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There are many methods for polishing and restoring clouded, discolored headlights. My question is: once headlights have been polished and appear quite clear what sort of treatment effectively preserves their clarity?

There are numerous headlight restoration sealant products out there. Are they effective? Some restoration kits contain a sealant and others do not. I have read various anecdotal accounts suggesting they are ineffectual. Wax is occasionally mentioned as the only necessary "sealant"/protectant that is necessary for headlights.

I am not interested in any particular recommended product. If a sealant or alternative product is advised I am only wondering what characteristics a consumer should look for when making their selection.

Additional background information could be helpful as well.

  • There is certainly variation in headlight plastics. Perhaps a single treatment is not universally appropriate.
  • Information about the finish of headlight surfaces by original manufacturers. Raw polished surface or additional treatment?

Related questions:

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  • Sure, you can polish and protect your headlight lens, but the same UV damage occurs at the reflector, and that affects the brightness even more than the clear plastic lens. My personal preference is to swap out the entire headlight assembly for a new one when it gets too bad.
    – tlhIngan
    Jun 30, 2016 at 5:12

3 Answers 3

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The best way to keep them looking good is to utilize clear spray lacquer which is is not affected by UV. UV light is what causes the cloudiness in the first place. By spraying the clearcoat on there, you effectively protect the lense from the harmful UV rays.

After you get through sanding the lense down, throw several light coats of the clear, then follow up with a thick coat (not enough to run, but thicker than the rest). This will give you durability so you won't have to do it again any time soon. Do this without ever letting the first coat dry completely, so only a 8-10 minutes dry time between. There are plenty of videos on YouTube for it ... in fact I think ChrisFix has a really good one.

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  • That's strange, why do manufacturers make headlight lenses out of non-UV resistant plastic? I thought road dust and debris sandblasts them and causes haziness. Jun 30, 2016 at 7:29
  • @IhavenoideawhatI'mdoing - Because it would be an added expense. Even if it costs $.50 per unit, think of all the hundreds of thousands of units which would have to be produced and multiply. It all adds to the bottom line. Jun 30, 2016 at 9:56
  • If saving is done so rigorously nowadays then modern cars really are crap. Headlight resistance to outdoor conditions is critical. Jun 30, 2016 at 10:22
  • The problem with using a clear coat is that it is not optically clear. A clear coat will cause light to refract when it comes out of the lens, altering the engineered design of the headlight. It is the reason that the manufacturers do not use clear coat on the lights, but do use it on the rest of the vehicle. (They use a very powerful professional UV protectant coating that you can have a professional painter apply to your lens at a high price and lasts 5-10 years depending on the amount of sun the lamps are exposed to.)
    – Paul
    Aug 30 at 14:29
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Step By Step ChangesBefore & AfterI used the 3M headlight restoration kit to restore my car's cloudy headlights and once they were clear, I sealed them with the Sylvania UV Block Clear Coat. This seems to have worked for me.

Also, here are some pics of the process. So far, they seem to be holding up well and I love the restored clean look. Step by step3

3M Headlight Restoration KitSylvania UV Block CLear CoatBefore & After

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I have just spent an inordinate amount of time researching this, and as best I can tell there are numerous methods for headlight lens restoration. Most of them include common first steps:

  1. Remove the UV damaged layer of plastic. Usually this is done using several different grades of sandpaper, starting withe a coarse grade and finishing with a fine grade. Note this step may vary based on severity of lens damage.
  2. Restore the lens clarity using some additional product or products.

After these steps have been completed, one of several UV protectant options may be used:

Consumer UV protectant. Most common is to apply a UV protectant that may be in the form a spray or compound applied via a cloth. These protectants offer light protection and it is generally recommended to reapply the protectant every 12 months. Failure to reapply the protectant may result in damage that requires the prior to steps to be performed again.

Polish. A similar option is to use a polish or wax. Usually these options require even more frequent reapplication than the previous option, as these products are generally not intended to protect for the same period as the UV protectants.

OEM UV Protectant. Another option is to go to a professional painter and apply the professional grade UV protectant that is more similar to the protectant from the vehicle manufacturer. This is an expensive process for small batches due the equipment and skilled technician requirements.

Clear coat. A clear coat is intended to provide very long lasting protection against UV damage and is commonly used on top of car paint. However, the reason the auto manufacturer does not use clear coat on the headlight lens is it will cause refraction of the headlight beam.

Plastic outer cover. This option is a manufactured plastic cover that sits just above the headlight lens. This is among the fastest and easiest methods to use, but changes a vehicle's appearance and on some vehicles customers report that the headlight lens will still end up yellowing.

Vinyl film. The vinyl film option uses a film that is most likely originally engineered to protect a vehicle's paint or for applying graphics to a vehicle. Popular brands advertising their films to be safe for use on headlight lenses do not publish data regarding optical clarity, refraction, or attenuation that may be caused by their products when applied to a headlight lens. Manufacturers of films, such as 3M, explicitly do not recommend applying any of their films to a headlight lens. Similar to clear coat, the vinyl film may be very effective at protecting the headlight lens, it may also not be a good idea based on maintaining the engineered functionality of the headlight.

All plastics exposed to the sun will break down over time. Even for a new vehicle or replacement assembly, using a UV protectant will greatly extend the useful life of the lens. It is probably safest to use either a UV protectant spray or application intended for headlights or wax/polish, though the latter will not be a good option for people who are less likely to regularly reapply.

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