Fabric defect · Yarn - Neps and white specks in 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, neps and white specks are scattered spots.

Goldberg's 1950 glossary defines neps as "small bunches of tangled fibers generally observed in cotton yarns," and puts them down to poor cleaning or carding or to immature cotton fibers ¹. A U.S. federal glossary lists neps as "all definite fiber tangles" and neppiness as "a speckled condition of the cloth characterized by a number of neps" ². Cotton Incorporated calls a fabric neppy when an excessive amount of neps, small tangles or knots of fiber, appears on its surface ³.

White specks are neps that show after dyeing. USDA researchers describe them as small clusters of immature fibers that "appear as small white flecks on dyed fabrics," on woven and knitted fabric alike. Immature fibers have little secondary wall, so they are limp, flat and ribbon-like, and they tangle into neps. They keep very little dye, and their flat ribbons reflect light, so they show white on dark shades ⁴. A tangle of mature fiber still takes up dye; it is the tangles of very immature fiber that become "undyeable white-speck neps" ⁵.

Not every white speck is a nep. In one of Goldberg's cases, white specks in a gabardine came from bearing oil carrying traces of iron: in bleaching, the iron overbleached the yarn at each spot, which left it weaker and harder to dye. In filament fabric, broken filaments that ball up in the reed or drop wires can give the cloth a "neppy" look ¹.

Neps give the cloth a speckled look ². White specks show on the surface of a dark shade, or as uneven streaks in the fabric ⁴. In knitting, a nep can also leave a hole, by blocking a yarn guide or needle hook and breaking the yarn ⁸.

White specks are usually not seen until after dyeing ⁴. Goldberg notes that immature fibers do not come out in the weaving mill or the finishing plant, and show as undyed or lighter dyeing specks ¹.

In one of Goldberg's cases, a twill woven with a viscose rayon warp and a cotton filling showed light specks in the filling: neps of immature cotton ¹.

Cotton Incorporated's grading guide lists neppy fabric among isolated defects ⁹, and its defect glossary rates a neppy sateen as major ³.

Count a speck only if it shows at normal inspection speed from one yard or one metre ⁹. On the 4-point scale a defect up to 3 inches scores 1 point ¹⁰, and no linear yard or metre gets more than 4 points ¹¹. For a fabric that is neppy all over, buyer and supplier can agree on how large and how frequent a speck can be before it counts as a defect ⁹.

The cost comes late. As one USDA scientist put it, "the money is spent to dye the fabric, and it comes out spattered with white specks where the dye didn't take" ⁵.

A USDA scientist used a scanning electron microscope to confirm that white-speck neps come from underdeveloped cotton, which researchers had suspected since the 1940s. Under the microscope the neps showed as mats of ribbonlike material ⁵.

Bel and Von Hoven, citing a 1988 study, write that more than 90 percent of neps in finished fabric hold immature fiber ⁴. Their 2007 paper measured white specks in dyed fabric by count, average size and percentage white area, noting that no standard method existed. It found that the count alone does not fully account for how the dyed fabric looks ⁴.