Single Jersey Loop Instability and Yarn Twist Multiplier Control
Single jersey spirality is controlled by capping yarn twist multiplier below 3.5, optimizing loop tightness, and autoclaving to neutralize torsional torque.
Snarl Count
Torsional Index
Quantitative tally of helical kinks and spontaneous loops that develop along a slackened yarn length under zero mechanical tension measures yarn liveliness. Unbalanced residual torque generated during rotor, ring or friction spinning operations drives this spontaneous self-entanglement when yarn packages unwind without tension control. High twist factors, inadequate heat setting and uneven filament torque increase the snarl count across open yarn segments.
The measurement ceases to characterize the material once twist levels balance completely or when yarn undergoes chemical fixation that eliminates residual mechanical memory.
Kinematic Cause
High twist levels impart internal torsional stresses into single yarns by compressing helical fibres against one another around the core axis. When yarn tension decreases during downstream transfer, these stored mechanical energies release by twisting the yarn around itself to form double-helical kinks. The snarl count increases directly with higher twist multipliers and larger yarn diameters, complicating automated unspooling sequences.
Unwaxed or inadequately steamed yarns exhibit lively behavior, turning stable single strands into snarled masses during beam warping and circular knitting.
Testing Procedure
Standard laboratory assessments determine this metric using automated or manual twist-liveliness testing equipment governed by standards such as ISO 3344. Technicians draw a predetermined length of yarn from a package, apply a small initial tensioning weight, and gradually bring the two ends together along a calibrated horizontal rail. As the distance between package clamps closes, the yarn loops upon itself to dissipate internal torsional strain.
The number of complete twisted loops visible along the slack loop constitutes the registered count, identifying yarns that require additional autoclaving.
Weaving Impact
Excessive yarn liveliness causes severe stoppages on air-jet and rapier weaving looms by causing pick insertion failures. When filling yarns unwind from the accumulator at several thousand meters per minute, sudden deceleration triggers spontaneous snarl formation within the weft insertion channel. These snarled kinks catch on warp yarns within the shed, creating fabric defects such as tight picks, loops and short picks.
Yarn manufacturers apply vacuum autoclaving using saturated steam to relax internal twist stresses, bringing residual package liveliness down to acceptable commercial limits.