Textile Structure
how cloth is put together
Concept

Wicking — where it appears

The movement of a liquid through a fabric under the pull of the fabric's own pores, with no pressure applied from outside. It is driven by the pore's own curvature, so a finer pore pulls harder and fills more slowly, and the two effects trade against each other.

Named by 11 essays across 4 fields — each of them below, with the objects they name alongside it.

The sett moves the flux and not the height. A 20 tex cotton yarn woven at every sett from 8 to 34 threads per centimetre. Above: the hole between the threads lifts from 27 to 234 mm as the cloth closes, while the space between the fibres lifts 6.37 m at every one of them — so the cloth's maximum is the flat line, and the sett does not touch it. Below: the permeability of those holes falls by a factor of 292 over the same range. Both curves are monotone, so there is no optimum — only an interval, ending at the jam at 34.6 threads per centimetre.

The sett decides how much, not how high

Every essay on wicking so far has found the sett deciding something. This one finds it deciding nothing at all: a cloth's maximum rise is 6.37 m at eight threads per centimetre and 6.37 m at thirty-four, because the sett cannot reach inside a yarn.

setting · Sett Two pore systems in one cloth — 24 threads per centimetre. A plain weave of 20 tex cotton in section, at 24 threads per centimetre, so the yarn is 167 µm across and the clear hole between two picks is 250 µm. That hole's hydraulic radius is 124.8 µm. Inside the yarn, fibres 14 µm across packed at 0.6 leave spaces of hydraulic radius 2.33 µm — 53 times finer, and by Jurin's law 53 times higher: 6.37 m against 119 mm. The yarn's interior is magnified 6 times and the two discs at the foot are the only part drawn at one scale.

How high a cloth wicks

A woven cloth has two capillary systems and they are a factor of twenty to a hundred apart. The one every diagram draws — the hole between four threads — lifts 119 mm. The one nobody draws, inside the yarn, lifts 6.37 m.

applied · Wicking What a coating does to seven properties of a cloth. Seven quantities computed for uncoated fabric, with what each becomes once a film bonds the crossings: the shear a cloth will take — changed in kind; tear strength — changed in kind; the loss from a hole — reversed; wicking — halved; air permeability — reversed; the sett's effect on strength — unchanged in sign; areal weight — added to. Two of the seven reverse outright. The table is a collection rather than a computation, and each row points at the essay whose result it qualifies.

Coated is a state

Almost every mechanism in a woven cloth assumes threads that can move relative to one another — the bias is a mechanism because the crossings rotate, a tear runs because threads gather, a cloth takes a hole without minding because the neighbours pick the load up. A film bonds the crossings. Two of those results reverse outright, the rest change in kind, and a fabric's quoted numbers almost never say which state they belong to.

finishing · Coating A front on a thread with 8 per cent crimp. Three rows at one scale. The top row is the warp end laid out straight, with the wetted front marked at four equal quarters of its own length — which is where Washburn's law puts it at four times whose square roots are evenly spaced. The middle row is the same thread crimped at 8 per cent, so it covers 92.6 per cent of the paper the straight one did. The bottom row is the cloth, and the four fronts on it are the four above pulled back by 1.08. A coefficient is a length squared over a time, so it comes down by 1.1664 — exactly (1 + c)², with no property of the liquid or the fibre in it. The thread's thickness is not drawn and neither is the liquid: a meniscus in a 2.33 µm pore is finer than any line on this canvas.

Wicking is slower along a crimped thread

A front travelling up a warp end travels the thread's path, which is longer than the cloth by exactly the crimp. So the wicking coefficient measured on the fabric is the yarn's own divided by (1 + c)² — 14.3 per cent lost at eight per cent crimp, whatever the liquid.

applied · Wicking One canopy, two opposite outcomes, decided by a sign. What a canopy does to a drop, for sheeting raised 32-fold. A rough surface multiplies the cosine of the intrinsic contact angle by its roughness ratio, which here is 2.0 — a hair is a cylinder and contributes πd of surface for every d of shadow. So a fibre that wets at all is driven to complete spreading, and one that does not is driven to a Cassie state sitting on 32.4% solid and air. The dashed diagonal is what the bare fibre would do; the canopy pushes every point away from ninety degrees, in whichever direction it already lay. Raising is therefore not a wetting treatment or a repellency treatment — it is an amplifier, and which one it turns out to be was settled by the chemistry before the raising machine was switched on. What the figure cannot show is which state a real drop reaches, because both are available near the hinge and the one it finds depends on how it arrived.

