pigment

/pig"meuhnt/, n.

1. a dry insoluble substance, usually pulverized, which when suspended in a liquid vehicle becomes a paint, ink, etc.

2. a coloring matter or substance.

3. Biol. any substance whose presence in the tissues or cells of animals or plants colors them.

v.t.

4. to color; add pigment to.

v.i.

5. to become pigmented; acquire color; develop pigmentation: a poor quality of paper that doesn't pigment well.

[1350-1400; ME < L pigmentum paint, equiv. to pig- (s. of pingere to PAINT) + -mentum -MENT]

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Any intensely coloured compound used to colour other materials.

Unlike dyes, pigments do not dissolve; they are applied as fine solid particles mixed with a liquid. In general, the same ones are used in oil-and water-based paints, printing inks, and plastics. They may be inorganic compounds (usually brighter and longer-lasting) or organic compounds. Natural organic pigments have been used for centuries, but today most are synthetic or inorganic. The primary white pigment is titanium dioxide. Carbon black is the most usual black pigment. Iron oxides give browns, ranging from yellowish through orange to dark brown. Chromium compounds yield chrome yellows, oranges, and greens; cadmium compounds brilliant yellows, oranges, and reds. The most common blues, Prussian blue and ultramarine, are also inorganic. Organic pigments, usually synthesized from aromatic hydrocarbons, include the nitrogen-containing azo pigments (red, orange, and yellow; see azo dyes) and the copper phthalocyanines (brilliant, strong blues and greens). Chlorophyll, carotene, rhodopsin, and melanin are pigments produced by plants and animals for specialized purposes.

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▪ chemistry

      any of a group of compounds that are intensely coloured and are used to colour other materials.

      Pigments are insoluble and are applied not as solutions but as finely ground solid particles mixed with a liquid. In general, the same pigments are employed in oil- and water-based paints, printing inks, and plastics. Pigments may be organic (i.e., contain carbon) or inorganic. The majority of inorganic pigments are brighter and last longer than organic ones. Organic pigments made from natural sources have been used for centuries, but most pigments used today are either inorganic or synthetic organic ones. Synthetic organic pigments are derived from coal tars and other petrochemicals. Inorganic pigments are made by relatively simple chemical reactions—notably oxidation—or are found naturally as earths.

      Inorganic pigments include white opaque pigments used to provide opacity and to lighten other colours. The most important member of the class is titanium dioxide. White extender pigments are added to paints to lower their cost or improve their properties. This class includes calcium carbonate, calcium sulfate, diatomaceous silica (the remains of marine organisms), and china clays. Black pigments are primarily created from particles of carbon. Carbon black, for example, is used to give black colour to printing inks. Iron-oxide earth pigments yield ochres (yellow-browns), siennas (orange-browns), and umbers (browns). Certain compounds of chromium are used to provide chrome yellows, oranges, and greens, while various compounds of cadmium yield brilliant yellows, oranges, and reds. Iron, or Prussian, blue and ultramarine blue are the most widely used blue pigments and are both inorganic in origin.

      For the most part, organic pigments are presently synthesized from aromatic (aromatic compound) hydrocarbons. These are compounds containing structures of carbon atoms with hydrogen atoms attached that are formed in closed rings. Organic pigments include azo pigments, which contain a nitrogen group; they account for most of the organic red, orange, and yellow pigments. Copper phthalocyanines provide brilliant, strong blues and greens that are unusually colourfast for organic colours. Some pigments, such as fluorescent ones, are simply dyes that have been rendered insoluble by chemical reaction.

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