Measuring Paint Thickness?

[SeaDweller]

Greetings,

I have micro-swirl marks and scratches in my paint that I'd like to polish out. I plan on using 3M Perfect-It II, along with an orbital buffer. I realize a rotary buffer is more efficient, but I'm a big believer in doing a little at a time!

I understand that there are measurement devices that can determine paint thickness, and I'd like to do this before getting underway with the polish. The car has been garage kept and waxed prodigiously its entire life, and with that much waxing, I wonder how much paint is left. Problem is, I can't find a shop in my area that has one of these devices!

Anyone know of someone in the Tampa Bay area that does? Is it something I should be concerned with? I'd sure hate to see primer through my original, near flawless Guards Red paint!!

Thanks!

[911pcars]

Try your local auto body paint store. They should have one of several measuring instruments on the market. The cost is commensurate with their accuracy. The least costly is about $40 and they go up from there. Not sure about Porsche color coat/clear coat mil thickness in '85. An experienced body shop might be able to tell you (or someone on this board). I know that late model cars using water-based paint is thinner than with solvent-based paint jobs.

You're doing this the right way. After "mapping" out the paint thickness in the buffing area, you can buff and detail knowing how much you can remove before getting too thin. Use a foam bonnet. A successful paint detail won't need any glazing compound to hide swirl marks.

Sherwood Lee
http://members.rennlist.org/911pcars

[SeaDweller]

Interestingly, I've contacted all of the "high end" body shops in my area, not to mention the detailers that the local high end car dealers use, and not a single place uses one of these tools. They all tell me "I can tell by looking at it." Maybe they can, but I'm not going to bet an original paint job on it.

I used the 3M Perfect-It on my SC, after wet sanding most of the car, and it's fabulous stuff. Definitely no need for glazing, as the Perfect-It creates a mirror finish. Follow with a good coat of wax, and viola!

[911pcars]

"They all tell me "I can tell by looking at it."

Those paint shop folks must have better eyes than the rest of us mere mortals. You can do a search using Google or equivalant under "paint thickness gauge". Most are electronic and expensive. The more affordable, but less accurate gauges are of the mechanical "pull-off" type.

Not knowing how much paint or clear coat remains on a panel before color sanding, buffing, etc. is scary. I guess these shops just cross their fingers and proceed.

Hope this helps,
Sherwood

[911pcars]

You would have to get primer, color and clear coat thickness information from the manufacturer or from a body shop who has carefully documented the layers they uncover during repairs (yeah, right). Manufacturers know the average thickness of all these layers - even more so now that painting is done robotically. Does PNA have a tech line? Maybe one of the body and paint experts at PCA (Paterek)?

Sherwood

[911nut]

I agree with Brian.
A paint thickness gage will give you an overall reading, that's all. That's most likely why all the shops in your area don't have them.

If you aren't doing any wet sanding with 600 grit paper, polishing the car with a orbital polisher isn't going to get you into trouble.

[911pcars]

"If you aren't doing any wet sanding with 600 grit paper, polishing the car with a orbital polisher isn't going to get you into trouble."

Paul,
In one of Michael's responses he did wet sand the car. Does he know if the PO (if not orig. owner) wet sanded it before? If clear coat is 3mil, how many more times can one wet sand and buff? All I'm trying to say is, one should if at all possible, get a baseline reference point of the average thickness of each coating layer before one starts sanding and buffing away. I doubt many detail shops will care as much as an owner who also may not be aware of this fact. The manufacturers who produce the chemicals and processes are aware of this dilemma (Meguiars, 3M). The information is out there. We're not talking about a limited-production vehicle. There were what, 20,000 + 911s produced over the years?

Sorry for the rant,
Sherwood

[SeaDweller]

Just to clarify, I haven't wet sanded this particular car. My late '78 SC was the car I was speaking of.

I spoke to a guy who works at a well known Porsche body shop here in town, and he said for purposes of polishing, measuring the thickness isn't necessary. He said the amount of material that polishing will remove is so thin, that if the paint were thin enough to get buffed through with a polish, you could tell by looking at it. Well, there's that "looking at it" comment again.

I guess I shouldn't run into too much trouble if I stay off the edges...........

[Randy Webb]

Try Scratch-X (from Meguairs) first. You may not need to mech. polish.

[thomschoon]

If you still want to measure the thickness, call a couple of powder coat shops or somebody who sprays aerospace. There are set mil thicknesses for both and a good shop should have a gauge

[johnco]

It's called a mil gauge. I have one you're welcome to use if you were closer. try any sand blasting/painting company. we had to follow thickness codes for the various primers and paints we used on offshore structures we built.

[wcroty]

It’s called a mil gauge. I would try one of your local paint reps (Dupont, BASF or Akzo Nobel) I believe Akzo Nobel has a Branch in Tampa.
Total system should be 4.5 to 5.5 mils
Just a quick tip do not wet sand a single stage product (no clearcoat)

Good luck,

Bryan