I've been playing around with Greg's Highland PTG. I'm starting to re-think the necessity of the three layer reading Defelsko...
My primary use of a PTG would, of course, be to determine the thickness of the clear coat. I was thinking that would only be possible using the Defelsko, since it will actually tell you the thickness of each layer (primer, base, and CC). Well, there may be other options.
This isn't an exact way to tell the thickness of the clear coat, but I think it might be close enough. By raising the hood of my car, I can see where the clear coat layer of my front quarter panels stop. Now assuming that the base color layer was applied uniformly to the entire quarter panel, I took thickness readings along the entire length that didn't have clear coat applied to it. I came up with an average reading of 2.3 mils. I then also took readings of other panels (like under the hood, and around the trunk) that had been painted but not clear coated. I think that some of these panels didn't have as thick of a color base applied to them. I got readings as low as 1.5 around the trunk. I decided to use the readings from the quarter panels, since I thought it would be likely that the area right adjacent to the part that was clear coated would have the same thickness of color layer.
So assuming that the readings from the quarter panels more accurately represented the thickness of the color layer, I used 2.3 as my base reading for the thickness of the primer/base. I then took readings all over the car.
On panels that I hadn't compounded, I averaged 5.3 mils. The horizontal surfaces (that had seen
multiple passes of SIP and purple foamed, as well as multiple passes of finishing polishes averaged 5.0, with a low of 4.8(!). So I'm assuming that my clear coat is approximately 2.5 to 3.0 mils thick, and this is after all the polishing I've done. I guess that would make sense, assuming that clear coats are usually a bit thicker than the primer and color layers combined. It would also appear that in several areas I have reached the max recommended clear coat removal of .5 mils.
However, I'm starting to have second thoughts about the "max recommended clear coat removal" numbers. It would seem to me that an actual minimum clear coat thickness would be more important than an amount removed. Even afer removing as much as I have, in the thinnest areas, I still have about 2.5 mils of clear left.
I'm also thinking it would be helpful to have some sort of minimum basline clear coat thickness established for doing customer cars. It's impossible to know the cars history before you got it. How would you ever know if the recommended max clear removal numbers of .3 to .5 mils was already reached? It would be far more practical to say something like "well, this car has 2.4 mils of clear on it, and since the minimum safe clear thickness is (and this is just a guess) 1.8, I do have some clear to work with."
This is starting to make my head spin.... Help!
