How Flax Fibre Is Graded into Linen Yarn
Flax fibre grading determines spinnable yarn count, where hackling yield and fibre fineness dictate wet-spinning efficiency and landed cost per metre.
Capacitive Evenness
Mass Uniformity
Continuous measurement of mass variations per unit length in yarn relies on the electrical properties of the material as it passes through a testing field. In laboratory testing of spun flax, capacitive evenness represents the uniformity of the yarn across a given length. High variation in mass leads to thin places that break during weaving or thick spots that spoil fabric appearance.
Spinning mills rely on this metric to assess the stability of the drawing and drafting processes before winding yarn onto cones for delivery.
Measurement Protocol
The testing instrument passes the flax yarn between two parallel condenser plates, monitoring the electrical capacitance of the intervening gap. Because the dielectric constant of flax exceeds that of air, changes in yarn mass alter the voltage across the circuit. The system records these shifts continuously to calculate the coefficient of variation of yarn mass.
It is essential to control the ambient humidity in the testing room because moisture significantly affects the dielectric properties of linen. Dry flax has a much lower dielectric constant than wet flax, which means that unregulated humidity can distort the results and lead to incorrect yarn grades.
Process Evaluation
Spinning mills use the resulting data to identify defective drafting rollers or worn gears in the spinning frames. Frequent spikes in the mass diagram indicate periodic faults that must be addressed immediately to prevent downgrade reports from the weaving mill. The final buyer of the linen yarn sets a maximum coefficient of variation below which the lot is accepted.
Yarn Count and Evenness Checks before a Cone Lot Ships
Verify conditioned skein count, capacitive CVm evenness, and cone hardness against ISO tolerances to stop defective flax yarn before freight release.