My daughter Kayla is doing a Zentangle on the front window of Sandy's gallery. She is doing a beautiful job, come by and check it out. She is using the Chalk Ink Wet Wipe Markers which we have in several colors. As you can see they show up well on the window. They also can be used on chalkboards, mirrors, plastics and ceramics. Chalk Ink erases easily from non-porous surfaces with water or an ammonia based cleaner.