Oh boy, do I need advice. I made these beautiful pots with glass mosaic, grouted them, painted the inside and then sprayed polyurethane to seal the paint and make it more durable. Worked great on the paint, bad for the glass tiles. They have a bubbly residue on them. Uh-oh. What else can I use to make these pots more durable, or should I just polyurethane the paint inside and forget the outside?? Feeling a little discouraged at this point, thought I had it all figured out! Thanks.