It’s just common sense. You are only as good a driver as your ability to see and for your brain to process what’s in your vicinity. Take it from me — I wear corrective lenses, but my vision is not all that poor. The astigmatisms don’t allow light to come to a focal point in the right spot, and this is what hinders my ability to see. During daylight, I have no problem identifying objects in my path, nor navigating a vehicle safely. But, when nighttime comes about, you had better keep your distance if I don’t have my glasses on. With a lack of light, my eyes’ ability to produce a clear image for my brain to process is extremely negatively affected. It’s crucial that my field of vision be properly illuminated and having a set of headlamps to cast a brilliant beam is what it takes to make nighttime driving or navigating in poor weather conditions safe and comfortable for me. Regardless of how brilliant the casted beam is, it won’t illuminate our path if encroached upon by a hazy headlamp lens.
How bright is “bright?”
Car headlamps are among the most important devices that secure safety for drivers and pedestrians during nighttime driving or inclement weather conditions. The brilliance of a headlamp’s output is crucial and typically rated in candlepower. Many states here in the US still implement a vehicle safety inspection program. In my home state of Pennsylvania, one of the criteria is adequate headlamp brilliance. According to the Pennsylvania Vehicle Equipment and Inspection Regulations, the specification required for low-beam headlamp brilliance on a passenger vehicle is a minimum candlepower of 7500. It is also required that drivers utilize the low-beam headlamps anytime a lack of sunlight inhibits the driver’s ability to see 1000 feet in front of the vehicle. Devices like the one seen in Figure 1 are used to not only check the aim of the headlamp beam but the brilliance, as well.
An article published by ReasearchGate references a study that was conducted to show the relationship between low beam headlamp detection distance and nighttime traffic safety. To analyze detection distance and reaction time by comparing features according to headlamp type, this study uses a computer simulation on 100 headlamp assemblies that were manufactured and imported for the past 10 years. The results showed a relationship between performance improvement and car accidents. Headlamps were categorized by year of manufacture (past 10 years), light source (halogen, HID, LED), and form (reflection type, projection-type) for analysis. Over the past 10 years, detection distance has increased by 6.6 meters and reaction time has increased by 0.34 seconds; the reaction times' of the High-Intensity Discharge (HID) headlamp and the Light Emitting Diode (LED) were 0.81 seconds and 0.23 seconds longer than that of halogen lights, respectively. Also, the decreased fatality rate according to the increase of reaction time of headlamps shows that the increase of headlamp performance has had a positive effect on the decrease in road fatalities. Just take into consideration how much of an effect projected light has on overall driving performance.
The cloudiness of an oxidized headlamp lens
We’ve all seen them, many of us had the pleasure of night-time driving with them, but what is it that makes the “cloudy-lens” so cloudy? It’s similar to seeing through an eye that suffers from a cataract (Figure 2). Research conducted by AAA reveals that clouded or yellowed headlights generate only 22 percent of the highlights capable output from new. Most headlights are made of polycarbonate plastic and exposure to sunlight breaks down the plastic coating, causing discoloration that obscures the amount of light produced. Depending on where and how the vehicle is used, headlights can begin showing signs of deterioration as early as three years to five years. The damage to protective plastic coatings, results in discoloration that considerably diminishes the headlight’s ability to provide adequate light output.
The fact is more than 50 percent of crashes occur at night and many of them can be attributed to an inability to see properly, due to poor headlamp output. To understand this better we will refer to a diagram of a headlamp lens that is extremely weathered (Figure 3). The degraded plastic acts as a screen and redirects light (just like my astigmatisms) away from its intended target. Again, regardless of how well the bulb functions or how much candlepower the beam is rated at, if its headlamp has to cast its beam through the cloudiness of a weathered lens, the performance is drastically reduced. Replacing a headlamp is an option but typically very expensive. Restoring headlights, while the most cost-effective option, offered less of an improvement in light output than replacement but, still very effective nonetheless. Professional and DIY restoration returned light output to approximately 70 percent of when it was new. A tremendous improvement for a relatively inexpensive service.
The restoration process
Some headlamps see their surface get degraded due to sun fade (Figure 4). A common restoration technique involves using wet sandpaper (beginning with 600 grade) to remove the original protective film from the headlight lens (Figure 5). The resulting scratched surface of the polycarbonate is then polished using increasingly finer grades of sandpaper (up to 2500 grade) and a protectant film applied to the entire surface of the headlight lens (Figure 6). This technique effectively removes the oxidation and exposes an even surface, free from degradation. The finer scratches are removed with the higher grade of sandpaper and the surface is than sealed with a UV protective conditioner to prevent future degradation. This restores the headlamp to is original luster which not only improves the vehicle's appearance but more importantly, restores the headlamps' brilliance and performance.
