Inspired by this lively video, I decided last-minute to whip out some drink coasters for holiday gifts. Some just solid wood resawn from scraps, some laminated from scraps (think of a small, thin laminated long grain cutting board). All the scraps had been in my shop for a couple years. I'd resaw, sand off the bandsaw marks, and finish the top and sides with spray lacquer, BLO, or mineral oil, depending on the wood. Final sanded thickness ~3/16". Fun little project.
My problem arose when I started gluing felt on the bottoms. (I used Titebond II, the wood was unlaminated walnut, mineral oil finish on top/sides, unfinished bottom, just stuck a heavy book on them while glue dried). When the glue had dried, the coasters were cupped & wobbly.
Would a different glue prevent this? Is this less likely to happen on the laminated ones? Or should I just give up on gluing felt on the bottom? And, while I'm at it, is the cupping going to happen anyway the first time someone puts a cold drink on them, or the humidity changes?