# Is a paint thickness gauge essential ?



## rusey93 (Dec 24, 2008)

Hi,

I am looking at buying a kestrel das-6 dual action, I can afford the machine and then meguiars kit, but cannot afford a paint thickness gauge on top  

would you say it is a 'must' to have one? there like £150 *eekkkk*

how many people are machine polishing without one? 


thanks,

Jordan


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## Dave KG (Feb 23, 2006)

If you are only doing your own car, then I wouldn't say the paint thickness gauge is necessary, but so long as you are aware of the risks of the machine polishing and are happy with that... If you can, see if someone local will lend you a gauge for an hour to do readings on the car and that will give some confidence.

Ultimately, many polishing methods on a lot of paints only remove a few microns of paint so its generally speaking very safe but that is not to say that you wont be an unlucky one and hit a thin spot of the paint... but like above, small risk so if you are willing to take it, then no, you dont need the gauge.

Machine polishing other people's cars - then to me a gauge is a must, because its no longer your paint you are taking that small risk on.


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## badly_dubbed (Dec 11, 2008)

ive done machining without one, however i dont recommend it i only used the lightest of combos and was carefull,

if your planning to do other peoples cars its a must as it could cost you thousands in the long run  

but i would and am getting one soon anyway


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## The Doctor (Sep 11, 2007)

The ones that measure the total thickness are pretty useless to anyone using a machine on the car anyway. You need one that gives you the reading for each layer.


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## TriBorG (Feb 14, 2007)

What about if you are detailing with a PC rather than rotery would the need still be there how long would it take for a pc to burn through the paint as aposed a roterey
Thanks

Gary


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## badly_dubbed (Dec 11, 2008)

a rotary will burn through quicker (didnt someone on here do a sub 20second burn thru?) on purpose obviously,

a DA will take longer though but that doesnt mean it cant......


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## rusey93 (Dec 24, 2008)

Dave KG said:


> If you are only doing your own car, then I wouldn't say the paint thickness gauge is necessary, but so long as you are aware of the risks of the machine polishing and are happy with that... If you can, see if someone local will lend you a gauge for an hour to do readings on the car and that will give some confidence.
> 
> Ultimately, many polishing methods on a lot of paints only remove a few microns of paint so its generally speaking very safe but that is not to say that you wont be an unlucky one and hit a thin spot of the paint... but like above, small risk so if you are willing to take it, then no, you dont need the gauge.
> 
> Machine polishing other people's cars - then to me a gauge is a must, because its no longer your paint you are taking that small risk on.


okay then.... how much realistically do i need to put aside for one?

thanks,


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## karl_liverpool (Sep 25, 2008)

rusey93 said:


> okay then.... how much realistically do i need to put aside for one?
> 
> thanks,


you can get them off ebay for £125 delivered from a seller called usmanimports or something like that. (they are in germany)


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## rusey93 (Dec 24, 2008)

karl_liverpool said:


> you can get them off ebay for £125 delivered from a seller called usmanimports or something like that. (they are in germany)


ok thanks will look into it, next pay day :thumb:

thanks


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## PJS (Aug 18, 2007)

The Doctor said:


> The ones that measure the total thickness are pretty useless to anyone using a machine on the car anyway. You need one that gives you the reading for each layer.


Sorry, but that's absolutely rubbish advice to give, no matter how well intentioned, or simply misinformed.
A total depth is a damn sight more useful than nothing at all.
Separate layer ones, are all well and good, but still aren't absolutely accurate - just a higher tolerance, until you get into the realms of £5-10K for effectively lab grade tools, which the car manufacturers would use in-house.


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## The Doctor (Sep 11, 2007)

PJS said:


> Sorry, but that's absolutely rubbish advice to give, no matter how well intentioned, or simply misinformed.


How is it rubbish advice? If anything a single reading can lead you into thinking you have plenty clearcoat to play with when infact you have very little. In that case a guage giving single readings can actually be the cause of somebody striking through!



PJS said:


> A total depth is a damn sight more useful than nothing at all.


Not really. There are so many variables and circumstances that can lead to a high overall reading that a single reading can actually be anything but useful. Using an overall reading as a measure of clearcoat thickness is pretty much as risky as using no guage at all. The only thing you know with a single reading is how far off the actual metal you are!



PJS said:


> Separate layer ones, are all well and good, but still aren't absolutely accurate - just a higher tolerance, until you get into the realms of £5-10K for effectively lab grade tools, which the car manufacturers would use in-house.


At least with a seperate layer guage you get an idea of what is left on the clearcoat. I never said i would trust one to the micron but id much rather work from the readings on a seperate layer gauge than a single layer gauge wouldnt you?


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## A20 LEE (Feb 20, 2007)

Think your missing the point. If you measure a total thickness, do a set of passes then re-measure you may find 10 microns has gone indicating soft paint if your using 106FA for example. That bit of info lets you know that using 3.02 would lead to trouble and you be better moving to 85RD instead. If you can see how much is coming off its better than knowing nothing.


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## Bigpikle (May 21, 2007)

having seen Jon use his full set of gauges I can tell you there is a SIGNIFICANT difference in the multi-layer and single layer gauge readings. The multi-layer gauges seem to under-read the total paint thickness and their ability to pick up the different layers on some cars seems patchy at best.... It seems the assumptions used in these gauges mean they have some flaws for using for estimating layer thicknesses and it does seem that a reasonable degree of technical knowledge of the paint and gauge itself is a prerequisite. I actually think that using a multi-layer gauge to try and measure clearcoat by itself is a very risky business, as you really have no idea of whether that is actually the clear, or maybe the clear and the next layer or 2! All they tell you is that they have detected a change in the paint at a certain thickness, but it doesnt mean this is necessarily the difference between clear and one of the base layers - it could in fact be clear + colour etc etc...

These are all just additional pieces of information to help you build a picture of the vehicle in front of you 

I would really like a gauge that reads plastics etc though - that does eem a useful tool :thumb:


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## The Doctor (Sep 11, 2007)

A20 LEE said:


> Think your missing the point. If you measure a total thickness, do a set of passes then re-measure you may find 10 microns has gone indicating soft paint if your using 106FA for example. That bit of info lets you know that using 3.02 would lead to trouble and you be better moving to 85RD instead. If you can see how much is coming off its better than knowing nothing.


Im not missing the point at all. In your scenario your saying the gauge is useful because it lets you know how much you have removed from the *total thickness*. You still do not know how far into the clearcoat you are or if one more pass will lead to strike through. How do you know the car has not been machined 3 times in the past and the clear is now mega thin but there are 12 various colour/primer coats underneath which are giving you a high reading?

If you have a reading of 300 microns you would think you have loads to play with which is infact not always the case. There are so many variables as i said before that a single layer gauge is pretty much useless on anything but a brand new car and even on a new car there is still an amount of guesswork required.


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## drive 'n' shine (Apr 22, 2006)

The Doctor said:


> If you have a reading of 300 microns you would think you have loads to play with which is infact not always the case. There are so many variables as i said before that a single layer gauge is pretty much useless on anything but a brand new car and even on a new car there is still an amount of guesswork required.


Then at the other end of the scale I have seen readings of 60 um which enabled me to know not to go to heavy on those areas - so any info is better than no info! Which is what you seem to be advocating.

As for you saying there is a lot of guess work involved not really, you get to know what sort of thickness to expect from a factory finish so any deviation from this will let you know that a) the car has had paintwork or b) been heavily polished in the past


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## The Doctor (Sep 11, 2007)

drive 'n' shine said:


> Then at the other end of the scale I have seen readings of 60 um which enabled me to know not to go to heavy on those areas - so any info is better than no info! Which is what you seem to be advocating.


Granted. In that case you would know the paint was very thin but then do you stop short and not touch that area or do you machine it lightly with the least abrasive product you have got? The clear at that reading could be one light pass away from strike through. Who knows? Your certainly no wiser as to if its safe to lightly machine it or not.



drive 'n' shine said:


> As for you saying there is a lot of guess work involved not really, you get to know what sort of thickness to expect from a factory finish so any deviation from this will let you know that a) the car has had paintwork or b) been heavily polished in the past


Not at all. Once the car has seen paint there are too many variables. Whilst you may know what sort of thickness to expect from a factory finish you still are non the wiser about the painted areas and most cars over a few years old have seen paintwork. Different painters have different techniques,mix the paint different ratios,apply different amount of coats etc. etc.

Im not trying to stop anybody using paint guages. If your happy to guess the thickness of layers then thats your personal choice but the original poster asked if a PTG was essential and i gave my opinion that a single reading gauge is pretty much useless and ive outlined my reason for thinking that way.


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## Paul-T (Nov 2, 2006)

I think it's an agree to disagree. While I do understand your argument, I think a single reading gauge would be better described as 'limited', rather than useless

In the example above on a 60 micron panel, you at are now in a position to choose an approach, rather than just hacking on regardless.


