The thread: Exactly this many — page 4
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.
No cloth derives into more than three others
Every weaving manual opens by saying the three basic weaves generate the rest. This collection counted the reach and found nine of 426, and left the nine as a count. It is not a count: every derivation the manuals name is a relabelling of the grid or a complementation of it, both invertible, so they generate a group — and that group cuts the 426 cloths into 157 closed pieces of which the largest holds four. The claim is not merely wrong about how much derivation reaches; derivation cannot reach more than four cloths from anywhere, by any sequence of operations, however long.
An even shading cannot keep its surface level
Sixty-four six-end shadings hold every middle tone to a float of two, and the question left over was whether any of them keeps a tone ramp's surface level the way a twill read in order does. None does, and all of them sink by exactly the same depth — 43.3 micrometres on a sheeting, a sixth of the cloth. The reason is a counting argument a recording engineer would recognise: a limit on how long a thread may float is a limit on run length, and a run-length limit forces a floor on how often the thread changes face. A level ramp needs every tone at the extremes' rate, which needs a float of half the repeat at the midtone and more beside it — exactly the floats the twill in order has.
A tuck is the one stitch that links twice
Knitting has three stitches and only one of them makes a new link. A knit stitch links a loop to the loop below; a miss links nothing; and a tuck holds two loops in one head — which is why a tuck stops a run and why the three cannot be described by one number.
A float limit leaves one row-free satin
A satin is chosen so that no diagonal forms, and an earlier essay found that most of them fail: the interlacings lie on a lattice, every lattice has a shortest step, and the marks line up along it unless two steps tie — which happens at twelve of the thirty-five orders from five to forty. The other constraint was named and not applied. An n-end satin floats over n − 1, so a yarn that will not carry a float longer than eight admits four orders in all, and exactly one of them is row-free: the five-end satin, which is the one everybody already weaves.
A jersey has no float for a wire to catch
Only a float can be raised, and the four-by-four census answers which woven cloths qualify: two. Asked of a knit the same question needs this collection's knitted float rather than a draft's, and the answer is that a plain jersey has no float at all — not a short one, none — while the ribs and cardigans have none either and the interlocks and milanos have floats every one of which is interior. Of 1,135 two-bed structures a machine could make, twenty present a float a wire could hook, and not one of them presents it on both faces.
A net of three directions beats a voile one way at a time
A tulle's threads run three ways at sixty degrees and a voile's run two ways at ninety, so a net hung over a voile could show one family of fringes, three, or a lattice of them. It shows two, at right angles, and they are nothing alike. Along the voile threads that lie parallel to one of the net's, the net beats exactly as a one-directional net does: six-millimetre fringes from three metres. Across them no set of the net lies anywhere near, and the only slow beat comes from a line of points two sets make together at √3 over the net's pitch — fringes four times wider and a fifteenth as strong, with a null at 8.8 metres where the strong family has none.
A circular machine leans its courses whatever the yarn
Spirality is blamed on the yarn, and the yarn is most of it. The rest is the machine's. A circular knitting machine's needles make wales that run straight along the tube, and its feeders lay one course each per turn, so every course climbs its feeder count in every round: on a 96-feeder machine, 48 millimetres round 162 centimetres of tube, an angle of 1.7 degrees. The helix has no machine size in it, its hand is set by the way the cylinder turns, and it survives every remedy aimed at the yarn — a steamed yarn, a plied one, S and Z on alternate feeders, and a rib.
An irregular satin scatters where a regular one lines up
A regular satin's marks lie on a lattice, so its closest pairs all run along one vector and make a row. An irregular satin has no lattice at all, so its closest pairs may point several ways at once — and at seven and nine ends, where every regular satin at the best spread has a row, an irregular one reaches the same spread with its closest pairs scattered over four directions and no more than a third in any one. At eight and eleven ends there is no such satin: the best spread is reached by regular satins alone, and irregularity has nothing to offer.
