Textile Structure
how cloth is put together
Series

Firmness — the series

6 essays on one idea, from the one that introduces it to the one that assumes the rest.
  1. What an interlacing costs. Each weave's interlacing count beside the closest it can be set in the same yarn. The two run opposite ways, because a thread that changes face often has to bend often and a bend takes room.

    Interlacings and firmness

    Every time a thread changes face it has to bend, and a bend takes room. That one sentence decides how densely a cloth can be set, how firm it feels, and why the two run in opposite directions.

    part 1 · weaves
  2. Every thread's interlacings in an eight-end satin stripe on a plain ground. An eight-end satin stripe on a plain ground on point paper, with a bar under every end and beside every pick for the share of its crossings at which it changes face. The warp's fewest is 0.25 a crossing against an average of 0.88, and the weft's 0.83 against 0.86; the draft's single firmness number is 0.87. What the bars cannot show is the friction at each crossing, which turns a count into a grip.

    A cloth slips at its least-interlaced thread

    A weave's firmness is quoted as one number, the interlacings per crossing averaged over the whole repeat. A cloth does not fail on average. A thread pulled through a seam or out of a cut edge is held by its own crossings, the grip is exponential in them, and the thread with fewest goes first. In every four-by-four draft but plain weave some thread interlaces twice a repeat — the fewest possible — whatever the average says, and a satin stripe on a plain ground averages 0.87 while its satin ends grip at a seventh of the average thread.

    part 2 · weaves
  3. The selvedge turns of a 2/2 twill, 4 ends wide, from the left. A strip of 2/2 twill 4 ends wide over 8 picks, the first thrown from the left, with the weft's turn between every pair of picks drawn at the edge it reaches. 0 of the 8 turns are caught, where the edge end is on the other face on the second pick, and 8 slip. Across all its edge placements the weave catches every turn at 8 of 16. What the drawing cannot show is how far a slipped loop travels, which the beat-up and the weft tension decide.

    A selvedge holds only where its edge end changes face

    A shuttle weft goes out on one pick and back on the next, and between them it turns round the end at the edge. The turn is caught only if that end is on the other face on the second pick; otherwise the loop has nothing to wrap and slides off. Plain weave catches every turn at every width. A 2/2 twill catches them at half its widths, and only if the first pick is thrown from the right side. A 3/1 twill, a hopsack and every satin catch them nowhere, and of the 22,874 four-by-four drafts, 9,636 cannot hold a selvedge at any width at all.

    part 3 · weaves
  4. The selvedge turns of a 2/2 basket, 8 ends wide, from the left. A strip of 2/2 basket 8 ends wide over 8 picks, the first thrown from the left, with the weft's turn between every pair of picks drawn at the edge it reaches. 4 of the 8 turns are caught, where the edge end is on the other face on the second pick, and 4 slip. Across all its edge placements the weave catches every turn at 0 of 16. What the drawing cannot show is how far a slipped loop travels, which the beat-up and the weft tension decide.

    A weave holds its selvedge with two of its own columns, or not at all

    A selvedge holds where its edge end changes face at every turn of the weft there, and the turns at one edge fall on alternate pick boundaries. So an end can hold the right edge only if its column changes face at every odd boundary, and the left edge only at every even one. Whether a weave can hold a selvedge is then whether its set of columns contains one of each kind, and nothing about its width matters. Two ends re-entered on the right shafts make 13,238 of the 22,874 four-by-four drafts hold at any width, where 3,262 did. The other 9,636 need a shaft of their own. A weave with an odd number of picks has no column of either kind, and never can.

    part 4 · weaves
  5. The tucked-in edges of a 2/2 twill, 8 ends wide. A strip of 2/2 twill 8 ends wide over 8 picks, woven with tucked-in edges: every pick is cut at both edges and each tail is laid back into the next shed, so between every pair of picks there is a turn at both edges. 8 of the 16 tucked turns are caught, where the edge end is on the other face in the next shed, and 8 are not. Across all its edge placements the weave catches every tucked turn at 0 of 16. What the drawing cannot show is the tail itself, which lies alongside the next pick for the tuck's length and doubles the weft there.

    A tucked-in edge asks every weave the odd repeat's question

    A shuttle weft turns at one edge per pick, alternately, and that alternation is what let a 2/2 twill hold both selvedges with two ends re-entered on its own shafts. A rapier or air-jet loom cuts every pick at both edges and tucks both tails into the next shed, so every boundary between picks is a turn at both edges — the question an odd repeat always asked. Only a plain column answers it. Of the 22,874 four-by-four drafts, 10,382 can still hold their edges on their own shafts, against 13,238 under a shuttle; the 2/2 twill is among the 2,856 lost. And the tucked zone carries two picks in every shed, which lies flat only below between a half and two thirds of a weave's maximum pick density.

    part 5 · weaves
  6. One warp feed, in the body and in a tucked zone of plain weave. A section along one warp end of 20 tex cotton, in plain weave woven at 70 per cent of its maximum pick density, in the body of the cloth and in the tucked zone with two picks to a shed. Both ends are fed the same length per pick, so the zone's end rises only 0.124 mm against the body's 0.161 mm, and the weft takes up the difference. The cloth is 0.341 mm thick in the body and 0.377 mm in the zone, 11 per cent thicker. The climb between crossings is drawn smooth rather than as the model's arcs and tangent.

    A tucked edge stands proud because its warp goes straight

    A tucked zone holds two picks in every shed, and the obvious account is that the pairs run out of room and bulge. The loom says otherwise: the warp is let off as one sheet and the cloth taken up at one speed, so the zone's ends have only the body's length to spend. They rise less. The weft takes up the height, so the edge is proud well before the pairs stop fitting, and they stand up well after the count says they must.

    part 6 · weaves

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