resinous substance secreted by the lac insect upon the twigs and young branches of certain trees, the chief of which are species of fig. Lac is a product of southern Asia, particularly northern India. The term is the same as the numerical lac (or lakh), meaning 100,000, and denotes the myriad insects that swarm upon the trees. The lac insect, Laccifer lacca, is of the Coccodae superfamily (see SCALE INSECT,). Females insert their long proboscises into the bark of the twigs or branches, drawing their foodstuff from the sap. They exude a secretion that accrues and coalesces, forming hard, resinous layers that completely cover their bodies. The ovaries contain a crimson fluid called lac dye, resembling cochineal, which was once used as a dye.

Crude lac, known as stick-lac, consists of the resin, the encrusted insects, lac dye, and twigs. When crushed and washed free of the dye, twigs, and insects, it becomes granular and is known as seed-lac or grained lac. After melting and further purification, the resulting lac resin is solidified into thin layers or flakes that constitute commercial shellac.

Shellac varies in color from yellow to deep orange. When bleached it is known as white shellac. The term shellac is often applied to a solution of the resin in alcohol, used as a varnish. Shellac has been used in the manufacture of a variety of products, including phonograph records, sealing wax, and lacquer. Synthetic materials have replaced lac in many uses.

See PAINT AND VARNISH,. See also Lacquer Work; Resins.