For drawing or marking on any clean, oil free vitreous surface. Surface can be coated with light spray of hairspray or artist’s adhesive prior to using crayons. Pre-enameled steel or copper can be slightly warmed prior to using crayons resulting in solid applications of crayon marks. Crayons are water soluble. Fire at 1350°F-1400°F for 2 minutes or until glossy. A cover coat of transparent enamel is desirable.