Report and pics showng how much clearcoat is removed during machine polishing

[craigdt]

My wife is about to sell her worn out 2006 Chevrolet Aveo, so what better time to answer one of life's greatest mysteries:
How much clearcoat is removed during *aggressive* swirl removal?

To try to answer this question, I used the following approach, which was somewhat popular ~4 years ago with the average hobbyist detailer:
G110V1 speed 6, moderate pressure
4" Orange LC pad
Meguiars M105

To give us a good idea of how much clearcoat we are starting with, I took paint reading around the door sill area, as it is generally not clear coated:

Average of 94 microns.

Here is the hood of the subject, to show you how bad of shape it is in:

Now testing the hood, we see the average total paint thickness reading over 5 spots in roughly a 1sq ft area is 133 microns:

So we can deduce that we have about 39 microns of clear coat to work with.

After about 8 passes, this is the result:

Now, just how much clear coat is left?

An average of 126 microns, meaning that we removed about 7 microns, or about 18% of the total clear coat layer.

Now 7 microns doesnt sound all that much, but I would think you would only want to remove at most, maybe 20-25 microns, or just over half of the available clear coat before you start to run into trouble, such as clear coat failure. Now, I am not a professional, so maybe they can chime and correct me if I am off base with this supposition.

A couple other things:
1-I was probably a bit more aggressive than I normally would be with this test. I'd probably make a few less passes, and probably use less pressure on a nicer vehicle that I cared about.

2- This really enforces the importance of proper wash/general care techniques, since you may only have 2 or 3 chances at heavy compounding before you might start to think twice and choose a lighter polish.

3- Different vehicles will have different thicknesses of clearcoat. So what may get you in trouble on one vehicle would be perfectly fine on another. A paint thickness gauge could very well save you from a bad day.

4- Detailing is fun

 

[Stokdgs]

How do you know that the microns difference between the paint in the door jamb (97um) and paint on the hood (134um) is not because the robot sprayed LESS Paint in the door jamb ?
Dan F

 

[craigdt]

You dont- it's an assumption based on standard practices that many car manufacturers seem to follow. Either no clear coat or very thin.
Maybe that was your point- you have to make some educated guesses when using a PTG.
They just give you data- you have to determine how to interpret it.

If you are interested, I could do some hand polishing on the door jamb to see if I get any color transfer.

 

[Mike lambert]

The industry average of clear is 2.0/2.5 mils, it is advised by the paint companies that no more than .5 mils be removed over the life of the car. That protects against clear failure. One seriously aggressive compounding session can do that. That's it for correction unless you want to own a repaint or you just don't care!

 

[Accumulator]

craigdt- Thanks for doing this and posting it up!

Regardless of how much clear there really is to start with, that illustrated perfectly how much is removed by "moderate correction". You didn't even come *close* to what so many people do, yet you took off so much!

As I keep harping on- this simply doesn't get enough attention, it's not taken seriously enough. In my area I see *SO* many vehicles with cc failure and in most cases I can see exactly how they were "corrected" (scare-quotes intentional...because they sure don't look "correct" now), like..."and he gave it a few more passes on that area, and his pad didn't reach over to that area".. etc. With today's polishers and products, it's become *so* easy to take off a lot of clear, for better and for worse.

 

[imported_JustinTRW]

Very surprising!

 

[Stokdgs]

Appreciate all the work you did, your pics and write up !

The PTG is measuring, with a little error, the total thickness of all the material on the surface... Not just the clear coat, but everything, including primer, sealer, etc., and all the paint that may be mixed with clear coat, so there might not really be any extra clear coat on it anyway..

Unless its that $2500.00 + DeFelsko tool, that measures each layer with a little error, no one really knows how many layers of what, and how much actual clear coat ONLY is on there...

I tried to find out more about this factory paint process and have not really hit on the exact search words to get better info..

Cant really go with assuming what the Factories have done, and they will all be different anyway; all I can absolutely Know - for a fact is that the total thickness of whatever amount of each variable on the surface is less with each year on some models..

All I was able to determine and then again, its on the Internet, so can you really believe everything you read(?), is that the water-borne paint today takes a lot longer to dry than the good old solvent based paint and products of before...

I just go with Mike Lambert up there in Post #4 and take as little off as possible...

I Never measure in Mils, (1 Mil = 25.4 Microns ), I measure A LOT - but only in Microns and it if moves even .5 a Micron, I'm looking at stopping ..

Having painted before and knowing how much trouble that is to go through just doing repairs in the Shop, I don't really want to have to re-visit that for my own vehicles and especially a Client's "Baby"...
Good luck with your research !
Dan F

 

[jmsc]

After a lot of trial & error, anguish, guesswork over many years I broke down and bought a PTG from Highline last winter. It may not be a perfect instrument but it sure beats nothing at all. I purchased one due to a not-too-old a Ferrari I was asked to inspect. When I got readings in the redzone I just said to (myself and) the customer that I would not attempt a detail due to low remaining paint levels. Now, I sample paint thickness everywhere on new, late model, older, resprays, clearcoated, tricoated, single stage paint systems. I'm shocked at what I see.

Best buy for me since my first Porter Cable back in 2002.

 

[Accumulator]

...All I was able to determine and then again, its on the Internet, so can you really believe everything you read(?), is that the water-borne paint today takes a lot longer to dry than the good old solvent based paint and products of before...

I bet there are simply *countless* variables, but the water-borne stuff my Audi painter uses doesn't seem to take any longer than the old solvent-based stuff to attain max hardness. Eh, I bet we simply can't generalize anyhow...

I Never measure in Mils, (1 Mil = 25.4 Microns ), I measure A LOT - but only in Microns and it if moves even .5 a Micron, I'm looking at stopping ..

