Surface Evaluation
An optoelectronic measurement quantifies the total length of protruding fibre ends per unit length of yarn to assess surface hairiness. In linen spinning mills, the Uster hairiness index measures the cumulative length of flax fibres extending beyond the yarn core. Quality logs record these indices.
Spinning Performance
High hairiness leads to excessive friction, warp breakage during weaving, and an untidy fabric appearance. By analyzing the Uster hairiness index, spin managers identify spindle wear or inadequate fiber lubrication in the wet-spinning frame. Because flax fibres are stiffer than cotton, maintaining low hairiness is critical for producing smooth yarns suitable for high-grade linen.
Technicians adjust the draft settings and traveler weights based on these indices to keep hairiness within acceptable parameters, ensuring smooth and uniform yarn delivery for subsequent warping.
Quality Standard
The buyer’s contract specifies the maximum allowable hairiness index for each yarn count to ensure yarn weaveability and fabric clarity. These measurements are archived in the spinning mill’s laboratory system and printed on the test report accompanying each shipped yarn lot. Spun yarn that exceeds these hairiness limits is rejected or downgraded to weft-only use to prevent weaving defects.
This optical assessment provides a reliable metric of yarn quality for both the mill and the weaver.
