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Thread: how long does paint shrink?

  1. #1
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    Default how long does paint shrink?

    My 93 bonneville, body was painted Oct. 2008, and bolt on parts the next summer. So, the freshest paint is already 7 - 8 months old. I buffed the body last year, and the bolt on parts over the winter. I've re-sanded and re-buffed a few sections to deal with small areas of where the paint shrunk into sanding scratches... just a little work with 2000 wet did the trick. I am driving it on nice days, averaging 3 days a week for the past month. I'm still coming across new areas of shrinking on the body! It is certainly sanding scratches, because where there was no body work is fine. It is barely noticeable and easily fixed. But my gosh, how long does it take to finish shrinking? Dupont chromabase and chromaclear. Black. Thanks, Mike
    Mike

  2. #2
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    its probably the primer, not the paint. If you finish with 180, and get all the coarser scratches out, it would probably not be a problem. By now the areas you are finding now have been there for months and you didnt see them before

  3. #3
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    Quote Originally Posted by MikeP View Post
    My 93 bonneville, body was painted Oct. 2008, and bolt on parts the next summer. So, the freshest paint is already 7 - 8 months old. I buffed the body last year, and the bolt on parts over the winter. I've re-sanded and re-buffed a few sections to deal with small areas of where the paint shrunk into sanding scratches... just a little work with 2000 wet did the trick. I am driving it on nice days, averaging 3 days a week for the past month. I'm still coming across new areas of shrinking on the body! It is certainly sanding scratches, because where there was no body work is fine. It is barely noticeable and easily fixed. But my gosh, how long does it take to finish shrinking? Dupont chromabase and chromaclear. Black. Thanks, Mike
    Is the shrinking over body filler or all over the surface?

  4. #4
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    Default Up to a year.

    I've seen cars painted, colorsanded and looking great get texture up to a full year out. Fortunately, a quick pass with 2000 or even 2500 and polish is usually all it takes to put things right.

  5. #5
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    I've heard that you should let the primer dry 2-3 weeks before final sanding and painting, provided you have the time.

  6. #6
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    Quote Originally Posted by Tincup View Post
    I've heard that you should let the primer dry 2-3 weeks before final sanding and painting, provided you have the time.
    Most "good" primers are as hard as they're going to get in a few hours at 80+ degrees F. I usually leave it overnight and block it the next day. Cooler temps can add days to the the hardening process and some cheap primers remain unstable. Use quality products.

  7. #7
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    Thanks for the replies. The primer was dupont also, so I would think it was decent stuff. I have to think that it is over where the body filler is, as the whole car was primed and blocked with 400 before painting. And since this project was a long term deal, in some cases the primer sat for weeks or months, and never less than several days before I sanded. And I suppose it is possible that it was always there and I am just getting to see it now, when the lighting is perfect. I think I'll wait until the car is put away for the winter and tweak on it. You can't see it if there is dust on the car, and of course it is covered in pollen if it sits outside for more than 30 minutes this time of year. Thanks! Mike
    Mike

  8. #8
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    Quote Originally Posted by MikeP View Post
    Thanks for the replies. The primer was dupont also, so I would think it was decent stuff. I have to think that it is over where the body filler is, as the whole car was primed and blocked with 400 before painting. And since this project was a long term deal, in some cases the primer sat for weeks or months, and never less than several days before I sanded. And I suppose it is possible that it was always there and I am just getting to see it now, when the lighting is perfect. I think I'll wait until the car is put away for the winter and tweak on it. You can't see it if there is dust on the car, and of course it is covered in pollen if it sits outside for more than 30 minutes this time of year. Thanks! Mike
    I'm not a big fan of DuPont products mainly because I've run into several problems that I don't have when using other products but I've never used their primer so I can't say that's the issue here. Since the paint is black it has more stress on it than other colors because it gets so hot when the sun beats on it. In many cases the scratches that keep appearing can be caused by the type of body filler or the way the filler was leveled prior to applying the primer. If you finished the filler with 80 grit then used primer to fill those scratches the difference in the density of the materials can make them expand and contract differently and cause these scratches to sometime show especially in black paint because of its mirror-like finish and how hot it can get. IOW, the scratches may always come back when the temperature changes if certain products were used together.

  9. #9
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    It takes 1-2 weeks to dry the primer after that sanding and painting should be done for better results.

  10. #10
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    Quote Originally Posted by mighty View Post
    It takes 1-2 weeks to dry the primer after that sanding and painting should be done for better results.
    This guy obviously has no idea what he's talking about.

  11. #11
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    Thanks for the replies. I might be over-thinking things. I had the car out yesterday, gorgeous day, couldn't find a flaw, brought it into the garage with the flourescent lights, could find the flaws, maybe the same ones it has always had. I will wetsand and rub those spots again, see what happens. Maybe 4 spots total, biggest one the size of a silver dollar. Mike.
    Mike

  12. #12
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    Default You could try

    leaving the car outside, or not looking at it under the lights.

  13. #13
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    Quote Originally Posted by Len View Post
    This guy obviously has no idea what he's talking about.
    Right... smh

  14. #14

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    I can tell a big difference in primer sanded at 48 hrs old compared to 24 or less.
    But it usually takes a full summer for it to show and
    the average person doesn't notice it, just a very slight peel returns,
    and that's usually on a highly buffed out surface.
    That's much more than I do on my collision repairs.

  15. #15
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    Quote Originally Posted by JCCLARK View Post
    I can tell a big difference in primer sanded at 48 hrs old compared to 24 or less.
    But it usually takes a full summer for it to show and
    the average person doesn't notice it, just a very slight peel returns,
    and that's usually on a highly buffed out surface.
    That's much more than I do on my collision repairs.
    It all depends on which products are used. In most cases the better/more expensive coatings shrink a lot less even if they are applied a short time between coatings.

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