Raw Cotton Foreign Matter Classification and Ginning Extractions
Foreign matter extraction balances trash reduction against fiber damage, requiring Shirley analyzer and AFIS testing to price true clean lint yield.
Bark Strings
Contaminant Nature
Fibrous impurities in processed cotton lint consist of long, thin strips of inner bark peeled from the cotton plant during mechanical harvesting. These raw fibres are often tangled with bark strings that remain stubbornly attached after primary ginning stages. This type of cotton contamination represents a major grade reduction at the classing office.
Ginning Source
Aggressive cleaning during ginning fails to remove these fibrous contaminants because they resemble the cotton fibers themselves in size and weight. While normal plant trash is brittle and shatters, bark strings are strong and flexible, resisting mechanical separation. They are generated when cotton harvesting machines strip lint from plants under dry, brittle conditions.
Processing Defect
Yarn manufacturing processes suffer significant disruptions from the presence of these flexible plant skin remnants. Spun yarns develop frequent breaks and thin places, leading to reduced knitting efficiency. The contamination causes uneven dyeing since bark does not absorb colorants at the same rate as pure cellulose.
Testing Threshold
Visual inspection remains the primary method for identifying this specific plant impurity in ginned cotton. High volume instrument systems can classify the general trash content, but manual grading detects the elongated shapes that indicate bark strings. Standard classifications penalize the cotton bale by dropping its color or leaf grade by one or more levels.
This penalty directly reduces the market value of the fiber shipment, warning spinners of potential yarn breakage risks.