A
pigment is a material that changes the
color of reflected or transmitted
light as the result of
wavelength-selective absorption. This physical process differs from
fluorescence,
phosphorescence, and other forms of
luminescence, in which a material emits light.
Pigments for sale at a market stall in Goa, India.Many materials selectively absorb certain
wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have special properties that make them ideal for coloring other materials. A pigment must have a high
tinting strength relative to the materials it colors. It must be stable in solid form at ambient temperatures.For industrial applications, as well as in the arts, permanence and stability are desirable properties. Pigments that are not permanent are called
fugitive. Fugitive pigments fade over time, or with exposure to light, while some eventually blacken.Pigments are used for coloring
paint,
ink,
plastic,
fabric,
cosmetics,
food and other materials. Most pigments used in
manufacturing and the
visual arts are dry
colourants, usually ground into a fine
powder. This powder is added to a
vehicle (or binder), a relatively neutral or colorless material that
suspends the pigment and gives the paint its adhesion.
The worldwide market for inorganic, organic and special pigments had a total volume of around 7.4 million tons in 2006. Asia has the highest rate on a quantity basis followed by Europe and North America. In 2006, a turnover of 17.6 billion US$ (13 billion euro) was reached mostly in Europe, followed by North America and Asia.
[1] The global demand on pigments was roughly US$ 20.5 billion in 2009, around 1.5-2% up from the previous year. It is predicted to increase in a stable growth rate in the coming years. The worldwide sales will increase to US$ 24.5 billion in 2015, and reach US$ 27.5 billion in 2018.
[2]A distinction is usually made between a pigment, which is
insoluble in the vehicle (resulting in a suspension), and a
dye, which either is itself a
liquid or is soluble in its vehicle (resulting in a solution). The term
biological pigment is used for all colored substances independent of their solubility. A
colorant can be both a pigment and a dye depending on the vehicle it is used in. In some cases, a pigment can be manufactured from a dye by
precipitating a soluble dye with a metallic salt. The resulting pigment is called a
lake pigment.
Bismuth vanadateNatural ultramarine pigment in powdered formSynthetic ultramarine pigment is chemically identical to natural ultramarineCarbon blackPhysical basisPigments appear the colors they are because they selectively reflect and absorb certain wavelengths of
visible light.
White light is a roughly equal mixture of the entire spectrum of visible light with a
wavelength in a range from about 380 or 400
nanometres to about 760 or 780 nm. When this light encounters a pigment, parts of the spectrum are
absorbed by the
chemical bonds of
conjugated systems and other components of the pigment. Some other wavelengths or parts of the spectrum are reflected or scattered. Most pigments are
charge-transfer complexes, like
transition metal compounds, with broad
absorption bands that subtract most of the colors of the incident white light. The new reflected light spectrum creates the appearance of a
color.
Ultramarine reflects blue light, and absorbs other colors. Pigments, unlike
fluorescent or
phosphorescent substances, can only
subtract wavelengths from the source light, never add new ones.
So a BLUE PIGMENT is BLUE because it doesn't reflect RED and GREEN light, or because it reflects all colors but the complementary of the BLUE one, which is ORANGE
A PURPLE PIGMENT is PURPLE because it absorbs all GREEN light.The appearance of pigments is intimately connected to the color of the source light. Sunlight has a high
color temperature, and a fairly uniform spectrum, and is considered a standard for white light. Artificial light sources tend to have great peaks in some parts of their spectrum, and deep valleys in others. Viewed under these conditions, pigments will appear different colors.
A wide variety of wavelengths (colors) encounter a pigment. This pigment absorbs red and green light, but reflects blue, creating the color blue.
Color spaces used to represent colors numerically must specify their light source.
Lab color measurements, unless otherwise noted, assume that the measurement was taken 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 added to pure pigment chemicals also have their own reflection and absorption patterns, which can affect the final spectrum. Likewise, in pigment/binder mixtures, individual rays of light may not encounter pigment molecules, and may be reflected as is. These stray rays of source light contribute to the saturation of the color. Pure pigment allows very little white light to escape, producing a highly saturated color. A small quantity of pigment mixed with a lot of white binder, however, will appear desaturated and pale, due to the high quantity of escaping white light.
Sunlight encounters Rosco R80 "Primary Blue" pigment. The product of the source spectrum and the reflectance spectrum of the pigment results in the final spectrum, and the appearance of blue.History
Naturally occurring pigments such as
ochres and
iron oxides have been used as colorants since prehistoric times. Archaeologists have uncovered evidence that 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 at Twin Rivers, near Lusaka,
Zambia.
