Moisture Tolerance
Commercial contracts govern raw fibre purchases on dry mass adjusted by standard regain allowance, a permitted percentage added to bone-dry weight to account for ambient moisture absorbed during transport and storage. Hygroscopic materials such as cotton and wool continuously exchange water vapour with surrounding air, altering their mass independently of actual dry polymer content. Commercial transactions require a fixed reference baseline because natural humidity fluctuates constantly between loading ports and spinning mills.
Commercial weight equals bone-dry weight multiplied by one plus standard regain allowance divided by one hundred. Buyers and sellers settle invoices on this calculated mass rather than raw scale weight. Spinning mills reject consignments exceeding the specified moisture ceiling because excess water inflates purchase costs for dry fibre.
Calculation Boundary
Conditioning ovens determine bone-dry mass through high-temperature drying until successive weighings show constant mass. Technicians add the contractual moisture percentage to that dry mass to establish the legal billing weight. Variations occur when testing laboratories draw samples from exterior bales rather than core locations.
Core sampling prevents inaccurate moisture readings caused by surface drying during transit. Standard regain allowance stops applying once spinning preparation begins, because water content shifts during carding and drafting.
Hygroscopic Equilibrium
Natural polymers reach moisture equilibrium slowly when ambient relative humidity changes in spinning sheds. Atmospheric conditions inside processing plants alter moisture retention levels independently of established commercial limits. Relative humidity control systems stabilise room air to maintain consistent fibre handling properties during yarn formation.
Low moisture levels cause static electricity accumulation and high fibre breakage rates on high-speed ring frames. High moisture levels increase yarn friction and reduce production speeds across winding machinery.
Commercial Valuation
Purchasing departments establish raw material costs based on dry fibre mass rather than water weight. Financial settlements depend entirely on accurate regain application during yarn manufacturing contract disputes. Discrepancies between mill moisture meters and official laboratory certificates trigger commercial arbitration.
Standard regain allowance protects buyers against paying raw fibre prices for atmospheric water absorbed during ocean transport.
