Water-based opaque paint marker. Water and fade resistant ink will not bleed through heavyweight paper. Archival quality. Vibrant color stands out on light and dark surfaces. Exceptional for marking windows with advertisements. Will wash off non-porous surfaces, like glass, with window cleaner. Available in 5 colors. Non-toxic and acid-free. Safe for use by children. Sharpie Poster Paint Marker's ink is very similar to the Posca Marker. If you like Posca, you'll like the Sharpie Poster Paint Marker. Great for marking glass, chalkboards, mirrors and especially good for poster projects in school.