To Sand or Not to Sand…. That is the Question! Do-It-Yourselfers and novice detailers often ask, “When do I turn to wet-sanding as the best form of paint correction for my vehicle?” It is a question without a simple answer, but that doesn’t mean there aren’t a few different answers, so let us start by putting the question into perspective. The clear coat on your automobile is thinner than a dollar bill. Most paint correction specialists agree that since the top one-third of it is mostly UV protection, you would not want to remove more than 25 percent of it over the lifetime of the vehicle. Given the delicate nature of the paint and clear coat, the idea of using an abrasive like wet sand is enough to make any car lover squeamish.
Then consider the cost of “clear coat failure” ― a catastrophic term for the damage caused by a technician’s miscalculation or mistake in judgment while repairing a defect. As Mike Phillips, one of the auto appearance industry’s most knowledgeable experts, says, “…In all the years I’ve been teaching classes… most of the people that sign-up for the advanced class to learn how to wet sand, after they learn how to do it and what’s involved, they find they don’t really want to do it.” Now, by this point you may start to ask yourself the question, “If wet sanding is so dangerous, why is it used and why is it offered in every advanced detailing and paint correction seminar?” We respond to that question with a simple answer: Wet sanding is absolutely the most effective means for removing surface paint defects. The catch here is that it should only be done by someone with proper training. And even then a skilled professional should use a paint gauge to first check the thickness of the paint and clear coat to ensure it will support a wet sanding process. That said, body shops use wet sanding on a much larger level. They use it to even out new paint, to smooth out small runs and sags, to “knock down” orange peel, and remove any debris that fell on the paint while it was wet. By following up the wet sanding with a rubbing compound, the paint will virtually come back to life and give the vehicle the smooth, glassy look car owners love; however, unless you are painting an entire car by yourself, you are not likely to use wet sanding in that way. In terms of using wet sanding for larger jobs, we recommend exhausting all other options first. For instance, you may want to apply a compound to the entire vehicle first ― something like Correcting Polish, which is remarkably abrasive. If CP does not remove the deeper scratches or acid rain etching, you can then spot sand those spots.
Keep in mind that compounding or wet sanding does remove clear coat. Many detailers feel you have some wiggle room with the UV layers in the clear coat; however, one-third of the thickness of a Ziploc sandwich bag isn’t much at all, and one color correction is not the end of it. Assuming you or the car owner keeps the car for several years, you will require multiple cleanings, polishing, and in perfect cases, an annual color correction to maintain the paint and keep it free from swirls. You do not want to cut it so close on the first correction that you have no room to go from there. One of the less dangerous applications for wet sanding is in leveling touch-ups. By going lightly over a few localized spots with wet sandpaper, technicians can use spot sanding to “haze up” the paint enough to make polishing easier There are also cases where wet sanding is more effective than compounding. It doesn’t create the amount of heat that compounding does, yet, it is easy to get too aggressive. Mastering the “right touch” takes practice and finesse. In the same way you can burn the paint with a rotary buffer if not handled correctly, you can dig too deep with sand grit. As many professionals admit, neither compounding nor wet sanding is for the weak at heart. Even the most experienced detailing and paint correction specialists are aware they have very little room for mistakes and they would not risk weakening the paint or clear coat on a $100,000 automobile any more than they would a $15,000 vehicle. Again, according to Mike Phillips, “Sanding is the easy part. That is putting scratches into the paint. The tricky part is getting them out.”
There are times when wet sanding simply will not work, for instance defects that are deep enough that they cut through the clear coat and paint, all the way to the metal. This is common in vehicles that sit outside, uncovered for a couple of years, and suffer from deep acid rain etching. We also do not recommend using wet sand to remove contaminants since clay bar is the best way to do that. And here is another tip: never wet sand the basecoat! The basecoat is very thin and provides all the color on the vehicle. If you try it, you will find yourself sanding metal with a visit to the closest paint and body shop in your future! On the other hand, I think personality has a lot to do with it. Most of the detailers I know approach the paint on every car with the same intolerance for imperfections that make them geniuses at their trade. If there are still heavy imperfections you feel compelled to remove or lighten, after compounding, buffing, and polishing have failed, then spot wet sanding is the best process for doing that.
This compulsion to remove flaws the average customer would never notice, lead some to claim paint correction professionals do it for the money they can charge. I find that unlikely since most of them are much more concerned about the quality of their work than the monetary return. Multistage paint correction is a passion rarely if ever driven by money. Over all, it is good to have a healthy skepticism about when to wet sand, but fear should not prevent you from doing it if experience and training back up the need. So wrapping up, “When do I turn to wet-sanding as the best form of paint correction for a vehicle?” Our short answer is, “Not often, but occasionally, and carefully!”