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## drive 'n' shine (Apr 22, 2006)

The Doctor said:


> Not at all. Once the car has seen paint there are too many variables. Whilst you may know what sort of thickness to expect from a factory finish you still are non the wiser about the painted areas and most cars over a few years old have seen paintwork. Different painters have different techniques,mix the paint different ratios,apply different amount of coats etc. etc.


I can pretty much guarantee that the amount of clear laid down by a hand finish will be a lot more than is applied by the factory robots


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## byrnes (Jul 15, 2008)

In a word yes but also no.

As has been said, if its just your own car, You should be ok, I had done some machining on mine without a PTG. But once I got my PTG i went over the car and there is alot of changing readings.

Different cars and different paints will all be different and its almost if not impossible to tell by eye


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## Dave KG (Feb 23, 2006)

I'm sorry, but I simply have to disagree with the statements that a single reading of paint thickness (ie, not indicidual layers) is useless, and not worth investing in such a gauge.

One should be very careful as to how the reading is interprested but basing your evaluation on experience and factor in some common sense and the single reading is hugely valuable and to dismiss it as anything else seems bad advice to me.

First off, when taking a paint reading of total thickness, pay no attention to the actual value - rather the range in which that value falls.. eg is it below 80um, above 200um - that kind of thing. Use this initial question to gauge first of all whether you believe the paint to be original (typically <200um unless the car has been painted by hand, for example a Ferrari F355). If it has been resprayed then you must proceed with caution, but then this is the first valuable piece of information the gauge has given you - not just that the thicknesses are different but that the paint is likely to behave differently under polishing as well and different combinations may be required for correction and finishing.

If the paint is falling in the original range, then divide this range up. Below 100um, begin to think about exercising caution. Below 80um, and one would be looking much more closely at what combinations to use. This is a very basic outline, but the total thickness gives a hugely valuable piece of information on which to base your polishing choices. 

On a recent detail, I found a thin spot on the paintwork - sub 60um - on a panel otherwise reading 120um. The panel required compounding with Fast Cut to achieve correction, but this could not be carried out on the very thin region. It would certainly have been a strike through. The gauge prevented this, and this was based on a total thickness reading. This car was a Bentley, I'd say the gauge paid for itself in that very car.

And to answer any sceptical question about how one would know we would get strike through at 60um, I have demonstrated this in the past with thin spots on scrap panels - a 307 door, where the paint was 100um in most places, and 80um in one patch. Compounding was fine on all but the 80um patch, where as you would expect, strike through occured.

Deciding upon the lower limit is naturally difficult and to some degree this is where experience plays a role too. However, a guesstimate (educated) can also be had by measuring the inside of the door where the paint typically sees less lacquer, and this allows one to infer the amount of clearcoat. Not accurately, but definitely a good educated guess which in my experience has proven to work well. 

Quite simply, if you are working on other people's cars, a gauge is a must - be that one that reads all the individual layers (and has been pointed out above, they are not always all they are cracked up to be, and this can also be down to how the car has been sprayed), or one that simply reads the full thickness. This is of course my opinion, but I feel it is necessary to stress my feelings here of just how important a gauge is as I am quite sure many other professional detailers will be able to recount countless times where their total thickness gauges have highlighted thin spots, thin panels that they may have otherwise compounded, and in turn saved them from the dangers of striking through.


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## Dave KG (Feb 23, 2006)

The above also neglects to mention, as has been mentioned by another member, how the change in the total reading (averages are best here, over a small area) can be used to indicate the softness of the paint... this is valuable in ensuring you do not remove too much paint, rememberring that the thickness of the clearcoat has a bearing on its performance and the thinner you make it, the less protection it will offer against UV... Thin clearcoat offers less protection to the layer where it "adheres" to the underlying colour coat, and if this becomes damaged by UV, it can result in paint peeling from failed clearcoat.

In other words, leaving it too thin can cause premature clearcoat failure later in the paint's life.

Knowing how much you are removing is therefore, to me at least, another vital piece of information the gauge offers.


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## The Doctor (Sep 11, 2007)

Shine On said:


> I think it's an agree to disagree. While I do understand your argument, I think a single reading gauge would be better described as 'limited', rather than useless
> 
> In the example above on a 60 micron panel, you at are now in a position to choose an approach, rather than just hacking on regardless.


True, you now know the car has mega thin paint. But how much is actually clearcoat? Can you afford to even touch it with the machine? but i do get what your saying, you now know the paint is thin. In real life terms though most cars that have seen paint will give much higher readings and we are back to the point i was making,you have no idea how much clear you have to go at on a panel that reads 300 microns.


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## Dave KG (Feb 23, 2006)

The Doctor said:


> True, you now know the car has mega thin paint. But how much is actually clearcoat? Can you afford to even touch it with the machine? but i do get what your saying, you now know the paint is thin. In real life terms though most cars that have seen paint will give much higher readings and we are back to the point i was making,you have no idea how much clear you have to go at on a panel that reads 300 microns.


But this is information the gauge has given you - you know its painted, and you now know that normal rules will not apply...

As Drive & Shine has said, generally speaking (as in in the majority of cases), the amount of cleacoat will likely be thicker on a painted region down to the painting process - yes there are lots of variables, but this seems a very consistent result "in the field".


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## VIPER (May 30, 2007)

Just playing devil's advocate here, how much is the cheapest multi layer reading PTG?


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## drive 'n' shine (Apr 22, 2006)

Pit Viper said:


> Just playing devil's advocate here, how much is the cheapest multi layer reading PTG?


About £1500


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## VIPER (May 30, 2007)

drive 'n' shine said:


> About £1500


That's what I thought, so doesn't that pretty much render any DIY marketed DA machine (and especially a rotary) pretty redundant if there's no point having a machine that most amateur/hobby detailer can afford if you can't use it without an accompanying machine costing £1500?

G220, Kestrels, UDMs, PCs and the like are a waste of time for the guy in the street then aren't they?

Again, I'm only playing Devil's Advocate here and posing the question.


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## The Doctor (Sep 11, 2007)

Dave KG said:


> But this is information the gauge has given you - you know its painted, and you now know that normal rules will not apply...
> 
> As Drive & Shine has said, generally speaking (as in in the majority of cases), the amount of cleacoat will likely be thicker on a painted region down to the painting process - yes there are lots of variables, but this seems a very consistent result "in the field".


The guage has told you the panel has been painted but so what? Do you know how much clear is on there? No

A hand painted panel will be thicker than a robot painted panel but so what? Do you know how much clear is on there? No. It could of been mopped to hell in the bodyshop leaving hardly any clear behind. The painter could of decided one coat of clear would do.

There are too many variables Dave. You have no idea whatsoever how far into the clear you are, you are just guessing and hoping.


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## drive 'n' shine (Apr 22, 2006)

^^Ok mate whatever you know best!


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## Dave KG (Feb 23, 2006)

Pit Viper said:


> That's what I thought, so doesn't that pretty much render any DIY marketed DA machine (and especially a rotary) pretty redundant if there's no point having a machine that most amateur/hobby detailer can afford if you can't use it without an accompanying machine costing £1500?
> 
> G220, Kestrels, UDMs, PCs and the like are a waste of time for the guy in the street then aren't they?
> 
> Again, I'm only playing Devil's Advocate here and posing the question.


Of course not  .. I can see why you are asking this, but as said above, if its your own car and you are happy with the risk (small) then you dont need a gauge of any sort...

If you are using your machine on more cars, especially if you move to having folks paying for your services, you really need a gauge for the valuable information it can give you - and by that I mean one that gives total thickness. They are around £200. More expensive than a G220, yes, but if it was not my car but a mate's car, I'd want the information it gave me before using the machine polisher.


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## The Doctor (Sep 11, 2007)

drive 'n' shine said:


> ^^Ok mate whatever you know best!


What a great answer. Why not answer the question-Do you know how far into the clearcoat you are?


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## VIPER (May 30, 2007)

So, if I'm reading this correctly 'The Doctor' you are saying that a hobby detailer (which is pretty much 95% of DW) has three choices when it comes to machining their car, and I'm only focussing on amateurs here as the pros probably do have, or could justify the cost of a PTG costing thousands:-

No PTG at all and hope for the best, which I'm assuming you wouldn't advise even though many people on here do it on their own car, and that includes me.

A single layer reading PTG which from your posts so far it's clear again you don't advise.

Or a multi layer reading PTG, which costs upwards of 10 times the cost of the machine itself and so places itself way outside the reach of the vast majority of members.

I'm not looking to get into an argument here, I just want to clarify the facts


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## Dave KG (Feb 23, 2006)

The Doctor said:


> The guage has told you the panel has been painted but so what? Do you know how much clear is on there? No
> 
> A hand painted panel will be thicker than a robot painted panel but so what? Do you know how much clear is on there? No. It could of been mopped to hell in the bodyshop leaving hardly any clear behind. The painter could of decided one coat of clear would do.
> 
> There are too many variables Dave. You have no idea whatsoever how far into the clear you are, you are just guessing and hoping.


