Recently I had the chance to pick up some paint and finish tips from Edwin Alvarez at Corvettes by J & D in Bellflower, California, where they do first-rate professional restorations of classic Corvettes. When they get through with a car, its paint looks so deep, dazzling, and liquid that you could almost go swimming in it. There is no hint of orange peel or other imperfection anywhere in the finish.
To achieve such a level of perfection takes hours of preparation before the car is painted, and more hours of careful hand sanding after the paint has cured, but it is worth it. None of it is easy, and it's anything but quick, but the results are spectacular. This final finishing process is called color sanding, and that is what makes the difference between a trophy winner and an also-ran, but preparation, especially on a fiberglass car, is also important.
Alvarez tells me painting a car such as a Corvette is not like painting a metal-bodied car. That's because fiberglass moves, shrinks, and changes with time. Even the most perfect fiberglass body will, in time, start to show the seams where it was glued together and will show small, shrunken flat spots as well.
This story started out to be about color sanding the new urethanes, but after hanging around at J&D for a few days, I realized there was much more to the story. We won't go into the actual shooting of the paint because that is another story in itself, but we will talk about some of the unique problems fiberglass car painters face, as well as how to color sand the new urethanes to a show-quality finish.
In The Beginning
The major challenge that faces Corvette restorers is getting the old paint off. You don't want to use conventional methyl chloride paint strippers because they can cause damage to the plastic below. About the best way to remove the old finish is to use an air or electric circular sander and 300-grit open coat, dry sandpaper. This process, using such fine sandpaper, takes more time, but it also minimizes the risk of damage to the fiberglass underneath.
Another advantage to sanding the old finish off your Vette is that it also takes out the little flat spots and shrunken areas that have developed in the body surface, and it helps clean up and hide body seams. Just be careful not to linger on sharp fender crowns and edges while sanding. In fact, if you want to strip your Corvette, find a damaged fiberglass panel to practice sanding on because if you aren't confident and experienced with a spinning sander, you could do some real damage. Small problems can be fixed with a thin layer of filler later, but deep grooves would be an expensive mistake.
Don't get impatient. Coarser sandpaper would take the paint off faster, but it could leave deep grooves that would weaken the car's body. And given that fiberglass panels are more flexible than metal ones, and if the panel is weakened, any filler you use to hide deep mistakes would be very liable to cracking. Plastic filler or Bondo-the brand name of one of the original makers of the stuff, and the slang term for it-works well if it is not bent or subjected to vibration, but it was never intended for flexible panels or to repair the sharp edges of hoods or doors.
Before beginning to strip the car of old paint, remove all the trim and triple tape anything you might accidentally scratch, such as window glass. Put on at least a particle mask before starting, and then begin sanding. Do not apply heavy pressure and keep the sander moving at a steady pace at all times.
Let the sandpaper do its work, and when it starts to clog, stop the sander and brush the dust out of the disk. As soon as the sandpaper starts to lose its "tooth" or cutting ability, change the paper rather than increasing the pressure. Otherwise you risk damage to the car's body. Just remember, sandpaper is cheap, but body panels are expensive.
Painting a fiberglass car is essentially the same as painting any other car, and exactly how you go about it depends on the paint system you choose. Suffice it to say you should always stick with just one brand of paint and one paint system because modern paints have very sophisticated chemistry and may not be at all compatible with one another. Most cars these days are painted with the new urethanes because they are so durable, and because they meet environmental rules concerning VOC (volatile organic compounds) in the atmosphere, so that is what we will be working with here.
Whether you paint the car yourself or have someone else do it, just make sure you put on enough paint to allow for color sanding. One-stage urethanes must go on a little thicker to allow for sanding, and with basecoat/clearcoat systems, you should also shoot on a little extra clearcoat to allow for color sanding.
Everyone by now has seen cars that were painted with basecoat/clearcoat systems where the clearcoat is clouding and flaking off. That happens because with wear and polishing, the clearcoat gets too thin and allows UV rays through the topcoat, and that makes the clearcoat pop off.
