Catechu, << KAT uh choo, >> also called black cutch, is a brown, tarlike or resinlike substance obtained chiefly from the wood of acacia trees. It is rich in tannic acid. Catechu makes rich brown dyes used in coloring leather. Craftworkers use it to dye and print cotton cloth, such as khaki or calico. Fishing crews apply catechu to sails and nets to preserve them. It was once used in certain medicines. To extract catechu, processors cut the heartwood (inner wood) of the acacia into pieces and boil them in water. When the extract is partly hardened, it is formed into rough blocks or balls for marketing. See also Acacia ; Tannic acid .
