: I used to use up to 220 but started using 400 and it worked well
: for me. I use 600 on balsa because it is so soft. No problems
: with adhering- it soaks up epoxy like a sponge! I have always
: wanted to do a weight test- taking one board foot of different
: woods, coat them each with epoxy, and weigh them. I bet the
: softer woods would gain more weight than the hardwoods. I'm
: going to start playing around with Paulownia because it's
: lightweight but not as absorbent as Balsa. I theorize that it
: would absorb less resin and end up close to the weight of balsa
: when it's all said and done.

I suspect if you pre-coat the balsa it'll end up being lighter. Just apply a coating of epoxy as thin as you can get it and let it set before you glass will seal the wood and keep it from absorbing more epoxy.

Perhaps you already do?

I have to do the same thing on the Dacron when I cover a SOF before I glass it, otherwise it's an epoxy sponge and will suck up an amazing amount of epoxy.

Bill H.