A nap is paid for by the taper of the pattern
A raised cloth's fibres lean, so a panel turned end for end shows a different amount of fibre and every piece of a garment has to lie the same way along the bolt. What that costs is not a property of the cloth. A rectangle costs nothing laid one way; a tapered panel costs (1 − r)/(1 + r) of extra cloth in lanes, where r is its narrow width over its wide one; and the best any one-way lay can do is exactly half of that, because a trapezoid's difference body is a hexagon and hexagons tile. On a real width it arrives in whole panel lengths: six skirt gores take 75 centimetres two ways and 150 one way.
A figured warp needs a beam for every share of its figure
Figure and ground take up warp at different rates, so a figured cloth on one beam is bounded in how long its figure may run, and a second beam is the obvious escape. It escapes only for ends that live wholly in one region. An end that crosses the figure for part of the repeat consumes warp at its own rate, and two ends can share a beam only if they spend the same share of the repeat in the figure and never drift a slack apart inside it. So a round figure twelve blocks across needs four beams, ninety-six blocks across needs twenty-nine, and any crimp difference at all — a third of a per cent will do — costs every one of them over a piece.
A colour-and-weave look costs its cheaper order
The finest colour-and-weave effects need the rarest loom because a weft order is thrown pick by pick and a warp order is laid out once, so an effect's price was said to be its weft. That is true of a construction and false of a cloth. The same cloth can be woven lying across the loom, with its warp order thrown as weft and its weft order laid in the warp, and then it costs the other order. Over every two-colour look twelve small weaves make with orders up to six threads — 4,036 of them — 55 per cent need a loom picking at will as drawn and 31 per cent need one either way round. The looks turning rescues are the ones fine in one direction only, and not one of the trade's named effects is among them.
A specification can name a cloth that is not there
The three notations measured so far write drafts, and every draft is a cloth somebody could weave. A mill works from none of them: it works from a count, two setts and a weave quoted together, and that is the first notation whose image has holes in it. Of 2,560 specifications across the trade's own working range, 2,097 name no cloth at all — and in the 240 where the weave field decides anything, both numbers the trade quotes to decide it rank the catalogue wrongly.
A grade charges by the length and a cutter pays by the panel
The four-point system scores a fault by how far it runs — one point to three inches, four beyond nine — and caps a linear metre at four points however many faults it holds. A cutting room pays by how many panels the fault lands in. Below a panel's length every fault costs exactly one panel while its score runs from one to four; above it the panels grow without bound and the score does not move at all. Two fifty-metre pieces built to the same 267 points a hundred square metres lose 33 per cent of their panels and 92.
A tuck decides whether a third of two-bed fabrics lean
A jersey leans because every loop is on one bed and a rib does not because its loops are mirrored across two, and the count that says so treated a tuck as nothing. A tuck is a loop of the same lively yarn wrapped round a needle of one bed, and nobody here has measured how much of a knit loop's lean it carries. It matters. Of the 1,135 two-bed fabrics a two-needle, two-course frame can make, 135 are balanced whatever a tuck carries and 612 lean whatever it carries — and 388, a third, are balanced under one answer and lean under the other. A half-cardigan leans a third of a jersey if a tuck carries nothing and not at all if it carries a full loop's torque, which makes it the instrument that would settle the question.
A satin's row belongs to its sett
Point paper draws an end and a pick as equal squares, and every result about which satins have a row was taken there. A cloth is not square: it is set at so many ends and so many picks a centimetre, and in cloth the ties that made twelve satin orders row-free are ties between steps of different shape, which break at the first per cent of unequal sett. The reverse happens too. An eight-end satin, rowed on paper, has no row at exactly 1.291 ends per pick; an eleven-end at 1.265 and 1.528. And the only scatter that survives a range of setts is an irregular satin whose closest steps are mirror images — which nine ends has from the first per cent and ten only by 1.3.
A turned block is a moved origin
An eight-end satin figured on a 2/2 twill fails on 55,536 profiles at a block eight picks by two ends and on none at two by eight, and that was read as a property of the block's shape. Sweep the relative origin as well and the two shapes trade places: at every one of the sixteen origins exactly one of them fails, and over the sixteen they fail equally often. A shape asymmetry that no origin removes exists, and it needs a satin whose move squared is not one.
