Textile Structure
how cloth is put together
Generator

The angle a watered finish has to hit

The angle a watered finish has to hit
The angle a watered finish has to hit. A ribbed cloth of 0.5 mm pitch folded on itself and pressed. The figure's size is the beat of two identical grids at a small angle, so it goes as one over the angle: the whole usable range is 0.48° to 29.0°, and at the large-figure end a hundredth of a degree moves the figure by 1.3 mm. No two pieces of moiré taffeta match because no two are folded at the same angle.

A ribbed cloth of 0.5 mm pitch folded on itself and pressed. The figure's size is the beat of two identical grids at a small angle, so it goes as one over the angle: the whole usable range is 0.48° to 29.0°, and at the large-figure end a hundredth of a degree moves the figure by 1.3 mm. No two pieces of moiré taffeta match because no two are folded at the same angle.

2 essays call watered. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the weave its essay argues about.

Where it is called

Changing this generator changes every one of these figures.

A beat at 19.1 mm from grids at 0.5 mm. Two grids at 0.5 and 0.5 mm pitch, the second turned by 1.5°, over a 30 mm window. The dashed rules are one predicted beat period apart. The pattern between them is 38 times the pitch of either grid and neither grid has anything at that scale. Pattern and colour

Watered silk is a beat

Fold a ribbed cloth on itself and press it, and a figure appears at a scale neither ply has — fifty times the rib pitch, wandering across the piece. It is the difference of two wavevectors, it is enormous because the angle is tiny, and no two pieces match because no two are folded at the same angle.

 The magnification a cloth will carry. The largest magnification a moiré can be read at, against the irregularity of the cloth making it. The points are measured: a grating whose spacings are drawn from a seeded lognormal is laid against a perfect one, the fringes are found from the phase difference, and the gain is recorded at which their count first departs from what the ideal beat predicts. The product of the irregularity and that gain comes out at 0.82 to 0.84 across every irregularity tried, so the ceiling is 0.84 divided by the coefficient of variation — the solid curve. The dashed curve is the accumulated-wander model, in which position errors random-walk and the ceiling goes as the inverse square; it is wrong by a factor of 42 at a two per cent irregularity. What the plot cannot show is what a cloth's spacing irregularity actually is: it has not been measured, and the curve is therefore a prediction with an unmeasured input. Pattern and colour

A moiré is a vernier, and it magnifies the error too

Two gratings a per cent apart in pitch beat at a hundred pitches, so a moiré reads a pitch difference at a hundred times — which is what a vernier is. The magnification is free and its ceiling is not: the fringes split when one thread's own spacing error reaches 0.84 of the pitch difference the beat is built on, so the usable gain is 0.84 divided by the cloth's coefficient of variation, inversely and not inverse-squarely. At an ordinary yarn's spacing irregularity, a moiré carries a magnification of five.

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