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Does anyone have experience in color sanding a freshly painted vehicle?
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12-01-2008, 09:31 PM | #1 |
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Does anyone have experience in color sanding a freshly painted vehicle?
Today I was hired by a body shop to color sand and buff a black chevy suburban. I sanded it down first with a da sander and 1500 grit disc. Then I sanded it with a 3000 grit disc. I then started to compound the panels and noticed first that the paint really wasnt cutting that well. So I switched to a more aggressive pad and then it seemed to be ok. After I compounded the dryness out of all the sanded panels I then switched to menzerna s.i.p. and polished all the sanded panels. After this I then polished all panels with 106ff. The side that I was polishing was in the shade this whole time so I needed to turn it around into the sun to check my work. It looked great for about five minutes and then all of a sudden all of the scratches that I had just spend hours polishing started to come back again. I do not believe that the paint was cured on this vehicle yet as it was very soft and wasnt reacting like normal paint. A friend of mine who used to color sand and buff cars at a body shop said that this is a problem he used to have all the time. On cars that have been freshly painted they appear to be perfect but after a couple minutes in the sun they look terrible. I compounded the scratches with a wool pad and with a foam pad so its almost impossible for the scratches to still be there. Has anyone else ever experienced this or does anyone have a better explanation.
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12-01-2008, 09:45 PM | #2 |
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So you work at a body shop wet sanding cars, yet you have no experience doing so? That doesn't sound too comforting , this is why body shops get a bad rep. I wouldn't recommend learning how to color sand on someones car. As for your problem, what is probably happening is the oils in the polish/compound you are using are most likely filling the defects. You are probably not removing all the sanding marks, try going with a more aggressive pad and do an isopropyl alcohol wipe down after compounding the sanding marks to check your progress. If there are no more sanding marks left then move on to the next step.
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12-01-2008, 09:53 PM | #3 | |
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12-01-2008, 10:05 PM | #4 |
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Hey Chris, two things sprung to mind; the second was filling, but you mentioned that wasn't it, so it must be the first.
On freshly painted cars the paint hasn't fully cured, obviously. When heavily compounding the paint can swell and it will appear that you've removed all the sanding marks. As the paint cools the sanding marks will re-appear. There is some info on this at Autopia and on MOL. Look for posts by Anthony Orosco, he's mentioned swelling a number of times. He actually theorized it might be worse with some of the ceramiclear polishes (like sip and 106) because of the way they are made. Actually, Meznerna had some articles about it too (on some german site, wish I could find it). The marks you saw re-appearing were the sanding marks, right? Almost looked as if you'd rounded off the edges? I assume you don't mean holograms from compounding. In any event, I've had this happen before too. I wanted to wait and re-sand but the body shop couldn't wait (and they swore the paint would be too hard after it cured), so I just went over the car with 4000 grit then re-compounded. The second time around I did 105, 83, FPII (normally I would have done 105, sip, 106ff). Oh, just re-read your post. Which compound did you use on the wool prior to SIP? PG, 105? |
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12-01-2008, 10:17 PM | #5 |
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I tried Megs 105 and Megs Diamond Cut Compound, I also tried Power Gloss and 3M and 3M Extra Cut Compound but nothing worked! You are definitely on the right path to what I am talking about. My friend who used to work at the body shop said that it used to happen to him all the time. Also the Meguiars training center says that the paint just cant finish off nicely if its not cured. The paint is heating up and changing form so it appears done. But then once it cools it takes back to the shape of sanding and appears scratched again. After about a million times of compounding most of the scratches appeared to be gone but the paint still wouldnt finish off nicely. I stepped down from wool to foam on the compound. I went from s.i.p. on the orange to s.i.p. on the white cause I knew the clear was soft for sure. Then finished with 106ff on a brand new white pad at only 1000 rpm and it still would appear great for about five minutes and then just go right back to hazy again. I advised the body shop of my thoughts and they too told me that they cant wait. All advice ive gotten up to this point from Meguiars and so on is wait, wait, wait. They say its simply not ready to be buffed and they should park it outside for a few days. However customers want their cars back asap so its gives us this situation. I wonder if when you resanded with 4000 again if you helped the overall drying of the paint and caused it to finish off nicely. I have to return to the shop on thursday to finish the job so I would like to be as prepared as possible. Thanks again for always having good advice
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12-01-2008, 10:44 PM | #6 |
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Glad you didn't take my post the wrong way, after reading it over I think I could've worded it differently, sorry about that. I'm curious as to what kind of wool are you using? Also since the paint is so soft maybe you are just be chasing the sanding marks now when compounding? I would say give the 4,000 grit a try as picus suggested, as it will give you a more level surface to start with. Also when finishing, try following with a black pad and some 85rd, it should prevent any holograms from coming back if you follow the 106ff/white pad with it.
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12-01-2008, 11:06 PM | #7 | |
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12-02-2008, 07:40 AM | #8 | |
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You may want to try some abralon 4k grit. Trizact 3k is nice but the 4k is like buttah. Just a thought for the future, it really is nice. I am not sure if it's the answer in this case because of what I am about to say... On the haze, I think I might know what that is too. You may be trapping solvents as they try to escape when you heat the paint up. I've had that happen to me too, believe it or not. I was compounding (not sanding) a ~1 week old painted 'cuda and it was hazing like nuts a few min after compounding. I wiped it down with alcohol and water and the hazing went away *mostly*, but not entirely. I had to lightly re-polish it a week later. When you go back try going over the haze with 8rd on a light foam pad, then remove the residue with isa:water. It's worth a shot. On the re-sanding, you are removing paint every time you compound so, suffice it to say, you should be careful. Do you have a paint thickness gauge? That should help determine if you're ok to remove more. |
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12-02-2008, 08:59 AM | #9 | |
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12-02-2008, 05:02 PM | #10 |
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Ya, that will likely be a good thing. It might be a bit tougher to remove the haze that's on there now, but it will come off. On the 'cuda I did I removed it with 8rd on a black foam pad, ~1200 rpm, so really light polishing. Let us know how it goes.
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