The water based formula of Model Color has been specifically developed for adherence on difficult surfaces such as metal and plastic, but the product is not toxic, not flammable, and does not give off noxious fumes. Errors can be corrected immediately with water or alcohol Model Color dries quickly to a matte, even and waterproof finish. Exact drying time depends on the temperature and humidity of the environment, on the surface which has been painted, and on the thickness of the paint layer - although the colors are dry to the touch within minutes, the water content keeps on evaporating, and the paint does not acquire its true permanence until several weeks after application.