Dew-Retted Heilongjiang Flax against Imported Water-Retted Bales
Dew-retted Heilongjiang flax provides cost savings for medium counts, while imported water-retted bales deliver the fineness needed for yarn counts above Nm 50.
ISO 2370 Air-Flow Permeametry
Fiber Porosity
Air permeability testing governs the evaluation of raw flax fibers before wet spinning operations begin inside Chinese textile mills. ISO 2370 Air-Flow Permeametry measures the specific surface area and fineness of loose bast fibers by forcing a regulated stream of compressed air through a compacted plug of a known mass. Technicians determine fiber maturity and fineness from the resulting pressure drop across the porous bed, which correlates directly with spinning consistency.
Bast preparation lines rely on this measurement to sort raw material lots into appropriate count categories before carding and drafting occur. Mill quality certificates record these permeability values alongside moisture regain percentages to verify lot uniformity for buyers.
Resistance Verification
Operator technique dictates the accuracy of airflow measurements during routine testing cycles within the preparation room. Sample preparation requires precise weighing of conditioned flax fibers to establish the exact bulk density inside the perforated test cylinder. Plungers compress the loose mass to a predetermined volume, creating a uniform porous bed that prevents air channeling along internal walls.
Air pressure regulators maintain a constant volumetric flow rate while manometers register the steady-state differential pressure across the sample plug. Calibration blocks verify sensor accuracy daily against reference plugs of known permeability before production testing resumes.
Specification Thresholds
Fiber fineness measurements separate acceptable spinning lots from material destined for coarser yarn counts or alternative industrial applications. Buyers specify strict air flow resistance ranges in purchase contracts to ensure predictable drafting behavior on ring frames. Exceeding upper permeability limits indicates immature or coarse flax that causes uneven yarn drafting and excessive breakage rates during spinning.
Falling below lower thresholds points to over-retted or damaged fibers that lack sufficient tensile strength for fine linen production. Final export declarations incorporate these verified grading parameters to satisfy commercial quality guarantees agreed upon by processors and international merchants.