Science Fair Project Encyclopedia
Pigment
In biology, pigment is any material resulting in color in plant or animal cells which is the result of selective absorption. Some biological material has so-called structural color, which is the result of selective reflection or iridescence, usually done with multilayer structures. Unlike structural color, 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 color, although many of them contain pigment as well. Creatures that have deficient pigmentation are called albinos.
Because pigment color 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 no well-defined dividing line between pigments and dyes, however, and some coloring agents are used as both pigments and dyes. In some cases, a pigment will be made by precipitating a soluble dye with a metallic salt. The resulting pigment is called a "lake".
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List of pigments
Heme/Porphyrin based
Light emitting
Lipochromes
- Carotenoids
- Alpha and Beta Carotene
- Cyanins
- Lycopene
- Rhodopsin
- Xanthophylls
- Canthaxanthin
- Zeaxanthin
- Lutein
Photosynthetic
Other
- Hematochrome
- Melanin - Which causes human skin coloration
- Pthalocyanine blue
- Urea
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 )
- Phthalocyanine (Pthalo Green, Pthalo 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 )
- Venetian Red
- Yellow ochre
- Zinc white
External links
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