Fabric defect · Holes, threads and stains - Oil stains and grease spots on fabric: causes and how they count

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, an oil stain is a spot, and an oily yarn is a line along or across the roll.

Cotton Incorporated's defect glossary describes oil spots as "deposits of oil that have fallen onto the fabric from some processing step," "typically round or tear drop in shape," though "they can also have an irregular shape" ¹. In its examples, a soiled filling is "the result of a drop of dirty oil on a bobbin of filling," and a soiled end "apparently had grease spun into it during the spinning operation" ¹.

Not every drop of oil becomes a defect: Goldberg notes that contamination removed in normal scouring never comes to attention ².

Ultraviolet light makes mineral oil easier to see. Goldberg lists mineral oils among the substances an ultraviolet lamp can show ², and Cotton Incorporated notes that "fabrics with streaks that exhibit glow suggest improper preparation" ³.

Cotton Incorporated lists a soiled filling as a weft line, across the fabric, and a soiled end as a warp line, along it ¹. In knit fabric, oil from the needle tricks makes oil lines that "appear in the fabric, in the lengthwise direction, even after dyeing" ⁵. In one of Goldberg's cases, oil pads beside the selvedges left dark sections about 4 inches wide along each selvedge ².

A spot's look alone may not name its source. Goldberg traced black spots in one fabric to paint on cotton-bale straps, notes that similar black stains had been traced to roof leaks or belt dressing, and warns that "only a chemical analysis can be relied upon to trace such stains to their true source" ².

Cotton Incorporated's defect glossary rates one oil spot example minor and another major, and its soiled filling and soiled end examples major ¹. Its grading guide lists oil spots among isolated defects, and notes that a minor defect for one end use may be a major for another ⁷.

On the 4-point scale a spot scores 1 point up to 3 inches, 2 points over 3 up to 6 inches, 3 points over 6 up to 9 inches and 4 points over 9 inches ⁸. A soiled filling that runs across the full width is longer than 9 inches, so it scores 4 points. An oily yarn that runs on along the roll is a running defect: one buyer manual, which follows the 4-point system of ASTM D5430, gives up to 4 points to each linear yard or metre it covers ⁹.

Goldberg's casebook shows how oil can outlast the scour. In a khaki twill with short, light warp streaks, ultraviolet light showed "a marked fluorescence in the streaky sections, indicating traces of unremoved mineral oil." The dirt had come out in dyeing and finishing, "but enough of the oil remained to act as a resist in dyeing" ².

In another case, stains around dirty yarns in greige dress goods had been spot-washed at the greige mill. Laboratory scouring seemed to clear them, "but upon dyeing, they reappeared as lighter colored resist spots." The goods had been held for more than 8 months, and the spot-washing compound had changed with age, so the spots were hard to remove unless the finisher kier-boiled the goods ².

A 2020 study of greige knit fabric from one circular knitting mill ranked stains fourth of the six defects it found by the inspection points they cost. In 1x1 rib, stains were one of the two most common defects. The authors trace stains to fiber and fluff in the needle tricks that stay soaked with oil, and to too much oiling ⁴.