Pigment

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Pigments for sale at a market stall in Goa, India. Indian pigments.jpg
Pigments for sale at a market stall in Goa, India.

A pigment is a colored material that is completely or nearly insoluble in water. [1] In contrast dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compounds. Pigments of prehistoric and historic value include ocher, charcoal, and lapis lazuli.

Contents

Economic impact

In 2006, around 7.4 million tons of inorganic, organic and special pigments were marketed worldwide. [2] estimated at around US$14.86 billion in 2018 and will rise at over 4.9% CAGR from 2019 to 2026. [3] The global demand on pigments was roughly US$20.5 billion in 2009. [4] 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 red is valued at $300 million each year. [5]

Physical principles

A wide variety of wavelengths (colors) encounter a pigment. This pigment absorbs red and green light, but reflects blue--creating the color blue. Simple reflectance.svg
A wide variety of wavelengths (colors) encounter a pigment. This pigment absorbs red and green light, but reflects blue—creating the color blue.

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. [6] Light of other wavelengths are reflected or scattered. The reflected light spectrum defines the color.

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.

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. Complex reflectance.svg
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.

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. [7] 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. [8] 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, 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. These were more consistent than colors mined from the original ore bodies, but the place names remained. Also found in many Paleolithic and Neolithic cave paintings are Red Ochre, anhydrous Fe2O3, and the hydrated Yellow Ochre (Fe2O3.H2O). [9] Charcoal—or carbon black—has also been used as a black pigment since prehistoric times. [9]

Synthetic pigments were introduced as early as the second millennium BCE. [10] White lead (basic lead carbonate, (PbCO3)2Pb(OH)2) is one of example. [11] and blue frit (Egyptian Blue). Another early synthetic pigment is blue frit, calcium copper silicate, made by heating glass with a copper source, such as malachite. Later premodern synthetic pigments include vermilion, verdigris, and lead-tin-yellow. Vermilion, a mercury compound, was favored by old masters such as Titian. Indian yellow was once produced by collecting the urine of cattle that had been fed only mango leaves. [12] Dutch and Flemish painters of the 17th and 18th centuries favored it for its luminescent qualities, and often used it to represent sunlight.[ citation needed ] Since mango leaves are nutritionally inadequate for cattle, the practice of harvesting Indian yellow was eventually declared to be inhumane. [12] Modern hues of Indian yellow are made from synthetic pigments. Vermillion has been parttially replaced in by cadmium reds.

Because of the expense of lapis lazuli, substitutes were often used. Prussian blue, the oldest modern synthetic pigment, was discovered by accident in 1704. [13] 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 and Cerulean blue were also introduced. In the early 20th century, Phthalo Blue, a synthetic metallo-organicc 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 dye, 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.s. The development of organic chemistry diminished the dependence on inorganic pigments. [14]

Manufacturing and industrial standard

Natural ultramarine pigment in powdered form Natural ultramarine pigment.jpg
Natural ultramarine pigment in powdered form
Synthetic ultramarine pigment is chemically identical to natural ultramarine Ultramarinepigment.jpg
Synthetic ultramarine pigment is chemically identical to natural ultramarine

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 (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:

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, 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:

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. 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 2.2, using the sRGB color space. The further a display device deviates from these standards, the less accurate these swatches will be. [16] 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 [17] 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 [18] 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.

#990024
PR106 – #E34234
Vermilion (genuine)
#FFB02E
PB29 – #003BAF
PB27 – #0B3E66

Biological pigments

In 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 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 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, 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 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 wings typically contain structural color, although many butterflies have cells that contain pigment as well.