You are not just guessing and hoping, you are using the reading you get and using your experience of painted finishes (which as has been pointed out to you above, generally have thicker clear than a standard finish owing to being sprayed by hand). If I see a high reading, pointing to a painted finish, the first valuable piece of information is just that - painted panel. Would you describe that as useless information? I certainly wouldn't!

Next - say you get 400um... Now, no, you cannot infer from that how much clearcoat there is. But as it has been sprayed, use your experience - in the field, when a car has been painted, they have thicker clearcoat owing to being sprayed by hand. But you would have to exercise caution as you are quite correct in your assertion you have no cast iron guarantees.

But, that you know the thickness is invaluable for guiding your polishing process. On a car which has seen no paint (and many of us work on them), a total layer thickness is invaluable for the reasons I have described above, and many others have also taken time to point out.

Not to mention the information you can yield from the amount of paint removed - no, you dont know for certain how much clear is left to the exact micron (a multilayer wont give you this info either), but you can use your experience and educated guestimates to be far further forward and armed with far more information that if you simply went in blind. Total removal is important for gauging paint hardness as well, as outlined above.

If you dont believe in the gauges, then that is your prerogative. Myself, and many other detailers believe in the vital information a gauge can give you and for good reason - I would personally hate to see a lot of people machine polishing blindly given the valuable information a guage can give you just because they have read that a total thickness reading is "useless".


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## The Doctor (Sep 11, 2007)

Dave KG said:


> Of course not  .. I can see why you are asking this, but as said above, if its your own car and you are happy with the risk (small) then you dont need a gauge of any sort...
> 
> If you are using your machine on more cars, especially if you move to having folks paying for your services, you really need a gauge for the valuable information it can give you - and by that I mean one that gives total thickness. They are around £200. More expensive than a G220, yes, but if it was not my car but a mate's car, I'd want the information it gave me before using the machine polisher.


Like i said im not trying to stop anybody from using a total thickness gauge but im saying you still have no idea what the thickness of the clear is on a car that has been painted and that is exactly what a detailer wants to know.

I suppose at least we know which people own total thickness gauges now


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## Dave KG (Feb 23, 2006)

The Doctor said:


> Like i said im not trying to stop anybody from using a total thickness gauge but im saying you still have no idea what the thickness of the clear is on a car that has been painted and that is exactly what a detailer wants to know.
> 
> I suppose at least we know which people own total thickness gauges now


What a detailer needs to know is how much paint is on the panel, and a detailer can (as has been discussed above, countless times) using their experience make the best decisions from that for a paint finish.

The _exact_ thickness of clearcoat is of little relevance, it is the _range_ which is important and how you interpret the information with which you are presented.

Many detailers use total layer thickness gauges, myself included, and use them to great effect during detailing - ownership of a multiayer gauge does not make one a better detailer, or a safer detailer as you seem to be implying from your final sentence


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## The Doctor (Sep 11, 2007)

Dave KG said:


> You are not just guessing and hoping, you are using the reading you get and using your experience of painted finishes (which as has been pointed out to you above, generally have thicker clear than a standard finish owing to being sprayed by hand). If I see a high reading, pointing to a painted finish, the first valuable piece of information is just that - painted panel. Would you describe that as useless information? I certainly wouldn't!


Yes id say as far as attacking with a machine it is pretty much useless. How thick is the clear? Apart from knowing the panel is painted you still have no idea how thick the clear is that you will be polishing owing to the many variables.



Dave KG said:


> Next - say you get 400um... Now, no, you cannot infer from that how much clearcoat there is. But as it has been sprayed, use your experience - in the field, when a car has been painted, they have thicker clearcoat owing to being sprayed by hand. *But you would have to exercise caution as you are quite correct in your assertion you have no cast iron guarantees.*


So your saying i am right with the red bit yet your saying the gauge is invaluable. Basically then you are just hoping that the hand painted bit was done properly and it wasnt attacked with G3 and a mop at some point in the past and there where no variables present.


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## The Doctor (Sep 11, 2007)

Dave KG said:


> What a detailer needs to know is how much paint is on the panel, and a detailer can (as has been discussed above, countless times) using their experience make the best decisions from that for a paint finish.


In an ideal world where there are no variables.



Dave KG said:


> *The exact thickness of clearcoat is of little relevance*, it is the _range_ which is important and how you interpret the information with which you are presented.


Are you for real? The thickness of the clearcoat is of every relevance!!



Dave KG said:


> Many detailers use total layer thickness gauges, myself included, and use them to great effect during detailing - ownership of a multiayer gauge does not make one a better detailer, or a safer detailer as you seem to be implying from your final sentence


I never stated owning a multilayer gauge made anyone better. Just pointing out that it seems to be those that own the total thickness gauge who are quick to defend it to the hilt.


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## VIPER (May 30, 2007)

So the question remains - should 'Joe Bloggs' machine his car if he doesn't have a multi gauge PTG?


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## Paul-T (Nov 2, 2006)

I think the point here is that you don't seem to appreciate any middle ground. It's either all telling, or completely useless. 

My Positector 200 is a great bit of kit, and yes it gives seperate layer readings under certain circumstances, but would I trust it 100%? No. Am I grateful for the guidance it gives? Most certainly. If I didn't have it, would I still be better off with a single reading gauge than nothing? Undoubtedly.


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## drive 'n' shine (Apr 22, 2006)

The Doctor said:


> What a great answer. Why not answer the question-Do you know how far into the clearcoat you are?


Jeez! We are clearly never going to agree on it!

I like to think from my years of professional experience that I can safely know how far I can go in terms of removal, using the readings I get get from my PTG I will at least have *some* idea of paint thickness whether it be total or split layers, which IMO is better than having *no* idea of what thickness I have to play with.

I would be looking at clearcoat levels on a factory finish to be around 30 - 50 microns, again this is from years of experience and hundreds of readings (and I'm sure most other detailers will back me up on this!).

Hand painted, as I said before, I will guarantee will have more clear than a factory finish simply because a human can't match the consistency that a robotic system can, and any painter will tell you this.

I like to work on the principle of never removing more than 10% of total thickness and it has served me well over the years, preferring to leave some deeper marks (although improving then where possible) which would risk compromising the clear, leaving it for the client to then decide whether they warrant further work through painting.

Now all of the above is not saying you *need* a PTG if only machining your own car, but when people are paying you to do their cars, and your professional reputation relies on you being able to carry out the work competently and safely, and in an industry where you are only ever as good as your last job, then it would be foolish not to have PTG as a guide, IMO of course


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## CupraRcleanR (Sep 2, 2007)

PTG is not perfect but together with experience and an element of educated guessing make it a safer option than using total guesswork. IMO. I don't regret my £150

On a car with 115um average uniform accross the car I would feel safer than knowing naff all. If it had 70um I wouldn't touch it but at least I knew.


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## The Doctor (Sep 11, 2007)

Pit Viper said:


> So, if I'm reading this correctly 'The Doctor' you are saying that a hobby detailer (which is pretty much 95% of DW) has three choices when it comes to machining their car, and I'm only focussing on amateurs here as the pros probably do have, or could justify the cost of a PTG costing thousands:-
> 
> No PTG at all and hope for the best, which I'm assuming you wouldn't advise even though many people on here do it on their own car, and that includes me.
> 
> ...


Anybody using a machine polisher on other peoples paint should be extremely careful. The total thickness gauage is pretty much useless IMO unless you are using it on a brand new car and even then readings can vary. Basically i see no real gain in knowing the total thickness of paint on a second hand car thats seen patches of paintwork other than those with really low all over reading in which you might tell the customer his/her paint is too thin to correct.

I would not advise buying a total thickness gauge no as it can be just as much an hinderance as a help. I would advise anybody starting off detailing to perfect there machine skills and product choices rather than relying on gauges. Most of the time strike through is brought about by user error rather than simply polishing so much paint off that you strike through.


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## Dave KG (Feb 23, 2006)

The Doctor said:


> Are you for real? The thickness of the clearcoat is of every relevance!!
> 
> Just pointing out that it seems to be those that own the total thickness gauge who are quick to defend it to the hilt.


The total thickness, to the exact micron, is of no relevance... its like quoting a scientifric result to too many significant figures - its meaningless... you are looking for the range in which the numbers fall, nothing more and nothing less. If you want to take the exact number, to the exact micron,then what exactly is that telling you (given the error of the gauge is typically +/-3um?!). What I am saying, and have been saying all along is that using the gauge gives an indication of the range of total thickness and this alone is very valuable for the reasons I have discussed and you have dismissed, and I dont agree with your reasons for dismissing them so we will have to agree to disagree here.

On painted panels, sprayed by hand, the paint layers are generaly thicker anyway, and the total layer gauge gives an indication of softness - more very valuable information.

