Ch. 9: Dyes

The dye industry goes back several thousand years. The early dies were obtained mainly through plants roots, leaves, bark or berries. Most of the dies produced did not adhere permanently to untreated fibers and therefore fabrics had to be treated with mordants, which are compounds designed to help fix the color to the textile fiber. While many dies in c.3000 BCE were highly treasured and very expensive there was several problems with the dyes themselves. The dyes were difficult to obtain, color range was limited, and the colors were not strong, but faded quickly to dull colors in the sunlight. Dyes are organic compounds that are Incorporated into the fibers of textiles. The molecular structure of these compounds allows the absorption of certain wavelengths of light from the visible structure. The relationship between the wavelength absorbed and the chemical structure depends on the presence of double bond alternating with single bonds. The Primary colors, Blue, Red, and Yellow all come from either Indigoton, alizarin, or crocetin respectivly. (Le Couteur & Burreson 162-180)

Blue dyes were especially valued because, compared with red or yellow, blue shades were not as common in plants. The blue dye was harvested from the Indigofera tinctoria. The fresh leaves of this indigo producing plant are at first colorless, But after fermentation under alkaline conditions followed by oxidation, the blue color appears. Indican, indigoton's parent molecule contains an attached glucose unit. Fermentation of Indican splits off the glucose unit which produces the indoxol/indigoton molecule. Indican is initially colorless, but after it goes through the fermentation process and turns into indiogoton, the color changes to blue. The same is true for alizarin, and crocetin. Initially, they are colorless, but after a chemical reaction the gain their color. (Le Couteur & Burreson 162-180)


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