Glass Chalk Sponge Marker. Certified nontoxic, water soluble marker for use on any glass, paper, posterboard, or plastic surface. Indoor or outdoor temporary paint. Once dry it will not wash off in the rain but can be wiped off with a wet towel. While there are many uses for this product the primary use is the decoration of automobile and retail storefront windows. Will stain molding and fabric. 1 oz.