IMAGINATION STARTERS Chalkboard Crayons are the perfect item for our chalkboard placemats. They are washable, non-toxic and wipe off our mats with water. So go ahead and have a little fun and create, wash, and create again and again! These can be used on non-porous chalkboards but since no one can ever tell for sure, please test these before using on any chalkboard that isn't ours. ALSO TAKE NOTE: These crayons are not for use on chalkboard paint or porous surfaces.