The shortest notation has the longest mistakes
Four essays of this account have asked what each notation can express. None has asked what happens when one is written down wrong, and the answer is an identity rather than a tendency: a notation's symbols partition the cloth, so the count of symbols times the reach of one is the piece, in every notation, with nothing to trade. One threading digit decides 810,000 intersections of a square metre and one of a jacquard's holes decides one — and only the threading can be wrong while the cloth is right.
The count that decides how flat
A knitted fabric's demanded flattening is a function of its tightness factor, and a tightness factor is the square root of a count over a loop length. So a coarser yarn at the same loop is flatter — which is a prediction about a spinner's choice that nobody has framed as one.
A fault map is worth most where the grade is worst
A cutter who knows where the faults are can slide the marker or break it, and only one of those is worth anything: sliding a rigid tiling to its best offset recovers two panels of fifty-five, and letting the tiling break recovers twelve — two panels in five more cloth from the same roll. The gain has a maximum in the middle of the range, because there is nothing to recover on a clean bolt and nothing to be done on a ruined one. And the prediction the grading essay made, that a map is worth most on a bolt whose faults are bunched, is false: bunching leaves clear runs for the blind cutter too.
A cloth's derivation class is its census of small patches
The manuals' derivations cut the 426 four-by-four cloths into 157 orbits, and an orbit is found by searching a group of 256 operations. The question left was whether a short list of numbers read off a draft could do the same job. The familiar ones cannot. Marks, interlacings, layers, plane group, float lengths, crossings per thread and distinct ends and picks are all invariant, and all seven together tell 120 of the orbits apart. A census of the two-by-two patches a draft contains tells 127 apart. A census of its three-by-three patches tells all 157 apart — a complete invariant of derivation, computed by counting windows rather than by searching operations.
A covered cloth cannot be calendered
A calender widens a section at conserved area, and a thread may widen until it meets its neighbours. So the flattening is capped by the cover the cloth already has — ×30 on a scrim, ×1.32 at a cover of nine tenths, and exactly one at full cover. The plateau a calender buys falls to nothing along with it, which makes the lustre a nip can add and the cloth's opacity the same constraint read twice: a cloth that cannot be seen through is a cloth a calender cannot help.
Two bars cannot share a beam
Two guide bars each make one overlap a course and one underlap, and the overlap is the same object on both — the same needle, the same loop. So the difference in what they consume is exactly the difference in their underlaps, with no model of a loop in it: a cord bar wants 111 metres more yarn per wale than a tricot bar over a hundred-metre piece, and a satin bar 232. A shared beam is one course spacing of slack out after less than half a course.
The colour order that hides least
A caption on this account's top essay left a question: whether a warp of long runs against a weft of short ones hides less than either would against itself, and called it a lever nobody uses. Sweeping all sixteen orders against all sixteen says the lever is real and the caption named the wrong variable. Run length has nothing to do with it — the blind count, the separation and the largest confused class all depend on the two orders' colour counts and on nothing else, and what a mixed pair saves is exactly the square of the difference between them.
A second wrong digit is silent only by cancelling the first
One wrong threading digit leaves the cloth exactly as it was 576 times in 252,968, all on three-shaft drafts. The obvious guess about two was that silence would become the rule, since two changed digits can swap two shafts and swapping shafts is the harness's own freedom. Counted over all 1,074,972 pairs, two wrong digits are silent 1.29 per cent of the time — five and a half times as often, on fifteen times as many cloths — and never by adding one silent slip to another. Every silent pair is two audible errors cancelling, and at two errors point paper and lifting plans, which can never be wrong silently by one symbol, are silent almost as often.
A weight fixes the fibre and not the drape
Every plain cotton cloth of 150 grams a square metre contains the same fibre, and the count decides only how it is arranged. Across the counts that can make that weight, thickness rises threefold and cover falls in step, so their product holds still. The bending length does something stranger: at the bound a woven yarn actually sits near, it depends on neither the count nor the weight, only on the fibre.
