Classification Mechanics for Pure Linen Woven Fabrics under Heading 5309
Classification under HS Heading 5309 requires verifying an 85% clean dry flax mass fraction after stripping non-cellulosic sizing and applying standard regain.
Non-Cellulosic Finish Removal
Fabric Preparation
Pre-treatment of grey linen fabric involves the extraction of sizing agents and natural waxes to prepare the textile for subsequent dyeing. The process of non-cellulosic finish removal dissolves pectin, hemicellulose, and applied starches from the surface of the woven cloth. This operation is carried out in the continuous washing range of the finishing department, with chemical dosages documented on the batch processing sheet.
Thorough cleaning creates a highly absorbent surface that ensures uniform dye uptake during the coloring stage.
Desizing Treatment
Hot alkaline baths and enzyme solutions break down the starch-based sizes used to protect the warp yarns during weaving. In the execution of non-cellulosic finish removal, the concentration of sodium hydroxide is carefully measured to avoid damaging the underlying cellulose structure. Technicians monitor the bath temperature and the dwell time within the washing compartments to guarantee that all residues are fully suspended and rinsed away.
This step is necessary to prevent patchy dye absorption, which occurs when residual waxes act as a resist on the fabric surface. Removing these impurities also improves the soft drape and handle of the finished linen.
Chemical Verification
Incomplete extraction leads to uneven coloring and poor color fastness. Finishing mills run a droplet absorbency test on the treated fabric to confirm the success of the non-cellulosic finish removal process. A rapid water absorption time proves that the barrier has been eliminated.