Some other DIY remedies to removing the degradation from the surface of the headlamp seem to be pretty effective. For instance, one remedy is to first clean the surface of the headlamp lens with glass cleaner, to remove any dirt and other surface contaminants. Afterward, isolate the surface of the headlamp from the painted surface of the vehicle with painter's tape to prevent any damage to the paint.
The second step is to use a cutting pad along with some polishing compound like this example from Maguire’s (Figure 7). This will be used to remove the oxidized plastic that has been caused by the effect of the UV rays from the sun.
The third and final step is to protect the newly restored surface of the headlamp lens. This involves applying a carnauba wax on a finishing pad. These can be found in almost any store carrying automotive products. What is left is a beautiful shine and protected surface that will leave the headlamps sparkling. It certainly makes the vehicle look years newer and more importantly, allows the headlamps to perform brilliantly, as they did when they were new. All in all, you're looking at about a 30-minute job with beautiful results. Her you can see both before restoration (Figure 8) and afterward (Figure 9).
Crazy, but effective remedies
Some of these more seemingly insane remedies I wouldn’t believe could work until I saw it with my own eyes. One involves using a toothbrush and toothpaste! (Figure 10). After cleaning the surface of the headlamp as was done in the prior examples, a light coating of toothpaste is applied to the surface of the headlamp lens and rubbed in with your hand (preferably one that has baking soda as this serves as a grit to help remove the degraded surface of the headlamp). You can lightly polish the surface with the toothbrush. You'll then spray the headlamp assembly with water and use a paper towel and some "elbow-grease" to buff the toothpaste away. The final step is to use some wax to seal the surface of the headlamp and protect it from the harmful effects of the sun and prevent the future degradation of the plastic surface of the headlamp lens. Now, I will admit that this method is not as effective as the previous but is far less expensive and certainly can't hurt to try to save some cash.
Although I do not recommend this following method for headlamp restoration, I have seen it performed and it does work. Applying an insect repellent to a towel and with moderate pressure, rubbing it into the surface of the headlamp lens does somewhat restore it. You must use a repellant containing the chemical DEET. The chemical reaction occurs with the DEET in that it causes it to melt the plastic a bit. It’s not as effective as the previous method and the results only last a few months. One of the benefits of this method is that it’s extremely inexpensive and simple to perform. The downside of this method is that the results only last a few months. More importantly, the chemical reaction could ruin the surface of the headlamps and cause some major damage to the paint on the car. Again, this method is not one we recommend!
Another effective method to restoring the condition of your vehicle's headlamp lenses is by applying WD-40 rust inhibitor. WD-40 was initially designed to work on missiles as when applied, it fills the surface of the missile’s minor imperfections with oil. The WD-40 serves the same purpose on the surface of the headlamp lens. The microscopic imperfections caused by the oxidation are filled with oil, preventing the light from being refracted away from its intended focal point. Simply apply the WD-40 with a microfiber towel and wipe it along the surface of the headlamp lens. It's as simple as that and the process can be repeated about every 6 months or so. A very inexpensive and least time-consuming and safe method I can think of.
Another simple and safe remedy is to create a mixture of baking soda, dish soap, vinegar. It can be made into a paste. Applying this slightly abrasive paste of home products to the headlamp and scrubbing the lens provides for some pretty dramatic results. The paste effectively removes all of the oxidation and typically doesn't require too much "elbow grease" to get the job done. It is safe for the environment too! Be careful with this method as too much “elbow grease” can permanently damage the lens.
It may seem trivial that the headlamp's performance drastically affects the safety of everyone on the road. It should be obvious that as drivers if we can't see properly, we can’t react properly to the conditions surrounding us on the road. Even a well-functioning headlamp circuit with a bulb of an adequately rated wattage cannot do its job effectively if it is hindered by the cloudiness of sun damage and oxidation. Take a moment to evaluate the condition of your customer's headlamp assemblies. Consider including the evaluation as part of your routine multipoint inspection so it becomes habitual. Most of the headlamps you will encounter requiring restoration will be extremely obvious. However, if faced with a headlamp that may seem marginal, perhaps consider using a tool similar to the tool in Figure 1 to evaluate the headlamp's performance. You can even use the tool to prove that the restoration had a positive effect on the headlamp's performance and give both you and your customer peace of money that time money was well-spent. Besides providing better illumination of the road ahead of your customer, they’ll find the appearance of their vehicle to be more appealing too and can be a nice profit -producer for you and your shop!