How do you determine clearcoat thickness with PTG?

I'm not sure how to measure clearcoat thickness amongst other layers of the finish. Additionally, what is the best way to determine a vehicle's original clearcoat thickness to ensure no more than 25% of the clearcoat is removed?

 

Bump . . . TTT

 

Well to be honest even with my PosiTector 6000 I can't read the different layers of paint and clear coat. My PosiTector 200 in the other hand does distinguish between clear coat and paint/primer.

Here is how I see things but again this is just my point of view.

The car industry has standards for how much clear coat to apply along with primer and paint. Thanks to my friend Gerry who owns a body shop he told me what numbers to be looking out for, for the most part a vehicle with 120microns and more has plenty of clear coat for a cut polish. If you come across a vehicle with say 60microns and lower, well that's when you really need to pay close attention to what your doing and you shouldn't be doing an aggressive polish/compound to the vehicle.

Also if you come across a vehicle that's given you some ridiculous numbers say 200microns and more well that's a sign of repaint and you would have lots of clear coat to play with.

However, don't be fooled, just because you get a high number doesn't mean that you have lots of clear coat to play with. What the PTG is giving you is the total amount of primer, paint and clear coat. So you don't really know how much clear coat you really do have to play with. I know there is a gauge out there that acts the same as the PosiTector 200 that can provide readings of each layer but it's very, expensive and for me I couldn't justify spending over $10,000.00 on a paint gauge..well not yet at least lol.

Again this is just my input, hope it helps.

 

An additional note to Nica's
"However, don't be fooled, just because you get a high number doesn't mean that you have lots of clear coat to play with"

Not that you truly want to use your eyes as a guage but I believe that you can actually see a thin clear coat. It looks similiar to single stage paint, theres a lack of depth to it.

If you were to hold up a single stage black panel and a repainted base coat/clear coat black panel you would be able to distinguish that difference with your eyes. Its an additional red flag you can use to be safe and reduce the potential of burning through.

Just my opinion.

 

Paint Film Thickness:


Automotive paint systems comprise of up to five different layers of paint. The system typically consists of:

A galvanized steel substrate with a thin crystalline tri-cation phosphate treatment to enhance adhesion and improve corrosion protection;
An E-coat is then added which is the first protective layer. This is electrodeposited and then cured

Lower panels have an anti chip layer, which is a thick layer designed to give protection against impact from stones

This is then followed by a primer (2.0 Mils) and a basecoat (1 – 2.0 Mils) layer, which is the colour layer

And finally polyurethane clear coats 2 – 3.0 Mils. The clear coat provides protection from a hostile environment and an excellent brilliance, but is easily scratched; once it is compromised repairs involve re-painting, as the base colour has no brilliance, shine or depth, start with the least abrasive product to accomplish desired results, and only if necessary move up to the next grade of abrasive.

Most factory paint jobs range from 3.5 to 5.5 mils (87 to 137 microns) (this will vary between manufacturers) for this reason, it’s also recommended that paint be measured when buffing since you can’t see how much paint is being removed during the buffing process. If an insufficient thickness of clear remains after polishing premature failures such as fading or delamination may occur as the colour coat won't be protected from ultra violet (UV) radiation and a warranty issue may develop in the future. Such risks can be alleviated by monitoring and minimizing the amount of top coat removed, which is best done through quick and easy measurements with an electronic paint gauge, and maintaining a record on a paint thickness template.

German and Japanese cars: 4-5 Mils (1 Mil=1000th of an inch)
With the exception of:
Lexus-White and Tan: 5-7 Mils, Lexus- Black and Silver: 4.5-6 Mils
BMW: Silver: 6-7 Mils
FORD: Approx. 5.5-7 Mils
GM Cars and Trucks: Approx. 4.5-6.0 Mils, Jimmy’s and Blazers: approx 7 Mils
Chrysler: Approx. 5.5-7 Mils (Note Sebring hoods are fibreglass)
Dodge Cars: Similar to Chrysler
Dodge Trucks and newer Ram Pick-ups: Cab approx. Mils and the boxes approx 9 Mils
Jaguar: approx. 6-7.5 Mils (but they tend to vary)
Jeep Grand Cherokee: These read approx. 6-8 Mils, Wranglers: approx. 4.5-5.5 Mils

Note- the above are provided for information only