lac


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lac,

resinous exudation from the bodies of females of a species of scale insect (Tachardia lacca), from which shellacshellac,
solution of lac in alcohol or acetone. In commerce the name is applied to the resinous substance (lac) itself rather than to the solution. It ranges in color from orange to light yellow depending upon the extent to which it has been purified; the darker shellacs are the
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 is prepared. India is the chief source of shellac, although some is obtained from other areas in Southeast Asia. The insects feed on the sap of the twigs of certain tropical trees, some of which are cultivated for this purpose. The resinous secretion hardens upon exposure to air and forms a protective incrustation around the female and young, which are thus held fast to the twigs. The twigs are scraped to remove the incrustation; this crude lac material is known as stick lac. If the stick lac is crushed, the wood splinters and other foreign materials removed, and the red coloring matter produced by the insects dissolved out, the residue when dried is seed lac. Seed lac is melted, filtered, and stretched into thin sheets, which are broken into flakes when cool. Orange-colored shellac is made from these flakes by dissolving them in alcohol. White shellac is made from bleached lac.

Lac

 

a resin secreted by special glands of the lac insect (the scale Laccifer lacca, a sucking insect that lives on the shoots of certain tropical plants). The nonmotile lac insect coats the surface of the plant from above with a lac scale. The lac, used to make shellac and varnish, is scraped off the shoots and collected; it contains resin (65–80 percent), shellac wax (4–8 percent), and up to 18 percent impurities (plant parts and insect remains).

lac

[lak]
(materials)
A resinous material secreted by some insects that live on the sap of certain trees, principally in India; used in the manufacture of shellac.

lac

A resinous insect secretion used as a base for shellac, lacquer, and varnish.

lac

a resinous substance secreted by certain lac insects, used in the manufacture of shellac
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