The hairs decide the sign of the wetting

Raising a cloth is not a wetting treatment and it is not a repellency treatment. It is an amplifier, and which of the two it turns out to be was settled in the dyehouse before the raising machine was switched on — by whether the fibre's own contact angle was above or below ninety degrees.

cloth · Water A print is as sharp as the hairs are long. How far ink carried on a hair reaches past a printed edge into the unprinted cloth, for sheeting in three states. A hair lying near the edge bridges as far as its own length, and the number bridging at least a distance x is (n_A λ/2)e^(−x/λ) — an exponential with the population's own decay length — so the visible feather is a quantile rather than a mean, taken here at one hair per 50 millimetres of edge. As woven the feather is 1911 µm, which is a fifteenth of an inch and coarser than any screen worth engraving: the cloth cannot hold better than 7 lines to the inch whatever the printer does. Singeing caps it at the flame's own reach of 200 µm and takes the cloth to 63 lines — a factor of 10, bought by burning off a fraction of one per cent of the cloth's mass. That is why singeing comes before printing and why nobody prints a fine figure on a raised cloth.

A print is as sharp as the hairs are long

Singeing comes before printing in every finishing route ever written down and the reason given is that the cloth must be smooth. The reason is sharper than that: ink carried on a fibre end reaches as far as the fibre is long, so the feather on a printed edge is a quantile of a hair population and nothing else.

finishing · Coating Where a wet cloth keeps its water. For four cloths of this collection's own table, the share of the water a saturated cloth holds that sits inside the fibre as regain, between the fibres inside the yarn, and between the yarns in the cloth's own holes. muslin at 99 grams a square metre holds 183 per cent of its own weight, 4.6 per cent of it in the fibre; sheeting at 155 grams a square metre holds 113 per cent of its own weight, 7.5 per cent of it in the fibre; poplin at 100 grams a square metre holds 165 per cent of its own weight, 5.2 per cent of it in the fibre; duck at 207 grams a square metre holds 139 per cent of its own weight, 6.1 per cent of it in the fibre. The fibre's own water — the property cotton is sold on — is a twentieth to a thirteenth of the total, and the other nineteen twentieths are geometry. What the bars cannot show is the hair layer, which holds water outside all three of these and which this arithmetic has no place for.

A cotton's own water is a twentieth of what a cloth holds

A wet cloth keeps water in three places and only one of them is the fibre. A sheeting saturated holds 113 per cent of its own dry weight: 7.5 per cent of that inside the cotton as regain, 39 per cent in the channels between the fibres of its yarns, and 54 per cent in the holes four threads bound. The same construction in polyester, whose regain is a fortieth of cotton's, holds 105 per cent — an eight-point difference from a fortyfold one, because absorbency is a geometry with a fibre in it rather than a fibre with a geometry round it.

cloth · Water How high each pore system stands while the cloth is drying. The height at which supply up the cloth balances loss from its faces, for the two pore systems, against the evaporation rate. The coarse system between the yarns barely moves — 137 millimetres at the dry end against 109 at the wet — while the fine system between the fibres falls from its sealed-tube height of 6375 millimetres to 52. The two cross at 1553 grams a square metre an hour.

