Just got my coating thickness guage

David Hayward

David Hayward

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Does anyone have a link to a thread or article on some guidelines for using this? I've read so many mixed opinions on what a good thickness is. My car has been hit with megs d300 on a cutting mf pad and then v38 on a polishing pad. My thickness measures anywhere from 97 to 114 microns. So to check I did my wife's 2011 Honda fit and on the hood and roof it gets as low as 85 and tops out at 106 on the doors. So how thin is too thin? My car is a 2011 vw cc and I also did my buddies 2014 vw Jetta and it was ranging from 104-117.

So really I'm looking for guidelines on how to use the gauge as a tool to make decisions. Can i finish polish my car every year with sf4500 or 4000 or is it too thin?
 
There are a few schools of thought on this... First knowing the history of the car helps. If it was bought new, no accidents, and never polished before - your pretty much dealing with factory paint at factory thickness. But, in real life - that is not always the case.

Second, consider what kind of car it is. Econo cars are going to generally have thinner paint. Big BMW and Mercedes luxo wagons usually have thicker paint. A lot of cars can be in between.

Another guide that is sometimes recommended is to measure the paint on the rocker panel on the inside where the door closes. This can sometimes give you an idea of how thick the paint was originally - as nobody has likely polished here. You can also try another location that likely was never polished - like underneath the license plate. This will give you an idea of factory thickness and AN IDEA of how much clear coat was removed. It's just a gauge though.

Readings all over? That can be normal. A very high reading on a panel usually will mean it's been repainted. But, your variations sounds fairly normal. Basically, most Japanese cars are on the thinner side anyway - the PTG is just a guide. Try to be more careful on areas with lowest readings. There is no absolute cut off point.
 
Thanks a lot that helps a ton. I haven't thought of the hit an area not typically polished thing but that's a great idea.
 
PTG's are invaluable when confronted with a middle aged or older vehicle. Detailers that do it right make sure they take readings of paint thickness before taking a machine to the paint. You can't simply eyeball paint thickness and measuring it to actually quantify it's depth is one of the "best practices" of the pro's. A PTG can forewarn you of thin spots and can certainly help to avoid any mistakes that are too late after you encounter them.

And Trutech, i wouldn't worry about finish polishing anything ranging from 97-114. I would recommend taking an inconspicuous area...take a measurement first and then hit it with your finish polish effort. Then take another reading after. You'll probably find such a miniscule variation and that should give you some reassurance of how little you removed.
 
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