I am defending here the advice given out by myself and others as I truly believe that recommending a total layer thickness gauge as useless and you'd be better off just going in blindly, as wreckless and dangerous information - sounds strong, but I'm sorry that is what I believe and I personally do hope that anyone who is considering machine polishing someone else's car strongly consider a PTG, a total layer thickness one which is within the reach oif many enthusiast detailers. The information they give is invaluable when it is interpreted correctly, and they can save you from strike through, certainly a lot more so than simply going in blindly not knowing anything about the paint thickness or the removal rates.


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## The Doctor (Sep 11, 2007)

Dave KG said:


> The total thickness, to the exact micron, is of no relevance... its like quoting a scientifric result to too many significant figures - its meaningless... you are looking for the range in which the numbers fall, nothing more and nothing less. If you want to take the exact number, to the exact micron,then what exactly is that telling you (given the error of the gauge is typically +/-3um?!). What I am saying, and have been saying all along is that using the gauge gives an indication of the range of total thickness and this alone is very valuable for the reasons I have discussed and you have dismissed, and I dont agree with your reasons for dismissing them so we will have to agree to disagree here.


I have never stated that you need to know the thickness of anything to the exact micron so i dont see why your bringing this up. I stated that ideally a detailer needs to know how much clearcoat is on the car-something a total thickness gauge gives you no idea of on a car thats seen paintwork no matter how you dress it up due to the variables that can occur.



Dave KG said:


> On painted panels, sprayed by hand, the paint layers are generaly thicker anyway, and the total layer gauge gives an indication of softness - more very valuable information.


The thickness of hand painted panels are of no relevance. Why? Because there are once again too many variables. The hand painted panel may of been wet sanded then hammered with G3 before leaving the bodyshop. I see what you are saying but thinking that just because a hand painted panel has thicker coats is like thinking we live in a perfect world with no variables.



Dave KG said:


> I am defending here the advice given out by myself and others as I truly believe that recommending a total layer thickness gauge as useless and you'd be better off just going in blindly, as wreckless and dangerous information - sounds strong, but I'm sorry that is what I believe and I personally do hope that anyone who is considering machine polishing someone else's car strongly consider a PTG, a total layer thickness one which is within the reach oif many enthusiast detailers. The information they give is invaluable when it is interpreted correctly, and they can save you from strike through, certainly a lot more so than simply going in blindly not knowing anything about the paint thickness or the removal rates.


Thats your opinion but as ive already stated,the safest method for machine polishing is knowing how to use the machine and selecting the right products. Most strike throughs are caused by incorrect usage rather than simply going in blind as you put it (personally i think your just as blind on a second hand car with a total thickness gauge).


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## Dave KG (Feb 23, 2006)

The Doctor said:


> Thats your opinion but as ive already stated,the safest method for machine polishing is knowing how to use the machine and selecting the right products. Most strike throughs are caused by incorrect usage rather than simply going in blind as you put it (personally i think your just as blind on a second hand car with a total thickness gauge).


This is something that nobody is disagreeing with, and those professionals doing this day in day out for a living will be well aware of correct machine use, as am I.  ... That does not mean I do not find the total thickness gauge an invaluable resource, again for all the reasons mentioned aboved which I see no point in repeating ten times over. They give valuabkle information - oin *any* car, and to dimiss nit as anything else to me is incorrect. But that is my opinion, based on my experience. It would seem many seasoned professionals share this opinion as well, based on their experience.

If there is a thin spot on the paint, then you can go through by polishing correctly (correct techniques) as you will be removing paint - I have seen it happen to folk, and I have demonstrated it to people on my tuitio dyas as well. The gauge highlighted where I would expect to strike through, and sure enough, it was right. Can you dismiss such useful information off hand? I don't and would never recommend anyone else does.


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## The Doctor (Sep 11, 2007)

Dave KG said:


> This is something that nobody is disagreeing with, and those professionals doing this day in day out for a living will be well aware of correct machine use, as am I.  ... That does not mean I do not find the total thickness gauge an invaluable resource, again for all the reasons mentioned aboved which I see no point in repeating ten times over. They give valuabkle information - oin *any* car, and to dimiss nit as anything else to me is incorrect. But that is my opinion, based on my experience. It would seem many seasoned professionals share this opinion as well, based on their experience.
> 
> If there is a thin spot on the paint, then you can go through by polishing correctly (correct techniques) as you will be removing paint - I have seen it happen to folk, and I have demonstrated it to people on my tuitio dyas as well. The gauge highlighted where I would expect to strike through, and sure enough, it was right. Can you dismiss such useful information off hand? I don't and would never recommend anyone else does.


I guess you were lucky Dave. Lucky in the sense that the bits of the panel that read thicker had not been painted and blended in. Had the panel your refering to been blended in at some point then already machine polished you may not of been as lucky.


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## FinstP (Nov 29, 2008)

I have to agree with those people who think a total thickness gauge is useful, for the many reasons given already. It is a requirement in the USA that painters must now demonstrate proficiency with an electronic paint thickness gauge in order to become certified to do refinish warranty work for General Motors Corp. (GM) vehicles.

However, what interests me (because I lay down and measure film thicknesses of multi-layer coatings every day, each to accuracies of the order of 0.002 micron) is how accurate these simple multi-layer gauges are in practice. The ultrasonic ones that I know of say that the minimum thickness of a layer that can be measured is around 13 microns. Does anyone know of other types and does anyone here have experience of using one?


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## Dave KG (Feb 23, 2006)

The Doctor said:


> I guess you were lucky Dave. Lucky in the sense that the bits of the panel that read thicker had not been painted and blended in. Had the panel your refering to been blended in at some point then already machine polished you may not of been as lucky.


Consistently lucky over various test panels? I think not.

The panels were original paint, and you could tell that from the initial readings taken when they arrived with me. Over time and product testing, I have polished the paint levels down... I then purposefully put in thin spots, and used them as a demonstration of the importance of the gauge. Slightly conceived maybe, but having seen dealers repair scratches by sanding them out, and thus leaving thin spots, its a demonstration I find vital.

Look at the boot on my car, and you will find a scratch that the dealer previously tried to deal with... there is a thin spot around the area. Its 50um thinner than the surrounding paint!! The total layer gauge picked this up clearly, and indicated that compounding this particular region of paint would not be adviseable. This kind of information is utterly invaluable - dismissing a total thickness gauge dismisses this vital information and its a fool's errand to do so in my opinion and I can't personally see any feasible argument against it.

Luck has little to do with the demonstrations I have discussed. Using the gauge correctly indicates regions which could be compounded and regions that couldn't be, later verified by the strike through demonstration. Quite simple.


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## drive 'n' shine (Apr 22, 2006)

I do find it funny that this thread is in the aptly named 'Tools' forum :lol:


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## The Doctor (Sep 11, 2007)

Dave KG said:


> Consistently lucky over various test panels? I think not.
> 
> The panels were original paint, and you could tell that from the initial readings taken when they arrived with me. Over time and product testing, I have polished the paint levels down... I then purposefully put in thin spots, and used them as a demonstration of the importance of the gauge. Slightly conceived maybe, but having seen dealers repair scratches by sanding them out, and thus leaving thin spots, its a demonstration I find vital.
> 
> ...


What your saying is you put thin spots in the paint on purpose (so you knew you had done so,nothing to do with the gauge other than it showing a smaller overall reading on factory paint).

You knew the paint was original (i have been on about resprayed panels or touched up/blended in panels).

Was it not a case that you hammered the thin spots with the buffer to demostrate a strike through?

Ok lets look at a different scenario.

Lets say a panel has been repaired. It has been prepped using high build primer in one spot to cover some slight defects. Along comes a cowboy painter who gives it 2 coats of red and one coat of clear. He then machines the panel with G3 leaving it looking ok and you cant see the repair but in reality its got mega thin clear in one spot. Because he used high build primer the reading on the panel is reading around 120 micron total thickness all over. You come along and think the reading is pretty consistant all over so its all original when in truth your dicing with very very thin clear and before you know it youve struck through.

How do you get around that scenario?


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## drive 'n' shine (Apr 22, 2006)

^^ You seem to be assuming that every car, bar new ones, have had resprays!

You carry on with your blinkered opinions, as even with several people pointing out the advantages of using any sort of PTG, you still seem to think it is better to go at it blind without any point of reference at all.


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## The Doctor (Sep 11, 2007)

drive 'n' shine said:


> ^^ You seem to be assuming that every car, bar new ones, have had resprays!


Do you actually live in the real world? Most cars over a few years old have had touch ups/paint jobs.



drive 'n' shine said:


> You carry on with your blinkered opinions, as even with several people pointing out the advantages of using any sort of PTG, you still seem to think it is better to go at it blind without any point of reference at all.


