I was going to use balsarite to seal the wood before glassing. I will be using water based poly to glass and the wood needs to be sealed or it will soak up a lot of water from the poly before it has the chance to evaporate.

I dont remember where I read it but in one of the how to articles that I read said you could use the balsarite to seal the balsa.

I would be interested to hear what other folks have found.