So the resin was cured enough 24 hours later to take a look at how this experiment turned out. Conclusion: changes need to be made. First, I think I should have kept the sea glass within the edges of the clear backer glass. I can fill in empty spaces with glass chips / frit, or leave them plain resin. I think it is better to tape off the edges so that no resin spills over the edge. Keeping the sea glass inside the backer glass area will allow me to do that. Second, I think I should try to tape off the mirror glass. The resin did not smooth out well over this mirror, so it ends up with a “fun house” look when you are using it. The overall piece is pretty to look at, but not functional.
I’m not sure how best to tape off the mirror for my second try at this, but I have a few ideas.