Blinkered opinions? Why is that? Because i dont agree with you and have my own opinion on the subject? I didnt know i was supposed to just agree with everyone?

I will carry on without a PTG. You carry on reading total thickness and hoping that none of your cars have been touched up :thumb:


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## Nickos (Apr 27, 2006)

Sorry Doc, I'm with them, how can you cut something when you don't know the thickness!


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## Dave KG (Feb 23, 2006)

The Doctor said:


> What your saying is you put thin spots in the paint on purpose (so you knew you had done so,nothing to do with the gauge other than it showing a smaller overall reading on factory paint).
> 
> You knew the paint was original (i have been on about resprayed panels or touched up/blended in panels).
> 
> ...


What I am saying, and I thought I was making it obvious, was that I put thin spots into the paint in a way I have seen put in to paint in the past to replicate a real world example, and then used it to demonstrate the usefullness of the gauge - quite clearly, and without argument (reasonable argument at least), the gauge showed exactly its worth. Without the reading, you would not know of the thin spot and you could easily strike through. Can you see how the gauge worked here? _I_ knew where the thin spots were, those seeing the demo did not until the gauge hit the paint. The results of polishing the thin spots are then clear to see. The working of the gauge here is to me proven beyond doubt, for a real world situation as well.

I did not need to hammer a couple of the panels - one was Knighthawk Black Honda, very soft, so Intensive Polish by rotary was enough to remove the clearcoat from the thin spots to strike through while not achieving desired correction of the RDS also in the panel. When confronted with RDS, many people use an aggressive cutting combo to correct, this is one method, and the usefulness of the gauge in assessing the safety of that technique is obvious.

You have continually mentioned resprayed panels, yes - however your first post was to dismiss the gauge completely and many of us have consistently presented in this thread why the gauge is useful, using panels that have not been resprayed (many cars I have worked on have not been sprayed) as examples... but you still dismiss the gauge completely and would rather people polish blind on original paint, risking strike through and a trip to the bodyshop? As this is what your posting seems to represent, and how many of us are interpreting it it would seem - but feel free to correct here. As I read it, you believe the gauge is useless in all scenarios and you wouldn't bother with one? Correct? If so, can you see why I disagree with that sentiment based on what I have responded to (repeatedly) in my posts?

Returning to your example now... You would measure that panel and see consistent thickness, so yes with a total thickness gauge you would be unaware of the thin spot on the first reading. However, if the panel has been resprayed, it will be obvious from when you start polishing it that the panel is behaving differently to the rest of the paintwork... when a car is sprayed, it is sprayed up to a swage line, so there wont be a tiny region that has been done. It is good practice when detailing to _always_ start from the lowest and build up your polish combo up - you'll find me doing that panel by panel which is why machine polishing takes me quite some time, as I am always looking for the best solution round a car to minimise paint removal while maintaining correction and this varies not just from car to car but from section to section... A change in the behaviour of the paint, which is generally obvious on the rotary as removal rates and correction rates change, will point to there being work. You can then use the fact the reading is very thin (120um) for repaired paint to exercise great caution on the section. Now this comes from experience, granted, but its still using the gauge information combined with experience to achieve the best result most safely.

Is it impossible for someone to be caught out with a single thickness gauge? No, of course not, but then where are any of us saying that it is? We are stressing that the single thickness gauges offer vital information which when interpreted correctly offer much more confidence than simply machine polishing blind... not knowing anything about the thickness and you are far more likely to be caught out than if you know the total thickness. Dismissing this minimisation of risk to me seems a fool's errand.


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## Dave KG (Feb 23, 2006)

The Doctor said:


> I will carry on without a PTG. You carry on reading total thickness and hoping that none of your cars have been touched up :thumb:


By that train of thought, if you carry on without a PTG (and we're not trying to stop you, rather trying to offer good advise we believe to be true based on our own experience), you are hoping none of the cars you work on have ever had any dealer touch-ups - as in, quick wet sand and polishes to get rid of scratches here and there... Think they dont happen often? Go have a look around a few local dealerships and you'll see why I set up my test panels with thin spots as I did


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## The Doctor (Sep 11, 2007)

Nickos said:


> Sorry Doc, I'm with them, how can you cut something when you don't know the thickness!


The overall thickness is irrelevant especially on a used car that has maybe been touched up in various places and has varying thickness of clearcoat. On a new car it gives you a slight idea but still only a very rough estimate of how much you can polish.

It is the clearcoat that we have to preserve not the overall thickness as we dont know how thick the clear actually is on a car thats been touched up.


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## drive 'n' shine (Apr 22, 2006)

The Doctor said:


> Do you actually live in the real world? Most cars over a few years old have had touch ups/paint jobs.
> 
> Blinkered opinions? Why is that? Because i dont agree with you and have my own opinion on the subject? I didnt know i was supposed to just agree with everyone?
> 
> I will carry on without a PTG. You carry on reading total thickness and hoping that none of your cars have been touched up :thumb:


:lol: Well I have spent a very large % of my life detailing cars for a living so I hope I do live in the real world. And I have seen plenty of used cars in my years that haven't had any paintwork.

No ones asking you to agree with me, and you are entitled to your own opinion, but your argument against PTG doesn't stack up TBH.

You also seem to presuming that every car that has been painted has had a cheap crappy paint job.

One question, say you had a car that had never seen paint, but had in the past been heavily compounded a couple of times, how would you know it was safe to machine polish again without compromising the clearcoat? By divine intervention?


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## drive 'n' shine (Apr 22, 2006)

The Doctor said:


> The overall thickness is irrelevant especially on a used car that has maybe been touched up in various places and has varying thickness of clearcoat.


At least by using a PTG I'll know where these touched in areas are  and be able make a more informed decision on how best to tackle them


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## The Doctor (Sep 11, 2007)

drive 'n' shine said:


> :lol: Well I have spent a very large % of my life detailing cars for a living so I hope I do live in the real world. And I have seen plenty of used cars in my years that haven't had any paintwork.


So you dont agree that most used cars have seen some touch ups? Of course there will be a few that have not but to speak as though most cars have original paint is madness.



drive 'n' shine said:


> No ones asking you to agree with me, and you are entitled to your own opinion, but your argument against PTG doesn't stack up TBH.


I have given you plenty scenarios where a total thickness reading is useless yet you dismiss them. Im still waiting for an answer to my scenario of the touch up job with the high build primer. That argument stacks up perfectly.



drive 'n' shine said:


> You also seem to presuming that every car that has been painted has had a cheap crappy paint job.


On the other hand you seem to presume they all have good paint jobs with no variables thrown into the mix eg. high build primers,thickness of base coats,previous compounding,blend coats.



drive 'n' shine said:


> One question, say you had a car that had never seen paint, but had in the past been heavily compounded a couple of times, how would you know it was safe to machine polish again without compromising the clearcoat? By divine intervention?


You wouldnt. The same way you wouldnt know if it was safe with your total thickness gauge as you have no idea how thick the clear is after 2 heavy compounding sessions! You could guess the thickness of the base coats and primer and deduct it from the overall reading but thats all it would be-a guess/stab in the dark.

We are never going to agree on the subject we are just going around in circles. IMO total thickness guages are pretty much useless on used/older cars that have seen paintwork,in your opinion they are not.


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## PJS (Aug 18, 2007)

PJS said:


> Sorry, but that's absolutely rubbish advice to give, no matter how well intentioned, or simply misinformed.
> A total depth is a damn sight more useful than nothing at all.
> Separate layer ones, are all well and good, but still aren't absolutely accurate - just a higher tolerance, until you get into the realms of £5-10K for effectively lab grade tools, which the car manufacturers would use in-house.





The Doctor said:


> How is it rubbish advice? If anything a single reading can lead you into thinking you have plenty clearcoat to play with when infact you have very little. In that case a guage giving single readings can actually be the cause of somebody striking through!
> 
> Not really. There are so many variables and circumstances that can lead to a high overall reading that a single reading can actually be anything but useful. Using an overall reading as a measure of clearcoat thickness is pretty much as risky as using no guage at all. The only thing you know with a single reading is how far off the actual metal you are!
> 
> At least with a seperate layer guage you get an idea of what is left on the clearcoat. I never said i would trust one to the micron but id much rather work from the readings on a seperate layer gauge than a single layer gauge wouldnt you?


Okay, haven't bothered to read the rest of the replies since yours, so this may have already been touched upon or cleared up totally for you. In any case, here goes.......

What you've failed to appreciate or understand in the practical application of using a PTG, measuring total thickness of paintwork, is that you don't simply plonk it on the surface, take a few reading in an area, then decide the amount of clearcoat is exactly 1/3rd of the total.
What you do do, is measure areas at the door shut, under the bonnet, where the manufacturer hasn't bothered to clearcoat, to save money!
Once you know the average of what is there, you subtract that from the measurements you find on the outer surfaces, and that gives you an approximation of what you're playing with.

