spray painted bottle caps, paint a tray white, arrange dry caps on dried tray, next use "acrylic water" to pour over the caps. 2 part epoxy is sold at HL & Michael's, but it is cheapest at Walmart, in Floral Dept. Follow the directions, mix the compounds and pour it on. It's self-leveling, which is great! The tough part is waiting 48 hours, because it cannot be disturbed at all! The acrylic hardens without incident & is ready for use!
Remember the Mod Podge + food coloring technique for painting clear glass? That was cool and all, but I spotted another method using Vitrail glass paint and acetone (nail polish remover) that allows the bottles and jars to be used as actual vases, as the finish is waterproof! This treatment provides for more depth of color as well.