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Fixing cloudy, fogged, or pitted headlights
Over time, plastic headlamp lenses often become yellow, cloudy, and pitted. While manufacturers have moved to more durable anti-UV coatings, many drivers of older cars are faced with ineffectual headlights because the cloudy lenses absorb the light instead of passing it through.
If your headlights are still only mildly cloudy, use the least aggressive approach you can, such as Meguiar's Body Scrub or TR3 blue-label car polish; that will preserve some of the factory protective coating. If they look like the ones in the picture above or resist the gentle approach, keep reading.
“beans,” using information from the Allpar forums, suggested the following steps.
- Wet sand with 600 grit sandpaper until the surface is smooth.
- Wet sand with 800 grit and then 1000 grit sandpaper.
- Polishing begins with 1200 grit wet sandpaper.
- Buff out with very light cutting compound (e.g. Meguir’s #2 swirl remover).
- Finish polishing with a good plastic polish (e.g. PlastiX).
He used an electric buffer for around 20 seconds with the swirl remover on each light, followed by hand buffing. Gloves are recommended for the wet sanding.
Numerous people confirmed their success in making terrible-looking, almost useless headlight lenses look brand new. A variety of kits are sold, mainly using sandpaper or electric drill disks with adhesive foam pads. Individual sheets of sandpaper are available from well stocked auto supply stores, with highly variable pricing. Mark tried a wet kitchen scouring pad followed by Brasso.
Allpar trial #1: sandpaper plus PlastiX
We tried one method on the left headlights, another on the right headlights.
On the first headlight, we started with 800 grit, which added considerable time to the process — our headlights were bad enough to merit starting with 600 grit. We went to 1000 next, then PlastX; we recommend using the 1200 sandpaper between them. In all cases we wet-sanded.
You can't see what you're doing because the headlight is covered under a milky coating of loose polycarbonate, unless you've got a constant stream of water going. Be thorough and get all areas of the headlight. It took us around ten minutes working by hand on a 300M headlight to get most of the effects of aging off, with the most coarse sandpaper, but we later went back and did it again for a more thorough job.
Next, we get rid of the pits and scratches introduced by the 800 sandpaper by using the finer grades, gently and thoroughly. Don’t be shocked when you've finished with the 1000 grit sandpaper and your headlight now looks like it's a frosted shower window. As it dries, it will look worse.
Finally, use the PlastiX as indicated - unless you've noticed an area you want to hit with the 600 grit again, and then go up through each step until the PlastiX. You don’t want to start over, and PlastiX is expensive. Based on our experience, I’d suggest spending more time, rather than less, on that first step, because we had to go back and do it again. You can barely see the fog on the bottom of the headlights; and they are still somewhat cloudy in the following photo.
When you’re done, it should look as good as new. But do both headlights on the same day unless you want your car to look funny for a while!
This was not necessarily the ideal solution; the hazing slowly started to return within a few months, and we did not manage to get the surface as perfectly smooth as we'd have liked, no doubt due to our lack of sanding prowess and probably due to limited time. In the end we found that the DoubleHorn sealant helped to restore the perfect clarity of the original headlights.
The DoubleHorn headlight restoration kit
Daniel Stern, automotive lighting expert of worldwide repute, recommended that we try the $30 (including shipping) DoubleHorn headlight restoration kit, saying it was the only kit worth the bother. Dan’s credibility is high in our book so we called DoubleHorn and quickly got a headlight kit (along with a metal kit for restored cars that we’re going to try to test this year.)
The DoubleHorn kit comes with a generous amount of each of its materials, which a reasonably talented person could probably stretch out to three or four cars. The 3M pad showed no wear (though we did get the rough side dirty when using the fine side), and was much easier to use than sandpaper. The cleaner and polish and protective coating were all given in generous quantities. All materials were biodegradable, the protective coating met California requirements, and the box was no larger than needed (with useful compartments for long-term storage) and made of a thin cardboard.
The down-side is that, for cars with very bad headlights, you could spend hours and hours using their mildly abrasive pad and cleaner. They will work, but be very time consuming on cars with headlights that are very far gone, like ours were. In these cases, start out with the 600 sandpaper, then move to the 800, then move to the DoubleHorn cleaner, then the PlastiX, then the DoubleHorn final fine polish, then the sealant. (The PlastiX worked much faster than the DoubleHorn Micro Abrasive Gel, in our experience.)
Once the headlights are nice and smooth, the DoubleHorn spray is remarkably forgiving and easy to apply. Mask off the surrounding area (we quickly stuck and unstuck 3M masking tape to our pants leg to make it even less sticky), spray one thick coat, and step back to enjoy it. We had two runs on our first spray but they both dissipated quickly and disappeared on their own; the headlight looked like it was covered in gel for around 20 minutes, then dried to a shiny, clear finish, looking brand new. Because the DoubleHorn sealant replaces the original factory UV protection, it should look that way for years to come, though we won’t know that for a while (written April 2009).
The real test is whether, with the headlights on, you can see specks and such on the front of the headlights, looking from the side. The light should be going through the lens, not sticking to it. The sealant seems to take care of some minor “glitches,” filling them in with a smooth surface. The difference is striking, and we don’t know if other kits have the same qualities. (Compare the photo below with the “after” photo above.)
The DoubleHorn kits — and other relatively non-intrusive methods described here — are also good for sidelights, tail lights, and any other lenses, which may be more helpful for those with vintage cars than modern vehicle owners.
Some may ask why they can't just use DoubleHorn’s sealant. A can of the resin sealant is available, cheaply, from the company - at $9.95. However, you have to have a $10 order to check out, and then shipping adds around $12 more, and you end up paying about as much as you would for the kit, which at $29.95 includes free shipping. Unless you want two cans of the sealant (which DoubleHorn calls “Clear Protective Coating”), it pays to just get the kit and have some bits left over for other projects.
One year later: doing it again
The headlights relapsed after just a year, and by October 2010, we had to do it again. This time, we simply bought the $15 3M kit at the local AutoZone. It attaches to a drill, and while mine is a fairly cheap model, I was able to keep it at roughly the right speed by keeping it fairly slow, while much faster than a cordless screwdriver. Again, I started out with a coarse grade of sandpaper, only it was on a Velcro-ized disk; this step took only a few minutes, as did the next two, which both involved finer grades of sandpaper. Finally, I squeezed some of their included polish onto their foamy thing, and the result was — better than the hour or two I'd spent the first time, manually wet-sanding.
3M’s instructions, with photos, are fairly clear, and their kit is easy to use; what’s more, I can use the same kit next year.
Those of you who can remove your headlights or feel comfortable spraying it, I was told by someone who should be trustworthy that clear engine spray paint may hold off the aging. If the headlights revert again next year, and there’s no reason to think they won’t, I’ll probably give it a shot.
In the end, our conclusion is that if your headlights are just foggy, and do not look as though they’ve been coated with a baked-on gunk (as ours did), you should try the least abrasive means possible. If your headlights need more work, a drill-based kit, like the 3M one we used, is the way to go.