Re: [FWDLK] To undercoat or not---
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Re: [FWDLK] To undercoat or not---



Hello,
A couple of comments about the undercoating products.
The old factory type of undercoating had a couple of purposes. Theory seemed
to be road noise, vibration reduction, abrasion resistance and it covered up
a whole lot of manufacturing boo-boos. It was a petroleum base product with a
ton of filler in it. It made for a great film build (thick) with lots of
texture and ridges. The airless spray equipment used to apply it was a big
part of the finished texture. The stuff dried up hard in a short time.  It
was also great at blocking drain holes and bridging the seams of the metal
panels. Get any moisture trapped behind this undercoating and you get
problems. The factory coverage depended on what kind of day the guy in the
undercoating "Pit" was having. Sometimes target practice, sometimes... not a
pretty sight. This stuff has an uncanny ability to only stick to places where
you don't want it.

What's available to the aftermarket today is different. Spray cans of
undercoating are usually "rubberized" or have lots of solvent to make them
sprayable. You can get the film build but the texture looks very different.
Commercial rustproofing products have waxes and solvents to keep them soft
and flexible. OK for rustproofing, but again a different texture and look.

You don't want to depend on either product to keep a restored car from
rusting again. That work should be done as part of the restoration process.
There are thin seam penetrating rustproofing materials that can be sprayed in
the box sections and seams (after painting). When done right, they won't
show.  The undercoating application should be considered a cosmetic
restoration issue only. Our cars will never be driven hard enough again to
have this stuff ever make difference.

Without the airless spray equipment getting anything to "Look" like factory
undercoat will be tough.  After all, if you're going to put this material on
it should look factory. Try to get the cheapest product you can and apply it
badly (dry spray) and you could get close with some persistence. Just keep a
gallon of mineral spirits handy to clean up the mess!

Jim



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