Thangka is an of painting unique to Tibtan Buddhism. It is usually done on linen. or on coarse wool cloth, and sometimes on silk for precious ones. The base of the painting is prepared using a paste of animal glue and fine lime. After the paste dries, carbon and paints using natural mineral and plant colors, such as yellow, mineral green, azurite and cinnabar, are applied. All the colors are mixed with animal glue and ox bile to keep them bright. The subjects of most Thanka paintings are religious, but sometimes folklore themes intrude.