Before the
Industrial Revolution, the range of color available for art and decorative uses was technically limited. Most of the pigments in use were earth and
mineral pigments, or pigments of biological origin. Pigments from unusual sources such as botanical materials, animal waste,
insects, and
mollusks were harvested and traded over long distances. Some colors were costly or impossible to mix with the range of pigments that were available.
Blue and
purple came to be associated with
royalty because of their expense.
Biological pigments were often difficult to acquire, and the details of their production were kept secret by the manufacturers.
Tyrian Purple is a pigment made from the
mucus of one of several species of
Murex snail. Production of Tyrian Purple for use as a
fabric dye began as early as 1200 BCE by the
Phoenicians, and was continued by the
Greeks and
Romans until 1453 CE, with the fall of Constantinople.
[3] The pigment was expensive and complex to produce, and items colored with it became associated with power and wealth. Greek historian
Theopompus, writing in the 4th century BCE, reported that "purple for dyes fetched its weight in
silver at
Colophon [in Asia Minor]."
[4]Mineral pigments were also traded over long distances. The only way to achieve a deep rich blue was by using a semi-precious stone,
lapis lazuli, to produce a pigment known as
ultramarine, and the best sources of lapis were remote. Flemish painter
Jan Van Eyck, working in the 15th century, did not ordinarily include blue in his paintings. To have one's portrait commissioned and painted with ultramarine blue was considered a great luxury. If a patron wanted blue, they were forced to pay extra. When Van Eyck used lapis, he never blended it with other colors. Instead he applied it in pure form, almost as a decorative glaze.
[5] The prohibitive price of
lapis lazuli forced artists to seek less expensive replacement pigments, both mineral (
azurite,
smalt) and biological (
indigo).
Spain's conquest of a New World empire in the 16th century introduced new pigments and colors to peoples on both sides of the Atlantic.
Carmine, a dye and pigment derived from a parasitic insect found in
Central and
South America, attained great status and value in Europe. Produced from harvested, dried, and crushed
cochineal insects, carmine could be, and still is, used in fabric dye, food dye, body paint, or in its solid
lake form, almost any kind of paint or
cosmetic.
Natives of
Peru had been producing cochineal dyes for textiles since at least 700 CE,
[6] but Europeans had never seen the color before. When the Spanish invaded the
Aztec empire in what is now
Mexico, they were quick to exploit the color for new trade opportunities.
Carmine became the region's second most valuable export next to silver. Pigments produced from the cochineal insect gave the
Catholic cardinals their vibrant robes and the English "Redcoats" their distinctive uniforms. The true source of the pigment, an insect, was kept secret until the 18th century, when biologists discovered the source.
[7]While Carmine was popular in Europe, blue remained an exclusive color, associated with wealth and status. The 17th century Dutch master
Johannes Vermeer often made lavish use of
lapis lazuli, along with Carmine and
Indian yellow, in his vibrant paintings.
Development of synthetic pigmentsThe earliest known pigments were natural minerals. Natural iron oxides give a range of colors and are found in many
Paleolithic and
Neolithic cave paintings. Two examples include Red Ochre, anhydrous Fe
2O
3, and the hydrated Yellow Ochre (Fe
2O
3.H
2O).
[8] Charcoal, or carbon black, has also been used as a black pigment since prehistoric times.
[8]Two of the first synthetic pigments were white lead (basic lead carbonate, (PbCO
3)
2Pb(OH)
2) and blue frit (
Egyptian Blue). White lead is made by combining lead with vinegar (
acetic acid, CH
3COOH) in the presence of CO
2. Blue frit is calcium copper silicate and was made from glass colored with a copper ore, such as
malachite. These pigments were used as early as the second millennium BCE
[9]The
Industrial and
Scientific Revolutions brought a huge expansion in the range of synthetic pigments, pigments that are manufactured or refined from naturally occurring materials, available both for manufacturing and artistic expression. Because of the expense of
Lapis Lazuli, much effort went into finding a less costly blue pigment.
Prussian Blue was the first modern synthetic pigment, discovered by accident in 1704. By the early 19th century, synthetic and metallic blue pigments had been added to the range of blues, including
French ultramarine, a synthetic form of
lapis lazuli, and the various forms of
Cobalt and
Cerulean Blue. In the early 20th century, organic chemistry added
Phthalo Blue, a synthetic,
organometallic pigment with overwhelming tinting power.
Discoveries in color science created new industries and drove changes in
fashion and taste. The discovery in 1856 of
mauveine, the first
aniline dye, was a forerunner for the development of hundreds of
synthetic dyes and pigments like
azo and
diazo compounds which are the source of wide spectrum of colors. Mauveine was discovered by an 18-year-old chemist named
William Henry Perkin, who went on to exploit his discovery in industry and become wealthy. His success attracted a generation of followers, as young scientists went into
organic chemistry to pursue riches. Within a few years, chemists had synthesized a substitute for
madder in the production of
Alizarin Crimson. By the closing decades of the 19th century,
textiles, paints, and other commodities in colors such as
red,
crimson, blue, and purple had become affordable.
[10]Development of chemical pigments and dyes helped bring new industrial prosperity to
Germany and other countries in northern Europe, but it brought dissolution and decline elsewhere. In Spain's former New World empire, the production of cochineal colors employed thousands of low-paid workers. The Spanish monopoly on cochineal production had been worth a fortune until the early 19th century, when the
Mexican War of Independence and other market changes disrupted production.
[11]Organic chemistry delivered the final blow for the cochineal color industry. When chemists created inexpensive substitutes for carmine, an industry and a way of life went into steep decline.
[12]New sources for historic pigmentsBefore the
Industrial Revolution, many pigments were known by the location where they were produced. Pigments based on minerals and clays often bore the name of the city or region where they were mined.
Raw Sienna and
Burnt Sienna came from
Siena,
Italy, 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 that were more consistent than colors mined from the original ore bodies. But the place names remained.
Historically and culturally, many famous natural pigments have been replaced with synthetic pigments, while retaining historic names. In some cases the original color name has shifted in meaning, as a historic name has been applied to a popular modern color. By convention, a contemporary mixture of pigments that replaces a historical pigment is indicated by calling the resulting color a
hue, but manufacturers are not always careful in maintaining this distinction. The following examples illustrate the shifting nature of historic pigment names:
- 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. In the novel Girl with a Pearl Earring, Vermeer's patron remarks that Vermeer used "cow piss" to paint his wife.[13] 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.
- Ultramarine, originally the semi-precious stone lapis lazuli, has been replaced by an inexpensive modern synthetic pigment, French Ultramarine, manufactured from aluminium silicate with sulfur impurities. 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. Since synthetic ultramarine is chemically identical with lapis lazuli, the "hue" designation is not used. French Blue, yet another historic name for ultramarine, was adopted by the textile and apparel industry as a color name in the 1990s, and was applied to a shade of blue that has nothing in common with the historic pigment ultramarine.
- Vermilion, a toxic mercury compound favored for its deep red-orange color by old master painters such as Titian, has been replaced in painters' palettes by various modern pigments, including cadmium reds. Although genuine Vermilion paint can still be purchased for fine arts and art conservation applications, few manufacturers make it, because of legal liability issues. Few artists buy it, because it has been superseded by modern pigments that are both less expensive and less toxic, as well as less reactive with other pigments. As a result, genuine Vermilion is almost unavailable. Modern vermilion colors are properly designated as Vermilion Hue to distinguish them from genuine Vermilion.
Manufacturing and industrial standardsBefore the development of synthetic pigments, and the refinement of techniques for extracting mineral pigments, batches of colour 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 years of the 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 (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) and the
American Association of Textile Chemists and Colorists (USA), 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,
Phthalo Blue 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 (Thalo 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
Phthalo Blue pigments are designated by a generic colour index number as either PB15 or PB16, short for pigment blue 15 and pigment blue 16. (The two forms of Phthalo Blue, PB15 and PB16, reflect slight variations in molecular structure that produce a slightly more greenish or reddish blue.)
Scientific and technical issuesSelection of a pigment for a particular application is determined by cost, and by the physical properties and attributes of the pigment itself. For example, a pigment that is used to color glass must have very high heat stability in order to survive the manufacturing process; but, suspended in the glass vehicle, its resistance to
alkali or
acidic materials is not an issue. In artistic paint, heat stability is less important, while
lightfastness and
toxicity are greater concerns.
The following are some of the attributes of pigments that determine their suitability for particular manufacturing processes and applications:
SwatchesPure pigments reflect light in a very specific way that cannot be precisely duplicated by the discrete light emitters in a
computer display. However, by making careful measurements of pigments, close approximations can be made. The
Munsell Color System provides a good conceptual explanation of what is missing. Munsell devised a system that provides an objective measure of color in three dimensions: hue, value (or lightness), and chroma. Computer displays in general are unable 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 2.2, using the
sRGB color space. The further a display device deviates from these standards, the less accurate these swatches will be.
[14] 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. Different brands and lots of the same pigment may vary in color. 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
[15] 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
ICCrendering intent.
Biological pigmentsIn
biology, a pigment is any
colored material of plant or animal cells. Many biological structures, such as
skin,
eyes,
fur and
hair contain pigments (such as
melanin).
Animal skin coloration is often achieved with specialized cells called
chromatophores, which in animals such as the
octopus and
chameleon can be controlled to vary the animal's color. Many conditions affect the levels or nature of pigments in plant, animal, some
protista, or
fungus cells. For instance,
Albinism is a disorder affecting the level of melanin production in animals.
Pigmentation is used in organisms for many biological purposes including
Camouflage,
Mimicry,
Aposematism (warning),
Sexual selection and other forms of
Signalling,
Photosynthesis (in plants), as well as basic physical purposes such as protection from
Sunburn.
Pigment color differs from
structural color in that it 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 wings typically contain structural color, although many butterflies have cells that contain pigment as well.
Pigments by chemical compositionTransition metal compounds. From left to right, aqueous solutions of: Co(NO3)2 (red); K2Cr2O7 (orange); K2CrO4 (yellow); NiCl2 (turquoise); CuSO4 (blue); KMnO4 (purple).Metallic and carbon- Cadmium pigments: cadmium yellow, cadmium red, cadmium green, cadmium orange
- Carbon pigments: carbon black (including vine blac, lamp black), ivory black (bone char)
- Chromium pigments: chrome yellow and chrome green
- 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, viridian
- Iron oxide pigments: sanguine, caput mortuum, oxide red, red ochre, Venetian red, Prussian blue
- Clay earth pigments (iron oxides): yellow ochre, raw sienna, burnt sienna, raw umber, burnt umber.
- Lead pigments: lead white, cremnitz white, Naples yellow, red lead
- Mercury pigments: vermilion
- Titanium pigments: titanium yellow, titanium beige, titanium white, titanium black
- Ultramarine pigments: ultramarine, ultramarine green shade
- Zinc pigments: zinc white, zinc ferrite
Structure of copper phthalocyanine (Phthalocyanine Blue BN)
Biological and organic- Biological origins: alizarin (synthesized), alizarin crimson (synthesized), gamboge, cochineal red, rose madder, indigo, Indian yellow, Tyrian purple
- Non biological organic: quinacridone, magenta, phthalo green, phthalo blue, pigment red 170
See alsoNotes- ^"Market Study: Pigments". Ceresana Research.
- ^"Market Report: World Pigment Market". Acmite Market Intelligence.
- ^Kassinger, Ruth G. (2003-02-06). Dyes: From Sea Snails to Synthetics. 21st century. ISBN 0-7613-2112-8.
- ^ Theopompus, cited by Athenaeus [12.526] in c. 200 BCE; according to Gulick, Charles Barton. (1941). Athenaeus, The Deipnosophists. Cambridge: Harvard University Press.
- ^Michel Pastoureau (2001-10-01). Blue: The History of a Color. Princeton University Press. ISBN 0-691-09050-5.
- ^Jan Wouters, Noemi Rosario-Chirinos (1992). "Dye Analysis of Pre-Columbian Peruvian Textiles with High-Performance Liquid Chromatography and Diode-Array Detection". Journal of the American Institute for Conservation (The American Institute for Conservation of Historic) 31 (2): 237–255. doi:10.2307/3179495. JSTOR 3179495.
- ^Amy Butler Greenfield (2005-04-26). A Perfect Red: Empire, Espionage, and the Quest for the Color of Desire. HarperCollins. ISBN 0-06-052275-5.
- ^ ab"Pigments Through the Ages". WebExhibits.org. Retrieved 2007-10-18.
- ^Rossotti, Hazel (1983). Colour: Why the World Isn't Grey. Princeton, NJ: Princeton University Press. ISBN 0-691-02386-7.
- ^Simon Garfield (2000). Mauve: How One Man Invented a Color That Changed the World. Faber and Faber. ISBN 0-393-02005-3.
- ^Octavio Hernández. "Cochineal". Mexico Desconocido Online. Retrieved July 15, 2005.
- ^Jeff Behan. "The bug that changed history". Retrieved June 26, 2006.
- ^ There is no evidence that the real patron said this.
- ^"Dictionary of Color Terms". Retrieved 2006-07-20.
- ^"Chromatic Adaptation". cmp.uea.ac.uk. Retrieved 2009-04-16.
References- Ball, Philip (2002). Bright Earth: Art and the Invention of Color. Farrar, Straus and Giroux. ISBN 0-374-11679-2
- Doerner, Max (1984). The Materials of the Artist and Their Use in Painting: With Notes on the Techniques of the Old Masters, Revised Edition.. Harcourt. ISBN 0-15-657716-X
- Finlay, Victoria (2003). Color: A Natural History of the Palette. Random House. ISBN 0-8129-7142-6
- Gage, John (1999). Color and Culture: Practice and Meaning from Antiquity to Abstraction. University of California Press. ISBN 0-520-22225-3
- Meyer, Ralph (1991). The Artist's Handbook of Materials and Techniques, Fifth Edition. Viking. ISBN 0-670-83701-6
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