Pigments by elemental composition

Phthalo Blue Copper phthalocyanine.svg
Phthalo Blue


Biological and organic

See also

Notes

  1. Völz, Hans G.; Kischkewitz, Jürgen; Woditsch, Peter; Westerhaus, Axel; Griebler, Wolf-Dieter; De Liedekerke, Marcel; Buxbaum, Gunter; Printzen, Helmut; Mansmann. "Pigments, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_243.pub2.
  2. Pigments Market size
  3. Market Study Pigments, 3rd ed., Ceresana, 11/13. Archived 3 September 2010 at the Wayback Machine
  4. "Market Report: World Pigment Market". Acmite Market Intelligence. Archived from the original on 29 November 2010.
  5. Schonbrun, Zach (18 April 2018). "The Quest for the Next Billion-Dollar Color". Bloomberg Businessweek . Retrieved 2 May 2018.
  6. Thomas B. Brill, Light: Its Interaction with Art and Antiquities, Springer 1980, p. 204
  7. St. Clair, Kassia (2016). The Secret Lives of Colour. London: John Murray. pp. 21, 237. ISBN   9781473630819. OCLC   936144129.
  8. "Earliest evidence of art found". BBC News. 2 May 2000. Archived from the original on 3 June 2016. Retrieved 1 May 2016.
  9. 1 2 "Pigments Through the Ages". WebExhibits.org. Archived from the original on 11 October 2007. Retrieved 18 October 2007.
  10. Rossotti, Hazel (1983). Colour: Why the World Isn't Grey. Princeton, NJ: Princeton University Press. ISBN   0-691-02386-7.
  11. Lead white Archived 25 December 2015 at the Wayback Machine at ColourLex
  12. 1 2 "History of Indian yellow". Pigments Through the Ages. Archived from the original on 21 December 2014. Retrieved 13 February 2015.
  13. Prussian blue Archived 2 January 2016 at the Wayback Machine at ColourLex
  14. Simon Garfield (2000). Mauve: How One Man Invented a Color That Changed the World. Faber and Faber. ISBN   0-393-02005-3.
  15. Johannes Vermeer, The Milkmaid Archived 14 April 2015 at the Wayback Machine , ColourLex
  16. "Dictionary of Color Terms". Gamma Scientific. Archived from the original on 20 August 2014. Retrieved 25 June 2014.
  17. "Color Appearance". Hello Artsy.[ better source needed ]
  18. "Chromatic Adaptation". cmp.uea.ac.uk. Archived from the original on 29 September 2007. Retrieved 16 April 2009.
  19. Engineer Manual 1110-2-3400 Painting: New Construction and Maintenance (PDF). 30 April 1995. pp. 4–12. Archived (PDF) from the original on 1 December 2017. Retrieved 24 November 2017.

Related Research Articles

Blue Primary colour between purple and green

Blue is one of the three primary colours of pigments in painting and traditional colour theory, as well as in the RGB colour model. It lies between violet and green on the spectrum of visible light. The eye perceives blue when observing light with a dominant wavelength between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colours; azure contains some green, while ultramarine contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called Tyndall scattering explains blue eyes. Distant objects appear more blue because of another optical effect called aerial perspective.

Cyan Color visible between blue and green; subtractive (CMY) primary color

Cyan is a greenish-blue color. It is evoked by light with a predominant wavelength of between 490 and 520 nm, between the wavelengths of green and blue.

Yellow Color

Yellow is the color between orange and green on the spectrum of visible light. It is evoked by light with a dominant wavelength of roughly 570–590 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the RGB color model, used to create colors on television and computer screens, yellow is a secondary color made by combining red and green at equal intensity. Carotenoids give the characteristic yellow color to autumn leaves, corn, canaries, daffodils, and lemons, as well as egg yolks, buttercups, and bananas. They absorb light energy and protect plants from photodamage in some cases. Sunlight has a slight yellowish hue when the Sun is near the horizon, due to atmospheric scattering of shorter wavelengths.

Violet (color) Color

Violet is the color of light at the short wavelength end of the visible spectrum, between blue and invisible ultraviolet. It is one of the seven colors that Isaac Newton labeled when dividing the spectrum of visible light in 1672. Violet light has a wavelength between approximately 380 and 450 nanometers. The color's name is derived from the violet flower.

Purple Range of colors with the hues between blue and red

Purple refers to any of a variety of colors with hue between red and blue.

Brown

Brown is a composite color. In the CMYK color model used in printing or painting, brown is made by combining red, black, and yellow, or red, yellow, and blue. In the RGB color model used to project colors onto television screens and computer monitors, brown is made by combining red and green, in specific proportions. In painting, brown is generally made by adding black to orange.

Ultramarine Deep blue purple color pigment which was originally made with ground lapis lazuli

Ultramarine is a deep blue color pigment which was originally made by grinding lapis lazuli into a powder. The name comes from the Latin ultramarinus, literally "beyond the sea", because the pigment was imported into Europe from mines in Afghanistan by Italian traders during the 14th and 15th centuries.

