Fabric defect · Knit fabric - Spirality in knit fabric: why it twists

In knit fabric the wales should run at right angles to the courses. When they do not, the fabric skews to the right or the left, which Badr and colleagues call "fabric spirality", often seen in cotton single jersey ¹. Cotton Incorporated notes that torque, spirality, bias and shear distortion are often used for the same thing ².

Badr and colleagues treat spirality as a key part of the dimensional stability of weft knits, that is, whether they keep their shape and size. They note that such instability shows most in knit garments in use and after repeated washing and drying ¹. A university module calls spirality of more than 5 degrees clearly visible and objectionable, and notes that it generally grows after washing as the yarn's leftover torque relaxes ³.

Spirality is not a spot or a line. All the loops in the fabric take up a slant ³.

In a knitted tube, skew from the yarn makes the wales spiral around the tube at a steep angle, while the courses generally stay level ². For open-width finishing, a knitter may leave one or several adjacent needles out of the cylinder, which leaves a gap in the wales: the needle-out line, where the tube is slit ². Slit there and finished open width, the wales come out straight and the slant moves into the courses ².

ISO 16322-2:2021 measures spirality after laundering in woven and knitted fabrics ⁵. AATCC TM179-2025 measures skew change after home laundering ⁶, and ASTM D3882-08(2025) is the test method for bow and skew in woven and knitted fabrics ⁷.

Cotton Incorporated gives skew as a percentage or as an angle in degrees ². In its trials, a square was marked on the fabric before washing and tumble drying, and after five wash and dry cycles the square was measured for percent skew ².

In Cotton Incorporated's trials, alternating S and Z twist yarns on the feeders greatly reduced skew, because the courses of one twist lean right and the other left, and they cancel out ². Balanced plied yarns have been used for years to make torque-free fabric ².

The same trials found that a tighter stitch gave less skew, and that dyed goods straightened during drying skewed as much as the greige goods. Resin finishing gave the best control of skew ².

A 2008 study of the causes concludes that fabric from filament yarn spirals less than fabric from spun yarn. Among spun yarns, friction-spun yarn gave the most spirality, then ring-spun, open-end and air-jet yarn ¹.