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Lake  

Jo Kirby

Term derived from the early medieval Latin lacca to indicate both lake pigment and the products of the lac insect (Kerria lacca). The latter was imported into Europe from India, and it yielded both red dyestuff and, as a by-product, shellac (see Lacquer §I 2.). Until the 18th century lake, without further qualification, usually indicated red pigments only.

Lake pigments are prepared by the precipitation of a soluble organic Dye on to an insoluble, inorganic, adsorptive substrate. The pigment is formed by the chemical reaction that occurs when a suitable reagent, such as alum, is added to an aqueous solution containing the dyestuff and, usually, one or more other chemicals, such as sodium or potassium carbonate. These chemicals react with the alum to form the substrate, an insoluble product of the reaction. During the reaction the dyestuff becomes intimately combined with the substrate, in this example hydrated ...