Determination of Bast Fiber Fineness via Standardized Low-Pressure Air Permeability
Low-pressure air permeability tests determine bast fiber fineness by measuring specific surface area across standardized compressed fiber plugs under ISO 2370.
Metric Fineness Nm
Linear Density Definition
A numerical expression for the length per unit mass of yarn indicates how many meters of a single strand weigh one gram. This metric fineness nm functions as the primary standard for spinning output in Chinese flax operations. Higher values denote thinner yarn profiles, while lower figures correspond to coarser, heavier compositions.
Mills use this ratio to calibrate spinning frames for target yarn counts. Spinners verify compliance by reeling a specific length of product and weighing the resulting hank against a precision laboratory scale.
Production Classification
Quality control protocols rely on this ratio to sort spun lots during the finishing stage. Flax mills categorize their output based on these numerical counts before shipping material to weaving houses. Export documentation frequently includes these figures to verify that the batch matches the order specifications provided by the buyer.
A consistent yarn diameter prevents mechanical interference during the warping of linen looms. Mills prioritize batch uniformity to avoid tension failures throughout the weaving cycle.
Technical Application
Spinning technicians calculate the average diameter by dividing the total length in meters by the mass in grams. Deviations from the nominal count affect the cover factor and the hand feel of the finished textile. Buyers establish their own acceptance criteria for acceptable ranges of variance around the stated target, as natural fibre properties prevent absolute uniformity across long production runs.
A deviation exceeding five percent from the nominal count usually triggers a rejection of the entire lot during final inspection. Accurate calculation of this measurement maintains stability in fabric density across multiple loom shifts.