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A pigment is a powder used to add or alter
color Color (or colour in English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is the visual perception based on the electromagnetic spectrum. Though co ...
or change visual appearance. Pigments are completely or nearly insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use. Dyes are often
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
s whereas pigments are often
inorganic An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inor ...
. Pigments of prehistoric and historic value include ochre, charcoal, and lapis lazuli.


Economic impact

In 2006, around 7.4 million tons of
inorganic An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inor ...
, organic, and special pigments were marketed worldwide. According to an April 2018 report by '' Bloomberg Businessweek'', the estimated value of the pigment industry globally is $30 billion. The value of titanium dioxide – used to enhance the white brightness of many products – was placed at $13.2 billion per year, while the color
Ferrari Ferrari S.p.A. (; ) is an Italian luxury sports car manufacturer based in Maranello. Founded in 1939 by Enzo Ferrari (1898–1988), the company built Auto Avio Costruzioni 815, its first car in 1940, adopted its current name in 1945, and be ...
red is valued at $300 million each year.


Physical principles

Like all materials, the color of pigments arises because they absorb only certain wavelengths of visible light. The bonding properties of the material determine the wavelength and efficiency of light absorption. Light of other wavelengths are reflected or scattered. The reflected light spectrum defines the
color Color (or colour in English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is the visual perception based on the electromagnetic spectrum. Though co ...
that we observe. The appearance of pigments is sensitive to the source light. Sunlight has a high color temperature and a fairly uniform spectrum. Sunlight is considered a standard for white light. Artificial light sources are less uniform. Color spaces used to represent colors numerically must specify their light source. Lab color measurements, unless otherwise noted, assume that the measurement was recorded under a D65 light source, or "Daylight 6500 K", which is roughly the color temperature of sunlight. Other properties of a color, such as its saturation or lightness, may be determined by the other substances that accompany pigments. Binders and fillers can affect the color.


