Percentage Metric
Mass balance fractions in bast fibre decortication quantify the proportion of short, tangled flax strands recovered during mechanical extraction relative to input straw mass or total fibre output. In scutching and hackling facilities, tow yield measures the generation of non-parallel short fibres separated from long line flax. Extraction efficiency indices evaluate raw material quality, distinguishing secondary short fibres used for coarse dry spinning from premium continuous line flax bundles.
The application of this calculation stops at the mechanical hackling boundary. Waste measurements do not track the combing noil extracted later during wet-spinning preparation or the carding waste accumulated during roving preparation.
Mechanical Extraction
Mechanical scutching turbines strike deseeded flax straw with rotating blades to fracture the brittle wooden shive and detach long bast bundles. Straw conditioning directly influences tow yield because excessively dry stems shatter under blade impacts, turning potential long line flax into broken tow fragments. Processing mills monitor scutching turbine speed and breaker roll clearances to control tow generation.
Quality technicians record daily scutching mass inputs against the output of scutched line flax and scutching tow, calculating the yield percentage on a daily shift tally sheet. A scutching run yielding fifteen percent tow alongside twenty percent long line indicates standard extraction efficiency for high-grade European dew-retted straw.
Commercial Valuation
Purchasing departments in spinning complexes track hackling tow yield to establish the real raw material cost per kilogram of wet-spun yarn. Long line flax commands up to three times the market price of hackling tow on international commodity markets. When scutching or hackling yields excessive tow, the financial balance sheet of the spinning mill suffers, prompting raw fibre supplier claims based on verified yield logs.