A cam easer gives its slack too early
The essay before it left the crossing end with fifteen millimetres it could not use at half the shed, and three things it might do with them. All three are decidable. It cannot reach the shuttle, because the same eyes that trapped the kink keep the slack behind the harness — and the margin is negative, so that friction is not a nuisance here but the reason a leno weaves at all. It cannot snarl, because the span is under half this account's own threshold. It sags seventy-two millimetres where the easer gives it, and the repair is a cam cut to the demand rather than to the shed.
The shog is the anisotropy
An underlap is a straight run from one needle to another on the next course, so it is a hypotenuse — and its length is fixed while the two spacings are not. Pulling the fabric wider turns it towards the horizontal and pulls the courses together, on a circle. Every state a warp knit's underlaps allow lies on that circle, its as-knitted point sits where the shog puts it, and the ratio of the length it can give to the width it can give runs from 2.3 at a tricot to 218 at four needle spaces.
An eight-end shading is pinned at three everywhere but its centre
At six ends every even shading holds its middle tones to a float of two, and every one sinks to the same depth. The question left was whether eight ends does the same. It cannot even start: at eight ends no shading can hold its second tone to two, a float of three there needs the second mark of every pick exactly opposite the first, and then the third mark cannot undo it. Tones two, three, five and six are pinned at a float of three, only the centre is free, and a family with a free centre does not sink to one depth — it sinks to at least six.
A calender's best cloth is the one its nip fills
A calender's lustre is a length of crown line times a width of plateau. A closer cloth has more crown line and less room to widen each thread into, and the product was expected to peak at some interior cover that would move with the weave. It does not peak at all on the cap alone — per unit of crown line it falls all the way from the most open cloth. The peak is made by the nip: a nip that flattens by f has one best cloth, the one it exactly fills, at a cover of d over the flattened width, and there the lustre is (f − 1)/f. No yarn, and no weave, moves it.
What a closed thread cannot choose
A thread whose ends are held has a quantity it cannot change without breaking: the total number of times its material winds about its own axis, plus the number of times that axis winds about itself. The two can trade, and everything a twisted yarn does when it is let go is that trade happening.
The energy has no crimp ratio to give
The account left a gap at its top: a construction whose preferred crimp ratio lies outside the interval its geometry admits sits at a boundary, and boundary states had not been studied. Profiling the whole energy rather than its minimum says there are two regions and a frontier — six of the eight cloths in the table of cloths here fall to an end of their own interval with the weft dead straight, and the two that do not have wells 3.27 and 0.52 per cent deep, against a rigidity known to within a factor of 408.
A band presses where the limb turns
Every compression pressure is quoted as a band's tension over the limb's radius, and a limb has no radius. It has a curvature that changes all the way round, and a band presses each point with its tension times the curvature there. The round-limb number survives exactly — as an average over the band's length — and is the pressure almost nowhere. On a calf with a ridge down its front the ridge takes ten times it and the flat face beside it takes none; on an ankle, two bones and a tendon carry nearly three quarters of the force on under a fifth of the girth.
A heel turns a right angle because of the loop
A sock's heel is knitted in short rows on half the needles until a third are left, then back out again. Down the back line that adds a length of courses, and a tube's back line longer than its front by that much has turned through π times two thirds over the loop's own aspect — 93.8 degrees, on any needle count, in any yarn. The trade's third is the loop's shape in disguise. What the rule does not do is make a bend: the heel supplies two thirds of the fabric a true right angle needs, and every missing stitch is on its sides.
A blind set hides less the thinner it is spread
Two colours showed that where a cloth's threads match in colour the draft underneath is invisible, and that how many intersections match is not what decides how much is hidden. More colours say what does. A third colour lets the blind count take every value from nought to ten; a fourth lets the blind intersections sit one to a thread. At a fixed count, the catalogue keeps more of its cloths apart the more threads the blind set is spread across — 3,632 surfaces for four scattered blind cells, 2,402 for the same four in a square.
A knitted disc is flat at one shape of loop
A disc lies flat only if its circumference grows by exactly 2π per unit of radius, and a knitted disc's growth is a count of loops in one direction over a count in the other. So it is flat at one value of the loop's aspect and no other. Knitted sideways in wedges of short rows the growth falls as the loop gets wider; knitted outward in rounds it rises. Four wedges and ten increases every two rounds are each flat at an aspect inside the range plain knit moves through when it is washed — and they cross it in opposite directions.
