Basic body work part 4: Wet sanding, buffing and polishing

Per
By Per Schroeder
Jun 20, 2022 | Paint, Body Work, GRM+, Polishing | Posted in Shop Work , Restoration & Renovation | From the April 2008 issue | Never miss an article

Photography by Tom Heath

Paint work is more than just a wafer-thin candy coating. It’s a complex surface treatment that fills holes, reflects light and protects your car’s metallic structure. A DIY paint job isn’t over when you’ve sprayed your last droplet of paint—there’s still plenty left to do to make the car shine, even if it doesn’t quite come out the way you intended. 

After the paint is fully cured, you can remove contaminants like bugs and dust, sand down runs and orange peel, and even fill small holes with more paint. The trick is understanding that the human eye is trained to notice inconsistencies and differences in a finish; if everything looks similar, even if it’s similarly irregular, all that registers in most people’s minds is good paint work. 

Step 1: No Runs, No Drips, No Errors

A paint run or sag is simply a place where the paint’s viscosity can’t support its own weight on a vertical surface. The more thinner or reducer the paint contains or the thicker it’s applied, the more runs you’ll see in the finished product. 

You can use a hand-held paint planer to remove fully cured runs. A paint planer is a small piece of file that is mounted on a block of wood. There are also versions that use a razor blade to cut off the top of a run. 

Step 2: Paper or Plastic?

Extremely fine grit sandpaper can be used to knock down surface irregularities. For rough texturing, you should start out with 1200-grit and work up to 1500 and 2000. If the finish is pretty good, just go with the 1500. Sand until the surface of the paint is uniform—uniform irregularity like a light orange peel can be good enough. All you’re trying to do is fool the eye into thinking that everything is level.

Step 3: Slippery When Wet

Don’t just start sanding bare paint. Liberally use water to lubricate the sandpaper as it removes excess paint. We’ve had good luck adding a few drops of soap to a bucket of water to make the paint even easier to sand. Make sure that you don’t sand all the way through the paint—be especially careful around ridges and edges.

Step 4: Polish to a Shine

After the car has been wet sanded, you can break out the polishing compound. We have successfully used inexpensive polishes to bring the shine back to our paint. It can be applied by hand or with a random orbital polishing tool. 

Step 5: Tools of the Trade

Polishers like this inexpensive model from Harbor Freight don’t accomplish much more than hands do. However, a polisher can save you some muscle energy. Keep in mind that polishers are much less likely to burn through thin paint than high-speed buffers.

Step 6: Wax On, Wax Off

After the paint has been polished, it’s time to put a coat of wax on it. We’ve had good luck with P21S carnauba wax—it’s not inexpensive, but it applies very easily and creates a nice shine.

Step 7: Maintain the Finish

Maintaining a paint job is a matter of making sure the paint is clean and well-waxed. Use a paint cleanser or a clay polishing bar to remove surface contaminants before the next application of wax.

Step 8: The Finish Is Finished

All done. Now go get it dirty!

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