It's best to have them firmly held in position; we usually use some old micro-fibre towels to protect the plastic casing, before clamping to our bench-vice, but you can work without, as shown in these pictures.
The trick is to use the finest grade of wet and dry paper you can get away with (frequently dipped in clean soapy water), to first sand off the lacquer coating completely.
This can be 600, 800 or 1,000 grade, depending on how badly your lights are faded, but the finer the grade you start with, the less work you'll have to do to get a scratch free finish at the end. Use ¼ sheet at a time and avoid re-using old sanding paper for the 2nd headlight.
If say, you stated with 800 grade, after the first pass, your headlight should look something like this:
Next, use 1,000 grade and spend a generous amount of time sanding over the surface of the lens, paying particular attention to edges and corners.
Once finished, repeat with 1,200, then 1,500 and finish with 2,000 grade.
For the next stage, an orbital paintwork polishing machine is preferable (but it is possible to polish by hand if you don't have one. If you have to do it manually, it's preferable to use a circular motion. Keep changing the area of Microfiber cloth you use for polishing and use fresh compound frequently).
Using a clean hard-foam pad, apply some plastic polishing compound to the headlight lens surface, then once spread evenly - polish at highest speed setting.
Avoid pressing too hard or staying on the same spot too long as Polycarbonate can crack or melt easily.
If you don't have plastic polishing compound amongst your car care products, micro-compound can be used as an alternative. Essentially, with each treatment, you're removing a finer and finer layer, until the final treatment is so fine – scratches are no longer visible to the naked eye. To finish, use some car wax to provide a protective, water repellant layer.
Polishing off the residue with a clean microfiber towel should reveal a perfect finish. If there are some small surface scratches, then you'll need to repeat the fine sanding process, then polish again, but remember to use the finest paper you can get away with… For removing residual fine scratches we use 1,500 grade or finer.
Some people will say it's best to apply fresh clear lacquer, to refinish the headlight coating, but in our opinion, this is best avoided. Lacquer from a spray-can is typically not very high quality and if the surface of the headlight is not well cleaned of silicone residues (White Spirit is good for doing such, by the way), then the finish can be spoilt.
Also, as most people will typically only have access to spray cans for lacquer coating, these are typically poor quality and the lacquer may only last a couple of years before degrading, peeling, etc.
If you polish your refinished Polycarbonate headlights with car-wax or light polishes from time to time, they'll continue to look like near new and help preserve a fresh & well cared for look of your pride & joy.