It's not exact to the _n_th degree, but within 5µm on average - and most manufacturers using the automated paint application system, will be dropping around 40µm of clearcoat, from what I can glean from info out there.
Of course, you wouldn't assume there's 40µm, but you can if you want - so long as you assume the risk of potentially striking through the clearcoat layer if your assumption doesn't hold true.

So, in that respect, a PTG - even with a ±5µm margin of error - is a better prospect to have, than mere hope and pray guesswork.


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## PJS (Aug 18, 2007)

Bigpikle said:


> having seen Jon use his full set of gauges I can tell you there is a SIGNIFICANT difference in the multi-layer and single layer gauge readings. The multi-layer gauges seem to under-read the total paint thickness and their ability to pick up the different layers on some cars seems patchy at best.... It seems the assumptions used in these gauges mean they have some flaws for using for estimating layer thicknesses and it does seem that a reasonable degree of technical knowledge of the paint and gauge itself is a prerequisite. I actually think that using a multi-layer gauge to try and measure clearcoat by itself is a very risky business, as you really have no idea of whether that is actually the clear, or maybe the clear and the next layer or 2! All they tell you is that they have detected a change in the paint at a certain thickness, but it doesnt mean this is necessarily the difference between clear and one of the base layers - it could in fact be clear + colour etc etc...
> 
> These are all just additional pieces of information to help you build a picture of the vehicle in front of you
> 
> I would really like a gauge that reads plastics etc though - that does eem a useful tool :thumb:


Those same ones that use Ultrasound, are suitable for plastic measurements, but of the couple of manufacturers I've spoken to whom don't have ones in their line-up for plastic usage, they have said exactly the same thing - they are not confident with them being accurate enough, since the plastic material of bumpers is very close to that of the paint/primer/clearcoat's transmission characteristics.
As a consequence, they've not bothered to make something just for the sake of having one to rival their competitors.

The nearest solution to doing what you're wanting, is going to be in the £18-2000 region, including probe.


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## The Doctor (Sep 11, 2007)

PJS said:


> Okay, haven't bothered to read the rest of the replies since yours, so this may have already been touched upon or cleared up totally for you. In any case, here goes.......
> 
> What you've failed to appreciate or understand in the practical application of using a PTG, measuring total thickness of paintwork, is that you don't simply plonk it on the surface, take a few reading in an area, then decide the amount of clearcoat is exactly 1/3rd of the total.
> What you do do, is measure areas at the door shut, under the bonnet, where the manufacturer hasn't bothered to clearcoat, to save money!
> ...


I can see your thinking but if you read through the pages i am talking about cars that are over a few years old and have maybe been touched up and blended etc etc on various parts. The original poster asked if he needed a PTG and unless he is doing all brand new cars which i highly doubt! then IMO a total thickness gauge is pretty useless due to the many many variables that come into play. I think everything has already been said on the subject if you can be bothered to trawl through all the pages!


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## PJS (Aug 18, 2007)

Dave KG said:


> But this is information the gauge has given you - you know its painted, and you now know that normal rules will not apply...
> 
> As Drive & Shine has said, generally speaking (as in in the majority of cases), the amount of cleacoat will likely be thicker on a painted region down to the painting process - yes there are lots of variables, but this seems a very consistent result "in the field".


You can almost guarantee the clearcoat layer will be thicker due to the process being done by hand, and the equipment used.
That, and the body shop will be doing work on the clearcoat once cured, so they'll want a greater margin of error level too, to save more costly time on a respray if they screw up themselves when polishing.

It's not exactly rocket science - more a case of simple common sense, something there seems to be a distinct lack of for some people.


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## The Doctor (Sep 11, 2007)

PJS said:


> You can almost guarantee the clearcoat layer will be thicker due to the process being done by hand, and the equipment used.
> That, and the body shop will be doing work on the clearcoat once cured, so they'll want a greater margin of error level too, to save more costly time on a respray if they screw up themselves when polishing.
> 
> It's not exactly rocket science - more a case of simple common sense, something there seems to be a distinct lack of for some people.


Not another one living in an ideal world!

I was going to leave it but i cant let this go.

So the paint is thicker by hand? Maybe when done proper. Who says the paint was done proper? Who says it has the right number of coats of clear? Whos to say the bodyshop didnt hammer it with G3 to remove defects/dust nibs? The reality is we dont live in an ideal world,not all cars have good paint repair jobs.

I really do fail to see how you can judge the amount of clear left on panel thats seen paintwork. You cant,you are simply guessing and hoping. I can do the same with no PTG and regulary do and have done for 15 years!


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## PJS (Aug 18, 2007)

The Doctor said:


> Anybody using a machine polisher on other peoples paint should be extremely careful. The total thickness gauage is pretty much useless IMO unless you are using it on a brand new car and even then readings can vary. Basically i see no real gain in knowing the total thickness of paint on a second hand car thats seen patches of paintwork other than those with really low all over reading in which you might tell the customer his/her paint is too thin to correct.
> 
> I would not advise buying a total thickness gauge no as it can be just as much an hinderance as a help. I would advise anybody starting off detailing to perfect there machine skills and product choices rather than relying on gauges. Most of the time strike through is brought about by user error rather than simply polishing so much paint off that you strike through.


So just what exactly *is* a strikethrough if not removing too much clearcoat/paint (on singletages)? 
Of course it's user error - with or without the aid of a full thickness only PTG!

I think you've placed yourself in an untenable position from your original post, and rather than backtrack, you'd rather look foolish defending it to the hilt.
Perhaps you should call it a day, and take some time to rethink your stance.


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## The Doctor (Sep 11, 2007)

PJS said:


> So just what exactly *is* a strikethrough if not removing too much clearcoat/paint (on singletages)?
> Of course it's user error - with or without the aid of a full thickness only PTG!
> 
> I think you've placed yourself in an untenable position from your original post, and rather than backtrack, you'd rather look foolish defending it to the hilt.
> Perhaps you should call it a day, and take some time to rethink your stance.


I should of really expected a surly obnoxious reply from you (you seem to have a habit of it if somebody doesnt agree with you) after reading your previous posts

I am going to call it a day now thanks. You keep believing you can calculate how much clearcoat there is on older paintwork with your total thickness gauge.


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## PJS (Aug 18, 2007)

The Doctor said:


> Not another one living in an ideal world!
> 
> I was going to leave it but i cant let this go.
> 
> ...


I'm guessing by the sound of your repetitious statements, you've seen a fair bit of botched repainting, otherwise you wouldn't keep pulling it up as a point worth noting.
What can I say to possibly convince you?
Probably nothing, because you're set in your ways now, and can't teach an old dog new tricks?

At this juncture, I don't think there's anything more left to discuss - you've your ideology, and those of us in agreement, have ours.
Each to their own is all that's left to say then.


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## PJS (Aug 18, 2007)

The Doctor said:


> I should of really expected a surly obnoxious reply from you (you seem to have a habit of it if somebody doesnt agree with you) after reading your previous posts
> 
> I am going to call it a day now thanks. You keep believing you can calculate how much clearcoat there is on older paintwork with your total thickness gauge.


Surly?
Obnoxious?

Nope - I just call a spade, a spade, and do so without any hesitation or beating about the bush.
It's got bugger all to do with anyone agreeing with me or not - I call everyone when I see nonsense, BS, and/or FUD, being spouted.
There are no back doors for me - I speak my mind, whether you like it or not.

Your postings here are nothing more than FUD, when *many* of us have pointed out the invaluableness of an entry level PTG.
You're the only one who can't/won't get their head around others having a difference of opinion from your own.

Like I said above, you put yourself in an untenable position with your "useless" remarks, and have only managed to make a fool of yourself by maintaining that stance in the face of contrary "evidence".

Still, if it makes you feel better, I'll concede that you're right - the rest of us are all wrong.

Goodnight good sir.


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## kogenx (May 22, 2008)

Well i havent been reading all the posts on this thread, but ive kinda read somewhere from this or other forums.For most "like myself" who are not able to afford the top end PTG.
Measure with your PTG - to get total paint thickness. on the bonnet, then measure the inside of your door or some painted parts on the inside *this may vary in different cars* most of the time it doesnt have a clear coat on them. So you would take the total thickness*bonnet* subtract the total thickness*inside of the door or other parts* you would get a rough estimate of the clear coat thickness. I have personally tried it on a 1996 honda civic. Quite simple. but not 100% accurate. at least it will give you some sort of guide better than none. 

Let me know if i have got any of this wrong. Ill try to search for the thread i have read this on. But through personal experience ive tried it. Like i said it could vary from different makes and type of cars. 

This could very well educate you "the doctor" on some of the great points of the PTG.


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## Dave KG (Feb 23, 2006)

The Doctor said:


> I have given you plenty scenarios where a total thickness reading is useless yet you dismiss them. Im still waiting for an answer to my scenario of the touch up job with the high build primer. That argument stacks up perfectly.


