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A lake pigment is a pigment made by precipitating a
dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and ...
with an inert binder, or mordant, usually a metallic salt. Unlike vermilion, ultramarine, and other pigments made from ground minerals, lake pigments are organic.K. Hunger. W. Herbst "Pigments, Organic" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim, 2012. Manufacturers and suppliers to artists and industry frequently omit the ''lake'' designation in the name. Many lake pigments are
fugitive A fugitive (or runaway) is a person who is fleeing from custody, whether it be from jail, a government arrest, government or non-government questioning, vigilante violence, or outraged private individuals. A fugitive from justice, also known ...
because the dyes involved are not lightfast. Red lakes were particularly important in Renaissance and
Baroque The Baroque (, ; ) is a style of architecture, music, dance, painting, sculpture, poetry, and other arts that flourished in Europe from the early 17th century until the 1750s. In the territories of the Spanish and Portuguese empires including th ...
paintings; they were often used as translucent glazes to portray the colors of rich fabrics and draperies.David Bomford and Ashok Roy, ''A Closer Look - Colour'', National Gallery Company, p. 41.


Etymology

The term "lake" is derived from the term
lac Lac is the resinous secretion of a number of species of lac insects, of which the most commonly cultivated is '' Kerria lacca''. Cultivation begins when a farmer gets a stick that contains eggs ready to hatch and ties it to the tree to be infe ...
, the secretions of the Indian wood insect '' Kerria lacca'' (formerly ''Laccifer lacca'' or ''Coccus lacca''). It has the same root as the word ''lacquer'', and comes originally from the Hindi word ''lakh'', through the Arabic word ''lakk'' and the Persian word ''lak''.


Chemistry

Many lake pigments are
azo dye Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C-N= ...
s. They characteristically have
sulfonate In organosulfur chemistry, a sulfonate is a salt or ester of a sulfonic acid. It contains the functional group , where R is an organic group. Sulfonates are the conjugate bases of sulfonic acids. Sulfonates are generally stable in water, non-ox ...
and sometimes
carboxylate In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an ion with negative charge. Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,...; ''carboxylat ...
substituents, which confer negative charge to the
chromophore A chromophore is the part of a molecule responsible for its color. The color that is seen by our eyes is the one not absorbed by the reflecting object within a certain wavelength spectrum of visible light. The chromophore is a region in the molec ...
(colored species). The metallic salts or binders used are typically colourless or almost so. The organic component of the dye determines the color of the resulting precipitate. In ancient times
chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...
, white
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
, and crushed bones were used as sources of the
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...
salts. Today metallic salts are typically chromium or cobalt, and the resulting lake pigment is diluted with an inert material such as alumina.


History and art

Lake pigments have a long history in decoration and the arts. Some have been produced for thousands of years and traded over long distances. The red lakes were particularly important in the history of art; because they were translucent, they were often used in layers of glazes over a more opaque red (sometimes the mineral-based pigment vermilion, or sometimes a red lake mixed with lead white or vermilion) to create a deep, rich red color. They are common in paintings by Venetian artists of the 16th century, including Titian, to depict fine draperies and fabrics. * Indigo lake was originally produced from the leaves of woad, and was known in ancient Egypt. In the late Middle Ages, a fashion for woad as a textile dye led to overplanting and soil exhaustion in many parts of Europe. After trade routes opened to the east, indigo was imported from India as a substitute for woad, and the cultivation of woad became uneconomical in Europe. Today, the dark blue dye known as indigo once produced from woad and ''Indigofera tinctoria'' is largely of synthetic origin. * Rose madder lake, originally from the root of the madder plant, is also known as alizarin crimson in its synthetic form. Since rose madder is fugitive when exposed to light, its use has been largely superseded, even in synthetic form, by quinacridone pigments. * Carmine lake, also called crimson lake, was originally produced from the
cochineal The cochineal ( , ; ''Dactylopius coccus'') is a scale insect in the suborder Sternorrhyncha, from which the natural dye carmine is derived. A primarily sessile parasite native to tropical and subtropical South America through North America ...
insect, native to
Central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known a ...
and South America. When the Spanish conquered the
Aztec Empire The Aztec Empire or the Triple Alliance ( nci, Ēxcān Tlahtōlōyān, �jéːʃkaːn̥ t͡ɬaʔtoːˈlóːjaːn̥ was an alliance of three Nahua city-states: , , and . These three city-states ruled that area in and around the Valley of Mexico ...
(1518–1521), they encountered Aztec warriors garbed in an unknown crimson color. Cochineal became their second most valuable export from the New World, after silver, and the Spanish zealously guarded the secret of its production for centuries.
Carminic acid Carminic acid (C22H20O13) is a red glucosidal hydroxyanthrapurin that occurs naturally in some scale insects, such as the cochineal, Armenian cochineal, and Polish cochineal. The insects produce the acid as a deterrent to predators. An aluminum ...
, the organic compound which gives carmine its color, was synthesized in 1991. Researchers are now examining the potential to genetically engineer microbes to produce carminic acid. Indigo and rose madder are now produced more cheaply from synthetic sources, although some use of natural products persists, especially among
artisan An artisan (from french: artisan, it, artigiano) is a skilled craft worker who makes or creates material objects partly or entirely by hand. These objects may be functional or strictly decorative, for example furniture, decorative art, s ...
s. The food and cosmetics industries have shown renewed interest in cochineal as a source of natural red dye.


References

{{Reflist, 30em Pigments