Colorants are characterized by heir ability to absorb or emit light in the visible range (Zollinger, 2003, p. 1). Light of a given wavelength is perceived as the indicated color. The perception of color by the human eye does not solely depend on absorption wavelength, although it is crucial, but also on the shape of the bands involved. Man has used natural colorants long years ago. Substances that impart color to a material are dyes and pigments.

In term of chemical structure, colorants can be inorganic or organic compounds. Both groups can be subdivided into natural and synthetic representatives. (Christie, 2001, p. 24).

Colorants classified in to two separate ways, either according to their chemical structure or according to the method of application, they are dyes and pigments. Every color is representative of light that is at a particular wavelength or frequency. For example, what we consider as red is light that has approximately 780 - 620 nm wavelength (Christie, 2001, p. 24).

When light interacts with molecules, the molecules absorb the energy from that particular light. This energy can do something to the molecule. For example, certain wavelengths can make molecules vibrate, make the bonds rotate, or make the electrons within the molecule become more energetic. Certain molecules can only absorb certain energies. (Argonne National Laboratory, 2005).



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Originally published in: New Cloth Market, July-2010