Yield Measurement
Industrial laboratory testing uses a gravimetric measurement of non-cellulosic matter removed during alkaline treatment of flax fibres. This evaluation determines the chemical extraction loss by recording the weight difference of a dried sample before and after boiling in a standardized sodium hydroxide solution. The result indicates the proportion of hemicellulose and pectins that will be dissolved during wet processing.
Mill records use this metric to adjust boiled weight expectations. The standard protocols define a maximum acceptable loss threshold of twelve percent for long flax fibres destined for high-grade weft yarns. If the value exceeds this limit, the lot is downgraded to coarser counts.
Process Mechanism
Alkaline solutions dissolve the binding elements that hold individual ultimate fibres together in the bast bundle. During this reaction, the chemical extraction loss occurs as the pectins in the middle lamella break down, freeing the pure cellulose fibres for spinning. Control of the temperature and concentration prevents the degradation of the crystalline cellulose.
Over-extraction can weaken the fiber.
Spinning Impact
High extraction losses during the boiling stage reduce the final yarn yield and alter the drafting behaviour of the roving. Spinners adjust the draft ratio on wet spinning frames to compensate for the reduced bulk of the treated roving. When the chemical extraction loss exceeds the mill’s baseline limit, the finer fibres tend to cluster, causing draft failures.
Consistent extraction maintains yarn uniformity.
