Glass Clay is a mix of powdered glass frit with a mixing medium based on CMC and several other modifiers. The COE is based on the COE of the powder used to make it.
I teach a course on Glass Clay. the first hour is how to make it. The next 12 hours is on how to use it. It is a lot of fun (like playing with clay) and creates some beautiful elements to use on your glass.
I have a page dedicated to glass clay on my site. The only problem is that it is difficult to get the 3d effect of glass clay elements in photographs. All the pieces on that page are 3D.
Web Site http://www.kaiserglass.com
Glass Classes: http://www.Kaiserglass.com/classes.html