After the lint is baled at the gin, samples taken from each bale are classed according to fiber strength, length, length uniformity, color, non-fiber content and fineness using high volume instrumentation (HVI) and the aid of an expert called a Classer. Scientific quality control checks are made periodically to ensure that instrument and Classer accuracy is maintained.
Cotton of a given variety produces fibers of approximately the same length. Since the fibers may vary within a bale, length uniformity allows a determination of the variability within that bale.
Other quality factors also are important. The fiber’s fineness is important for determining the type of yarns that can be made from the fiber—the finer the cotton fibers, the finer the yarns. Color or brightness of the fibers also is important. Cotton that is very white generally is of higher value than cottons whose color may have yellowed with exposure to elements before harvesting. Cotton, being a biological product, typically contains particles of cotton leaves called trash. The amount of trash also influences the cotton’s value since the textile mill must remove trash before processing. The fiber’s strength also is an important measurement that ultimately influences the fabrics made from these fibers. The U.S. Department of Agriculture (USDA) establishes classing standards in cooperation with the entire cotton industry.