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A
dye can generally be described as a colored substance that has an affinity
to the substrate to which it is being applied. The dye is generally applied
in an aqueous solution, and may require a mordant to improve the fastness
of the dye on the fiber. Both
dyes and pigments appear to be colored because they absorb some wavelengths
of light preferentially. In contrast with a dye, a pigment generally is
insoluble, and has no affinity for the substrate. Some dyes can be precipitated
with an inert salt to produce a lake pigment.Archaeological evidence shows
that, particularly in India and the Middle East, dyeing has been carried
out for over 5000 years. The dyes were obtained from animal, vegetable
or mineral origin, with no or very little processing. By far the greatest
source of dyes has been from the plant kingdom, notably roots, berries,
bark, leaves and wood, but only a few have ever been used on a commercial
scale.
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