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Old 03-26-2013, 08:26 AM
Brian Martin,Freelance adviser
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Originally Posted by John long View Post
Let me ask a question? Would a heavy coat of polyester primer work as well as a skim coat? What would be the advantages or disadvantages of each?

John L

If I could toss something out there on the difference, I find that with the clean up and over spray and the other things you need to deal with spraying I reserve it for use on a very large panel, one with a lot of body lines, or one that is flexible.

Or of course a combination of those three reasons. It is PERFECT in my opinion for stuff like firewalls and the first time I ever used it, on the tail gate of my truck. Repairing an original tail gate with all the lines and the name stamped into it, spreading filler is of course very difficult. So to rough out the work with very coarse paper that cuts very easy to get it into shape with filler. Then applying a nice application of polyester primer and now you can sand it to perfection with finer paper that will leave it more paint ready than if you were to try to sand the filler applied with a spreader around all those body lines and what not.

Same on a fire wall or something like that, all the holes and body lines and seams, working around that is a bear with a spreader and filler. Polyester primer is the way to go there.

On large flat panels like a hood it works great because you don't have to sand off so much that isn't doing a thing for your final product, all the little lumps from the edge of the spreader and passes of the spreader with filler. You rough it out with coarser paper that cuts fast on that flexing panel so you don't have to push down hard to sand and flex the panel. Once it's all flat, a few coats of polyester primer to fill all those coarser sand scratches and small flaws and you can sand it much easier than putty being it again, doesn't have all the ridges and what not.

I have done some tests with that stuff that you wouldn't believe and it passed with flying colors. How about spraying it over filler sanded with 36 grit brand new, sharp paper, one application of a couple of coats. Sanded that with 120-180-220-320-400 and then painted black bc/cc over it. Six months later I was able to examine it and it showed ZERO shrinkage, pretty cool stuff.

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