Hollow glass forms must be evenly heated through out the whole piece. There is an intricate balance between the kiln, the glass and the investment mold. The jade-like coloring is made by a specific texture he gets from chipping and crushing clear glass, then adding powders and frit sized colored glass to the clear glass. Another intricacy to Charlie's work is the detail he puts into the work. Patina is added to bring out the fine details in the glass. These castings are an architectural marvel.