Fabric defect · Finishing - Bow and skew in woven and knit fabric

Cotton Incorporated's defect glossary describes bow as yarns that "lie in an arc across the width of the fabric", the filling in wovens and the courses in knits. Its entry for bias, the slant, covers filling off-square to the warp and courses off-square to the wales, and it files both as major finishing defects ¹. Cotton Incorporated's grading guide adds that the purchaser and the supplier must agree on the list of defects used in grading and on their severity ².

Goldberg describes bow as filling that strays from an "exact straight-line or right-angle relationship to the warp yarns, producing a distorted or bowed effect from selvage to selvage" ³. A U.S. federal glossary lists bias filling and bowed filling together as "cloth in which the filling yarn does not run at right angle to the warp" ⁴.

For knits, a U.S. military glossary defines bowing as "a horizontal arc across the width of the fabric" where colored or raised rib structures have been stretched out of a straight line, and skewing as a line that is straight "but not perpendicular to the selvage" ⁵. Cotton Incorporated defines skew in knits as wales and courses displaced from their right angle, and notes that torque, spirality, bias and shear distortion are often used for the same thing ⁶.

Bow runs across the width from selvage to selvage ³. Skew is a straight line across the fabric that is not at right angles to the selvage ⁵.

In open-width knits slit on a needle-out line, a gap in the wales knitted with one or more needles left out, the wales come out straight and the distortion shows as skewed courses ⁶.

ASTM D3882-08(2025) is the standard test method for bow and skew in woven and knitted fabrics ⁸. For skew that appears after washing there is AATCC TM179-2025, a test method for skew change in fabrics after home laundering ⁹.

Cotton Incorporated gives skew in knits as a percentage or as an angle in degrees ⁶. One buyer manual, which follows the 4-point system of ASTM D5430, treats skew as a continuous defect, with up to 4 points for each yard or metre that has it ¹⁰. Cotton Incorporated's grading guide lets the purchaser and the supplier agree how large a fabric characteristic can be before it counts as a defect ², so agree a tolerance for bow and skew with your buyer.

Goldberg describes women's rayon slips whose panels came out uneven in length after sewing. Several finished pieces had been framed slightly on a bias, or off square, and once cut, the panels straightened out as they were sewn. It was a finishing defect, and the dyer corrected it when told ³.

In Cotton Incorporated's trials on single jersey, dyed goods that were straightened during drying skewed as much as greige goods, and finishing the fabric with the skew already let out worked better than straightening it ⁶.