A knit's weight nearly names its yarn
A woven cloth's weight is one equation in four unknowns, and a hundred and fifty grams can be woven from anything between twenty tex and two hundred. A plain jersey's weight has the loop in it and nothing else to spare, and the loop is bounded by the yarn it is knitted from. Put the two together and the loop cancels: the weight is a constant times the tightness times the root of the count, so at one weight the count is fixed to within half again — and in each relaxed state it is fixed to a different half.
A blade leaves loose fibre in every tuft
The account of hair, nap and pile ended on a clean claim: a blade collapses a population's length to one value, so a cut pile has no tail and nothing in it reaches past the rest. The tips are one length. The fibres are not. A tuft cut from staple yarn is a length of yarn with fibre ends scattered along it, and every fibre end that lands in a leg leaves a piece between it and the blade that nothing in the draft holds — a fifth of the pieces in an ordinary wool carpet, none in a filament one.
Silence lives in the lifting plan
Two wrong threading digits leave a four-end cloth exactly as it was 1.3 times in a hundred, and the question left was whether a longer repeat makes that rarer or commoner. At eight ends the answer depends on something the question did not name. With a lifting plan of unrelated rows, silence all but vanishes; with a twill's plan — one row slid a pick at a time — nine four-shaft threadings in ten can be silently mis-threaded, and even single errors are silent one time in five hundred. The repeat hardly matters. The plan's symmetry does.
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.
The width of a bolt is worth what its faults leave it
A fault map lets a cutter move panels along a bolt and across it, and the length was expected to matter far more than the width, because a bolt is fifty metres long and three panels wide. That is true of two kinds of fault and false of the third. Against a fault across the whole width the width is worth exactly nothing; against a scatter of points it is worth between a sixth and two fifths of what the length is; and against a missing end, which runs the whole length, the length is worth nothing and the width is worth everything.
A knitted ball's short rows have to slow down
A knitted disc needs one count to meet 2π; a sphere needs a count that follows a sine. Knitted sideways in gores, a ball's short rows must turn one stitch apart at the pole and ever further apart towards the equator — evenly spaced turns knit two flat discs joined at the rim. The pole is the disc again, so gores come in fours; the equator's row pairs have to come out whole, so only some sizes knit round; and a wash moves a four-gore ball from a ruffled pole to a round one.
A figured warp pays in tension before it needs a beam
Figure and ground take up warp at different rates, and counted against a fixed slack, any difference at all — a third of a per cent — made a round figure need four beams. A real let-off holds tension, not length. Ends that consume more pull harder, and an end pulled harder gives up crimp, until every end consumes alike. For an eight-end satin figure on a five-end satin ground that costs a hundredth of a newton an end, and one beam serves. For a satin on plain it costs more crimp than the ground has, and no tension will do.
The loom hands the crimp to the weft
Bending alone gave the fixed-sett energy nothing to say: six of eight cloths fell to the end of their interval with the weft dead straight. Put the warp's tension in and the answer is not a well but a switch. The crimp changes hands across a factor of two or three in tension, at a few hundredths of a newton — and the loom holds its warp at half a newton, so on the loom every cloth's warp is as straight as its geometry allows.
A proof plan has no slide in it
A threading error that a 2/2 twill hides is invisible in the cloth and still wrong on the loom, and it shows only when the loom is re-pegged. Re-weaving every silent error under eight other plans says which do the showing. The twill run the other way and plain weave never expose one. A 1/3 twill exposes 44 per cent, a broken twill 70, and a plan of eight unrelated rows all but 864 — and those 864 are not errors at all, because each is the right threading started at another end. So the plans nest: whatever a broken or a point twill hides, the 2/2 hides too, and a threading proved under a 2/2 twill has passed the weakest test there is.
The section that changes both stiffnesses
A thread's two rigidities are in the ratio 2G/E, and that is a fact about a circular section: a circle's polar second moment is exactly twice its flexural one. A yarn in cloth is not circular, so a yarn in cloth has three constants rather than two — and the ratio a whole ladder rests on is a lower bound.
