Fabric defect · Dyeing and printing - Shade variation in fabric: listing, ending and tailing

A U.S. federal glossary of fabric imperfections defines off shade as "not within established shade tolerance, shaded side to side, side to center or end to end" ¹. A U.S. military glossary of knitting imperfections uses nearly the same words ².

A 1985 EPA report on dyeing names the two forms that jig dyeing makes: "Ending is the variation in shade depth or hue from one end of the fabric to the other. Listing is the variation in shade from side-to-side." It calls both major defects ³. Cotton Incorporated's grading guide says the purchaser and the supplier must agree on the list of defects used in grading and on their severity ⁴. In pad-batch dyeing, Cotton Incorporated warns of "tailing of color throughout the fabric length" ⁵.

A shade change can also come from the yarn. In Cotton Incorporated's chambray example, with natural warp and dyed filling, the change "is due to filling shade variation." A loom bar is "a change of shade due to a build up of tension in the loom shuttle just before a filling change" ⁶.

The names say where to look: listing runs side to side and ending from one end of the fabric to the other ³, and off shade can also run from side to center ¹.

On a dye beam, the selvedges dye paler when the overlap is too large ³, and tailing runs through the fabric length ⁵. In winch dyeing, Goldberg found that "the shorter pieces were always lighter than the longer pieces" ⁷.

Between rolls, one buyer manual, which follows the 4-point system of ASTM D5430, treats roll to roll shading as a continuous defect, with up to 4 points for each yard or metre of the shipment that has it ⁹.

Shade can be checked roll by roll. The same manual has the inspector cut a swatch from every roll, compare the swatches within each lot in a lightbox kept in a dark place and shielded from ambient light, make a shade blanket where it applies, and separate and mark the rolls by shade group ⁹.

Finished rolls can also be sorted into shade groups. Cotton Incorporated describes grouping each roll of a khaki twill as slightly red, slightly yellow, slightly blue, slightly deep or slightly light, so each buyer gets as consistent a shade as possible. Sorting works well for high volumes of one shade on one fabric, and less well for small volumes over a wide range of shades ¹⁰.

The light matters. Two fabrics can match under one light and observer and differ under another, which is called metamerism ¹⁰. AATCC EP9 sets out how to assess color difference by eye ¹¹, and Cotton Incorporated notes that it gives no definite pass or fail tolerances for shade matching ¹⁰.

Instruments put a number on the difference. Cotton Incorporated points to AATCC test method 173 and its Delta E cmc as a measure of whether a trial is acceptable against its standard ¹⁰. ISO 105-J03 covers the calculation of color differences ¹². Cotton Incorporated strongly recommends judging color with instruments and by eye together ¹⁰.

Denim makers use a method called sequential dyeing, based on the idea that indigo yarn dyed at one time most closely matches the yarn dyed just before and just after it. Cotton Incorporated reports that it cuts color variation after garment washing much more than shade sorting alone ¹³.