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      12-01-2008, 10:31 PM   #1
Chris J
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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.

Thanks for you input!
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      12-01-2008, 10:45 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, 10:53 PM   #3
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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 and 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.
No no no. I have years of experience in color sanding cars. Im completely aware of all the normal reasons for this. What im saying is this is an out of the ordinary situation that I have never seen before. And I dont work for the body shop I am their detailer. Whenever the need a detail they call me and I come do it. However this vehicle acted like no vehicle I have ever done before. So what im saying in a nutshell is has anyone ever seen this before. It is not oils filling as I explained I compounded the truck twice. Once with wool ( a couple passes per panel) and once with foam (another couple passes). Then on to S.I.P. and then to 106ff. I think this may be more of a problem with the paint not being fully cured yet and this causes it to not polish out perfectly. I dont think any american body shop would invest in menzerna let alone know about it unless someone told them. And I for sure dont think that some body shop detailer who makes 9 bucks an hour would care to log on to a forum to try and find out an answer to the problem. So if you might have experienced this before or if anyone else has I would appreciate your help on this specific situation. Once again I completely aware of filling and in this application its simply not the case. This is something different.
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      12-01-2008, 11:05 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, 11:17 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, 11:44 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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      12-02-2008, 12:06 AM   #7
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Originally Posted by 328i View Post
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.
This is good advice however 3M 3000 grit (trizact) on a da sander barely barely barely leaves sanding marks. It looks more kind of like a cloudiness not sand marks. It is so light on a cured vehicle you could almost literally just take some compound by hand and start taking out marks. My main problem was in the beginning the sanding marks but my main problem was then end finishing. I stepped down one little step at a time taking every precaution I could to have it finish off nicely. I polished with s.i.p. until it virtually clear and also with 106ff. Even s.i.p. alone should take out such fine sanding marks. I completely understand what you are saying about 85rd I love the stuff! However its not necessarily holograms that im seeing. Its a strange circular haze that appears on the panels about five minutes after polishing. As I wrote earlier most detailers believe this to be the paint not cured yet and is heating up(changing form) and then cooling (returning to its original form). So far like Picus said it is one of two things....either filling which I dont believe or this other strange situation which some people are saying. But im hoping to see if someone has any other explanations besides these two. And if it is indeed the situation picus is talking about hopefully the 4000 grit would work. I have all the way up to 8000 but if I am cutting every time I dont want to run out of paint and according to meguiars every time I have been buffing even though it may not appear so it really is cutting paint. The advice from meguiars was to wait until its cured and absolutely not touch it again until its cured. Because the paint is very very likely to burn. However this body shop wants toi deliver this car on thursday so I want to be ready. Also in regards to 85rd I apoligize I forgot to mention it earlier I did try it with a black pad at 1000 rpm and it looked great for a while but it also then turned into a haze. Thanks for your comments so far and no worries about the previous comment.
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      12-02-2008, 08:40 AM   #8
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Quote:
Originally Posted by Chris J View Post
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
Two more things.

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, 09:59 AM   #9
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Quote:
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Two more things.

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.
Yeah thats pretty much what I have been hearing is that the solvents are trying to escape. So hopefully I will have better luck on thursday. I will give you a call if I just cant figure it out. I sure hope I can though. They are supposed to bake the truck again and then infared it again also. Hopefully this will cause all the solvents to dry out and make it polishable again.
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      12-02-2008, 06:02 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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