The medium is the means by which ink, pigment, or color is delivered onto the drawing surface. Most drawing media are either dried (eg graphite, charcoal, pastels, Conté, silverpoint), or water-based (marker, pen, and ink). Watercolor pencils can be used dry like ordinary pencil, then moistened with a wet brush to achieve various painterly effects. Very rarely, artists have drawn with (usually deciphered) invisible ink.