Opinions on paint thickness of my GM Single stage black paint

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imported_detail1

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I took out my Highliner II meter, calibrated it and went to work. Here are paint readings from my 1987 Grand National with original single stage black lacquer. I carefully took alot of readings in microns. Lots of Grand Nationals were repainted right out of the showroom because there was a defect in the paint primer that would cause the paint to crack. Fortunately, my car does not have this problem.

I just want to get rid of some spider webs. Paint is shiny & glossy.





Hood: 83, 95, 106, 108, 98, 82, 90, 91, 107, 82, 109,107, 115, 106, 93, 91, 91, 103, 102, 106, 87, 98, 117, 103, 127, 92, 105,110. Average =96



Trunk: 112, 135, 127, 112,108, 138, 122, 116, 125,121,128 Average=122



Roof: (T-Top Car) 126, 133,121, 130, 125, 114,109, 110, 112,108, 127

Average=119



Fenders: 114, 116, 133, 260, 90, 97, 108, 91, 116, 119, 100, 106, 95, 90 Average=116



1/4 Panels: 122, 130, 132, 126, 133,153, 124, 146, 128, 91, 85, 90, 91, 83, 221, 132, 172 Average=119



Upper Doors: 103, 125, 125,138, 129, 131,121, 141, 122,112 Average=124



Lower Doors:120, 123, 118, 105, 102, 103, 125, 110, 114,92, 192, 180, 291, 162, 169, 188 Average =143



I know I took alot of readings but i want to know the right direction to take. "Measure twice & cut once!"

I was reading up on micron numbers and I believe that over 100 is safe.

I think the only problem area is really the hood.



The next thing that i will do is to retake measurements & record for each specific area, such as driver's side hood or passenger's side upper door and then average. This way I can definitely know the micron of each separate section & then decide whether to glaze or polish. It's alot of work but it's worth saving my paint. I have been doing alot of reading & researching. I am sure that this will lead to my choice of the best products & strategies to make this original paint look its best without further jeopardizing the thickness of the paint.



Please advise. Thanks
 
Be cognizant that ultra violet protection removal is not a liner process; and the first paint renovation will remove the most UV protection, therefore the above are probably conservative estimates. Two variables need to be established; how much clear coat is available and how much clear coat can be removed without compromising the paint systems long-term durability / paint warranty



A paint thickness reading of > 4 Mil ( 100 µ (Microns) is reasonably safe for polishing. 3 – 3.5 Mil ( 80-90 µ) I wouldn't use anything stronger than > 2000 grit polish, 2.75 – 3.0 Mil (70-80 µ) > 2500 grit polish and under 2.75 Mil (70 µ) use a glaze. The readings tend to vary from panel to panel and are thinner towards the panel edge.



Most light surface marring is ~1.27 µ (0 .05 Mils) a surface scratch that can catch your fingernail is ~1.01 µ (~ 0.04 Mils) Using a medium abrasive polish and a rotary polisher will remove approximately ~ 2.5 - 3µ (~ 0. 98 – 0.12 Mil) from the paint surface. To remove a scratch you need to level the paint to its lowest part, so if a scratch is 1 µ that’s the amount of paint (and UV protection) you need to remove to eliminate it. Note: 25.4 µ (micron) = 1 Mil



• 200µ + can be expected on older cars that have been hand painted or a re-painted vehicle

• 100 – 200µ 4 – 8 mil - normal paint thickness

• 80 – 100 µ - 3 – 4 mils, thin paint

• 80 µ < - less than 3 mil, very thin paint



Paint renovation can restore the finish on a car with paint correcting polishes; however there are some defects that are too deep to be repaired. There comes a point when you must judge wither removing a scratch will compromise the clear coat (> 0.1 µ) and if so you’ll have to ‘live’ with the imperfection (these can be aesthetically masked by using a Glaze)
 
It look like you have some room to work with but you can't take your measurement and use the average. The spots that you have the low readings on need to be checked and inspected more for localized polishing. I would recommend a paint thickness map and pay particular attention to the edges and center of panels.
 
Thanks for your reply. Can you educate me on paint thickness map or provide me with some good readings on it? Thanks! Education & research is the key!
 
detail1 said:
Thanks for your reply. Can you educate me on paint thickness map or provide me with some good readings on it? Thanks! Education & research is the key!
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There are a couple of car drawings here that I found but I'm posting from the phone so I can't find then. You take readings every foot or so and mark it on the diagram. When you look at it, it will show you the high and low spots. Then you can zero in on trouble areas. Basically a crude topographical map of the surface of your car.
 
Thanks- I will definitely take my time and use the diagram. Thank u - this will really help me to preserve my original paint and know where I can polish & where I can be moderate & use a glaze. Thanks
 
jmsc said:
Just a quick question.



About how many microns are removed with a semi-aggressive polish/pad?
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Rotary: using a medium abrasive polish and a rotary polisher will remove approximately 2.5 - 3µ(micron

(0. 13 Mil) from the paint surface, which is typically four passes at 1500-1800 RPM; however many variables such as polish/compound and speed / pressure used that may affect the paint removed)



Random orbital polisher: using a medium abrasive a cutting pad, speed #5 will remove ~ 4 µ (0.17Mil)





These numbers are offered as a guide only, as there are too many variables to provide any more than an approximation.
 
QUOTE=detail1;1493470]Thanks for your reply. Can you educate me on paint thickness map or provide me with some good readings on it? Thanks! Education & research is the key![/QUOTE]





PaintThicknessCarPlan.jpg
 
TOGWT said:


These numbers are offered as a guide only, as there are too many variables to provide any more than an approximation.
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That's the key, there is NO way to approximate. There are so many variables in play:



-paint

-polish/compound (amount AND type)

-pad

-machine and speed

-pad

-temperature
 
I haven't got a clue, since I and the vehicle manufacturers I always worked with, only use "mil" for paint readings. (did have one time when an anal Japanese from Mazda came over and was going on reading in and about microns and all the American Mazda guys and I just told him to eat raw fish)

Could reset either of my ETG, but why?

Mil's are just fine and less confusing, for many reasons.

Grumpy
 
I don't know how you are taking all these readings, but take a spot and take a reading. Imagine a cross and center it on the spot.. take the the 4 tips of the cross around an inch from the center and take your 4 reading..average it out and continue.
 
Ron Ketcham said:
...Mil's are just fine and less confusing, for many reasons.
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Eh, to each their own. I just prefer microns :nixweiss Might just be a matter of what one's used to..two-four numbers is two-four numbers whether there's a decimal involved or not.
 
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