The Glassline Pens are used as a lining and shading material for glass. They're simple in design, easy to use, and can be thinned with water. A metal tip set is recommended for fine line drawings on glass. The Glassline colors can be applied between multiple layers of glass or on the top surface for a complex dimensional look. Glassline colors are best fired to 1500 degrees F., but may be fired lower or higher depending upon desired results. Glassline products are lead-free and food safe when fired. Can also be used on glazed pieces. Call for more information