Dye

A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and may require a mordant to improve the fastness of the dye on the fiber.

General

Both dyes and pigments are colored, because they absorb only some wavelengths of visible light. Dyes are usually soluble in water, whereas pigments are insoluble. Some dyes can be rendered insoluble with the addition of salt to produce a lake pigment.

Types

There are two broad categories of dyes:

• Natural dyes: are dyes extracted from plants, insects, fungi or minerals. The majority of natural dyes are vegetable dyes derived from plant sources such as roots, berries, bark, leaves, flowers/petals and wood.
• Synthetic dyes: are also referred to as "coal tar dyes" because they are derived from substances that, until recently, could only be extracted from coal tar. A synthetic dye consists of a chromophore and an auxochrome added to a benzene derivative.

See also

• Azo dye

References

Relevant Sciencemadness threads

• Azo Dyes and Colored Smoke