Determining Clean Scoured Yield and Commercial Moisture Regain in Raw Cotton Sourcing
Commercial raw cotton mass requires adjusting gross scale weight for official moisture regain and non-lint content under standardized oven-dry test protocols.
Trash Content Allowance
Purity Threshold
An agreed maximum percentage of non-fibre impurities allowed in a raw cotton bale or wool shipment ensures that buyers only pay for usable textile material. The trash content allowance accounts for natural plant parts, seed coats, dust, and shale that remain after initial harvesting and ginning. If the actual percentage exceeds this limit, the buyer is entitled to a price discount or can reject the shipment.
Having a clear standard prevent disputes between the raw material supplier and the spinning mill.
Commercial Pricing
When raw cotton is purchased, the weight of the shipment is adjusted based on the measured impurity levels. The trash content allowance is subtracted from the gross weight to determine the clean dry weight of the textile fibre being purchased. When the trash level is higher than the allowance, the price is reduced to cover the cost of cleaning the material and the loss of usable fibre weight.
This financial adjustment keeps the transaction fair and protects the profit margin of the spinning mill.
Mill Processing
Cleaning raw fibres with high impurity levels requires additional passes through the opening and blowroom machinery, which can damage the strands. When the trash content is high, it can clog the carding machines and cause yarn breakages during spinning. This increases production downtime and raises the labor cost per kilogram of yarn.
Testing Procedure
Laboratories use specialized instruments like the Shirley Analyser to separate the non-fibre waste from the pure lint in a representative sample. This test measures the exact weight of dust, leaf, and seed fragments compared to the initial sample weight. Comparing this result to the trash content allowance determines whether the shipment complies with the contract specifications.
The test is performed on samples from each shipment to ensure consistent quality control before the bales are fed into the production line. Routine checks protect the spinning mill from processing sub-standard material that would compromise the strength of the final spun yarn.