Textile Structure
how cloth is put together
Knits and other structures

Ravel, fray and run

Cut a woven cloth and one thread comes loose. Break one loop in a knit and every loop above it follows. The two structures fail in opposite ways, and the reason is topology rather than strength.
14 min read 7 figures Does it hang togetherStructure before fibre

A snag in a woven shirt is a pulled thread. A snag in a knitted stocking is a ladder running from the ankle to the knee. Both fabrics were sound before, both were damaged in one place, and the outcomes are not remotely comparable.

One break, two outcomesThe same single break in a knit and in a weave. In the knit nothing holds the loop above the break, so the failure climbs the wale; in the weave every other thread is still held by the threads crossing it, and one thread comes loose.a knit — the break runs up the wale3 loops freeda weave — the break stays put1 thread freedcounted from the structure, not from experience
Fig. 1 The same single break in a knit and in a weave. In the knit nothing holds the loops above the break, so the failure climbs the wale. In the weave every other thread is still held by the threads crossing it, and one thread comes loose.

The difference is structural and it can be stated exactly.

What holds a thread in place

In a weave, every thread is held by the threads crossing it. A warp end passes over some picks and under others; to move, it must lift or depress every pick it is engaged with, against friction, all along its length. Remove a neighbouring end entirely and the rest are unaffected, because none of them was relying on it.

In a knit, every loop is held by exactly one thing: the loop below it, which it passes through. Remove that loop and nothing is holding it at all. It is free, and once free it releases the loop above it in turn.

That is the whole difference. A weave distributes the constraint on every thread across many other threads; a knit concentrates it in one.

The cascade, counted

The consequence can be put as a number, which is what the figure does.

Break one loop in a wale kk courses from the top, and the loops above it are freed one after another: kk of them, all the way to the edge. Break one thread in a weave and one thread is freed, regardless of where the break is.

So the damage from a single break is proportional to the distance to the edge in a knit and constant in a weave. That is a difference in kind rather than degree, and it is why a small snag is a catastrophe in one structure and an annoyance in the other.

One break, two outcomesThe same single break in a knit and in a weave. In the knit nothing holds the loop above the break, so the failure climbs the wale; in the weave every other thread is still held by the threads crossing it, and one thread comes loose.a knit — the break runs up the wale5 loops freeda weave — the break stays put1 thread freedcounted from the structure, not from experience
Fig. 2 The same break lower down. Five loops are freed rather than three, because the count is the distance to the edge — the cascade has more to work through. A woven break frees one thread wherever it happens.

What the count establishes

The figures on this page compute something exact, and it is worth saying precisely what.

For a break kk courses from the top of a knitted wale, the number of loops with nothing holding them is kk — each releases the next, all the way to the edge. For a break anywhere in a woven cloth, the number of threads with nothing holding them is one.

One break, two outcomesThe same single break in a knit and in a weave. In the knit nothing holds the loop above the break, so the failure climbs the wale; in the weave every other thread is still held by the threads crossing it, and one thread comes loose.a knit — the break runs up the wale5 loops freeda weave — the break stays put1 thread freedcounted from the structure, not from experience
Fig. 3 The same comparison with the break lower down. Five loops are freed rather than three, because the count is the distance to the edge; the woven figure is unchanged, because the count there does not depend on where the break is.

That is a topological statement about the structures and it is exact. What it does not establish is whether a given snag will actually run: that depends on friction, on how tight the loops are and on how much the fabric is handled afterwards, and nothing here computes any of them.

So the claim is that the potential damage differs by a factor that grows with the fabric, not that every knitted snag becomes a ladder. Plenty do not. The point is that in a woven cloth none can.

Why fraying is different

A woven cloth’s failure at an edge is not a cascade and it is not driven by the same thing.

Fraying happens because at a cut edge the crossing threads run off the end, so the threads parallel to the edge are no longer held along their whole length — only up to where their partners stopped. Friction holds them for a while, and handling works them loose one at a time.

Two things follow. Fraying is a surface phenomenon: it stops when it reaches threads that are still fully engaged, so a frayed edge reaches a depth and then stalls. And it depends on friction rather than on topology, so it varies enormously with yarn and finish — a hairy woollen frays reluctantly and a smooth filament satin frays enthusiastically.

The rate also depends on the weave. Plain weave frays least, because a thread must disengage from a crossing at every intersection to escape. A satin frays most, because its threads are gripped rarely and can slide.

Cut edges, and why knits are handled differently

The two failure modes lead to two completely different sets of workroom habits, and the habits are worth spelling out because they look arbitrary until the mechanism is clear.

A woven cut edge is unstable immediately and permanently. It frays with handling, and every seam allowance must be finished — overlocked, bound, pinked or turned — or the garment comes apart at the seams over its life. That is a fraying remedy: stop threads sliding out.

