Fiber Defect
Animal fibers containing a central hollow core of air cells are categorized as structurally deficient for premium yarn production. These structures, known as medullated fibers, occur frequently in coarse wool and specialty hair. They have different physical and optical properties compared to solid, healthy fibers.
Fabric Flaws
The presence of these hollow fibers reduces the strength and dyeability of finished yarns. Because the central medulla does not absorb dye in the same way as the solid cortex, these fibers remain pale after dyeing. This difference creates unsightly streaks on the surface of dyed fabrics, which spoils the appearance of fine apparel.
Additionally, the hollow core makes the fibers brittle and prone to crushing, which leads to premature wear in high-stress areas of garments.
Detection Method
Identifying these hollow structures involves examining the fibers under a microscope or using automated optical analyzers. The air-filled medulla appears as a dark line or channel running along the center of the fiber. Specialized liquid immersion tests can also reveal these channels by capitalizing on refractive index differences.
Quality Control
Wool processors set strict limits on the allowed percentage of these fibers in raw batches. Purchasing contracts often specify maximum thresholds to prevent yarn defects. Effective breed selection and flock management are the primary ways growers reduce the occurrence of these defective fibers in their clips.
