The Columbia Encyclopedia, Sixth Edition. 2001-07.
archil
(är´kl, chl) (KEY) or orchil (ôr´) (KEY) , blue, red, or purple dye extracted from several species of lichen, also called orchella weeds, found in various parts of the world. Commercial archil is either a powder (called cudbear), a pasty mass (called archil), or a drier paste (called persis).