Watercolor is a painting method in which the paints are made of pigments suspended in a water-based solution. Watercolor refers to both the medium and the resulting artwork. The traditional and most common support—material to which the paint is applied—for watercolor paintings is paper. Other supports include papyrus, bark papers, plastics, vellum, fabric, wood and canvas. Watercolor paper is often made entirely or partially with cotton. This gives the surface the appropriate texture and minimizes distortion when wet. Watercolors are usually translucent, and appear luminous because the pigments are laid down in a pure form with few fillers obscuring the pigment colors. Watercolors can also be made opaque by adding Chinese white. Watercolor painting is extremely old, dating perhaps to the cave paintings of paleolithic Europe, and has been used for manuscript illustration since at least Egyptian times but especially in the European Middle Ages.