A pigment is a colored material that is completely or nearly insoluble in water.
In contrast dyes are typically soluble, at least at some stage in their use.
Estimated at around US$14.86 billion in 2018 and will rise at over 4.9% CAGR from 2019 to 2026.
The global demand on pigments was roughly US$20.5 billion in 2009.
According to an April 2018 report by Bloomberg Businessweek, the estimated value of the pigment industry globally is $30 billion.
Main article: Spectroscopy
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.
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.
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.
Minerals have been used as colorants since prehistoric times.
Early humans used paint for aesthetic purposes such as body decoration.
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.
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.
Charcoal—or carbon black—has also been used as a black pigment since prehistoric times.
Synthetic pigments were introduced as early as the second millennium BCE.
White lead (basic lead carbonate, (PbCO3)2Pb(OH)2) is one of example.
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.
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 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.
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.
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.
- Paintings illustrating advances in pigments
Manufacturing and industrial standard
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.
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:
- ISO-787 General methods of test for pigments and extenders.
- ISO-8780 Methods of dispersion for assessment of dispersion characteristics.
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:
- Lightfastness and sensitivity for damage from ultraviolet light
- Heat stability
- Tinting strength
- Dispersion (which can be measured with a Hegman gauge)
- Opacity or transparency
- Resistance to alkalis and acids
- Reactions and interactions between pigments
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.
Reference standards are provided by printed swatches of color shades.
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.
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 further a display device deviates from these standards, the less accurate these swatches will be.
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.
Main article: Biological pigment
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
Main article: List of inorganic pigments
- Cadmium pigments: cadmium yellow, cadmium red, cadmium green, cadmium orange, cadmium sulfoselenide
- 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 pigments: sanguine, caput mortuum, oxide red, red ochre, yellow ochre, Venetian red, Prussian blue, raw sienna, burnt sienna, raw umber, burnt umber
- Lead pigments: lead white, cremnitz white, Naples yellow, red lead, lead-tin-yellow
- Manganese pigments: manganese violet, YInMn blue
- Mercury pigments: vermilion
- Titanium pigments: titanium yellow, titanium beige, titanium white, titanium black
- Zinc pigments: zinc white, zinc ferrite, zinc yellow
- Aluminum pigment: Aluminum powder
- Carbon pigments: carbon black (including vine black, lamp black), ivory black (bone charcoal)
- Ultramarine pigments (based on sulfur): ultramarine, ultramarine green shade
Biological and organic
- Biological origins: alizarin, gamboge, cochineal red, rose madder, indigo, Indian yellow, Tyrian purple
- Non biological organic: quinacridone, magenta, phthalo green, phthalo blue, pigment red 170, diarylide yellow
Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Pigment.