Restoring Plastic Headlight Lenses
The 3M Corp. of Minnesota is one of America's largest corporations, but not too large to put on seminars for about 40 old-car hobbyists at Gunner's Great Garage in Manawa, Wisconsin. The topic for one session was the restoration of plastic headlight lenses and we want to share the advice that was given in the seminar with restorers who visit Second Chance Garage online.
American automobiles started using plastic headlight lenses in the 1980s or 1990s, depending on when major model changes were done. Instead of the one-piece sealed beam headlight that was introduced way back in 1940, headlights swung back to having separate bulbs. However, the use of a clear plastic lens was totally new. The new lenses also fit into plastic housings and the screw-in bulbs were much smaller than the headlight bulbs of the '20s and '30s.
The plastic lenses gave car stylists more flexibility in the shape of headlight lenses. Another advantage was their ability to withstand minor impacts better than glass lenses. However, as the lenses aged, motorists complained that they were getting hazy and the headlights weren't as bright. The early plastic lenses degraded quickly, taking on a cloudy, scratchy look that could not be cleaned.
To fight the degradation of the plastic, automakers began applying a clear protectorant to keep UV rays from breaking down the clear plastic. This coating delayed the deterioration, but didn't eliminate it. The problem still surfaced after a couple of years. The American Automobile Association and the Institute for Highway Safety discovered that 90 percent of cars with plastic headlight lenses have hazy headlight issues. Now that hobbyists are collecting such models, both do it yourselfers and professional restorers are dealing with the problem.
Two Types of Restoration Kits
Luckily, 3M is now making two types of headlight restoration kits that can be used to restore hazy headlights. Which kit is best for you depends on your situation. The retail kit that costs $15-$19 in big box stores and auto supply houses is fine for the person who wants to clean the headlight lenses on one car. It includes the pads and compounds needed to do the work and is designed to be used with your own electric drill. A professional kit that sells for around $400-$600 includes a variety of pads and two special 3M tools that allow you to clean headlights faster and easier. And if you're planning to do this on many cars (perhaps as a business) the professional kit is actually cheaper because the cost per headlight is $1.50-$2, compared to about $7-9 with the retail kit.
The Basic Process
The basic process of plastic headlight lens restoration involves cutting and polishing the lens with progressively finer abrasive pads that are spinning at high rpms on your drill or on one of the special 3M tools. You begin cutting with a 500-grit dry pad and move to an 800-grit dry pad. After that, you go to a 1000-grit wet pad and finally a 3000-grit wet pad. The higher the grit, the smoother the pad. You will be using the 500-grit pad more than any other, because you have to take the top, roughed-up layer of deterioration off the lens first.
If you use a pad on a drill to do the cutting, the cutting pattern will be circular only and you'll need to go carefully and take more time. If you use the 3M tools from the professional kit, one tool is a buffer that orbits and the other is a DA (dual action) grinder that has a random orbit. Cutting with a DA is easier because the tool's random orbit really breaks up the scratching pattern and makes getting the plastic lens smooth a lot faster process.
After the 500-grit dry pad is used, you'll switch to an 800-grit dry pad and make things that much smoother. Then, you'll switch to the 1,000-grit pad for wet cutting. You mist water on to get it wet. This pad will take a while to start cutting. When it does, you'll see a white slurry coming up behind the disc. That means you're actually doing some cutting. If you make the pad too wet, it's just going to hydrplane because the 1000-grit mineral is so fine. If you run it too dry, it will melt the abrasive right off the foam because the dry pad generates too much heat.
The higher-grit pads use 3M's Trizact™ structured abrasives, which are made by putting the abrasive minerals in a slurry and putting the slurry on the foam backing. The pads can be used over and over again, so don't throw them away too soon. The professional kit comes with two cutting pads, two polishing pads, two interface pads, back up pads, two tools, abrasives and instructions. The kit pads should do eight to nine headlights and professionals get about $40 per headlight. To make the pads last, you have to keep the moisture level right.
According to 3M's demo team, the inclusion of the 3M tools in the kits is a new thing and a big improvement. They operate at variable speeds so you can control cutting and polishing action. The tools are very robust and the team said that even if the biggest guy attending the seminar put all his weight on the tool, it wouldn't stop the motor. Even 80-grit surfaces won't slow the tools. They have drop in motors and replaceable grips, so you can swap in larger or smaller grips.
After the plastic headlight lenses are polished, 3M Performance Finish can be put on them to give an extra layer of UV protection. Other films and clears are not DOT approved, because of lighting safety concerns. Headlight lens polishing can be done with the headlights on a car if you tape carefully around the body edges to prevent any paint damage from contact with the abrasive pads. In many cases, an $80 polishing can avoid replacing headlights that cost $300 or more.
3M™ Headlight Lens Restoration Kit, 02516, Contains:
3M™ Random Orbital Sander, Pistol Grip, 3", 1/8 inch orbit — 1 tool with manual and wrench
3M™ Buffer, Pistol Grip, 3 inch — 1 tool with manual and wrench
3M™ Clean Sanding Disc Pad Kit, 3" x 1/2" x 5/16" — 2 pads
3M™ Hookit™ Soft Interface Pad, 3" — 2 pads
3M™ Purple Clean Sanding Hookit™ Disc, 3", P500 — 50 discs
3M™ Purple Clean Sanding Hookit™ Disc, 3", P800 — 50 discs
3M™ Trizact™ Hookit™ Blending Disc, 3", P1000 — 15 discs
3M™ Trizact™ Hookit™ Foam Discs, 3", P3000 — 15 discs
3M™ Perfect-It™ Foam Buffing Pad, 3" — 2 pads
3M™ Perfect-It™ Foam Polishing Pad, 3" — 2 pads
3M™ Perfect-It™ Rubbing Compound (16oz.) — 1 bottle
3M™ Perfect-It™ Machine Polish (16oz.) — 1 bottle
3M™ Directions for Use — 1 piece
3M™ Headlight Lens System Tool Bag — 1 bag