ARCHIL, a purple dye obtained from various species of lichens. Archil can be extracted from many species of the genera Roccella, Lecanora, Umbilicaria, Parmelia and others, but in practice two species of Roccella—R. tinctoria and R. f uci f ormis —are almost exclusively used. These, under the name of "or chella weed" or "dyer's moss," are obtained from Angola, where the most valuable kinds are gathered ; from Cape Verde Islands; from Lima; and from the Malabar coast of India. The colouring properties are developed by special treatment. Archil is prepared for the dyer's use in the form of a liquor (archil) and a paste (persis), and the latter, when dried and finely powdered, forms 'So Plut. Agis, 3 (all mss.) . Following Cellarius, some authorities read Manduria or Mandyrium.
the "cudbear" of commerce, a dye formerly manufactured in Scotland from a native lichen, Lecanora tartarea. The manufac turing process consists in washing the weeds, which are then ground up with water to a thick paste. If archil paste is to be made this paste is mixed with a strong ammoniacal solution, and agitated in an iron cylinder heated by steam to about i4o°F. till the desired shade is developed—a process which occupies several days. In the preparation of archil liquor the principles which yield the dye are separated from the ligneous tissue of the lichens, agitated with a hot ammoniacal solution, and exposed to the ac tion of air. When potassium or sodium carbonate is added, a blue dye known as litmus, much used as an "indicator," is produced. French purple or lime lake is a lichen dye prepared by a modifica tion of the archil process, and is a more brilliant and durable colour than the other. The dyeing of worsted and home-spun cloth with lichen dyes was formerly a very common domestic employment in Scotland ; and to this day, in some of the outer islands, worsted continues to be dyed with "crottle," the name given to the lichens employed.