Products tried or evaluated:
Customer base: Everything from buy here/pay here to retail.
Having learned a few tricks over the years, I’d like to share some thoughts with others either presently restoring headlights or thinking of doing so.
First of all, I don’t believe there is a one size fits all approach to restoring headlights. It’s a function of each situation and is based on time, customer’s expectations, price and longevity. For example, at a low end used car lot, they want it to look good, be fast, cheap and last long enough to get it off the lot. At the other end is a Lexus owner who wants their headlights to look like new and last for years.
No single approach can meet these two situations. We use different procedures and products for different customers.
Since the late 1980’s, most automobile headlights have been made out of polycarbonate, a type of plastic. This plastic gives auto makers greater design freedom than conventional glass headlights. Polycarbonate is impact resistant and easily formed into complex shapes.
Unfortunately, polycarbonate is also very porous and easily damaged by ultraviolet exposure from the sun. To seal and protect polycarbonate, headlights are coated with a protective outer coating when manufactured.
It is the breakdown of this coating which causes yellowing and cloudiness. Until fairly recently, the only solution was to replace the entire headlight assembly, which can easily cost hundreds of dollars.
As headlights deteriorate, less light is projected forward where you need it. The ability to see clearly can be reduced 75% or more, creating a major safety hazard. This is especially dangerous during bad weather. Here’s what it cloudy headlights looks like.
When headlights get this bad, many drivers drive with their high beams on in order to see where they are going.
The original protective coating applied by the manufacturer absorbs ultraviolet rays preventing them from reaching the polycarbonate and also seals out moisture. While doing its job, this coating slowly oxidizes, causing it to become cloudy and yellow.
This is what you are looking at when you see a yellow and/or cloudy headlight. At the factory, the polycarbonate is coated with a primer, baked, then sprayed with a thick protective coating and cured with ultraviolet. This process cannot be efficiently duplicated in the field.
To restore headlights to full clarity the oxidized coating is removed, and then replaced with a new coating. Just stripping the old coating off will leave the polycarbonate exposed to ultraviolet and moisture and will quickly deteriorate.
Any product that does not replace the protective coating with a new one is a short term solution. Without replacing this coating, the headlights will quickly deteriorate since there’s no protection. Wax protection is temporary on headlights just the same as it is on paint.
If a headlight does not contain internal damage and is not cracked, punctured or contain deep scratches not repairable by sanding, it can be restored to look like new. It’s just a question of time and money.
Here’s the procedure we use:
1) Evaluate the headlight.
a. Is it restorable?
b. What constraints do I have?
c. Time allowed, price, customer’s expectations
2) Protective coat adhesion.
a. Can it be chemically stripped?
b. Abrasive stripped?
So you now ask, what is the best way or which protective coating should I use and how long will it last? I’ll try to answer some of these questions.
Best way/best coating- depends on the customer and condition of the headlight. Choice of coating is the same.
How long will it last? Polyurethanes, 6 months to 3 years; Specialized coatings, 3 years or more.
Durability- When you do research you will see postings indicating coating lifetimes all over the place. Here’s why:
If you’re talking about solvent based urethanes (such as Minwax/mineral spirits mix) there are 3 main factors:
- UV exposure: A headlight exposed to the sun every day will fail in a matter of months. Also, the angle of the headlight plays an important part; the less vertical, the more exposure.
- Coating thickness: The thicker the coating, the more UV protection. The flip side of this is the heavier the coat, the more difficult it is to apply correctly.
- Surface prep: The surface must be absolutely clean with some tooth for the urethane to hold on to.
If you’re talking about synthetic coatings/polishes/wax, it’s the same as applying to paint. It’s temporary. Why would it be any different on headlights?We don’t use much polyurethane coatings any more. Only on quick and cheap restorations or on acrylic plastic such as tail lights, backup lights, turn signals, emergency vehicle lights, etc.
Most of our restorations use specialty coatings developed for this purpose. These products are not cheap, but represent less than a dollar per restored headlight. If you do use this type of product, make sure you do the following:
Moisture/wax/silicone is your enemy. Do NOT use any compound containing wax when polishing. Don’t use any wax coated cups to mix coating in. Don’t use foam brushes to apply (It will leave air bubbles)
Aggressively scrub the headlight with pure alcohol, not any mixture that contains water such as rubbing alcohol, which is (30%) water.
Use a lint free towel to scrub.
Use a 3000 grit polishing pad as the last step. It’s not for appearance. Urethanes are famous for filling in sanding marks. It’s for tooth. (Something for the coat to adhere to)
And there you have it.