Glassline pens are a lining and shading material for glass. Glassline may be applied between multiple layers of glass or on the top surface for a complex, dimensional look. It is compatible with most types of glass, from float to 90 and 96 COE. While best fired to 1500 degrees, it may be fired lower or higher depending on your desired results. A metal tip set is recommended for fine line drawing on glass. Lead free and food safe - available in 29 vibrant colors.