Lac is a sticky substance given off by a kind of scale insect. The insects gather by the hundreds of thousands on the twigs and branches of the soapberry and acacia trees of India, Thailand, and Myanmar (see Scale insect ). The sticky substance these insects secrete is called lac. The term comes from a Hindustani word meaning hundred thousand. Shellac is made from lac (see Shellac ).
Lac insects pierce the bark of trees with their long beaks and feed on the sap. As they do so, they discharge a quantity of lac to protect themselves from their enemies. The female insect lays several hundred eggs before she dies. The young insects hatch as wormlike larvae. When the larvae grow into insects, they look for new, fresh twigs to feed on. This period in their life cycle is called swarming.
Lac is usually harvested by cutting almost all the twigs before the larvae mature. When the larvae are ready to swarm, the twigs are fastened onto trees where the workers want the insects to feed. The crude substance gathered from the twigs is called stick lac. Workers grind it between stones and wash it in water to remove the coloring matter. In this stage, the substance is called seed lac. Seed lac is processed either by hand, by machine, or through bleaching in hot sodium carbonate.
Shellac is made by dissolving processed lac in alcohol. Shellac is used in electric insulators and varnishes and to hold together pharmaceutical tablets and hard candies. Shellac is also used in printing ink and for hat stiffening.
