I'm just at the stage of making my first mold, it will be a mold taken from an existing fiberglass cowling. I've researched a fair bit across the net. Question is, what is the best type of paint to use if I paint the mold before laying in the glass cloth? acrylic, lacquer?? how long should I wait from spraying the paint in the mold to laying in the cloth, and is there any reason why painting the mold won't work with a standard "non-vacuum bagged" layup, as opposed to vacuum bagging.
From experience with same, do the following particularly if the lay-up uses epoxy laminating resin (any of them):
Wax the mold as if you were doing a non paint lay-up. Don't skimp on the wax layers.I really like Part All wax
Seal the wax with sprayed PVA. A couple med-lite coats are perfect and make sure you allow enough drying time. An hour is great. DONOTomit this step
Spray your paint or primer. I really like Klass Kote epoxy paints and their primer is terrific but extremely aggressive on its adhesion. If sprayed directly on the waxed surface, it will stick and you will ruin your mold. Polyurethane paints, heck, dope even, are all fine. Allow them enough cure time; DONOT lay-up epoxy and glass on wet paint
Do your layup. Vacuum is not required
Wait the appropriate amount of time for epoxy to settle down. If curing at room conditions a minimum of 24 hours is better unless you used an extremely slow hardener.
The part will come out of the mold easily. Peel one edge by hand and use an air gun to pop the rest of it off. Wash the PVA off with warm water....VOILA!!!
There are probably other techniques that are as successful. But I've re-discovered this method the hard way