Waterproof Finish for Drink Coasters?
I plan to make a set of drink coasters for my spouse. I have not decided on the wood, but it might be poplar or maple plus some walnut, because that is what I have in the shop right now.
The problem is that when a glass is on the coaster, there is a lot of water that pools up in the bottom. It is caused by condensation on the outside of the glass when the glass has a cold drink. I don't mind the pool of water in the bottom of the coaster, and I plan to include cut grooves in the bottom, so the glass rests above the pool of water.
I do not own any kind of finish sprayer. My past experience has been brush-on finishes from the 1980s (Deft), and the cutting board oil finish that I recently used on a cutting board.
1. Is there a finish that can waterproof the coasters so that it won't be damaged by a pool of water in the bottom for an extended period (hours, possibly longer until evaporation)?
2. Is there an easy, spray can finish that can do the job?
3. Will Titebond III hold up under "soaking" conditions? Does it matter, because the glue should be protected by the finish?
Keep in mind that it will be hard to sand the grooves once the coasters are glued up. A brush-sand-brush-sand-brush... type finish might not work too well in those grooves.