I have answered that question in my post, using a technique of the guage measurement and your experience of being able to read what the paint is telling you from the machine polishing (feel, removal and correction rates)... The argument is a good one, and I have answered with my solution to it, which I use and to good effect (not through luck, but through exercise common sense and combining with experience and knowledge).

As many are pointing out to you, you are selecting examples which are not as common as you make out - certainly not in most of our experiences in detailing, otherwise we'd be reporting strike through from detailers every other week. We are selecting examples also, examples which in my experience are far more likely to present themselves and clearly showing how the gauge (total thickness) is invaluable in these situations.

I do hope that for people reading this thread they can appreciate the usefulness of a PTG, total thickness one or not, and how valuable they are to highlighting thin spots which give a great indication as to what is "safe" and not "safe" to compound. Polishing completely blind is all good and well, but if you are working on a mate's car and its got a thin spot and you compound it... you strike through. If you had a gauge you'd have spotted the thin spot, and wouldn't have struck through. Best option? Its blatantly obvious in my, and mercifully most other people's eyes as well.


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## VIPER (May 30, 2007)

Guys, guys, do we think any of this has been usefull to the OP, or, as I suspect, he's ten times as confused now as before he asked the initial question? 

This 'locking of horns' and refusal to back down is all very admirable and I can understand it, but it might be an idea to put differences of opinion aside for second, and in the interest of the OP (and others who might have been thinking about the same question about PTGs), would it not be better to try and summerise things a little to give a bit of clarification that would answer the original post?


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## Dave KG (Feb 23, 2006)

My quick summary 

A PTG is a very useful tool to have and a total layer thickness one can give a lot of valuable information which will without reasonable doubt make the polishing process safer. Is it necessary? No. But you should be aware of the higher risks you are taking - they are not huge, but you should be aware of them. If doing other cars, to me a gauge is essential for the information that it offers and how it has saved many detailers in past years from striking through on thin spots. 

A PTG will minimise risk - to me, that is clear and obvious and beyond all reasonable debate.


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## Dave KG (Feb 23, 2006)

Pit Viper said:


> Guys, guys, do we think any of this has been usefull to the OP, or, as I suspect, he's ten times as confused now as before he asked the initial question?
> 
> This 'locking of horns' and refusal to back down is all very admirable and I can understand it, but it might be an idea to put differences of opinion aside for second, and in the interest of the OP (and others who might have been thinking about the same question about PTGs), would it not be better to try and summerise things a little to give a bit of clarification that would answer the original post?


I guess the reason you will see me defending the advice given in favour of the PTG so strongly here is I am fully aware of the benefits it brings, and I have seen in the past how the gauge has saved many detailers on cars where there are thin spots on panels which would otherwise have been compounded. I would hate to see people read advice that a total layer thickness gauge is useless and take it as read and not use one based on this - which to me is not correct for the reasons highlighted above. To me, this will see people unaware of thin spots that may be on a panel and lead to strike through which could otherwise be avoided. Not a good thing, and something nobody will be able to help with once its happended other than a bodyshop.


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## RandomlySet (Jul 10, 2007)

here's a question for you.

the diagrams that people use for cars to scribble readings on, where do you get them from?

i guess a generic diagram could be used for all cars, however, i have seen "car specific" ones. For example, a detailer is about to machine a Ferrari 360, and their sheet has a diagram of a ferrari 360


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## The Doctor (Sep 11, 2007)

PJS said:


> Surly?
> Obnoxious?
> 
> Nope - I just call a spade, a spade, and do so without any hesitation or beating about the bush.
> ...


There is calling a spade a spade and theres talking down to people if they dont agree with your opinion which you seem to be a master of. Your table manners really are not the best are they?



PJS said:


> Your postings here are nothing more than FUD, when *many* of us have pointed out the invaluableness of an entry level PTG.
> You're the only one who can't/won't get their head around others having a difference of opinion from your own..


My postings are FUD? Why is that because they do not match your opinion? I have given plenty scenarios where a total thickness gauge is pretty much useless. You seem to think that guessing the amount of clear left on a car is valuable,i personally do not. Isnt it you who is the one who cant get your head around other peoples opinions as demonstrated with your surly/obnoxious tone of reply?



PJS said:


> Like I said above, you put yourself in an untenable position with your "useless" remarks, and have only managed to make a fool of yourself by maintaining that stance in the face of contrary "evidence".


So because i think the total thickness gauges are useless and you dont you expect me to just back down and change my opinion so it matches yours? There never was no contrary evidence as you put it either. There was peoples opinion that the gauge saved them from strike through on rare occasions on panels that had seen no previous paintwork but there was no hard proof to say they would of struck through had they not had the gauge.



PJS said:


> Still, if it makes you feel better, I'll concede that you're right - the rest of us are all wrong.


That is just it! I have never wanted anybody to concede that i am right or wrong. I gave my opinion of the total thickness gauge yet you cannot live with it.

Once again ill spell it out for you. IN MY OPINION the total thickness gauge is pretty much useless due to the many variables and various circumstances that a detailer is confronted with. The reason i think this is because the gauge whilst giving a total thickness reading does not give you any idea of what clearcoat may or may be left on the car. You can guess how much is there but that is all you are doing guessing. Personally i do not think guessing the thickness of the clear is of any benefit especially if the panel has been repaired in the past.


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## The Doctor (Sep 11, 2007)

Pit Viper said:


> Guys, guys, do we think any of this has been usefull to the OP, or, as I suspect, he's ten times as confused now as before he asked the initial question?
> 
> This 'locking of horns' and refusal to back down is all very admirable and I can understand it, but it might be an idea to put differences of opinion aside for second, and in the interest of the OP (and others who might have been thinking about the same question about PTGs), would it not be better to try and summerise things a little to give a bit of clarification that would answer the original post?


I hope it has been useful to the OP. Maybe he will buy one on the strength of Dave's points which i personally do not agree with yet other do which is fair enough by me. Maybe he will take my way of thinking that you are still left guessing at the thickness of the clear.

Right enough is enough,im getting bored with the topic now im off to machine a car-without a PTG!! :buffer:


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## PJS (Aug 18, 2007)

The Doctor said:


> There is calling a spade a spade and theres talking down to people if they dont agree with your opinion which you seem to be a master of. Your table manners really are not the best are they?



Please don't presume things, since you know the square root of the sum total of sod all about me!
Written text can never convey tone, without a lot of explanation.



The Doctor said:


> My postings are FUD? Why is that because they do not match your opinion? I have given plenty scenarios where a total thickness gauge is pretty much useless. You seem to think that guessing the amount of clear left on a car is valuable,i personally do not. Isnt it you who is the one who cant get your head around other peoples opinions as demonstrated with your surly/obnoxious tone of reply?


They are FUD (fear, uncertainty, doubt) since other members, new to this hobbyart of ours, may think the £150 odd they were planning on spending on a PTG is pointless, yet you've read the anecdotal evidence provided by DaveKG (and others) about how finding low spots made correction on those areas off-limits or with extra care, rather than being a bit blasé.



The Doctor said:


> So because i think the total thickness gauges are useless and you dont you expect me to just back down and change my opinion so it matches yours? There never was no contrary evidence as you put it either. There was peoples opinion that the gauge saved them from strike through on rare occasions on panels that had seen no previous paintwork but there was no hard proof to say they would of struck through had they not had the gauge.





The Doctor said:


> That is just it! I have never wanted anybody to concede that i am right or wrong. I gave my opinion of the total thickness gauge yet you cannot live with it.


I can live with your opinion - it doesn't bother me one iota what YOU do, but it does concern me your opinion might be taken by others and result in them having to spend money on a respray for an area they weren't aware of as being too low to polish the marks out of fully.
User error - of course, but one that may have been mitigated against with an additional tool in their arsenal of products.



The Doctor said:


> ]Once again ill spell it out for you. IN MY OPINION the total thickness gauge is pretty much useless due to the many variables and various circumstances that a detailer is confronted with. The reason i think this is because the gauge whilst giving a total thickness reading does not give you any idea of what clearcoat may or may be left on the car. You can guess how much is there but that is all you are doing guessing. Personally i do not think guessing the thickness of the clear is of any benefit especially if the panel has been repaired in the past.





The Doctor said:


> Right enough is enough,im getting bored with the topic now im off to machine a car-without a PTG!! :buffer:


So, I'm right in assuming you don't use any gauge at all?
In that case, can you please explain to all those reading just how in hell's name you know how much clearcoat/paint you have in front of you?
I'm totally flummoxed as to how you can look at a surface, and KNOW what you've got to work with, without having to GUESS any or all of it!

It smacks me as typical of someone in the painting trade (which I'm presuming you are, as it comes across that way), whom when faced with making a mistake, can simply rectify it with a respray, and start over.
For most hobbyist detailers here, that's not an option.