History

Minerals have been used as colorants since prehistoric times. Early humans used paint for aesthetic purposes such as body decoration. Pigments and paint grinding equipment believed to be between 350,000 and 400,000 years old have been reported in a
cave Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance undergrou ...
at Twin Rivers, near
Lusaka Lusaka ( ) is the Capital city, capital and largest city of Zambia. It is one of the fastest-developing cities in southern Africa. Lusaka is in the southern part of the central plateau at an elevation of about . , the city's population was abo ...
,
Zambia Zambia, officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa. It is typically referred to being in South-Central Africa or Southern Africa. It is bor ...
. Ochre, iron oxide, was the first color of paint. A favored blue pigment was derived from lapis lazuli. Pigments based on minerals and clays often bear the name of the city or region where they were originally mined. Raw sienna and burnt sienna came from
Siena Siena ( , ; traditionally spelled Sienna in English; ) is a city in Tuscany, in central Italy, and the capital of the province of Siena. It is the twelfth most populated city in the region by number of inhabitants, with a population of 52,991 ...
,
Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...
, while raw umber and burnt umber came from Umbria. These pigments were among the easiest to synthesize, and chemists created modern colors based on the originals. These were more consistent than colors mined from the original ore bodies, but the place names remained. Also found in many
Paleolithic The Paleolithic or Palaeolithic ( years ago) ( ), also called the Old Stone Age (), is a period in human prehistory that is distinguished by the original development of stone tools, and which represents almost the entire period of human prehist ...
and
Neolithic The Neolithic or New Stone Age (from Ancient Greek, Greek 'new' and 'stone') is an archaeological period, the final division of the Stone Age in Mesopotamia, Asia, Europe and Africa (c. 10,000 BCE to c. 2,000 BCE). It saw the Neolithic Revo ...
cave paintings are Red Ochre, anhydrous Fe2O3, and the hydrated Yellow Ochre (Fe2O3.H2O). Charcoal—or carbon black—has also been used as a black pigment since prehistoric times. The first known synthetic pigment was Egyptian blue, which is first attested on an alabaster bowl in Egypt dated to
Naqada III Naqada III is the last phase of the Naqada culture of ancient Prehistoric Egypt, Egyptian prehistory, dating from approximately 3200 to 3000 BC. It is the period during which the process of state formation, which began in Naqada II, became ...
(''circa'' 3250 BC). Egyptian blue (blue frit), calcium copper silicate CaCuSi4O10, made by heating a mixture of
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
sand, lime, a flux and a copper source, such as malachite. Already invented in the Predynastic Period of Egypt, its use became widespread by the 4th Dynasty. It was the blue pigment par excellence of Roman antiquity; its art technological traces vanished in the course of the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
until its rediscovery in the context of the Egyptian campaign and the excavations in
Pompeii Pompeii ( ; ) was a city in what is now the municipality of Pompei, near Naples, in the Campania region of Italy. Along with Herculaneum, Stabiae, and Villa Boscoreale, many surrounding villas, the city was buried under of volcanic ash and p ...
and
Herculaneum Herculaneum is an ancient Rome, ancient Roman town located in the modern-day ''comune'' of Ercolano, Campania, Italy. Herculaneum was buried under a massive pyroclastic flow in the eruption of Mount Vesuvius in 79 AD. Like the nearby city of ...
. Later premodern synthetic pigments include white lead (basic lead carbonate, (PbCO3)2Pb(OH)2), vermilion, verdigris, and lead-tin yellow. Vermilion, a mercury
sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
, was originally made by grinding a powder of natural cinnabar. From the 17th century on, it was also synthesized from the elements. It was favored by old masters such as
Titian Tiziano Vecellio (; 27 August 1576), Latinized as Titianus, hence known in English as Titian ( ), was an Italian Renaissance painter, the most important artist of Renaissance Venetian painting. He was born in Pieve di Cadore, near Belluno. Ti ...
. Indian yellow was once produced by collecting the urine of cattle that had been fed only mango leaves. Dutch and Flemish painters of the 17th and 18th centuries favored it for its luminescent qualities, and often used it to represent
sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...
. Since mango leaves are nutritionally inadequate for cattle, the practice of harvesting Indian yellow was eventually declared to be inhumane. Modern hues of Indian yellow are made from synthetic pigments. Vermillion has been partially replaced in by cadmium reds. Because of the cost of lapis lazuli, substitutes were often used. Prussian blue, the oldest modern synthetic pigment, was discovered by accident in 1704. By the early 19th century, synthetic and metallic blue pigments included French ultramarine, a synthetic form of lapis lazuli. Ultramarine was manufactured by treating aluminium silicate with sulfur. Various forms of cobalt blue and Cerulean blue were also introduced. In the early 20th century, Phthalo Blue, a synthetic metallo-organic pigment was prepared. At the same time, Royal Blue, another name once given to tints produced from lapis lazuli, has evolved to signify a much lighter and brighter color, and is usually mixed from Phthalo Blue and titanium dioxide, or from inexpensive synthetic blue dyes. The discovery in 1856 of mauveine, the first aniline dyes, was a forerunner for the development of hundreds of synthetic dyes and pigments like azo and diazo compounds. These dyes ushered in the flourishing of organic chemistry, including systematic designs of colorants. The development of organic chemistry diminished the dependence on inorganic pigments. File:Johannes Vermeer - Het melkmeisje - Google Art Project.jpg, ''The Milkmaid'' by Johannes Vermeer (). Vermeer was lavish in his choice of expensive pigments, including lead-tin yellow, natural ultramarine, and madder lake, as shown in the vibrant painting. File:Tizian 041.jpg,
Titian Tiziano Vecellio (; 27 August 1576), Latinized as Titianus, hence known in English as Titian ( ), was an Italian Renaissance painter, the most important artist of Renaissance Venetian painting. He was born in Pieve di Cadore, near Belluno. Ti ...
used the historic pigment vermilion to create the reds in the oil painting of Assunta, completed . File:Tintoretto_-_Miracle_of_the_Slave.jpg, ''Miracle of the Slave'' by Tintoretto (). The son of a master dyer, Tintoretto used Carmine Red Lake pigment, derived 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 sessility (motility), sessile parasitism, parasite native to tropical and subtropical Sout ...
insect, to achieve dramatic color effects. File:Paul Cézanne 160.jpg, ''Self Portrait'' by Paul Cézanne. Working in the late 19th century, Cézanne had a much broader palette of colors than his predecessors.


