Single Jersey Curling and the Finishing Sold as a Fix
Single jersey curl stems from unbalanced yarn torque and asymmetrical loop tension; durable flat performance demands structural yarn balancing rather than temporary resin finishes.
Torsional Strain
Rotational Stress
Mechanical forces describe the rotational twist and torque experienced by yarn during spinning, knitting, or weaving processes. This force, known as torsional strain, accumulates as the fibres are twisted together to form a yarn, and it remains locked within the yarn structure until it is relaxed. It is the primary cause of fabric spirality and skewing in finished knitwear.
Torque Release
Yarns under tension will naturally seek to untwist to release their stored energy, causing the yarn to curl or snarl. In torsional strain, this untwisting force can be neutralized through thermal setting or by pairing yarns of opposite twist directions. If left unmanaged, the torque will deform the knitted loops, leading to twisted seams.
Spirality Impact
Knit fabrics are especially vulnerable to the distorting effects of torque because the loops have more freedom to move than woven yarns. Under torsional strain, the individual loops tilt to one side, which causes the entire fabric to skew diagonally across the roll. This makes it impossible to align patterns or seams during garment cutting, leading to high waste rates and rejected shipments.
To prevent this, mills use twist-less or twist-balanced yarns to stabilize the fabric without relying on heavy chemical treatments.
Thermal Setting
Steam and heat treatments are applied to yarn packages to relax the internal stresses and set the twist before knitting. This process minimizes the torsional strain and ensures that the yarn remains stable during subsequent manufacturing steps. It represents the standard method for preparing high-twist yarns for circular knitting machines.