Color Sanding - How much paint is removed?
04-20-2007, 04:05 PM
#1
Burning Brakes
Thread Starter
Color Sanding - How much paint is removed?
How much paint comes off during color sanding (2000 grit) with compounding to remove scratches on a 20 year old with single stage black paint - hopefully as a percentage of a layer of paint.
I color sanded last year without any problems. Filled in some paint chips after foolishly driving behind some p-cars through some mountains covered with salt and gravel. Need to level out the applied touch up paint but am a little nervous about getting down to the primer.
I color sanded last year without any problems. Filled in some paint chips after foolishly driving behind some p-cars through some mountains covered with salt and gravel. Need to level out the applied touch up paint but am a little nervous about getting down to the primer.
04-20-2007, 04:40 PM
#2
Burning Brakes
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I'm not experienced enough to 'eye a paint thickness' that is measured in 1/0000th of an inch, and a percentage of that for most would be impossible to guess.
I would strongly suggest anyone undertaking colour-sanding should purchase a digital paint thickness gauge and take measurements before commencement, during and after the work. If you have already colour-sanded the paint surface I would not attempt it again without knowing how much clear coat there is, if you remove too much and breakthrough it will require a re-paint.
This kind of work should only be undertaken by a very experienced enthusiast or a professional detailer, the paint sections / panels that are difficult and involve risk are usually those that are close to the edges of a panel (as this is were paint is usually thinnest) or highly contoured areas. Flat areas like the trunk, hood or roof involve minimal risk.
Wet-sanding levels the paint (and removes orange peel, harsh acidic or alkaline marks, etc) it removes approximately 0.025- 0.03 Mils (a Mil is 1/1000th of an inch) of paint from the vehicle using 2000 -grit finishing paper, Bear in mind that a clear coat has a thickness of 1.5 – 2.0 Mils, removing more that 0.3 – 0.5 Mils of clear coat may cause premature paint film failure. As a point of reference a sheet of Saran wrap measures 0.95 Mils
A digital paint thickness gauge will allow you to measure the film thickness of the paint system which includes the e-coat, primer, base coat (colour) and clear coat, total thickness is usually 4.0 – 6.0 Mils. Check the paint system both before and after wet sanding and this will tell you how much paint has been removed.
For these reasons all car manufacturers now specify that the paint thickness be measured in 0.1mil, or 1/1000th of an inch before and after any wet sanding or buffing. The following are the maximum allowable clear coat reductions the major USA car manufacturers will allow: Chrysler – 0.5 mils; Ford – 0.3 mils; GM – 0.5 mils.
I would strongly suggest anyone undertaking colour-sanding should purchase a digital paint thickness gauge and take measurements before commencement, during and after the work. If you have already colour-sanded the paint surface I would not attempt it again without knowing how much clear coat there is, if you remove too much and breakthrough it will require a re-paint.
This kind of work should only be undertaken by a very experienced enthusiast or a professional detailer, the paint sections / panels that are difficult and involve risk are usually those that are close to the edges of a panel (as this is were paint is usually thinnest) or highly contoured areas. Flat areas like the trunk, hood or roof involve minimal risk.
Wet-sanding levels the paint (and removes orange peel, harsh acidic or alkaline marks, etc) it removes approximately 0.025- 0.03 Mils (a Mil is 1/1000th of an inch) of paint from the vehicle using 2000 -grit finishing paper, Bear in mind that a clear coat has a thickness of 1.5 – 2.0 Mils, removing more that 0.3 – 0.5 Mils of clear coat may cause premature paint film failure. As a point of reference a sheet of Saran wrap measures 0.95 Mils
A digital paint thickness gauge will allow you to measure the film thickness of the paint system which includes the e-coat, primer, base coat (colour) and clear coat, total thickness is usually 4.0 – 6.0 Mils. Check the paint system both before and after wet sanding and this will tell you how much paint has been removed.
For these reasons all car manufacturers now specify that the paint thickness be measured in 0.1mil, or 1/1000th of an inch before and after any wet sanding or buffing. The following are the maximum allowable clear coat reductions the major USA car manufacturers will allow: Chrysler – 0.5 mils; Ford – 0.3 mils; GM – 0.5 mils.
04-20-2007, 10:22 PM
#3
Burning Brakes
Thread Starter
Thanks for the info TOGWT.
Fortunately for those of us with older Porsches, we don't have a clear coat. If I did, I wouldn't have color sanded the first time.
Fortunately for those of us with older Porsches, we don't have a clear coat. If I did, I wouldn't have color sanded the first time.
04-21-2007, 01:52 AM
#4
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You need a paint gauge tomcat. I use this one: http://www.defelsko.com/PosiTestDFT.htm It's crucial so you don't take down more than you need to. On average, I find the thickness on single stage to be around 120-160 microns. 27 microns = 1 mil As TOGTW mentioned, the clear on multi-stage paint is around 1-2 mils. Your single stage is a bit different as you already know which makes it even more risky. I think color sanding should be left to a very very qualified detailer with paint shop experience. I personally do not color sand becasue I don't feel me abilities are there yet. I do level the clear and correct it but using the high speed and compounds. Just my 2 cents