Manufacturing and industrial standards

Before the development of synthetic pigments, and the refinement of techniques for extracting mineral pigments, batches of color were often inconsistent. With the development of a modern color industry, manufacturers and professionals have cooperated to create international standards for identifying, producing, measuring, and testing colors. First published in 1905, the Munsell color system became the foundation for a series of color models, providing objective methods for the measurement of color. The Munsell system describes a color in three dimensions, hue, value (lightness), and chroma (color purity), where chroma is the difference from gray at a given hue and value. By the middle 20th century, standardized methods for pigment chemistry were available, part of an international movement to create such standards in industry. The
International Organization for Standardization The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. M ...
(ISO) develops technical standards for the manufacture of pigments and dyes. ISO standards define various industrial and chemical properties, and how to test for them. The principal ISO standards that relate to all pigments are as follows: * ISO-787 General methods of test for pigments and extenders. * ISO-8780 Methods of dispersion for assessment of dispersion characteristics. Other ISO standards pertain to particular classes or categories of pigments, based on their chemical composition, such as ultramarine pigments, titanium dioxide, iron oxide pigments, and so forth. Many manufacturers of paints, inks, textiles, plastics, and colors have voluntarily adopted the Colour Index International (CII) as a standard for identifying the pigments that they use in manufacturing particular colors. First published in 1925—and now published jointly on the web by the Society of Dyers and Colourists (
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
) and the American Association of Textile Chemists and Colorists (US)—this index is recognized internationally as the authoritative reference on colorants. It encompasses more than 27,000 products under more than 13,000 generic color index names. In the CII schema, each pigment has a generic index number that identifies it chemically, regardless of proprietary and historic names. For example, Phthalocyanine Blue BN has been known by a variety of generic and proprietary names since its discovery in the 1930s. In much of Europe, phthalocyanine blue is better known as Helio Blue, or by a proprietary name such as Winsor Blue. An American paint manufacturer, Grumbacher, registered an alternate spelling (Thanos Blue) as a trademark. Colour Index International resolves all these conflicting historic, generic, and proprietary names so that manufacturers and consumers can identify the pigment (or dye) used in a particular color product. In the CII, all phthalocyanine blue pigments are designated by a generic color index number as either PB15 or PB16, short for pigment blue 15 and pigment blue 16; these two numbers reflect slight variations in molecular structure, which produce a slightly more greenish or reddish blue.


Figures of merit

The following are some of the attributes of pigments that determine their suitability for particular manufacturing processes and applications: * Lightfastness and sensitivity for damage from ultraviolet light * Heat stability *
Toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...
* Tinting strength * Staining * Dispersion (which can be measured with a Hegman gauge) * Opacity or transparency * Resistance to alkalis and acids * Reactions and interactions between pigments


Swatches

Swatches are used to communicate colors accurately. The types of swatches are dictated by the media, i.e., printing, computers, plastics, and textiles. Generally, the medium that offers the broadest gamut of color shades is widely used across diverse media.


Printed swatches

Reference standards are provided by printed swatches of color shades. PANTONE, RAL, Munsell, etc. are widely used standards of color communication across diverse media like printing, plastics, and textiles.


Plastic swatches

Companies manufacturing color masterbatches and pigments for plastics offer plastic swatches in injection molded color chips. These color chips are supplied to the designer or customer to choose and select the color for their specific plastic products. Plastic swatches are available in various special effects like pearl, metallic, fluorescent, sparkle, mosaic etc. However, these effects are difficult to replicate on other media like print and computer display. Plastic swatches have been created by 3D modelling to including various special effects.


Computer swatches

The appearance of pigments in natural light is difficult to replicate on a
computer display A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls. T ...
. Approximations are required. The Munsell Color System provides an objective measure of color in three dimensions: hue, value (or lightness), and chroma. Computer displays in general fail to show the true chroma of many pigments, but the hue and lightness can be reproduced with relative accuracy. However, when the gamma of a computer display deviates from the reference value, the hue is also systematically biased. The following approximations assume a display device at
gamma Gamma (; uppercase , lowercase ; ) is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter normally repr ...
2.2, using the sRGB color space. The further a display device deviates from these standards, the less accurate these swatches will be. Swatches are based on the average measurements of several lots of single-pigment watercolor paints, converted from Lab color space to sRGB color space for viewing on a computer display. The appearance of a pigment may depend on the brand and even the batch. Furthermore, pigments have inherently complex reflectance spectra that will render their color appearance greatly different depending on the spectrum of the source illumination, a property called metamerism. Averaged measurements of pigment samples will only yield approximations of their true appearance under a specific source of illumination. Computer display systems use a technique called chromatic adaptation transforms to emulate the correlated color temperature of illumination sources, and cannot perfectly reproduce the intricate spectral combinations originally seen. In many cases, the perceived color of a pigment falls outside of the gamut of computer displays and a method called gamut mapping is used to approximate the true appearance. Gamut mapping trades off any one of lightness, hue, or saturation accuracy to render the color on screen, depending on the priority chosen in the conversion's ICC rendering intent.


