In past postings, I've advocated using Craft Foam Glue (Beacon brand) for gluing to foam. I need to change that recommendation. This glue works well for holding foam rubber and somewhat less well for laminating sheets of foam, but when I used it to cover a foam core with balsa, I ended up with "bubbles" of balsa that popped up several days after gluing (even on totally flat surfaces). I'll be using something else in the future.