A stepped stocking should step most at the ankle
A graduated stocking asks for a girth that rises smoothly up the leg, and a knitting machine gives it one girth, then the next. Over each step the tube is one size on a stretch of leg that is not, so it presses harder at the top of the step than at the bottom, and the pressure up the leg is a saw-tooth. Each tooth is the leg's change of girth across the step divided by the girth squared — so it is largest just above the ankle, where the leg is thinnest and widening fastest. Eight equal steps leave a ring of 4.8 mmHg there; eight steps spaced by the leg's own shape leave 2.7 everywhere.
A jersey's drape does not know its loop
A woven cloth's bending length at the free bound turned out to hold neither its count nor its weight — only the fibre. A plain jersey goes further. Its stiffness per width and its weight per area are both a number of loops per millimetre times something about one loop, so the loop cancels at every stiffness the yarn could have; at the free bound the count cancels too, and what is left is the fibre and which relaxed state the fabric is in.
A ball knitted in rounds washes the other way
A ball can be knitted sideways in gores or outward from one pole in rounds, and both have to follow the same sine. But a gore counts its meridian in stitches and its circumference in rows, and a round counts them the other way, so the loop's aspect sits underneath one construction and on top of the other. A wash raises the aspect — and closes a gored ball's ruffled poles while it opens a round-knitted ball's.
A cut pile sheds in two stages
Every cut tuft of staple yarn holds loose fibre pieces that nothing anchors but the twist, and at the tip the twist holds nothing: it runs out over a length the grip arithmetic already gives, five and a half millimetres in a wool carpet yarn. A loose piece lying wholly inside that run-out is free the day the carpet is laid; one reaching below it is held until walking opens the tip's twist. So the reservoir drains in two stages, and the pile height decides the split. A velvet sheds everything it will ever shed at once. A twelve-millimetre wool carpet sheds a fifth of its reservoir at once and four fifths later. A shag sheds almost nothing at first and fourteen per cent of its fibre eventually.
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.
A blind cell costs half the cloths at any real repeat
At four by four, spreading a blind set over more threads kept half as many cloths apart again as gathering it. At eight by eight the same rule holds, and it is almost nothing: three per cent for four blind cells, eight for eight. The reason is one factor. A blind set's surfaces are the count's bound, 2^(n² − b), times the chance that every thread it misses interlaces on its own, and at eight threads a thread lies all on one face once in 128 tries. So shapes that touch the same number of threads tie exactly, whatever their rectangles; every blind cell costs very nearly half the catalogue; and by twelve threads the arrangement is free.
Stacked increases knit a ball with flat sides
A ball knitted in rounds can put its increases anywhere in each increase round. Stack them in lines from pole to pole and every stitch between two lines has a flat knit's neighbours, so the ball is made of flat panels and all its curvature sits on the lines. Flat panels with straight rows close up without stretching in exactly one way: every round a regular polygon, each pole a point. At five lines that ball is 13 per cent taller than it is wide across its ridges and 40 per cent across its flats, and to make it round the stuffing has to stretch the middle of every panel by π²/4m² — nine per cent at five lines, less than a wash moves a course at ten.
A warp breaks in a tail no tensile test reaches
A 500 mm tensile test is the weakest of about eighteen staple lengths of yarn. A warp of four thousand ends by a thousand metres is the weakest of a hundred and forty million, and an end breaks wherever one of them is weaker than the shed's tension. Three strength laws fitted to the same two tensile tests agree within five per cent at every gauge a tester can clamp, and disagree by a factor of 375,000 on how many ends a warp will break at the back shaft.
Only one start in six can reach the shallowest shading
The even eight-end shadings — middle tones floating three, centre floating two — were too many to walk, and a walk stopped at a hundred thousand chains found six depths. Split at the centre, the family can be counted whole: 1,001,574,400 chains in fourteen depths, every one of them decided by the centre alone. Only 816 of the 5,040 ways to begin a shading can still reach the shallowest ramp, and a designer who wants it has to choose the first two parts before anything else.