How risky is wet-sanding?

[paudashlake]

It is hard for me to describe... When you are wet sanding how easy is it to go too far and ruin the paint? How much experience should a person have before starting such an advanced detailing job? What is the worst thing that can happen while sanding? As I said, it isn't the easiest question to ask.. Any sort of answer (or reassurance) would be much, much appreciated..

[hot rod]

Re: How risky is wet-sanding?

With the wrong paper very easy. I go about 10X's back and fourth then wipe of film to see what i did. I use a paint thickness gauge, not need but a great tool. I use to work at a body shop when i was 15. The guys thier were great they would show you everything. Just grab an old panel & start sanding. Hope this helps.
Jim

[Markus Kleis]

Re: How risky is wet-sanding?

Although the wet sanding itself is a fairly easy concept (it's sanding, but on paint), the removal of the sanding marks can vary greatly in complexity. I've had cases where I was able to remove wet sanding marks by hand, and others that required a high speed buffer, M105, and wool.

Furthermore, the difference in paint depth and hardness varies immensely from one car to the next. some new cars will allow for a decent amount of sanding and subsequent compounding and/or polishing without significant removal or problems, while others will burn through the clear in as little as 8-10 strokes of sand papers.

In a nutshell, it is not advisable to wet sand without a moderate amount of practice on extra panels, as well as knowledge and experience with the entire process.

I definitely don't recommend just jumping into wetsanding on your vehicle, or a customer's vehicle without practice and being prepared to pay for a re-paint if it comes down to it. It happens.

[Michael Stoops]

Re: How risky is wet-sanding?

If you press too hard, work too long, or fail to use a block or pad of some sort, you'll end up with uneven sanding marks at best, or go too deeply into the clear at worst. Use of a paint thickness gauge is a good idea so that you can keep track of how much material you're removing - remember, you do NOT need to go through the clear completely to cause problems down the road. Most manufacturers advise against removing more than 0.5 mil of clear (which is typically 2 mils thick) so you can see that "going through the clear" isn't the only problem you can run into.

Hand sanding without a block or pad will cause you to sand with pressure points under your fingers, and very little (if any) pressure in the spaces between your fingers. Yes, even with your fingers held tightly together. This results in uneven sanding with high and low spots. Obviously this is not a desirable effect!

The sand papers you choose can have a huge impact as well, often when it comes to the removal of sanding marks as Mark has alluded to. Inexpensive sand papers will have a wide range of abrasive particle size on a given sheet. You may have 2000 grit paper, but that 2000 grit is an average of the abrasive particle sizes on the sheet, so the larger particles are going to cut deeper and potentially leave tracers behind. These are the random, deeper sanding marks left behind by these larger particles, or from the build up of material caused by poor housekeeping practices while sanding. Meguiar's Unigrit Sanding & Finishing Papers will greatly reduce the potential for these tracers due to the very uniform size of the abrasive particles.

This next bit might seem counter intuitive, but it's true: D/A machine sanding is less aggressive than hand sanding when using equal grit papers. Yes, you might thing using a machine to sand has to be more aggressive than hand sanding, but it's actually more controlled, leaves a more uniform scratch, and is overall less aggressive. As a general rule of thumb, D/A sanding is like stepping to the next finer paper when compared to hand sanding - so using 1000 grit paper with a D/A is roughly equivalent to using 2000 grit by hand. Of course, this all assumes proper use of the D/A sander, etc.

The new Unigrit Sanding and Finishing Discs Meguiar's has just introduced can be used to great effect with our G110v2 dual action polisher to remove heavy oxidation or severe water spotting, swirling etc from very hard paint. When used properly, and to address the right issues, this D/A sanding can be less invasive than repeated rotary buffing with a wool pad and a heavy compound. And it's more controlled, too. The resulting sanding marks, when finishing down to 3000 grit, can be easily removed with a foam pad and M105 in very short order.

There is a time and place to wet sand, but no matter the reason for doing it you need to understand the process and the potential consequences. If ever there was a technique to practice first on a test panel, this is it. Wet sanding paint tends to be a multi step process, and you generally need a rotary buffer to pull out the sanding marks. So if you aren't familiar with that process, you may have more to learn than you first realized. But these are great skills to have and can help you accomplish all sorts of severe defect correction once you know how.

We're planning a write up in the very near future on the use of the G110v2 for D/A sanding to correct very severe defects, so keep an eye out for it.

[RDVT4ME]

Re: How risky is wet-sanding?

We're planning a write up in the very near future on the use of the G110v2 for D/A sanding to correct very severe defects, so keep an eye out for it.

That should be very interesting! Looking forward to seeing that.