A knitted cut edge is stable in a different way. It does not fray, because there are no parallel threads to slide out; it may ladder, which needs no handling at all and can happen months later from a single snag. So knitted seams are made with stitches that both join and secure — an overlock, which trims and encases in one operation — and the encasing is a laddering remedy rather than a fraying one.

The knitted loopOne thread, bent into a course of loops, each of them drawn through the loop below. Nothing here is straight, which is why a knit extends in every direction while a woven cloth extends only on the bias.a course runs acrossa wale runs down7 wales × 5 coursesevery loop passes through the one below itweft knit
Fig. 4 The structure the remedies are working on. Every loop depends on exactly one other, so securing an edge means giving those loops a second thing to hold on to — which is what a cast-off, a bound edge or an overlock does.

The asymmetry runs the other way too. A woven cloth can be cut in any direction and hemmed with a fold; a knitted one cannot easily be hemmed by folding, because the fold has no stability and the cut edge inside it can still ladder. Knitted garments are therefore finished with bands, ribs and bindings far more than woven ones, and the reason is structural rather than stylistic.

The two remedies are different

Because the mechanisms differ, the fixes do not transfer.

For fraying, anything that prevents the parallel threads from sliding out will do: an overlocked edge, a bound edge, a fused edge, a hem, or a selvedge — which is simply an edge where the weft turns back rather than being cut, so no thread ends there at all. Fray-check liquids work by gluing the threads together, which is exactly the constraint that was lost.

For laddering, none of that helps in the middle of a fabric, because the failure does not start at an edge. What works is changing the structure so that a loop is held by more than one thing: interlock and rib ladder far less than jersey, because their loops are engaged with wales on both faces. Warp knits — tricot, raschel — barely ladder at all, because each wale is formed from its own thread which also travels sideways into its neighbours.

The historical case is stockings. Fully-fashioned silk stockings were plain jersey and laddered constantly; nylon did not fix it; what largely fixed it was moving to knitted structures with more constraint, and to fine gauges where a ladder is narrow enough to be less visible.

Ravelling, which is the third word

The three words get used interchangeably and mean different things, which is worth sorting out.

Ravelling is a knit coming undone by pulling the free end of its thread — running the knitting backwards. It requires access to an end, and it undoes courses rather than wales. Pull the yarn from the cast-off edge of a jersey and the whole thing comes back as one continuous strand.

Laddering or running is a wale failing after a break, which needs no free end and no pulling.

Fraying is a woven edge losing threads to handling.

A weft knit does all of the first two. A warp knit does neither easily. A woven cloth does the third and neither of the others, since it cannot be pulled undone — a woven cloth has no single thread to pull, which is precisely what makes it two thread systems rather than one.

The connection to integrity

There is a link here to the check this site is built around, and it is worth drawing carefully because the two things are related without being the same.

Cloth integrity asks whether a structure is topologically one piece. A weft knit passes trivially — it is literally one thread, so nothing can be separated from anything.

And yet the knit is the fabric that fails more easily. Being one connected object is not the same as being robust, because the connectivity in a knit is serial: every loop depends on one other loop, in a chain, and a chain is only as good as its worst link. A weave’s connectivity is redundant: every thread is held by many others, so removing one changes little.

That distinction — connected versus redundantly connected — is the real content of the difference, and it is a familiar one from anywhere else that networks are studied. A structure can be perfectly connected and extremely fragile if all its paths run through single points.

What decides how bad a ladder is

Three factors, and only one is structural.

Loop length. A long, loose loop slips off its neighbour easily; a short tight one resists. Tightly knitted fabric ladders less, which is the main reason fine-gauge knitwear survives better than loose.

Friction. A hairy, high-twist or textured yarn grips itself and arrests a ladder; a smooth filament does not. This is why silk and early nylon stockings were notorious and why textured nylon was an improvement.

Structure. Interlock, rib, and warp knits ladder far less than plain jersey, for the reason above.

Only the third is a property the matrix-style analysis on this site can reach. The first two are yarn and finish, which is a reminder that the structural account is dominant rather than complete.

Where the two failures meet

There is one structure where both failure modes are present, and it is the exception that clarifies the rule.

A cut edge of a weft-knitted fabric frays a little — the cut ends of the loops can work free — and ladders a great deal. A woven cloth with very long floats can do something that looks like laddering: pull a float and the thread runs, because it is not gripped along that length. A satin snags in a way that a plain weave cannot, and the snag can travel.

The common factor is free length between constraints, which is the same quantity behind float length in weaving and loop length in knitting. Failure travels along a thread exactly as far as the thread is unconstrained, and no further.

Where the floats are in the 8-end satinEvery longest run of warp on the face, marked. A float is smooth because nothing interrupts it, which is the same reason it snags: there is a length of thread lying on the surface with nothing holding it down.8-end satinwarp floats of 7weft floats of 18 markedruns measured round the repeatfloat 7
Fig. 5 Why a satin can be made to run. Seven intersections of unconstrained warp, marked — a length that is gripped only at its ends and along which a pulled thread can travel.