Biological pigments

In
biology Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and ...
, a pigment is any
color Color (or colour in English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is the visual perception based on the electromagnetic spectrum. Though co ...
ed material of plant or animal cells. Many biological structures, such as
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...
, eyes, fur, and hair contain pigments (such as melanin). Animal skin coloration often comes about through specialized cells called chromatophores, which animals such as the octopus and chameleon can control to vary the animal's color. Many conditions affect the levels or nature of pigments in plant, animal, some protista, or
fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
cells. For instance, the disorder called albinism affects the level of melanin production in animals. Pigmentation in organisms serves many biological purposes, including camouflage,
mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. In the simples ...
,
aposematism Aposematism is the Advertising in biology, advertising by an animal, whether terrestrial or marine, to potential predation, predators that it is not worth attacking or eating. This unprofitability may consist of any defenses which make the pr ...
(warning),
sexual selection Sexual selection is a mechanism of evolution in which members of one sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ...
and other forms of signalling,
photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
(in plants), and basic physical purposes such as protection from sunburn. Pigment color differs from structural color in that pigment color is the same for all viewing angles, whereas structural color is the result of selective reflection or iridescence, usually because of multilayer structures. For example,
butterfly Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...
wings typically contain structural color, although many butterflies have cells that contain pigment as well.


Pigments by chemical composition

*
Aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
pigment: aluminum powder * Barium: barium white ( lithopone) * Cadmium pigments: cadmium yellow, cadmium red, cadmium green, cadmium orange, cadmium sulfoselenide *
Carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
pigments: carbon black (including vine black, lamp black), ivory black (bone charcoal) * Chromium pigments: chrome yellow and chrome green (viridian) * Cobalt pigments: cobalt violet, cobalt blue, cerulean blue, aureolin (cobalt yellow) * Copper pigments: azurite, Han purple, Han blue, Egyptian blue, malachite, Paris green, Phthalocyanine Blue BN, Phthalocyanine Green G, verdigris *
Iron oxide An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust. Iron ...
pigments: sanguine, caput mortuum, oxide red, red ochre, yellow ochre, Venetian red, Prussian blue, raw sienna, burnt sienna, raw umber, burnt umber *
Lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
pigments: lead white, Naples yellow, red lead, lead-tin yellow *
Manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...
pigments: manganese violet, YInMn blue * Mercury pigments: vermilion * Sulfur pigments: ultramarine, ultramarine green shade, lapis lazuli * Titanium pigments: titanium yellow, titanium white, titanium black * Zinc pigments: zinc white, zinc ferrite, zinc yellow


Biological and organic

* Biological origins: alizarin, gamboge, cochineal red, rose madder,
indigo InterGlobe Aviation Limited (d/b/a IndiGo), is an India, Indian airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 64.1% domestic market ...
, Indian yellow, Tyrian purple * Non-biological organic: quinacridone,
magenta Magenta () is a purple-red color. On color wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) color models, it is located precisely midway between blue and red. It is one of the four colors of ink used in colo ...
, phthalo green, phthalo blue, pigment red 170, diarylide yellow


See also

* Blue pigments * Lake pigment * List of Stone Age art * Red pigments * Rock art * Subtractive color


Notes


References

* * * * * * * * *


External links


Pigments through the ages

ColourLex Pigment Lexicon
* Sarah Lowengar
The Creation of Color in Eighteenth-century Europe
Columbia University Press, 2006 * , Chemical Heritage Foundation * , Chemical Heritage Foundation
The Quest for the Next Billion-Dollar Color
{{Authority control Painting materials