Fibre Characteristic
Fibre measurements that show two distinct frequency peaks represent a split in the population of plant tissue bundles. A bimodal bast distribution arises when primary and secondary flax bundles are harvested together, or when incomplete decortication leaves coarse clusters alongside fine single fibres. This non-uniformity impairs the drawing process during preparation and requires adjustment of the drafting rollers to prevent drafting waves.
Processing Impact
Sliver preparation in spinning mills relies on predictable fibre lengths to maintain tension and draft ratios. Mill logs record how a bimodal bast distribution affects the draw frame where short fibres float and long fibres break. This behavior increases the rate of thick and thin places in the drawn sliver, forcing operators to run the machinery at lower velocities.
Acceptance Criterion
Quality certificates for combed sliver detail the length distribution to ensure the material meets yarn specifications before spinning begins. Spinners reject shipments where the bimodal bast distribution exceeds five percent of the total sample weight because it causes frequent yarn breakages on the ring frames. Spun yarn undergoes testing for tenacity and mass variation on automated capacitive testers.
When the dual peaks in the fibre length remain uncontrolled, the resulting yarn displays low elongation and high hairiness, causing the material to fail the export quality threshold for fine warp yarns. Maintaining a narrow single-peak profile prevents these mechanical failures and secures the yarn strength needed for high-speed weaving.
