: I wrote Dr. Rot twice (the original question and one follow-up)

Sounds like you should write him a third time and ask for a clarification. You either wait two days before coating the stuff, or you wait 2 hours. Of course it could depend on the temperature, too. A few hours in a hot sun should boil off a lot of easily-evaporated solvents.

Of course there is always the nose test. If it stinks of solvents, then the solvents are still hanging around and you should let the thing air out longer.

Then again, it might not matter too much. You'll be applying the cpes and the finish coat on one side of the wood at a time. Even if you only wait a couple of hours before putting on your final coat of epoxy, the back of the wood is still open enough for those solvents to evaporate through that side when the front is completely sealed.

What I don't like is the possibility that some solvents would be trapped in the wood and CPES when you are applying the "final" coats of epoxy resin.

Polyester resins are thined with solvents which evaporate as the resin cures. The evaporating solvents create their own paths out of the resin, with the bubbles of gaseous solvents forming microscopic tubes or "wormholes" through the resin. After the solvents are long gone those microscopic holes remain. While they are far too small for water molecules to pass through, they can act a bit like Gore-Tex (R) and let the smaller molecules of watervapor through. It is a very slow process, but moisture that gets under the resin can eventually feed mold or rot spores, With drops in temperature it can condense back to liquid water, and if the boat is later left in the sun that moisture can turn to steam, which, when trapped under the resin causes it to delaminate.

The saturation of the wood with epoxy or CPES is going to deter rot, and probably not allow a lot of moisture in through the solvent holes -- if indeed any gets in at all. Ideally the solvent will be totally evaporated before the resin gels, allowing the weight of the resin to sag a microscopic fraction of an inch, and pinch closed any tubes or "worm holes" that may have been formed.

But, your authority here is Dr. Rot, so hit him up for a clarification, and let us know what his answer is.

then again, maybe he's been breathing those solvent fumes a bit to long and now he gets his facts scrambled at times. If that isn't a good reason for wearing a respirator I don't know a better one.

PGJ