AATCC 179 — spirality in knitted fabric

What AATCC 179 measures

AATCC Test Method 179 measures the skew change in fabric or garments after home laundering. For knitted fabric it is the standard reference for spirality — wales leaning off vertical, which turns into garments that twist on the body.

The defect is commercially expensive because it is invisible at the point of sale and obvious after the first wash, which makes it a returns problem rather than an inspection problem.

Typical acceptance thresholds

These are the figures most commonly written into apparel specifications. Confirm against your own buyer contract, which is the only binding source.

Causes, ranked by how often they are responsible

1. Residual yarn torque — unbalanced twist in single yarn, the dominant cause
2. Single jersey construction — structurally prone; there is no opposing loop to balance the torque
3. Inadequate heat setting or compacting in finishing
4. Machine speed relative to take-down tension during knitting
5. Twist direction versus machine rotation — Z-twist yarn on some machine directions compounds the lean

Practical control measures

• Specify twist-balanced or plied yarn for critical programmes
• Consider a balanced structure — interlock and rib are far less prone than single jersey
• Apply appropriate heat setting; for cotton, compacting under controlled tension
• Keep finishing tension consistent, especially at the stenter
• Test after laundering, not before — greige measurement is not predictive

Related knit tests buyers ask for