Hue Property of a color indicating balance of color perceived by the normal human eye

In color theory, hue is one of the main properties of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, orange, yellow, green, blue, purple," which in certain theories of color vision are called unique hues.

Natural Color System

The Natural Color System (NCS) is a proprietary perceptual color model. It is based on the color opponency hypothesis of color vision, first proposed by German physiologist Ewald Hering. The current version of the NCS was developed by the Swedish Colour Centre Foundation, from 1964 onwards. The research team consisted of Anders Hård, Lars Sivik and Gunnar Tonnquist, who in 1997 received the AIC Judd award for their work. The system is based entirely on the phenomenology of human perception and not on color mixing. It is illustrated by a color atlas, marketed by NCS Colour AB in Stockholm.

In the visual arts, color theory is a body of practical guidance to color mixing and the visual effects of a specific color combination. There are also definitions of colors based on the color wheel: primary color, secondary color, and tertiary color. Although color theory principles first appeared in the writings of Leone Battista Alberti and the notebooks of Leonardo da Vinci, a tradition of "colory theory" began in the 18th century, initially within a partisan controversy over Isaac Newton's theory of color and the nature of primary colors. From there it developed as an independent artistic tradition with only superficial reference to colorimetry and vision science.

Umber

Umber is a natural brown or reddish-brown earth pigment that contains iron oxide and manganese oxide. Umber is darker than the other similar earth pigments, ochre and sienna.

Phthalocyanine Blue BN

Phthalocyanine Blue BN, also called by many names, is a bright, crystalline, synthetic blue pigment from the group of phthalocyanine dyes. Its brilliant blue is frequently used in paints and dyes. It is highly valued for its superior properties such as light fastness, tinting strength, covering power and resistance to the effects of alkalis and acids. It has the appearance of a blue powder, insoluble in most solvents including water.

Oil paint

Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnish may be added to increase the glossiness of the dried oil paint film. Oil paints have been used in Europe since the 12th century for simple decoration, but did not begin to be adopted as an artistic medium until the early 15th century. Common modern applications of oil paint are in finishing and protection of wood in buildings and exposed metal structures such as ships and bridges. Its hard-wearing properties and luminous colors make it desirable for both interior and exterior use on wood and metal. Due to its slow-drying properties, it has recently been used in paint-on-glass animation. Thickness of coat has considerable bearing on time required for drying: thin coats of oil paint dry relatively quickly.

Azure (color)

Azure is a bright, cyan-blue color named after the rock azurite. It is often described as the color of the sky on a clear day.

Cerulean, also spelled caerulean, is a shade of blue ranging between azure and a darker sky blue.

Phthalocyanine Green G

Phthalocyanine green G, which has many commercial names, is a synthetic green pigment from the group of phthalocyanine dyes, a complex of copper(II) with chlorinated phthalocyanine. It is a soft green powder, which is insoluble in water. It is a bright, high intensity colour used in oil and acrylic based artist's paints, and in other applications.

Shades of blue Variety of the color blue

Varieties of the color blue may differ in hue, chroma, or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a blue or other hue mixed with white, a shade being mixed with black. A large selection of these various colors is shown below.

Synthetic colorant


A colorant is any substance that changes the spectral transmittance or reflectance of a material. Synthetic colorants are those created in a laboratory or industrial setting. The production and improvement of colorants was a driver of the early synthetic chemical industry, in fact many of today's largest chemical producers started as dye-works in the late 19th or early 20th centuries, including Bayer AG(1863). Synthetics are extremely attractive for industrial and aesthetic purposes as they have they often achieve higher intensity and color fastness than comparable natural pigments and dyes used since ancient times. Market viable large scale production of dyes occurred nearly simultaneously in the early major producing countries Britain (1857), France (1858), Germany (1858), and Switzerland (1859), and expansion of associated chemical industries followed. The mid-nineteenth century through WWII saw an incredible expansion of the variety and scale of manufacture of synthetic colorants. Synthetic colorants quickly became ubiquitous in everyday life, from clothing to food. This stems from the invention of industrial research and development laboratories in the 1870s, and the new awareness of empirical chemical formulas as targets for synthesis by academic chemists. The dye industry became one of the first instances where directed scientific research lead to new products, and the first where this occurred regularly.

References