I’ve recently started using Glassline glass paints with great results. It’s very versatile… you can do very graphic line drawings or use them like watercolors. While I do occasionally get bubbles if I sandwich the image between layers of glass, there are several techniques listed on this discussion board that may overcome that issue. (http://www.warmglass.com/phpBB/viewtopic.php?f=20&t=26081&view=previous)
I’ve used the glass on top of and between glass layers with great results… it’s very fun stuff! I found my paints on eBay but if you google Glassline paints you’ll find them in various sources.
On top of glass: (graphic lines)
Between glass: (watercolor effect)
Sue, Sulimos Design