Fabric defect · Yarn - Knots in yarn and fabric

ConductVision Textile is designed to flag each defect with its place on the roll, its size, its points and a still image. Your inspector names the defect and confirms or dismisses it.

On the defect map in the roll report, a knot is a spot.

A U.S. federal glossary of fabric imperfections lists the knot, in both the filling and the warp, as "self-descriptive," among imperfections that "cause places in the cloth to be thicker than normal" ¹. The military glossary of knitting imperfections also calls the knot self-descriptive ².

Ends are joined in winding, the last step of yarn production, where small spinning bobbins are wound onto a large package. The yarn breaks at weak places and is cut where faults are cleared, and "it is necessary to continue the winding process by splicing or knotting the broken or cut yarn ends" ³. A splice joins the ends by mingling their fibers instead, "so that the joint is not significantly different in appearance and mechanical properties with respect to the parent yarn," though the look of splices can be a quality issue too ³.

Goldberg's 1950 casebook counts knots among the costs of yarn that breaks too often: frequent end breakage degrades woven goods "due to excessive knots" ⁴. Some knots also hold dirt. In one case a dark spot in finished fabric "was found to be a dirty warp knot which resisted cleaning during normal wet processing of the fabric" ⁴.

A knot is a spot on one yarn: a warp end or a pick in woven fabric. A knot in the filling can also mark where the yarn changes. Goldberg describes filling bands that "may show changes at knots within the same filling package," and one light band that "began at a knot and ended at a shuttle change," woven from 32/1 yarn instead of the 50/1 specified ⁴. A dirty warp knot shows as a dark spot in the finished fabric ⁴.

Cotton Incorporated's grading guide lists knots among isolated defects and counts every defect visible at normal inspection speed from one yard or one metre. It also lets the purchaser and the supplier agree which small characteristics, where and how often, are not counted as defects ⁶. A knot that is counted is small, so it falls in the lowest band of the 4-point scale, up to 3 inches, and gets 1 point ⁷.

For military contract cloth, U.S. specifications score knots against a reference scale instead. A 2012 cloth specification scores only knots that exceed a set level on the scale, at 4 points for each yard in which they occur ⁸. A 2019 military standard sets one level for dress uniform cloth and another for combat uniform cloth ⁹.