Unless you're going to buy Defelsko that from what I've read can measure the actual clear coat I'm uncertain what the cheaper paint gauges will provide me?? Who cares if it reads 100 microns and 99 of that is the primer and base. We work within the clear coat and unless I can get a measurement of it everything else doesn't matter. Maybe I'm wrong? If so please explain.
You're correct... the only gauge that can read individual paint layers is an ultrasonic gauge like the Defelsko Positector B3 Advanced which retails for around $2300.
The other PTG that simply measure ferrous and non-ferrous metal substrates do not measure individual layers, but total film thickness from bare metal to the surface of the paint. Within this reading is the primer, base coat, and clear coat. So... this does not provide you with the critical info (ie clear coat thickness), but it does provide some good information to you nevertheless.
For instance, if you're taking readings on a vehicle, and the majority of the car is averaging around 120 microns (<- pretty typical readings in my experience... may range between 90-150, but a micron is an incredibly small unit of measurement, so this variance is expected from manufacturing), you then hit an area or maybe even an entire panel that is consistently reading 400+ microns. This will allow you to safely assume this panel was repaired/repainted. On the flip side, if you're taking measurements and then stumble upon a section or panel that is dangerously thin (say, sub 60 microns) you can safely assume this area was likely sanded or very heavily corrected in the past.
So what? You still don't know how much clear you have.
Well, yeah, that is very true... but you have MUCH more information than you did by just looking at the paint with your bare eyes. You now know that part of the car was repainted, so it may react differently to your correction process (or in worst case scenarios may be very fragile and more prone to damage) and you have identified areas where great caution is needed due to thin total thickness which ultimately means you likely have considerably less clear in that area.
So, to reiterate a comment I made previously in this thread, is a PTG absolutely necessary? No. It will not make or break you, however if you're a professional who is making good money correcting paint, it is a worthwhile tool to pick up. There are many options for under a few hundred dollars, which should equate to less than 1 day of work or less, so the small investment should be a no brainer for the peace of mind and potential savings by lowering your risk of damage.
If you're consistently working on high end vehicles, then in my opinion, you should absolutely invest in an ultrasonic gauge. The upfront investment is far cheaper than any potential damage to a supercar.
(on a side note - customers also really like seeing the tool. They're impressed with it and get the sense of a true high end service and know that their car is being taken care of since no one else will have this type of tool)
You've just got to arm yourself with the tools & equipment to gather information about the vehicles you are working on to make your life easier. If you don't think a PTG is needed, then don't buy one. Just like some people still use rotary polishers instead of da machines... there is no right answer, just preference.
-Zach