That gives a single sentence covering both structures. A break propagates as far as the structure leaves the thread free, which in a knit is up the whole wale, in a satin is along a float, and in a plain weave is nowhere at all.

What this account leaves out

Two limits.

It counts rather than predicts. The figures here count how many loops a break frees, which is a topological fact. Whether a given snag actually initiates a ladder depends on friction and force, and nothing here computes either.

It is about weft knits. Warp knits share the loop and not the failure mode, and almost every generalisation on this page fails for them.

The selvedge, and why it is not a hem

One structural feature exists purely to solve the fraying problem, and it is worth understanding because it is not what most people assume.

A selvedge is the edge of the cloth as it comes off the loom, where the weft turns back rather than being cut. No thread ends there: the weft is continuous, going out and coming back, so the constraint that fraying needs to remove is never absent.

That is why a selvedge does not fray and needs no finishing at all, and it is a structural property rather than an applied one. Nothing was added — the edge simply never lost anything.

Modern shuttleless looms cut the weft at each pick and have to manufacture a selvedge afterwards, by tucking the ends back in or by binding them with a leno thread. Those work, and they are visibly different from a true shuttle selvedge, which is why selvedge denim is identifiable and is sold on the strength of it.

The plainThe plain on point paper, a filled square meaning the warp is on the face. Its longest float, its interlacing count and the number of separable cloths it describes were all counted from the matrix that drew it.plainlongest float 18 interlacings per repeat1 separable clothrepeat 2 × 2generated, then counted2×2
Fig. 6 Plain weave, which frays least of any structure because a thread must disengage from a crossing at every intersection to escape. A satin, gripped once in five or eight, frays enthusiastically — the same interlacing count deciding another property.

The knitted equivalent does not exist, because a knitted edge’s problem is not threads escaping sideways. A cast-off edge is a chain of loops each secured through its neighbour, which is a construction rather than an absence — and it is why a cast-off has to be worked and a selvedge does not.

What a designer can do about it

Three levers, in decreasing order of how well they work.

Change the structure. Interlock, rib and warp knits ladder far less than jersey. This is the only remedy that removes the failure mode rather than making it less likely, and it is the reason most commercial knitwear is not plain jersey.

Change the yarn. Textured, high-twist or hairy yarns grip themselves and arrest a run; smooth filament does not. Textured nylon was a real improvement over flat, and it is why sheer hosiery moved to it.

Change the gauge. Tight knitting ladders less, because a short loop is harder to pull off its neighbour. It also costs yarn and stiffens the fabric.

Why one curls and the other does notA knitted loop is not symmetric front to back. Worked every course the same way, the asymmetries add along the edges and the fabric rolls; worked alternately, consecutive courses point opposite ways and cancel.the dots mark which way each course facesstockinette — every course the same0 face changes · curlsgarter — alternate courses reversed5 face changes · lies flatface changes counted, not the curl itself
Fig. 7 The same structural variable behind another property. Arrangement decides whether a knit lies flat; arrangement also decides whether it ladders, and both are consequences of how each loop relates to its neighbours.

For woven cloth the corresponding levers are the same in spirit. Fraying is reduced by a firmer weave, by a hairier yarn, or by a finish that binds the surface — structure, material, and treatment, in the order this site usually finds them.

Where the ladder goes next

The structure this all follows from is the loop, and the other consequence of its asymmetry is why stockinette curls.

The woven side of the comparison is plain, twill and satin, where fraying varies with the same interlacing count that decides everything else.

What the pictures here cannot show. The figures count freed threads, which is a statement about the structure. A real ladder is a dynamic event driven by friction and tension, and no static diagram shows why one snag runs and another does not.

Where this goes next

a course runs acrossa wale runs down5 wales × 4 coursesevery loop passes through the one below itweft knit The loop A knit is one thread bent into loops, each drawn through the loop below. Nothing in it is straight, which is why it stretches in every direction while a woven cloth stretches only at an angle. the bars mark which separable cloth each thread belongs toan ordinary 2/2 twillone clothevery end and pick interlacestwo separable clothsconnectivity of the above-and-below relation, computed Does it hang together A draft can interlace everywhere, have short floats, and describe two fabrics lying on each other rather than one. Nothing about the drawing says so, and the test that does is exact. plainfloat 1 · 8 interlacingsfirmness 1.002/2 twillfloat 2 · 16 interlacingsfirmness 0.505-end satinfloat 4 · 20 interlacingsfirmness 0.40a filled square means the warp is on the facecounted from the matrices, not from the pictures Plain, twill and satin Three rules, and everything else in weaving is a variation on them. What separates the three is not appearance but one trade — how often a thread changes face against how far it runs when it does not.