A drying cloth cannot lift what a sealed tube can

Every rise on this account is an equilibrium in a sealed tube, and a garment is neither sealed nor at equilibrium. Balancing the supply up a strip against the loss from its faces gives a quadratic whose width cancels exactly: in an ordinary room the fine system between the fibres stands at 500 millimetres instead of 6.37 metres, keeping 7.9 per cent of what a tube would give it, while the coarse system loses a third of a per cent. The forty-sixfold advantage becomes 3.7, and in a drying wind it reverses.

applied · Wicking The wicking front against time, in four rooms. The height of the wicking front in a sheeting-weight strip against time on a logarithmic clock. The fine system, the pores between fibres, rises to a steady height set by the room: 1064 mm at 20 g/m²·h, nine tenths of it after 4.1 h; 501 mm at 100 g/m²·h, nine tenths of it after 53 min; 255 mm at 400 g/m²·h, nine tenths of it after 14 min; 133 mm at 1500 g/m²·h, nine tenths of it after 3.7 min. The coarse system, the holes between yarns, stops at 137 mm after 17 s whatever the room, because gravity stops it rather than drying.

A wick reaches its ceiling in the time its cloth takes to dry

A drying cloth lifts water to a steady height and no further, and the question left was how long it takes to get there. The answer has no permeability and no surface tension in it. Where gravity is small the front climbs as the ceiling times the root of one minus a decaying exponential, and the exponential's time is the cloth's own pore water divided by the rate its faces lose water — the time the room would take to dry it. In an ordinary room that is half an hour, and the front is nine tenths of the way up in fifty-three minutes.

applied · Wicking How high a strip wicks a finite supply, in four rooms. The steady height of the fine pore system's wicking front against the supply of sweat at the strip's foot, both on logarithmic scales, for a sheeting-weight strip in four rooms. Below each room's capacity the height is the supply over twice the evaporation from each face, a line of slope one that no cloth property moves. It meets the room's drying ceiling at the capacity — 43 g/(m·h) at 20 g/m²·h, ceiling 1064 mm; 100 g/(m·h) at 100 g/m²·h, ceiling 501 mm; 204 g/(m·h) at 400 g/m²·h, ceiling 255 mm; 400 g/(m·h) at 1500 g/m²·h, ceiling 133 mm — and past it the strip takes no more. The marks along the bottom are four sweat rates from rest to hard work, fed from a contact patch 50 mm tall.

A sweating cloth wicks as high as the room can dry it

Every wicking height so far has had its foot in unlimited water. Skin is not a reservoir: it supplies sweat at a rate, and a cloth fed at a rate stands where the supply equals what its faces lose — the supply over twice the evaporation, with no pore, fibre or thickness in it. The cloth decides only when it has had enough, and it says so all at once: the holes between its yarns stay empty until the fine pores are carrying ninety-nine per cent of what they can.

applied · Wicking How tall a skin contact can be before its cloth floods. The tallest patch of skin contact whose cloth keeps the holes between its yarns empty, against the sweat rate, on logarithmic axes, for a sheeting-weight cloth in rooms evaporating 20, 100, 400, 1500 g/m²·h from each face. The patch evaporates from its outer face only and hands its surplus to the free cloth above, which spreads it until the fine system's capacity; so a contact floods when it is taller than 98.9% of that capacity over the surplus. Below the room's own evaporation rate no contact of any size floods. In an ordinary room a run floods any contact taller than 247 mm and hard work any taller than 90 mm.

Wicking borrows drying area from the cloth that is not touching

A shirt is fed with sweat across the whole of the skin it touches, not at the foot of a strip. Through its own thickness the cloth could pass sweat a hundred thousand times faster than a body makes it, so a patch pressed flat never lacks capacity; what it lacks is drying area, because it can give water to the room only from its outer face. Pressed flat everywhere, it floods as soon as the sweat exceeds the room's evaporation — light work, in an ordinary room. With free cloth above the contact, wicking carries the surplus to faces that are not touching, and the sweat decides how much area it needs: three times the contact's at a run, whatever the contact's size.

applied · Wicking

Named alongside it

The objects these essays reach for when they reach for this one.

PermeabilityInter fibre poreMoistureTwo pore systemsWashburn's lawContact angleHydraulic radiusJurin's lawPore radiusCanopy criterionCoatingFilm

All concepts