Dyes and Pigments

Dyes are dissolved in a solution and impart their color by staining or being absorbed. What makes one organic source a dye and another not depends on a particular groups of atoms called chromophores. Chromophores include the azo group, thio group, nitroso group, carbonyl group, nitro group, and azoxy group. Other groups of atoms called auxochromes donate or accept electrons and attach to the dye molecule, enhance the color and increase solubility. Auxochrome groups include amino, hydroxyl, sulfonic, and substituted amino groups.

Other than chemical structure, dyes are classified by their dyeing properties. There are a great number of dyes and a greater number of fibers and materials that incorporate colorants in their manufacture. Certain dyes are used for specific materials depending on the chemical properties of the dye and the physical properties of the material to be dyed, or dyeing properties. Dyeing properties are categorized as basic or cationic, acid and premetalized, chrome and mordant, direct, sulfur, disperse, vat, azoic, and reactive dyes.