Most modern headlamp lenses (within the last 20 years) are made of plastic (polycarbonate) as this allows car manufacturers more flexibility in design and also provides great protection for expensive headlamps. The downside, however, just as with the trim/molding on a car, is that headlamp lenses fade over time – even newer cars (~1-2 years old) can start to exhibit opaque/yellow/cloudy/foggy lenses. Faded headlamp lenses detract from the overall look of a properly detailed car. In this section we will attempt to understand why headlamp lenses degrade over time and describe some methods to restore them to like-new condition.
Why do headlamp lenses fade?
The main reason headlamp lenses begin to opaque/yellow/cloud/fog/occlude is due to their interaction with ultra-violet (UV) radiation. The plastic trim/molding on your car fades for the same reason. There are certainly other factors that contribute to lens degradation to include exposure to exhaust, extreme temperatures, salt, grime, oil, acid rain, etc., but the biggest culprit is UV light. The constant exposure of the lens to the elements leaves it looking pretty bad, to say the least.
Headlamp lenses are made of polycarbonate and, at their heart, consist of carbon-oxygen and carbon-hydrogen bonds. Polycarbonate offers great advantages as a lens material as it is light weight, moldable, cheap, etc., but also has its disadvantages as stated above. The physical reason for the lens degradation has to do with the fact that the energy of UV radiation is close to the disassociation energy of the chemical bonds – hence, over long periods of time, the UV radiation causes the bonds in the polymer to ‘disassociate’…and this leads to oxidation. To protect headlamp lenses from fading, manufacturers typically apply a coating to the lens – a hard, scratch-resistant, UV protected layer. Lenses that are exposed to sunlight (and the elements) for long periods of time, however, will eventually occlude as this protective coating starts to fail.
Headlamp lenses on most cars that are over 2 years old will undoubtedly show some signs of degradation unless the car is maintained regularly or garage kept. There are a lot of products on the market to restore headlamp lenses to like-new condition…some of them fail miserably, while others are quite good. Situations will arise, however, where the lens suffers from severe damage, due to extensive UV exposure, and, as such, it can not be restored using the below methods and will need to be replaced. It is cheaper to try to restore them initially and if you fail then you can always buy new headlamp fixtures.
Restoring Headlamp Lenses
Headlamp restoration is not too difficult provided you have the right products and equipment. As with all detailing processes, start with the least aggressive method first! Here we discuss three methods, from least aggressive to most aggressive, that should enable you to restore headlamp lenses to like-new condition.
Method 1: Least aggressive method – using an AIO
First and foremost, wash the lens with a dedicated car wash soap to remove any superficial contaminants that reside on the lens. At this point you will have a clean, yet foggy, lens. The least aggressive method of restoration is to use an all-in-one (AIO) cleaner. Some AIOs consist of a solvent only while others consist of a solvent with a mild abrasive. Independent of which one you try, this is indeed the least aggressive method (as compared to wet sanding that we will describe below). Klasse AIO, Zaino AIO, Poorboys World Polish with Sealant, or equivalent, may do the trick if the lenses are not too bad. All of these products are applied in a similar way – typically you apply a small amount of product to a foam applicator and work the product until a fresh, clean plastic surface appears. Different manufacturers have different application methods so be sure to check the manufacturer’s recommendations. Except for situations where lenses have shown very little deterioration, I have not found AIOs to be very effective…if an AIO doesn’t work for you then you will have to proceed to a more aggressive method.
Method 2: Next aggressive method – using a plastic polish
Following your attempt to use an AIO without success, you can try a dedicated plastic polish such as Meguiar’s PlastX, 3M Plastic Cleaner, Mothers Plastic Polish, etc. Most of these products contain diminishing abrasives that work to remove the top layer of your lens to reveal a like-new lens. Diminishing abrasives need to be applied a certain way in order to be effective. For the abrasives to breakdown appropriately (i.e. diminish) you will need to apply some pressure and work the product for a sufficient amount of time – in this way, the product will remove the discolored plastic and expose new plastic. As with the AIO, make sure you follow the manufacturer’s recommendations for application. I have used PlastX to a certain degree of success…similar to the AIO method above, however, if you are trying to restore a lens that shows excessive signs of deterioration then you may have to use a more aggressive method than a plastic polish will offer in order to see decent results.
Using a plastic polish is quite straightforward and can be done by hand or with an orbital buffer…using a buffer will provide the best results – the only drawback of using a buffer is that the pad size is usually too big and the pad will inadvertently polish some of the paint surrounding your headlamp unless you use a smaller pad or protect your paint appropriately. PlastX is a popular product that can be found at most automotive stores…so, in what follows, we will assume you are using PlastX although the steps will most likely be the same for other products.
- As with any product, make sure you shake the bottle thoroughly. This step is often overlooked but is absolutely necessary as the contents of the product tend to settle over time. Also, make sure the lens is clean before starting…simply wash with car wash soap.
