Reconciling Moisture Regain against Chemical Extraction Losses in Yarn Audits
Reconciling yarn commercial weight requires subtracting extracted chemical finish mass from oven-dry weight before applying standard moisture regain factors.
Paraffin Wax Residue
Yarn Lubrication
Spun linen yarn requires a thin coating of lubricant to reduce friction against the metal needles of high-speed knitting or weaving machines. The remaining paraffin wax residue must be measured to ensure that the yarn holds enough lubricant without compromising subsequent dyeing stages. This measurement occurs during the yarn testing stage and is recorded in the yarn certificate of analysis.
Chemical Extraction
To determine the amount of lubricant on the yarn, the laboratory extracts the paraffin wax residue using a solvent in a Soxhlet apparatus. The solvent dissolves the wax and is then evaporated, leaving the dry residue behind to be weighed. If the residual wax concentration is too high, it will block dye molecules from entering the linen fibers, causing uneven color or splotches in the finished fabric.
If it is too low, yarn friction increases during weaving, leading to frequent breaks and machine stoppages.
Weaving Performance
Monitoring the paraffin wax residue allows the mill to calibrate the waxing disks on the winding machines. The optimal wax percentage ranges between one tenth and three tenths of a percent of the total yarn mass. This narrow margin is essential for maintaining both yarn slip and fabric dyeability.