Textile Structure
how cloth is put together
Series

Dyeing — the series

4 essays on one idea, from the one that introduces it to the one that assumes the rest.
  1. One dip, two yarns: the same depth of dye. The cross-section of two cotton yarns drawn to one scale after a 20-second dip in a bath whose dye the fibres take up 10 times as strongly as the liquor holds it, each fibre shaded by the dye that reached its distance from the surface. 20 tex: 118 fibres, 167.1 µm across, dyed to 19.7 µm — 24% of its radius and 42% of its section; 74 tex: 435 fibres, 321.4 µm across, dyed to 18.2 µm — 11% of its radius and 21% of its section. The depth in micrometres is the same for both because a dip dyes a depth; the share is not, because the coarse yarn has more section behind the same ring. The fibres are drawn on a lattice and the count is computed; the affinity is an assumed value and every depth moves with its square root.

    A dip dyes a depth, not a share

    A yarn dyed after spinning is a cylinder the dye has to diffuse into through the liquor between its fibres, and the fibres slow it by taking dye out of the liquor as it passes. A twenty-second dip therefore dyes to a depth, some tens of micrometres, and that depth is almost the same in a fine yarn and a coarse one. So the same dip that colours two fifths of a shirting yarn's section colours a fifth of a denim warp's; eight dips deepen the shade eightfold and leave the ring where it was; and a tighter yarn rings more thinly, because packing closes the pores faster than it narrows the yarn.

    part 1 · finishing
  2. A ring-dyed yarn worn flat, step by step. One cotton yarn dyed in a ring 20% of its radius deep, cut flat from the top by an abrader to five depths: worn to 10% of the radius, 1.9% of the yarn has gone and 0% of its width is white; worn to 20% of the radius, 5.2% of the yarn has gone and 0% of its width is white; worn to 30% of the radius, 9.4% of the yarn has gone and 39% of its width is white; worn to 45% of the radius, 16.8% of the yarn has gone and 58% of its width is white; worn to 70% of the radius, 31.2% of the yarn has gone and 74% of its width is white. The olive line is the cut face and the red bar above it is the part of the face that has reached the undyed core. Nothing is white until the cut passes the ring, and then the white arrives quickly. The section is a circle and the ring's edge is drawn sharp; a real yarn is neither, and its fibres migrate, so the core's edge is ragged.

    A ring-dyed yarn whitens all at once

    Rub a yarn that is dyed in a ring, and for a while nothing shows. The abrader takes off blue fibre, the cut face is blue, and the yarn looks as it did. Then the cut reaches the undyed core, and the white arrives with a vertical tangent, as the square root of the wear past the ring: one per cent of the radius more and an eighth of the width is white. A ring a fifth of the radius deep hides the first five per cent of the yarn's loss and shows half its width white by thirteen. A yarn dyed through never shows white at all. Denim's high-contrast fading is that threshold, drawn over a cloth.

    part 2 · finishing
  3. Two ring-dyed faces worn to 5% of their mass. The faces of 3/1 twill and plain woven from the same ring-dyed 50 tex warp and undyed weft, at 24 ends and 16 picks a centimetre, each worn flat by an abrader until 5% of its thread has gone, drawn over two repeats: dyed warp dark, exposed undyed core red, weft pale, holes blank; the 3/1 twill shows 30% of its covered face as exposed core; the plain shows 17% of its covered face as exposed core. A float's crown is a line and is cut along its length; a plain weave's crowns are points and are cut through as small patches. The geometry is the plain-weave solution for these counts and setts with the floats drawn over it, which is more open than a real denim; what the figure cannot show is a denim at its real density.

    A float fades late and hard, a crossing early and soft

    Wear a ring-dyed face flat and the white arrives where the cut first passes the ring at a crown, which is the same depth for every weave. What differs is how much cloth has gone by then and how fast the white spreads after. A plain weave's crowns are points, cut through by almost nothing: it shows white after a fifth of a per cent of its thread and never shows much. A twill's floats are lines, cut along their length: a 3/1 twill shows nothing until more than one per cent has gone, then whitens faster than any plain weave can, 39 per cent of its face by a tenth worn against plain's 24. Denim's high-contrast fade is a float's; chambray's soft one is a crossing's.

    part 3 · finishing
  4. A crease along a 3/1 twill's floats and one across them, worn alike. A strip of 3/1 twill of ring-dyed 50 tex warp and undyed weft folded round a 2 mm radius, the ridge drawn across the page as a dashed line, worn by a flat abrader 50 µm into the ridge: above, with the ridge running along the warp and its floats; below, running across them. Dyed warp dark, bared core red, weft pale. crease along the warp: 83% of the crease's length white, in runs 1.72 mm long on average, the longest 2.08 mm; crease across the warp: 31% of the crease's length white, in runs 0.15 mm long on average, the longest 0.17 mm. On a twill the white along the warp lies in lines as long as a float's crown, across it in dashes one end wide; on a plain weave, with no floats, both are short. What the drawing cannot show is the fibre a real crease tears loose, which blurs every edge here.

    A crease across a twill fades in dashes

    A garment is not worn flat. It is worn along its folds, where the ridge of a crease stands out and is rubbed first, so the fade follows the crease. On a ring-dyed 3/1 twill a crease running along the warp bares the cores of the floats that lie under its ridge, float by float, and reads as a white line broken only where each float dives: at fifty micrometres of wear, 83 per cent of its length is white, in runs of 1.7 millimetres. The same crease across the warp meets every float at one point and reads as a row of dots, 31 per cent white in dashes of 0.15 millimetres, one end wide. It bares much the same core. A plain weave's creases are dashes whichever way they run.

    part 4 · finishing

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