Newbie question alert - Paint Depth Gauges

[danb986]

I'm probably going to embarrass myself now, but here goes anyway.
I'm totally new to detailing and have just been one of those guys that was a sponge and bucket once a month person in the past.

My question is about paint depth gauges. How do they work exactly? What I mean is, obviously it tells you how deep the paint is on the panel, but does it differentiate between lacquer, colour and primer.
If I put a gauge on a panel and it gives a reading saying that there's loads of paint to play with when machine polishing, how do I know it's not 4 coats of primer and the lacquer and top coat are actually really thin?

I know this is probably a stupid question to those of you in the know, but like I said, I'm new to all this and it's been something I've been trying to figure out.

 

[John @ PB]

The more basic gauges just show the total paint depth.

With them, you don't really have a means of knowing how much is lacquer, how much primer etc.

Assuming the readings indicate a factory paint finish, let's say 120microns; it'd be safe to say that between 30 and 50% of that is clearcoat.

The more advanced gauges do show the individual layers of paint but they're not that accurate; on metal panels the accuracy can vary by around 10%, on composite panels it's around 5%.

So on a metal panel, with a basic gauge, it gives you an indication of the paint thickness but equally importantly, it shows how much paint you're removing as you polish.

 

[danb986]

Thanks John, that was a great answer.
It would probably be more use as a gauge to see what you're doing, rather than what you can do (that made sense in my head when I wrote it)

 

[John @ PB]

Thanks John, that was a great answer.
It would probably be more use as a gauge to see what you're doing, rather than what you can do (that made sense in my head when I wrote it)

I know what you mean; use it as a monitor of your work.

It will give you an indication of the total depth which is useful and you can then have a more informed idea of how much clearcoat you have but yes, it certainly helps as you polish so you can monitor your paint removal.