Whereas I somehow got into the habit of using Microns, not that I do much measuring (especially these days). Funny how some guys like one and other guys like the other, not that it matters.

Gee, I haven't used my ETG since forever, but then I haven't done much correction for ages either.

 

[Detailology Oz]

I've tested compounds (which I no longer use) and rotary/wool pad and seen 3.8 to 5 microns removed at low to moderate speeds
Microfibre and DA large throw can remove same if not 7 to 8 microns

Most cars I've worked on that have 130 to 140 microns from a non tri layer reading PTG can have clear coat burn through once take it below 80 microns
in the 70's your definately in big trouble of going through or you've already gone through

Have had Nissan G35's from japan measure 80 total so I had to use a jewelling polish only and correct it via that

 

[Accumulator]

And even when you don't "go through" it's easy to thin the clear so much that a year or two of sun/UV exposure causes failure. IMO too many people just don't get that, or at least aren't thinking long-term. Eh, I know...I always sound like "The sky is falling!" on this topic

 

[OneQuickGT1]

Neat thread. In all honesty, this is why I am considering two things for my new DD - One is coating it. this way any damage is in the coating, think sacrificial layer. Or, not polishing unless it is absolutely needed, and if it is, using something like Prima Amigo or M205 on a very gentle pad.

I am leaning towards OPT Gloss Coat, as I think this is the ideal solution for a DD.

 

[Stokdgs]

Neat thread. In all honesty, this is why I am considering two things for my new DD - One is coating it. this way any damage is in the coating, think sacrificial layer. Or, not polishing unless it is absolutely needed, and if it is, using something like Prima Amigo or M205 on a very gentle pad.

I am leaning towards OPT Gloss Coat, as I think this is the ideal solution for a DD.

You are on the right track !

I went through and Perfectly corrected all the vehicles at the house and put Optimum Opti-Guard (Before Opti-Pro), on all of them and never looked back...

Lost track of the 3 others, but mine is still beautiful, and no damage or wearing off the original paint...

For the first few years, my Black Grand Cherokee never even got dirty - nothing stuck very well to the paint..

And all I have to do is wash it and wear it.. Much simpler... the clarity and gloss is still blinding in the sun... very little defects on the coating... I can go for weeks with not washing it, and it always looks very clean and glossy..,

If you are of the type that need to/want to wash your vehicle all the time, then there will always be the opportunity to put defects on the coating, so if you are ok with this, then that will be fine.. The paint will still be protected and you actually have not even touched it to start wearing it down...

And one less thing to worry about in the grand scheme of things, no ??
Good luck with your research !
Dan F

 

[allenk4]

And even when you don't "go through" it's easy to thin the clear so much that a year or two of sun/UV exposure causes failure. IMO too many people just don't get that, or at least aren't thinking long-term. Eh, I know...I always sound like "The sky is falling!" on this topic

I hear this all the time and do not necessarily disagree, but I have never seen a real world example of a vehicle that was in good shape, was then compounded to below a manufacturers suggested CC thickness and subsequently failed.

Not saying it doesn't happen, just that I have not seen an example posted here...or anywhere.

 

[DBAILEY]

People are always stating that they are using the least aggressive polish/pad combo that they needed but they always end up using M101/M100/M105, FG400 or something like that and MF or wool pads. They end up stating that nothing else was up to the task, but what they really meant is nothing clear the defects as fast as they wanted, which I'm sure it totally true. But they didn't need to cut that much clear coat to re-level the surface in the first place. They just didn't have the patience to use something less aggressive. Seems like way too many people go straight to the heavy duty compounds and many medium polishes never get considered.

 

[Accumulator]

allenk4- In my area it's incredibly common, to where it doesn't even really get my attention any more. I suspect "reconditioning" as in auction/dealerships/etc. Always on the horizontal surfaces. So far it's only on older vehicles, but it won't surprise me when I see it on something newer.

DBAILEY- I'm kinda guilty of that myself, but the way I see it I'm taking off the same amount of clear overall. But then, given my position on the topic, I might be a lot more careful about it than some people are.

 

[Stokdgs]

I have found it's the best to set the Client's Expectations First; you are going to need the vehicle (after you inspected it), for xx hours for the agreed upon level of work, and always give yourself extra time, so you dont have to rush it and go to heavier compounds, etc..

And I use Rotary Power, so I can knock out anything quickly - but I dont have to - and will use the least aggressive product from Menzerna for example, and work from there... Im all into saving the paint... Especially if this Client is going to be with me forever...
Dan F

 

[allenk4]

Unless its that $2500.00 + DeFelsko tool, that measures each layer with a little error...

Dan F

Which DeFelsko is this?

where did you find it for $2,500?



.

 

[allenk4]

allenk4- In my area it's incredibly common, to where it doesn't even really get my attention any more. I suspect "reconditioning" as in auction/dealerships/etc. Always on the horizontal surfaces. So far it's only on older vehicles, but it won't surprise me when I see it on something newer.

So, older vehicles and horizontal surfaces makes sense, but that is for all vehicles, wether they have been polished or not.

This is an observation, not a prove able correlation.



.

 

[allenk4]

.

DBAILEY- I'm kinda guilty of that myself, but the way I see it I'm taking off the same amount of clear overall. But then, given my position on the topic, I might be a lot more careful about it than some people are.

I agree with Accumulator.

If the scratch is 10 microns deep...you must remove 10 microns of substrate to remove the scratch completely.

It does not matter if you take the entire 10 microns off with a finishing polish or 9 off with a compound and the last micron off with a finishing polish.

Even an if you take all 10 microns off with something that leaves haze; removing that haze with finishing polish removes so little CC that it is inconsequential.