Fiberglass Fillers

Anything goes in the world of fiberglass and plastic



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PostPosted: Tue Sep 01, 2015 9:33 pm
im just a newbie but i have been having some problems with my first painting project and am curious about fiberglass fillers since the can advertises about holes, waterproofing, fixing rust, etc.

i had issues with metal being sanded with 40 grit and the fiberglass directly over it long after the wax and grease remover dried.

i tried the same thing with my rage filler and it did not lift the way the fiberglass stuff does? it scared the hell out of me so much that i grinded it all back down and left it in the cracks and put rage over it.

after struggling with how to get a car paint ready i found i was dumb and should have just stripped to metal. wasted lots of time and primer and believe i was having issues with original products.

i got some water on exposed repair which was done over a month ago, while doing some other work and it turned to soggy cardboard on top? so its NOT waterproof when cured at all????? i scraped this layer off and it was dry like when sanding originally underneath that layer but maybe it was just a matter of time before it turned soggy to?

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PostPosted: Wed Sep 02, 2015 10:54 pm
Well, my first question is, "Which fiberglass filler are you referring to....?" There's a bunch out there. I use USC's Duraglas and have (knock on wood) never had it fail in any manner that you've talked about here. Good quality fiberglass fillers are usually stated as water resistant not always waterproof. They have different chemistries that minimize the effects of water and most often don't contain the talc that regular fillers have which can draw moisture. I do always put it on raw roughened metal for best grip. Fiberglass fillers have always seemed more sensitive to "stale" hardener than regular fillers. If a hardener has become stale it will not properly catalyze the filler all the way through the fill.

I've never had Duraglass do that last thing you talked about there. When mixed and fully cured Duraglass will bead water until you wipe it off. Maybe you didn't have enough hardener in the mix, had stale hardener, etc. Oh, and here's another one that is kind of unusual. Never mix the stuff on brown or white cardboard. The filler is sensitive to the sodium hydroxide in the brown cardboard and that can indeed make it so it does not cure properly. White cardboard can be even worse since it can contain bleaches and ink pigments which again react with the filler. I always use polyethylene mixing boards for those fillers.
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