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Thread: Body work, What am I doing wrong?

  1. #1
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    Body work, What am I doing wrong?

    I am having issues with body work showing through the paint a month or two after being painted. This has happened to both of my kit cars now. Both cars are fiberglass bodies, I filled major flaws first with resin/fiberglass mat, then bondo, then a professional quality glazing putty. On one car the primer was evercoat superbuild with a top coat of single stage enamel, sprayed in a home garage. The other car was dupont primer with two stage dupont top coat sprayed in a paint booth by a local body shop.

    Both cars show depressions in the paint where there is small body work, and hairline cracks in the paint around the edges of lager body work areas.

    I don't think this is a paint issue since both cars had totally different top coats and painting procedures, but had the same problem. Which leads me to believe it is in my body work process.

    I will be fixing the flaws over this coming winter and repainting in the spring, and would like to figure out how to stop this from happening again. Any help or feedback would be greatly appreciated.

  2. #2
    Senior Member TwilightZ's Avatar
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    Don't quote me but, I've always been told you need to use a sealer as well as primer on fiberglass.

  3. #3
    Senior Member murcie-me's Avatar
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    Quote Originally Posted by TwilightZ View Post
    Don't quote me but, I've always been told you need to use a sealer as well as primer on fiberglass.
    BINGO!

    First off, glazing putty is worthless. Back in the day it was the thing to use because there were no hi-build primers like there are today. If to do ANY bodywork, whether its on fiberglass or steel, the repaired area must be sealed before painting. Both primers you listed are just that, "primers". Neither will seal the surface properly for paint, and yellowing is almost guaranteed to happen within 2 months of painting.
    You need to be using a quality primer/sealer like PCL or similar. This is a high build primer/sealer, replacing the use or glazing putty. It will easily fill in sand marks and air bubble holes in bondo, fiberglass and other materials, and as long as you don't sand all the way through will provide an excellent seal allowing for flawless color consistency over the entire car.

    Cracking in the paint around the repaired areas are usually a sign of bondo or resin being applied over the previous paint. Make sure to thoroughly remove all paint in the repair area before applying any new bondo or resin.
    Last edited by murcie-me; 08-02-2015 at 11:03 PM.
    Without talent experience is worthless

  4. #4
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    ^^^Great post.

    I would not say "Evercoat" is worthless though. That stuff is divine. I look at it as a primer so thick you have to apply it with a spreader and man is it supreme, like breaking out a choice wine after achieving some milestone. When the body work is "done" it's just one more fine layer to block out before primer. The guys at my supply store were going nuts about evercoat and their new formulas, how it has polymers that eliminate the need for epoxy primer over bare metal and then filler (I know a huge debate in the body world). I'm not saying primers can't finish the job but for 15$ a tube and spread so thin evercoat goes a looong way blending the substrate to nice level surface.

    Sealers are a beautiful thing. Why not start the coating process with yet one more solid unifying layer before painting color? Or I should say in the painting because sealers are not sanded, they basically are paint.

    OP I'm sure other pros can comment more about shrinkage that can occur with large areas of polyester resin/filler or chemical reaction between enamel paints vs. urethane and their associated undercoating. It sounds like you're matching compatibility by the book but one simple answer/factor beside sealer may be letting layers fully cure before finishing?

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