# Paint Depth Measurement Advice



## Jasonjo (Jan 2, 2019)

Hi All,

Recently got myself a paint depth gauge and recorded the following values from mine and the wife's cars:

2017 BMW 330D (mine)

Under bonnet 130-140
Inside filler cap 140
Most of car 190-230

2012 Range Rover Evoque (wife)

Under bonnet/door jams 120-130
Most of car 180-200
Bonnet 100-110!!

Are these safe to begin using a DA polisher with, or thoughts in general?

The figures for my wife's bonnet seem a little low, so any thoughts on that?

Thanks in advance! 

Cheers

JJ

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## muzzer (Feb 13, 2011)

Yes they are okay for you to use a polisher with but the best thing for you to do is to get a practice panel and practice practice practice before you go near your car with the polisher so you know how it will react around edges etc.

You think you're wife's bonnet is thin, my Peugeot bonnet is lower than that. :doublesho


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## v_r_s (Nov 4, 2018)

Is there like a chart for what car models should be ect. 

I take it the laquer is always just as thick but it's the thickness of paint underneath? 

Does it register how much clear cost is to play with? As it's not the pair your playing with its the coat ? Always confused me this


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## muzzer (Feb 13, 2011)

v_r_s said:


> Is there like a chart for what car models should be ect.
> 
> I take it the laquer is always just as thick but it's the thickness of paint underneath?
> 
> Does it register how much clear cost is to play with? As it's not the pair your playing with its the coat ? Always confused me this


I'm sure i've read that underneath the door, underneath the bonnet or around the rear hatch etc is where the paint is thinnest and this should give you an idea of how much top coat there is on the paint. 
You can buy a ptg that will measure the thickness of top coat but they are quite expensive if i remember rightly.


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## big dave 666 (Aug 2, 2014)

Defelsko do a PTG that will tell you the thickness of each layer. Think it's a couple of grand!!

Others especially the cheap ones won't. I used to use a PTG but don't bother anymore. There's no point imo as like you say we're concerned with the clearcoat only. You might have a reading of 150 microns but reading of say 100microns may have more clearcoat on it than the 150 microns area.
Some say measure an unlacquered area, such as under the bonnet. But that's totally flawed. If the paint was the same thickness all over it that theory would have some credibility. But as the Op has found the paint thickness varies somewhat.


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## Mugwump (Feb 17, 2008)

I think the idea of using a paint depth guage is more so that you have an idea how much you are taking off, rather than to tell you how deep the paint or clearcoat is to start with. 

Used as such, it can be a very useful aid to avoid strike through.


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## Andy from Sandy (May 6, 2011)

Do inside a door shut. That point usually has the thinnest clear coat.

So if there you find 100 but on the panel 140 you know you have at least 40 of clear coat to play with.

Work on the basis that each coat is a third of the thickness. So with 210 take it the clear is 70 thick.


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## big dave 666 (Aug 2, 2014)

Basically it's all guess work unless you have a gauge that tells you the thickness of the clearcoat!!


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## Jasonjo (Jan 2, 2019)

Thanks all...

So not as conclusive as I was truly hoping, but still useful to compare the two cars and at least look for inconsistencies between readings on different cars/panels

I also should have considered that the cars should probably been totally clean before testing to rule out and surface dirt in the measurements

I actually purchased two PDGs to see if I could try and tell the difference between them, the first one was £40, the second was £80.

Interestingly, once calibrated they both did a very similar job with almost exactly the same depth results (which is the bit I care about most, not extra features) - yes the cheaper one is a bit more basic and may not last as long, not sure I can justify double the cost though as a weekend warrior

Hence I will be keeping the £40 one and returning the other.

Given I'll only be using it once or twice a year, as a hobbyist, I think it's just about worth it for the price and also useful to have for checking out the paint (possible resprayed panels etc) on prospective future car purchases too.

Keeper: https://www.amazon.co.uk/ERAY-Thickness-Automotive-Backlight-Suitcase/dp/B07D337RPW

Returner: https://www.amazon.co.uk/Thickness-49-2mils-Non-Ferrous-Laboratory-Automobile/dp/B00MNEAMPE

Hope that's useful for any one else in a similar boat 

Cheers

JJ

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## minotaur uk (Dec 13, 2018)

Jasonjo said:


> Thanks all...
> 
> So not as conclusive as I was truly hoping, but still useful to compare the two cars and at least look for inconsistencies between readings on different cars/panels
> 
> ...


I'm glad you mentioned that the £40 PTG did the same job as I have just bought the same one. Looking forward to using it. Is the calibration process straight forward ?


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## Jasonjo (Jan 2, 2019)

minotaur uk said:


> I'm glad you mentioned that the £40 PTG did the same job as I have just bought the same one. Looking forward to using it. Is the calibration process straight forward ?


Be interested to see if I got lucky, or you agree 

The CEM one seems well regarded, so I was happy enough

Yes, you get a series of calibration shims to set it up - pretty easy but just make sure you are totally perpendicular when taking readings to get the best result (on the car too), I got mine very close to the calibration values on all shims with a bit of practice

I then measured the car and then came back in and checked the shims were still reading the same level (which they were)

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## scousefly (Jul 30, 2008)

*Whaaaaat*

Your £40 one is now more than double on amazon FFS. I was actually looking at it last week


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## Andy from Sandy (May 6, 2011)

A PTG does add value to your workflow.

Take multiple readings of a panel in a grid pattern. You might find someone has already polished your car. If you get consistent readings and then find a spot that is very much less you will know.

To just throw out there they have no value and you are going to polish a car blind is going to get you in trouble at some point.

They will also show what the removal rate is which could be useful another day on a similar car.


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