Scouring - Removal of Natural Impurities

Scouring removes natural non-cellulosic impurities from fibers improving absorbency, whiteness, and dye affinity. Cotton scouring—removing waxes (0.4-1.2%), pectins (0.4-1.2%), proteins (1.0-1.3%), mineral matter (0.7-1.6%), residual seed fragments creating hydrophilic surface. Process: alkaline treatment with sodium hydroxide (2-10 g/L NaOH, pH 11-13) at elevated temperature (90-100°C) for 30-120 min, optionally under pressure (kier boiling 130°C, 2 bar, 2-4 hours). Chemistry: saponification of wax esters (forming water-soluble soaps), hydrolysis of pectins (breaking down into soluble compounds), and dissolution/emulsification of fats. Additives: surfactants (anionic, nonionic 1-3 g/L improving wetting, emulsifying impurities), sequestering agents (preventing Ca²⁺/Mg²⁺ precipitation as insoluble salts), and hydrogen peroxide (5-10 g/L combined scouring-bleaching economizing process). Equipment: J-box/J-scour (continuous, fabric rope saturated with alkali, steamed in J-box 95-100°C, 30-90 min), open-width washing range (flat fabric), and batch processes (winch beck, jet dyeing machines for knits). Wool scouring—removing wool grease/lanolin (10-20% of greasy wool), suint (dried perspiration 2-5%), dirt (3-12%) using mild alkaline detergents (pH 8.5-9.5, 50-60°C, avoiding felting and fiber damage), recovering lanolin as valuable byproduct ($20-50/kg for cosmetic/pharmaceutical use). Synthetic fiber scouring—removing spin finish oils (0.3-1.5%), anti-static agents, production contaminants using neutral or mildly alkaline detergents (pH 7-9, 60-80°C). Assessment: water absorbency test (AATCC 79, fabric sinking time <5 seconds indicates adequate scouring), wettability (contact angle <90°, instant spreading), and residual wax/pectin analysis via extraction.