: I doubt simple immersion for 24 hours will tell you what you want
: to know. The test for waterproof glue is boiling for at least 30
: minutes.

I know of no plywood made with non-waterproof glues. Used to be at one time interior and exterior plywood, now the interior stuff uses the same glue as the exterior and marine grades do. I suspect that stocking two different glues got to be less than cost effective, or perhaps screwing up and using the wrong glue would get really expensive when someone's boat sunk because of it. Anyway, real baltic birch plywood (there are lots of plywoods called baltic birch that arn't) has waterproof glue. You'll know if you bought the real stuff, first it's odd sized, 60" x 60" I think and it's pretty expensive.

Bill H.