Alkaline Extraction
Alkaline extraction represents the chemical dissolution loss occurring during the boiling stage of linen production in Chinese mills, where alkali solutions remove non-cellulose components from flax roving. Pectin, hemicellulose and lignin undergo hydrolytic degradation under elevated temperatures inside pressure kiers, transferring into the liquor stream and leaving the pure cellulose skeleton behind. Mills measure this mass reduction through gravimetric analysis of dried roving samples taken before and after the boil, recording the resulting percentage drop in the mill technical dossier.
Flax supply variations alter the extent of this material removal, because immature stems contain higher proportions of alkali soluble cementing gums than mature bast fibers do. Chemical dissolution loss determines the final yield of usable cellulose entering the spinning preparation lines, separating standard textile fiber from degraded pulp.
Liquor Ratio
Bath volume parameters dictate the kinetics of alkaline extraction during pressure boiling operations, establishing how much solute transfers from solid flax fibers into the liquid phase. Liquor ratios express the mass proportion of alkaline solution to dry fiber weight loaded into the kier, remaining strictly controlled within strict mill parameters to prevent uneven degradation across dense packing zones. High fluid volumes accelerate the mass transfer rate of hydrolyzed non-cellulose matter away from the roving, protecting individual strands from localized overexposure to caustic soda.
Excessive fluid movement also dilutes the chemical concentration prematurely, halting the dissolution process before complete removal of natural gums occurs. Operators adjust alkali concentrations based on initial fiber analysis certificates provided by flax merchants, balancing chemical consumption against desired weight reduction targets.
Export Tolerance
Buyer acceptance criteria establish strict boundaries for allowable mass loss during chemical processing, separating acceptable export quality woven linen from defective lots. Commercial contracts define allowable tolerances for fiber weight reduction, protecting downstream fabric integrity from the structural weakening caused by excessive dissolution. Fabric grades require uniform tensile strength across warp and weft directions, meaning that unmeasured variations in fiber boiling damage the weaving performance later in the production sequence.
Independent inspection laboratories verify final mass metrics against specifications printed in the letter of credit documentation before goods clear customs for international markets. Strict adherence to these contractual limits prevents trade disputes arising from unexpected material thinning during finishing stages.
