Liquid Chalk is a water based ink which is designed for convenient use on different types of non-porous boards. The ink is water-resistant to light showers however once the surface is wet you only need to remove the liquid chalk with a damp cloth, or for more convenience you can use the Rainbow Board Cleaner.Product Specifications5mm nib bullet.Wet wipe erase with a damp cloth or Rainbow Board Cleaner.Suitable for indoor and outdoor use.Resistant to light showers.Valve activated to control ink flow.For use on chalkboards, whiteboards, windows, and non - porous surfaces.Water based & non - toxic.