Originally posted by Mr Ed
Yes fibreglass fillers are waterproof and yes us the primer sealer after completion of bodywork
"Fiberglass fillers" are NOT waterproof. They may and I mean MAY be water "resistant" but they are certainly not "water proof". I called Evercoat tech after this was brought up on another forum a few years ago. I was told it was "water proof"
after it was primed and painted! I laughed and said, "Cardboard is waterproof if it is coated with primer and paint!". All the fiberglass reinforced fillers like "Everglass", "Kitty hair" and the like have talc in them, just like "regular" filler in fact, they have MORE. Talc absorbs moisture. So, no, they are NOT waterproof.