The marker is generally divided into oil and water. The pigment of the former can be diluted with toluene and has strong permeability, especially suitable for drawing on tracing paper (sulfuric acid paper); The pigment of the latter is soluble in water, and is usually used for painting on tighter cardboard or coated paper. In the drawing of indoor perspective, oily markers are more commonly used. The technique of oil-based marker is also introduced here.