And since color sanding takes some paint off, you need to make sure there is enough to allow for it in the first place. By the way, some older single-stage finishes can be color-sanded to make them look good, but you shouldn't try it with an older basecoat/clearcoat system for fear of making the clearcoat too thin, especially on tops, hoods, and trunk lids.
After the car is painted, the first step in getting rid of all the orange peel and imperfections in your new finish is to wash the car carefully. Any small bits of grit or dirt will make deep scratches that may be impossible to sand out. And it goes without saying you will want to work in a clean, dust-free area. If you are working indoors, you can wet the floor to minimize contaminants, or you can work outdoors on a wet concrete driveway provided the air is clean and the wind is not blowing.
After you wash the car thoroughly, go over it with a tack rag to pick up any missed grit. Next, attach a disk of 1,000-grit open-coat sandpaper to the disk of a variable-speed orbital sander and set it to its lowest speed setting. Never use a constant-speed sander because they spin too fast and will take too much paint off. In the old days of lacquer and acrylic enamel, we used to do this preliminary sanding by hand, but the new urethane paints are so hard you need an orbital sander to make any headway with them.
Once again, put on your particle mask. Work fairly quickly using the orbital sander, never letting it linger in one spot. Use a rag or compressed air to blow off the dust. Check your progress frequently, and when there is no hint of orange peel left, move on to the next area. Don't go near fender crowns or hood, door, or trunk lid edges because the paint is very thin in such areas.
In fact, it is a good idea to tape along such areas using masking tape to prevent sanding them. A small, rubber sanding knob that takes disks of adhesive sandpaper is good for getting close to such areas. Once the car has been sanded completely so there is no orange peel showing anywhere, it is time to start wet-sanding. Put a few pieces of 1500-grit microfine wet and dry sandpaper in a bucket of clean water with a little dish detergent in it to soften the edges of the paper. Let this stand while you wash the car again and go over it with a tack rag to get rid of stray dirt.
Wrap a piece of sandpaper around your sponge rubber sanding pad. Now, using a soaked rag or a garden hose to keep the surface wet at all times, sand the surface to remove the fine scratches that the coarser sandpaper made. Work in short, six-inch strokes and don't apply much pressure, and keep your work wet at all times. Let the sandpaper do the work, and when it gets dull, change it rather than applying more pressure. Otherwise you could make grooves in the paint and damage the finish. And don't get in a hurry at this point because you could spoil a lot of hard work if you do.
Color sanding a car takes many hours, so put on a CD of your favorite oldies and relax while you work. You can check your work periodically using a squeegee. The whole car should have a smooth satin finish with none of the scratches from the 1,000-grit paper still in evidence when you are done.
Tack rag the car again, then get out your variable speed buffer and set it on the lowest speed setting. Unless you are a pro, never use a constant speed buffer to polish out a finish because they can burn and remove paint in a hurry if you aren't very careful. Tape off the edges and sharp crowns of the fenders to prevent damage. Attach a wool buffing pad, then shoot a little of the buffing compound on the car.
If you are right handed, use the 12:00 to 3:00 quadrant of the pad for buffing. Use the 9:00 to 12:00 position if you are a leftie. Never buff with the pad flat because you can't maintain adequate control that way. Also, never let the pad go dry of compound because you will burn the paint if you do. Again, work back and forth in a constant rhythm, never lingering in one spot. Use a soft, clean micro-finishing cloth to remove excess compound and dust.
By now your paint should look dazzling, with only the slightest indication of spider-webbing. Pop on the fine-foam buffing pad and go to the next compound, or if you have purchased a System One kit as we recommend, use the same compound you used for the first step. Buff the car again and then stand back and say wow! You will be amazed at how beautiful your classic looks.
Finally, to bring out the last bit of blinding dazzle, go over the car with a micro-finishing cloth and a little glazing compound. This will also help protect the finish without dulling it. And if you are going to be driving the car on the street or out in the weather, wax it with pure carnauba wax with no cleaners. By now, your car's finish will be so shiny that even the cleaners in most waxes will dull it.
System One polishing kits include all the buffing pads, the System One compound and glaze, plus sponges and micro-finishing cloths, and are available from: