   #copyright

Pigment

2007 Schools Wikipedia Selection. Related subjects: Materials science

   Natural Ultramarine pigment in powdered form.
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   Natural Ultramarine pigment in powdered form.
   Synthetic Ultramarine pigment is chemically identical to natural
   ultramarine.
   Enlarge
   Synthetic Ultramarine pigment is chemically identical to natural
   ultramarine.

   A pigment is a material that changes the colour of light it reflects as
   the result of selective colour absorption. This physical process
   differs from fluorescence, phosphorescence, and other forms of
   luminescence, in which the material itself emits light.

   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
   stabililty 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 colorants, usually ground into a fine powder. This
   powder is added to a vehicle (or matrix), a relatively neutral or
   colorless material that acts as a binder.

   A distinction is usually made between a pigment, which is insoluble in
   the vehicle, and a dye, which is either a liquid, or is soluble in its
   vehicle. 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.

Biological pigments

   The monarch butterfly's distinctive pigmentation reminds potential
   predators that it is poisonous.
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   The monarch butterfly's distinctive pigmentation reminds potential
   predators that it is poisonous.

   In biology, a pigment is any material resulting in colour of plant or
   animal cells. Many biological structures, such as skin, eyes, fur and
   hair contain pigments (such as melanin) in specialized cells called
   chromatophores. Many conditions affect the levels or nature of pigments
   in plant and animal cells. For instance, Albinism is a disorder
   affecting the level of melanin production in animals.

   Pigment color differs from structual color in that it is the same for
   all viewing angles, whereas structural colour is the result of
   selective reflection or iridescence, usually because of multilayer
   structures. For example, butterfly wings typically contain structural
   colour, although many butterflies have cells that contain pigment as
   well.

History of pigments

   An anonymous prehistoric cave painter used naturally occurring ochres,
   oxides of iron and charred wood or bone to depict paleolithic fauna at
   Lascaux, France.
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   An anonymous prehistoric cave painter used naturally occurring ochres,
   oxides of iron and charred wood or bone to depict paleolithic fauna at
   Lascaux, France.

   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 colour 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. 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]."

   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, 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
   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.
   Miracle of the Slave by Tintoretto (c. 1548). The son of a master dyer,
   Tintoretto used Carmine Red Lake pigment, derived from the cochineal
   insect, to achieve dramatic color effects.
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   Miracle of the Slave by Tintoretto (c. 1548). The son of a master dyer,
   Tintoretto used Carmine Red Lake pigment, derived from the cochineal
   insect, to achieve dramatic colour effects.

   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 used in fabric 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, but Europeans had never seen the colour before. When the
   Spanish invaded the Aztec empire in what is now Mexico, they were quick
   to exploit the colour 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.
   Girl with a Pearl Earring by Johannes Vermeer (c. 1665).
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   Girl with a Pearl Earring by Johannes Vermeer (c. 1665).

   While Carmine was popular in Europe, blue remained an exclusive colour,
   associated with wealth and status. The 17th century Dutch master
   Johannes Vermeer often made lavish use of lapis lazuli. Girl with a
   Pearl Earring, a novel by Tracy Chevalier, is a fictional account of
   one of Vermeer's most famous paintings. In Chevalier's novel, and in
   the film based upon it, the artist uses lapis to paint the headscarf on
   a young servant girl. Vermeer (played by Colin Firth in the film
   version) admonishes the servant girl Griet (played by Scarlett
   Johansson) to keep this secret from his wife, knowing that his wife
   will be jealous.

Development of synthetic pigments

   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 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, organic pigment with overwhelming
   tinting power.

   Discoveries in colour 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. 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.
   Self Portrait by Paul Cézanne. Working in the late 19th century,
   Cezanne had a palette of colors that earlier generations of artists
   could only dream of.
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   Self Portrait by Paul Cézanne. Working in the late 19th century,
   Cezanne had a palette of colors that earlier generations of artists
   could only dream of.

   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 1800's, when the Mexican War of
   Independence and other market changes disrupted production. Organic
   chemistry delivered the final blow for the cochineal colour industry.
   When chemists created inexpensive substitutes for Carmine, an industry
   and a way of life went into steep decline.

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 colour industry,
   manufacturers and professionals have cooperated to create international
   standards for identifying, producing, measuring, and testing colors.

   First published in 1905, the Munsell Colour System became the
   foundation for a series of color models, providing objective methods
   for the measurement of color. The Munsell system describes a colour in
   three dimensions, hue, value (or lightness), and chroma, 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 colour 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 colour product. In the CII,
   all Phthalo Blue pigments are designated by a generic colour index
   number as either PB15 or PB36, short for pigment blue 15 and pigment
   blue 36. (The two forms of Phthalo Blue, PB15 and PB36, reflect slight
   variations in molecular structure that produce a slightly more greenish
   or reddish blue.)

Physical basis behind pigments

   Pigments appear the colors they are because they selectively reflect
   and absorb certain wavelengths of light. White light is a roughly equal
   mixture of the entire visible spectrum of light. When this light
   encounters a pigment, some wavelengths are absorbed by the chemicals of
   the pigment, and others are reflected. This new spectrum creates the
   appearance of a colour. Ultramarine reflects blue light, and absorbs
   other colors, for instance. Pigments, unlike fluorescent or
   phosphorescent substances, can only subtract wavelengths from the
   source light, never add new ones.
   A wide variety of wavelengths (colors) encounter a pigment. This
   pigment absorbs red and green light, but reflects blue, creating the
   color blue.
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   A wide variety of wavelengths (colors) encounter a pigment. This
   pigment absorbs red and green light, but reflects blue, creating the
   colour blue.
   Sunlight encounters Rosco R80 "Primary Blue" pigment. The source
   spectrum, minus the absorbency spectrum of the pigment, results in the
   final spectrum, and the appearance of blue.
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   Sunlight encounters Rosco R80 "Primary Blue" pigment. The source
   spectrum, minus the absorbency spectrum of the pigment, results in the
   final spectrum, and the appearance of blue.

   The appearance of pigments is intimately connected to the colour of the
   source light. Sunlight has a high colour 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.

   Colour spaces used to represent colors numerically must specify their
   light source. Lab colour measurements, unless otherwise noted, assume
   that the measurement was taken under a D65 light source, or "Daylight
   6500K", which is roughly the colour 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 colour. 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.

Scientific and technical issues

   Selection 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 colour 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:
     * Lightfastness
     * Heat stability
     * Toxicity
     * Tinting strength
     * Staining
     * Dispersion
     * Opacity or transparancy
     * Resistance to alkalis and acids
     * Reactions and interactions between pigments

Pigment groups

     * Biological origins: Alizarin, Alizarin Crimson, Gamboge, Indigo,
       Indian Yellow, Cochineal Red, Tyrian Purple, Rose madder
     * Carbon pigments: Carbon Black, Ivory Black, Vine Black, Lamp Black
     * Cadmium pigments: cadmium pigments, Cadmium Green, Cadmium Red,
       Cadmium Yellow, Cadmium Orange
     * Iron oxide pigments: Caput Mortuum, oxide red, Red Ochre, Sanguine,
       Venetian Red, Mars Black
     * Chromium pigments: Chrome Green, Chrome Yellow
     * Cobalt pigments: Cobalt Blue, Cerulean Blue, Cobalt Violet,
       Aureolin
     * Lead pigments: lead white, Naples yellow, Cremnitz White, red lead
     * Copper pigments: Paris Green, Verdigris, Viridian
     * Titanium pigments: Titanium White, Titanium Beige
     * Ultramarine pigments: Ultramarine, Ultramarine Green Shade, French
       Ultramarine
     * Mercury pigments: Vermilion
     * Zinc pigments: Zinc White
     * Clay earth pigments (which are also iron oxides): Raw Sienna, Burnt
       Sienna, Raw Umber, Burnt Umber, Yellow Ochre.
     * Organic: Pigment Red 170, Phthalo Green, Phthalo Blue, Prussian
       blue, Quinacridone Magenta.

Swatches

   Pure 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 Colour System provides a good
   conceptual explanation of what is missing. Munsell devised a system
   that provides an objective measure of colour 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 colour 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 colour space to sRGB colour space
   for viewing on a computer display. Different brands and lots of the
   same pigment may vary in colour. Furthermore, pigments have inherently
   complex spectral reflectance functions that will render their colour
   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
   correllated colour temperature of illumination sources, and cannot
   perfectly reproduce the intricate spectral combinations originally
   seen. In many cases the perceived colour 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 colour
   onscreen, depending on the priority chosen in the conversion's ICC
   rendering intent.
   PB29 - #003BAF
   Ultramarine Blue
   PB27 - #0B3E66
   Prussian Blue
   #990024
   Tyrian Red
   PR106 - #E34234
   Vermilion (genuine)
   PBr7 - #CE7D35
   Raw Sienna
   #FFB02E
   Indian Yellow

   Retrieved from " http://en.wikipedia.org/wiki/Pigment"
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   with only minor checks and changes (see www.wikipedia.org for details
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