Pigments

For the drug referred to as "pigment," see black tar heroin.

In biology, pigment is any material resulting in colour in plant or animal cells which is the result of selective absorption. Some biological material has so-called structural colour, which is the result of selective reflection or iridescence, usually done with multilayer structures. Unlike structural colour, pigment color is the same for all viewing angles. Nearly all types of cells, such as skin, eyes, fur and hair contain pigment. Butterfly wings typically contain structural colour, although many of them contain pigment as well. Creatures that have deficient pigmentation are called albinos.

Because pigment colour is the result of selective absorption, there is no such thing as white pigment. A white object is simply a diffuse reflecting object which does not contain any pigment.

In the coloring of paint, ink, plastic, fabric and other material, a pigment is a dry colorant, usually an insoluble powder. There are both natural and synthetic pigments, both organic and inorganic ones. Pigments work by selectively absorbing some parts of the visible spectrum (see light) whilst reflecting others.

A distinction is usually made between a pigment, which is insoluble, and a dye, which is either a liquid, or is soluble. There is a well-defined dividing line between pigments and dyes: a pigment is not soluble in the vehicle while a dye is. From this follows that a certain colourant can be both a pigment and a dye depending on in which vehicle it is used. In some cases, a pigment will be made by precipitating a soluble dye with a metallic salt. The resulting pigment is called a "lake".

List of pigments

Heme/Porphyrin based

• Chlorophyll
• Bilirubin
• Hemocyanin
• Hemoglobin
• Myoglobin

Light emitting

• Luciferin

Lipochromes

• Carotenoids
  • Alpha and Beta Carotene
  • Cyanins
    • Anthocyanin
  • Lycopene
  • Rhodopsin
  • Xanthophylls
    • Canthaxanthin
    • Zeaxanthin
    • Lutein

Photosynthetic

• Chlorophyll
• Phycobilin

Other

• Hematochrome
• Melanin - Which causes human skin coloration
• Phthalocyanine blue
• Urochrome
• polyene enolates are a class of red pigments unique to parrots.

Painting pigments

• Alizarin (Alizarin Crimson)
• Bone black (also known as bone char)
• Cadmium pigments (Cadmium Green, Cadmium Red, Cadmium Yellow, Cadmium Orange)
• Caput Mortuum
• Carbon black
• Cerulean blue
• Chromium pigments (Chrome Green, Chrome Yellow)
• Cobalt pigments (Cobalt Blue)
• Crimson
• Fugitive pigments
• Gamboge
• Indian Yellow
• Indigo
• Ivory black
• Vine black
• Lamp black
• Mars black
• Lead pigments (Lead white, Naples Yellow, Cremnitz White, Foundation White, Red Lead)
• Paris Green
• Phthalocyanine (Phthalo Green, Phthalo Blue)
• Prussian blue
• Quinacridone (Quinacridone Magenta)
• Oxide Red
• Red ochre
• Sanguine
• Sienna (Raw Sienna, Burnt Sienna)
• Titanium dioxide (Titanium White)
• Ultramarine (Ultramarine Green Shade, French Ultramarine)
• Umber (Raw Umber, Burnt Umber)
• Van Dyke brown
• Venetian Red
• Verdigris
• Vermilion
• Viridian
• Yellow ochre
• Zinc white

External links

• Pigments through the ages
• Earliest evidence of art found