Textile Structure
how cloth is put together
The collection

Every essay — page 23

Page 23 of 23, continuing through the fields in the same order.

What cloth is Weaves Setting and geometry Knits and other structures Mechanics and drape Pattern and colour Compound and figured cloths After the loom Cloth doing a job

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Compound and figured cloths

Double cloth, pile, leno, and the loom that decides what can exist. Where a fabric stops being one binary matrix — a third thread system, a warp order that changes between picks — and where the integrity criterion runs out and friction takes over.

Where the weight on a shared leno easer comes to rest. The tension in the back span of each end of a leno pair — the length between its last heddle and the back rest, where an easing bar acts — at each fraction of the crossed shed, with one bar under both ends weighted at 1.0 N a pair, twice the warp's resting tension, so that it rests on its stop with the shed closed. The two back spans always sum to the weight. Closed, they share it equally. The partner, an ordinary end lying in the bottom of the shed, can take only 11 mm of the bar's travel before it goes slack, which it does at 37.5% of the opening; from there the crossing end's back span carries the whole 1.0 N. On a bar of its own, dashed, the same span stays at 0.50 N. What the chart cannot show is what the crossing end's other spans do with the extra tension, which the next views take up.

One weight under a leno pair ends on one end

A leno's crossing end wants about seventy millimetres eased to it at every crossed shed; its partner lies in the bottom of the shed as an ordinary end and wants none. One weighted bar under both is set where the closed shed shares its weight between them, but the partner can take only eleven millimetres before it hangs, and it is slack by three eighths of the shed. From there the crossing end carries the whole weight, twice the rest its own bar would hold it at, and its tightest span ends forty per cent over the working tension while the partner hangs thirteen centimetres behind the harness. No weight serves both, because a bar gives every end it carries one length.

6 figures · Leno A leno partner lifted by its doup's loop. The tension in each span of a leno's partner end at the full crossed shed, against how far the doup's loop lifts it above its own straight line 6 mm in front of its heddle on the doup's shaft. The partner is then three spans: fell to loop, loop to heddle, heddle to back rest. With the loop clear it is an ordinary end, 1.07 N in its front span. At a 4 mm lift the front span carries 1.48 N, +38% on the untouched partner, the span between loop and heddle 1.26 and the back span 1.00; with nothing gripping, dotted, all three would carry 1.12. At 8 mm the front span reaches 1.90 N. What the chart cannot show is how far a real loop lifts its partner, which the doup's standard decides and which is swept here rather than computed.

A leno's slackener eases the partner, not the doup

In a bottom-doup leno the doup's loop passes beneath the partner, and if it lifts the partner on its way up it puts a second turn six millimetres in front of the partner's heddle. A four-millimetre lift bends the partner through 74 degrees in two places, and its front span goes from 1.07 newtons to 1.48 — a tenth of that from the bend and the rest from grip. The back span, which is all an easing bar can feel, does not move. A slackener that drops the doup's standard four millimetres clears the partner exactly, gives the crossing end six per cent of its easing, and costs the shuttle nothing.

7 figures · Leno The partner's peak against how late a slackener starts. The largest tension the partner's front span reaches, against the share of the shed opened when the slackener starts to drop, at a 4 mm rise. It stays at 1.07 N for any start up to 0.748 of the shed, where the partner with no slackener passes that tension. Later than that, the peak is the touched tension at the moment it starts, up to 1.39 N at 0.95, against 1.48 N for no slackener at all.

A leno's slackener only has to arrive

A slackener that lets the doup down in step with the loop keeps a leno's partner clear at every moment of the shed, and it looked as though a real one would have to track that closely. It does not. A partner's tension only rises as the shed opens, so a slackener can leave its whole drop until three quarters of the way up and the peak does not move at all. Lateness is paid for elsewhere: starting later than 0.58 of the shed rubs the loop more than having no slackener, and above 234 picks a minute a falling weight cannot start as late as the partner would let it.

7 figures · Leno