- If you are using an orbital buffer, try to use a 3.5-inch backing plate with a 4-inch pad…if you don’t have smaller pads, that is fine – just be careful and protect the surrounding paint if you are concerned. Pad choice is important. Lake Country (LC) pads are the most popular…if using LC pads, start with a White pad. If you are not using LC pads, try to find an equivalent to the White pad. If applying by hand, simply use a foam applicator. Independent of what method you use, place a quarter-sized amount of product on the pad to start.
- If using a buffer, place the pad on the lens surface and turn on the buffer…if using the Porter Cable or equivalent, set the buffer to #5. Work the buffer over the headlamp lens in a back-and-forth, up-and-down motion (see video clip below). If applying by hand, move the applicator, with firm motion, over the lens – you can use horizontal, vertical, or circular motions. Continue polishing until all the polish is gone.
- At this point, wipe the lens with a damp microfiber towel to remove any residue and inspect the lens. In most cases you will have to repeat Steps 1-3 again until the lens looks new.
Method 3: Most aggressive method – wet sanding and polishing
Wet-sanding/polishing is the most aggressive method you can use…if wet sanding and polishing does not work then you will have to replace your headlamp fixture. I will forewarn you, there are some headlamps that have a coating that does not respond well to sanding – you should always test a small inconspicuous area first to ensure the process will work before moving onto the whole lens. Wet sand the corner of the lens – if the plastic starts to turn white, do not continue. I have never experienced a lens that could not be wet sanded but I have heard of it. There is a video below that shows this process.
- You will need some fine-grit wet/dry sandpaper…I recommend 1000 and 2000 grit…keep in mind that most polishes will remove 2000 grit and finer sanding marks…so your final sanding needs to be done with 2000 grit or finer. Fill a bucket with some water and soak the sandpaper in the bucket for about 30 minutes prior to starting. While the sandpaper is soaking, you may want to mask off the surrounding portions of the headlamp with blue painter’s tape in order to protect your paint finish.
- Prior to wet sanding, make sure the headlamp is clean. Take the 1000 grit sandpaper and sand the lens, side-to-side, applying light to medium pressure…the oxidation will begin to disappear and you will be left with a foggy lens again…but this time due to the sanding marks! Make sure you keep the lens and paper wet throughout the whole process.
- Now take the 2000 grit sandpaper and sand the lens top-to-bottom, applying light to medium pressure…what you will notice is that the lens will appear to clear up a little…this is due to the finer grit sanding. When you are done sanding, wipe the lens clean with a damp microfiber towel.
- At this point, you will need to polish the lens with a buffer to remove the 2000 grit sanding marks…I don’t recommend you attempt to polish the lens by hand. An orbital buffer, such as the Porter Cable 7424 (or variation), will work well. You will need two levels of polish and two different pads to properly polish the lens. You can use Meguiar’s 105/205 or Menzerna PO83/PO106FA…or another suitable two-level polish pair. In addition, you will need two pads…if using LC pads, Orange and White will work well…if using Meguiar’s pads, W-8006/W-9006 will work well. You may be able to get the sanding marks out with just one pad and PlastX but you will not achieve a high-quality end result – I highly recommend a two-step process.
- Start with the more aggressive polish/pad combo (e.g. PO83/Orange pad) and polish the lens thoroughly (see video below). When you are finished polishing, wipe with a towel to assess progress…you will most likely have to polish a second time – once you are complete, move on to the less aggressive polish/pad combo (e.g. PO106FA/White). Again, when you are finished polishing, wipe down the lens with a microfiber towel and inspect your work…if you see sanding marks present then repeat the polishing step with the most aggressive and then least aggressive. See the video clips below for the complete process.
Headlamp Restoration Video
IMPORTANT: Don’t forget to protect it!
Independent of what method you use above, you will need to protect the lenses when you are done…this is very important. Keep in mind that the plastic is now completely exposed to the environment and does not have protection – it will simply oxidize again in the near future if you don’t apply a sealant (such as Meguiar’s NXT Tech Wax 2.0 or equivalent).
- There are a plethora of plastic polish products on the market. I have not used a lot of them as I have had complete success with the methods above. I have read great reviews about the Novus line…Novus 1, Novus 2, and Novus 3…if you are not having success with the above methods then you may want to try these products. Keep in mind that most headlamp lenses are actually beyond simple oxidation/yellowing and the protective coating that the manufacturer applies is probably long gone. As a result, simple plastic polishes may not work for you but wet sanding/polishing should.
- If the headlamp lens is scratched, pitted, gritty, etc. then it is probably beyond repair of the methods above. You should still be able to get it clear but keep in mind that some defects may reside.
- You may be wondering why I keep calling them ‘headlamps’ as opposed to ‘headlights’. Well, the simple fact is that they are actually lamps…the light emanates from the lamp…it’s simply a mild form of obsessive-compulsive disorder.