Uni Posca Paint Marker Pens are filled with fluid, opaque, water-based ink and will write on virtually any surface. They are available in a range of nib sizes suited to all kinds of creative applications - whether you’re a fine artist, illustrator, crafter, designer or creative hobbyist! They make a valuable addition to mixed media work and can be used on most surfaces including paper, card, canvas, clay, rock, plastic, metal, wood, glass, fabric and much more! Once dry the ink is fully waterproof, so you can draw over previous layers to build up your designs or correct errors without bleeding or smudging.