Medical research

New understanding of how we see colors

(Medical Xpress)—Scientists have until now not fully understood how animals see in color, since visual pigments in eyes contain exactly the same chromophore (light absorbing segment of the molecule) and yet can absorb different ...

Medical research

Researchers discover tooth-enamel protein in eyes with dry AMD

A protein that normally deposits mineralized calcium in tooth enamel may also be responsible for calcium deposits in the back of the eye in people with dry age-related macular degeneration (AMD), according to a study from ...

Genetics

Dynamin-binding protein linked to congenital cataracts

Cataracts, a condition in which the eyes' natural lenses get clouded, are the most common cause of vision loss in older people and can be corrected by routine surgery. But congenital cataracts, which occur in infants and ...

Oncology & Cancer

Scientists identify weak point in deadly eye melanoma

A natural plant compound exploits a newly identified Achilles' heel in a cancer of the eye, uveal melanoma. In human cancer cells growing in the lab, the compound shuts down the overactive signaling that drives uveal melanoma ...

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Pigment

A 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.

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

The worldwide market for inorganic, organic and special pigments had a total volume of around 7.4 million tons in 2006. Asia has the highest rate on a quantity basis followed by Europe and North America. In 2006, a turnover of 17.6 billion US$ (13 billion euro) was reached mostly in Europe, followed by North America and Asia. The global demand on pigments was roughly US$ 20.5 billion in 2009, around 1.5-2% up from the previous year. It is predicted to increase in a stable growth rate in the coming years. The worldwide sales will increase to US$ 24.5 billion in 2015, and reach US$ 27.5 billion in 2018.

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

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