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.
Hackling Yield Allowance
Process Baseline
Industrial processing tolerances define the acceptable weight loss when raw agricultural fibers undergo mechanical refinement. For linen spinning mills, the hackling yield allowance establishes the standard percentage of long flax fiber expected from the combing and hackling of scutched flax. This benchmark accounts for the removal of short fibers, dust, and non-fibrous shives during processing.
Industrial Calculation
Mechanical combing lines separate the valuable long line fibers from the short tow fibers and coarse waste. Since raw flax contains varying amounts of moisture and wooden residues, the actual yield fluctuates with each batch. The mill compares the recovered fiber weight against the hackling yield allowance to evaluate the efficiency of the combing department and the quality of the raw material.
When the yield falls below the threshold, the processing parameters must be adjusted. This action maintains yarn quality while monitoring fiber waste.
Contractual Settlement
Yarn contracts incorporate these yield expectations into the pricing agreements between the fiber merchant and the spinning mill. If the actual fiber recovery rate is lower than the hackling yield allowance, the mill may claim a financial adjustment from the supplier. This calculation prevents mills from bearing the entire cost of low-quality scutched flax.