Examination of effects of contamination of naturally white cotton with naturally colored cottons

Dean Ethridge, Gustavo Abdalah, William Cole


The commercial availability of naturally colored cottons has inevitably raised concerns about contamination of naturally white cotton. Until recent years, the objective of cotton breeding programs has been to prevent the genes that impart Nnan-white" shades to cotton fibers from being expressed in the commercial varieties produced. But these natural colors are now being marketed as specialty fibers that, up to now, go through the textile manufacturing process without being dyed. The colors expressed within the existing gene pool of global cotto ns are limited to brown, red and green spectra; shades may be varied by blending these fibers with naturally white cottons and with other colored cottons. It is well known that the cottons designated as being naturally white are not uniform. The Upland cottons from different production areas and regions have different degrees of "yellow_ ness" and the extra long staple (£LS) cottons are much more "'creamy" (i.e., much less "white") than most Upland varieties of cotton. Even slight variations in cotton color can have detrimental effects on the results of dyeing. Such problems are a constant challenge to quality con trol in the dyeing and finishing processes of textile manufacturing. Bleaching is the primary technique for enabling a uniformity of color and shading that is adequate for discriminating consumers. It cannot be assumed that a typical bleaching process will overcome the effects of contamination by naturally colored cottons. n,erefore, it is no surprise that responsible leaders in the cotton/ textile complex are concer ned about this 2 risk. The coexistence of naturally colored cottons with the naturally white varieties brings, even with effec th~ regulatory controls, a possibility of minor contamination that worries the textile manufacturing sector and the cotton production sector that serves it. This study examines the color effects of known (quantified) contamination of naturally white cotton with existing varieties of naturally colored cottons, using bleaching procedures that are considered to be moderate in the U.S. textile industry. Results provide (1) perspective about the risk inherent in allowing naturally colored cotton varieties to be grown along with the naturally white cotton varieties, and (2) guidance to the textile industry in processing naturally white cotton that is contaminated with naturally colored cottons.

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