Detailing Black is used over the top of dried glass color for making detail lines or touching up outlines you may have went over with glass color. This product is a shiny finish and the GO-331 Outline Black is a matt finish, so if you use the "Detailing Black" you need to randomly use it throughout the design so it doesn't stand out from the rest of your outlines. DO NOT use directly on glass, only over dried color. Available in 1 oz.