Does anybody know how much air flows through unsealed MDF under vacuum?
My understanding is that it's reasonably high; MDF is pretty porous stuff.
Anybody have an actual data point? (Say, a tank of a certain size filling up at a certain rate just from flow through the bottom of an MDF platen, or vacuum-clamping surface, of a certain size?)
I'm also wondering what's the easiest, cheapest way to seal MDF pretty well. My understanding is that a lot of paints and varnishes don't do a good job---as they dry, they become microscopically porous where the solvent evaporates away. Even a bunch of coats won't help as much as you think. (I've used polyester & epoxy resins, but that's a bit of a pain in the ass, and a little more costly than I'd like.)