The Montana Cans CHALKSPRAY is a a solvent-based, high quality chalk based pigment spray ideal for outdoor marking (temporary only on non porous surfaces). This is a great medium for signage for events, advertisements, marketing campaigns and outdoor activities. Can be applied to surfaces such as sidewalks, walls, cardboard, canvas and glass that are non porous. The chalk markings will last from several weeks to several months, depending on climate and weather conditions. The chalk color pigments will wash away faster on non-porous surfaces like glass or metal, but some pigments may remain on porous surfaces. Sealing with Montana VARNISH sprays can seal the surface and create a permanent film over the CHALK holding the pigments in place.