Pigment

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. Most 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 useful 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 colorants, usually ground into a fine powder. This powder is added to a binder (or vehicle), a relatively neutral or colorless material that suspends the pigment and gives the paint its adhesion.

A distinction is usually made between a pigment, which is insoluble in its vehicle (resulting in a suspension), and a dye, which either is itself a liquid or is soluble in its vehicle (resulting in a solution). A colorant can act as either a pigment or a dye depending on the vehicle involved. 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. The term biological pigment is used for all colored substances independent of their solubility.

In 2006, around 7.4 million tons of inorganic, organic, and special pigments were marketed worldwide. Asia has the highest rate on a quantity basis followed by Europe and North America.

Types of pigments

Inorganic pigments

Inorganic pigments are pigments which are created by simple chemical reactions such as oxidation. They are usually more resistant to light and heat than organic pigments, and are often used in paints, plastics, and ceramics.

Organic pigments

Organic pigments are pigments which are created by complex chemical reactions involving carbon. They are usually less resistant to light and heat than inorganic pigments, but offer a wider range of colors.

Biological pigments

Biological pigments are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments.

See also

• Color
• Dye
• Paint
• Ink
• Plastic
• Fabric
• Cosmetics
• Food coloring

Pigment Resources
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