Editing Lake pigment

{{short description|Pigment made by precipitating a dye with an inert binder, or mordant}}

A '''lake pigment''' is a [[pigment]] made by [[precipitating]] a [[dye]] with an [[chemically inert|inert]] [[binder (material)|binder]], or [[mordant]], usually a [[metallic salt]].  Lake pigments are largely [[organic compound|chemically organic]].<ref name=Ullmann1>K. Hunger. W. Herbst "Pigments, Organic" in ''[[Ullmann's Encyclopedia of Industrial Chemistry]]'', Wiley-VCH, Weinheim, 2012. {{doi|10.1002/14356007.a20_371}}</ref> Manufacturers and suppliers to artists and industry frequently omit the ''lake'' designation in the name. Many lake pigments are [[Fugitive pigment|fugitive]] because the dyes involved are not [[lightfast]]. Red lakes were particularly important in [[Renaissance art|Renaissance]] and [[Baroque art|Baroque]] paintings; they were often used as translucent glazes to portray the colors of rich fabrics and draperies.<ref name="Ashok Roy p. 41">David Bomford and Ashok Roy, ''A Closer Look - Colour'', National Gallery Company, p. 41.</ref>

==Etymology==
The term ''lake'' is derived from the term [[Lac (resin)|''lac'']], the secretions of the Indian wood insect ''[[Kerria lacca]]'' (formerly ''Laccifer lacca'' or ''Coccus lacca'').<ref name="Stainsfile - How Stains Work">{{Cite news |url=//stainsfile.info/StainsFile/theory/mordant.htm |title=Stain Theory – How mordants work |last=Llewellyn |first=Bryan D. |date=May 2005 |url-status=dead|archiveurl=https://web.archive.org/web/20070814015208/http://stainsfile.info/StainsFile/theory/mordant.htm |archivedate=August 14, 2007 }}</ref><ref>"lake, n.6". OED Online. December 2011. Oxford University Press. 25 January 2012.</ref> It has the same root as the word ''[[lacquer]]'', and comes originally from the Hindi word {{Lang|hi-latn|lakh}}, through the Arabic word {{Lang|ar-latn|lakk}} and the Persian word {{Lang|fa-latn|lak}}.<ref>''Webster's New World Dictionary of American English'', Third College Edition, 1988.</ref>

==Chemistry==
[[File:Lithol rubine BK.svg|thumb|upright|alt=Molecular diagram; refer to image caption|A typical lake pigment: [[Lithol Rubine BK]].]]

Many lake pigments are [[azo dye]]s. They characteristically have [[sulfonate]] and sometimes [[carboxylate]] substituents, which confer negative charge to the [[chromophore]] (colored species).

The metallic salts or binders used are typically colourless or almost so.<ref name=Ullmann1 /> The organic component of the dye determines the color of the resulting [[precipitate]].  The metallic salts that induce the formation of lakes are typically salts of dications such as [[calcium|Ca<sup>2+</sup>]] or [[strontium|Sr<sup>2+</sup>]].<ref name=Ullmann1/>  The resulting lake pigment can be diluted with an inert material such as [[alumina]].

==History and art==
[[File:Titian - The Vendramin Family Venerating a Relic of the True Cross (detail) - WGA22811.jpg|thumb|upright|alt=Painting by the artist Titian|[[Titian]] used glazes of red lake to create the vivid crimson of the robes in ''[[Portrait of the Vendramin Family|The Vendramin Family Venerating a Relic of the True Cross]]'', c. 1550–60 (detail).]]

Lake pigments have a long history in decoration and the arts. Some have been produced for thousands of years and traded over long distances. In ancient times [[chalk]], white [[clay]], and crushed [[bone]]s were used as sources of the [[calcium]] salts.

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.<ref name="Ashok Roy p. 41" />

* [[Indigo dye|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, [[Indigofera tinctoria|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|Rose madder lake]], originally from the root of the [[madder plant]], is also known as [[Alizarin crimson (color)|alizarin crimson]] in its synthetic form. Since rose madder is [[fugitive pigment|fugitive]] when exposed to light, its use has been largely superseded, even in synthetic form, by [[quinacridone]] pigments. 
* [[Carmine|Carmine lake]], also called crimson lake, was originally produced from the [[cochineal]] insect, native to [[Central America|Central]] and [[South America]]. When [[Spanish colonization of the Americas|Spanish colonizers]] encountered the [[Aztec Empire]], they encountered Aztec warriors garbed in an unknown crimson color. Cochineal became the second most valuable export from the Spanish colonies in the Americas after [[silver]], and the Spanish zealously guarded the secret of its production for centuries.<ref>{{cite book |title=A Perfect Red: Empire, Espionage, and the Quest for the Color of Desire |author=Amy Butler Greenfield |date=2005 |publisher=[[HarperCollins]] |isbn=0-06-052275-5 |url-access=registration |url=https://archive.org/details/perfectred00amyb_0 }}</ref> [[Carminic acid]], the [[organic compound]] which gives carmine its color, was [[organic synthesis|synthesized]] in 1991.<ref>{{cite journal | author = Allevi, P. | year = 1991 | title = The 1st Total Synthesis of Carminic Acid | journal = Journal of the Chemical Society, Chemical Communications | volume = 18 | issue = 18 | pages = 1319–1320|display-authors=etal | doi = 10.1039/c39910001319}}</ref> Researchers in 2022 were examining the potential to genetically engineer microbes to produce carminic acid.<ref name="Miller">{{cite journal |last1=Miller |first1=Brittney J. |title=Cochineal, a red dye from bugs, moves to the lab |journal=[[Knowable Magazine]] |date=25 March 2022 |doi=10.1146/knowable-032522-1 |doi-access=free |url=https://knowablemagazine.org/article/technology/2022/cochineal-red-dye-bugs-moves-lab |access-date=28 March 2022}}</ref>

Indigo and rose madder are now produced more cheaply from synthetic sources, although some use of natural products persists, especially among [[artisan]]s. The [[food industry|food]] and [[cosmetics|cosmetics industries]] have shown renewed interest in cochineal as a source of natural red dye.<ref name="Miller"/>

==References==
{{Reflist|30em}}

[[Category:Pigments]]