Throughout this entire thread, you've offered absolutely NOTHING to it, other than put some potential buyers and users off of making an entry level PTG purchase.
Not once have you explained how they would be best served when faced with the type of scenarios you've made reference to, repeatedly - perhaps now's the time to enlighten them, with the benefit of your 15 years of experience and, I'm assuming, knowledge.
Your arrogance usurps any of my traits (I did say I pull people for spouting nonsense, and spreading FUD, as evidenced by my original reply to your original comments), especially in light of having it explained how and why an EL PTG can be useful, as opposed to useless, yet you keep on referring to having to know to a high degree of certainty, the thickness of the clearcoat.

So, to summarise your input on this thread, it goes something like this?
_"Don't use a total thickness PTG, as they are useless at telling you how much clearcoat/paint you have to do any correction on, you should use the £1K+ multi-layer machines instead.
Me? Oh, I don't use a guage - I've 15 years of experience to fall back on, which will guarantee I don't make mistakes, and consequently no need to have a PTG of any sort - least of all one which leaves you with guessing how much clearcoat/paint you have to work with."_

Yep, real sound advice to be giving newcomers to the paint correction element of this hobbyart we call detailing.
From what I've read, I consider it nothing more than sheer good fortune that you've not left many of the car's you've done, with a very thin layer of clearcoat/paint.
That or you've not corrected the paintwork as well as it could've been by being overly cautious, just in case.
To that end, it doesn't take 15 years to use common sense that it's best to err on the side of caution when faced with the uncertainty of how much there is to work with!

There really is nothing further to be gained here from toing and froing - so this is my swansong post in this thread.


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## Gleammachine (Sep 8, 2007)

Unfortunately this thread has turned into a bit of a farce, read through all the posts and it appears one person is in disagreement with the majority, despite those having many years experience on a day to day basis.

As already mentioned, having a ptg gauge no matter wether it breaks down the layers or reads a single overall reading, makes you better informed to assess the degree of polishing required and make a judgement than going at it blind without any indication at all and hoping for the best.

Also if detailing as a profession, a reading will enable you to communicate with the client ie.. if the reading is very low then you are able to discuss and make an informed decision to whats possible and advise upon it, if the reading is unusually high then the vehicle has most certainly had paint upon which the client may not be aware.

A PTG is an insurance policy and will guide you to whats required, any machine polishing has risks but through experience and information it makes the task more controllable.
Over the years I have learnt to recognise thin paint or painted areas by eye, had a Porsche last year and straight away new the bonnet had been heavily machined before, the ptg confirmed my thoughts reading in the low 70 um's opposed to 120-130 elsewhere, gave me the opportunity then to discuss with the client and to advise as to the best approach and technique in said area, still wouldn't have been happy without the reading and it's best to gather as much information as possible, rather than none at all.


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## kogenx (May 22, 2008)

Epictetus: It is impossible for a man to learn what he thinks he already knows
well put gleam machine ^_^


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## graeme (Jan 7, 2006)

I think i'll just try and remove my swirls by hand now:doublesho


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## peaumont (Mar 18, 2009)

*paint gauge new idea*

i am going to get my schlong out and get a bit of G3 on it then see how i can get my wingmirrors to come up

i have not got a PTG, but i have hope in god and all that


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## dazzerjp (Sep 3, 2008)

I am not sure the guy who protests has ever had a strike through?


To the original poster. Yes, the 150 PTG isn't 100percent perfect. But without some form of paint map, you are polishing in the dark.

Try looking at it this way;

How much will a panel cost to be re-clearcoated verses a PTG?


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## illyun (Mar 2, 2009)

You always get one like the Doctor on every forum


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## MattOz (May 15, 2007)

I for one am glad that I've recently ordered a PTG, and yes, it's a total thickness one! I was always ok at maths anyway  Whilst I've never struck-through, it will give me a better understanding of what I have to play with, and that could mean the difference between getting paid for a job and having to pay for a panel to be painted. 

Matt


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## FitzyJ (Mar 26, 2009)

I've just purchased one as well, I didnt fancy tackling my Dad's Golf GT and mucking the paint work up. I'm not rich enough to get panels resprayed lol.


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## IJM (Mar 11, 2006)

Okay. I'm convinced even if the Doctor isn't. Now. Where can I get one of these £150 PTGs?


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## nick-a6 (Jun 9, 2007)

i've just read most of this post and from what i can gather

neither of the meters total or layer thickness meters really give you a true reading of the clear coat thickness which i think we can all agree is the thickness that matters.
But both are to be used as a guide line, so having either one of the meters is better than non.
When it comes to working on someone elses pride n joy ignorance isnt bliss and i for one would want as much information as possible

my two pence worth anywho!


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## Epoch (Jul 30, 2006)

I've not fully read all of the above but get the gist, here's my little to add.

We recently worked on a drop head RR, 

After speaking to the manufacturer and understanding how and what they paint them with we were lead to believe the car if original would have around 160 to 180 microns of total thickness. There are reasons why it's known to be this thick but not for discussion here.

We went over the vehicle with the posi 6000 finding that all but two areas did indeed have around 160 to 180 microns. We found a patch that had been blown over that was reading high 300's and also the passenger door (that did show signs of buffer trials etc) which was measuring 79 microns. 

While I had the the Posi 200 with me it didn't take a brain surgeon to work out that somebody had been grinding this door for a while with a compound and anything less than light cosmetic finishing would be foolish. SOme clever polishing resulted in only 1 to 2 microns of removal (as agreed by the owner who is also a good friend)

Without overall measurement and the understanding we had gained from the manufacturer we may not have been able to advise the owner of the problem AND created ourselves an akward conversation afterwards.

The more you know, the less you guess i suppose

As Damon has mentioned the Posi 200 is flawed in design, but if you really understand how it works and what you can get it to show you its a very valuable tool. It may have a high purchase cost and the water a pain, but it's another sense to add the ones we have. 

It's certainly not as accurate in how it works as a metals gauge but knowledge is indeed power.


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## L200 Steve (Oct 25, 2005)

rusey93 said:


> Hi,
> 
> I am looking at buying a kestrel das-6 dual action, I can afford the machine and then meguiars kit, but cannot afford a paint thickness gauge on top
> 
> ...


No.

HTH:wave:


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## Keefe (Jun 30, 2008)

I do.

Will I buy?

If I have tons of money at my disposal. Otherwise:

Depends on how much polishing I do.

If ever I polish a car on a daily basis, it calls for the best PTG. I wouldn't mind the price cos it will pay for itself very quickly.


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## -Kev- (Oct 30, 2007)

thread from the dead! :doublesho


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## Prism Detailing (Jun 8, 2006)

-Kev- said:


> thread from the dead! :doublesho


On a positive note, at least people are reading through the archives :thumb:


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## Puntoboy (Jun 30, 2007)

Made some interesting reading that did.

I'm off out to buy some sandpaper and rub it across my bonnet.

Might even cut a panel in half and get my ruler out to measure the layers :lol:


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## big ben (Aug 25, 2009)

was a funny read :lol:

i would rather machine the hell out of my car for a while, then spend the 1500 on a bloody respray :lol:


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## Nanoman (Jan 17, 2009)

I wonder if 'the doctor' would retract any of his unusual statements. 

I'm new to detailing. I'm still perfecting my technique. I get a scrap panel and my DAS-6 and give it a bash. With no way of measuring how much clearcoat I've removed it could be 60 microns or 6 microns. With a total thickness PTG i've got a damn good idea of how much clearcoat I've removed. How can he say a total thickness ptg is 'pretty useless'?

When I'm doing my audi that I've had since new I can be pretty certain that the clearcoat is at least 10 microns. With a total thickness PTG I can measure how much was on it when I got it and how much I'm removing when I polish it. How is that information 'pretty useless'?

I'd say to the OP... no you don't need one but invest in one as soon as you can afford it. I did and I'm very glad I did.

I'd say to 'the doctor'... admit your statement that 'The ones that measure the total thickness are pretty useless' is wrong. Go on... you know you want to...

;-)


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## REFLECTS (Apr 7, 2008)

Thread resurrected - Goes off to get popcorn


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## T25DOC (Jan 11, 2010)

Ahhhhh that was a good read and although I could see the doctors point about not knowing the thickness of the clear coat - I do think his comment that PTG are useless was incorrect - all knowledge is powerful - whether it's a little or a lot....it will support you in your decisions and I guess aiding to reduce the risk....


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## Mirror Finish Details (Aug 21, 2008)

There are still plenty of areas on a car where there is no clear coat but plenty of paint, like under the boot shuts, bonnet shuts, under doors etc. I just measure those areas, get an average then measure the finished panel. I can then get a good idea of the clear thickness.

I had the luxury of testing a meter to measure all thicknesses and my normal meter and technique was only a few Um out.


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## Deano (Jul 7, 2006)

guys, threads nearly 12months old and doesnt need resurrecting, but (like me) it needs putting to bed.


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