Knitting
Spirality is residual yarn torque made visible. It shows up as twisted side seams after the first wash.
— %
Wale displacement over sample length
Spirality falls with plied or low-twist yarn, more feeders, and compacting. Measure after wash, not on greige, because greige readings flatter the fabric.
Spirality & Skewness Calculator — free, with the formula and a worked example, at Textile School.