UKH

A lot of clothing is described as having 4-way stretch. As there are only 3 dimensions and clothing material is in sheet form which is close to 2 dimensional what does the 4-way stretch designation refer to?

In reply to harold walmsley:

"Stretch fabric is a synthetic fabric which stretches. Stretch fabrics are either 2-way stretch or 4-way stretch.

2-way stretch fabrics stretch in one direction, usually from selvedge to selvedge (but can be in other directions depending on the knit). 4-way stretch fabrics, such as spandex, stretches in both directions, crosswise and lengthwise."

http://en.wikipedia.org/wiki/Stretch_fabric

In reply to harold walmsley:

Up, down, left, right.

Yes, technically it's only stretching two ways but that doesn't sound as good.

In reply to interdit:

I think I'd disagree with that definition, and suggest 2-way is stretch in warp and weft directions, with 4-way adding stretch on the bias directions. Which means that you can sensibly have 1-way stretch. I say sensibly, but it's not always a great idea for trousers, depending on the orientation...

In reply to interdit and purplemonkey:


Wow, that really is marketing speak then. Why stop at 2. A 4 way stretch fabric would also stretch if stressed along a diagonal or any intermediate direction so why not 8 way stretch ... or 16 way...or...? I trust claims for fabric performance less than ever.

In my experience claims of waterproofing are equally suspect once the original water-repellent coating has worn.

In reply to harold walmsley:

It isn't just 'marketing speak'; used properly, it's a technical description of the fabric construction.

That's not to say that marketing departments don't use and abuse technical terms to write copy...

In reply to harold walmsley:

Given that stretch has dynamic implications this introduces time as a factor.... How are we to reap resent time in this discussion therefore? 4-way squared or something?

In reply to captain paranoia:


Well what I was asking for is a simple explanation of what that "technical description" means. I can understand stretching up - down and stretching L - R but no-one on this thread has yet given an explanation I can understand of how the extra two ways of stretching arise.

In reply to harold walmsley:

Okay. As I explained earlier, the extra two ways are 'on the bias'; i.e. diagonally. If you want to say that gives an infinite number of ways of stretch, go ahead, but everyone will dismiss you as a pedant.

In reply to harold walmsley:

http://www.ukhillwalking.com/forums/t.php?n=609375&v=1#x7989025

Up-down, left-right and two diagonals.

(Edit: cross-post with captain paranoia.)

In reply to harold walmsley:

To me it just sounds like the advertisers and marketing men having nothing better to claim.

In reply to Bluebird:

Finally someone talking some sense. Manufacturers have for a long time designed to permit three way stretch. This simply refers to the fact that your trousers permit forward motion. A substantial development on tweed. The more recent addition of a fourth dimension introduced navigational competence. You experience this as a slight feeling of deja-vu as you leave the North Face car park: Your trousers have been there before and remember the way. Apparently fifth dimensional stretch is just around the corner. Your trousers are actually somewhere else where it isn't raining. You experience this as a slight feeling of smugness as you leave the North Face car park.

In reply to Mark Torrance:

I'm looking forward to fabrics woven from super strings, which should give us 26-dimensional stretch.

In reply to Billy the fish:


But used properly, it's useful information for a buyer who understands the term.

Polartec 100M fleece has anisotropic stretch: it stretches more in one direction than the other. This is good, provided you get the orientation right. The first fleece pullover I made with this fabric looked fine until you tried to put it on, even though, laid flat, it was the same size as one that went on fine. The problem? I hadn't noticed this anisotropy, and had cut the panels with the greater stretch running vertically. Great for over arm reach, but not so great at letting you get in to the thing...

The same care needs to be taken for trousers. I've seen items where anisotropic stretch is run across knees and seat, where you really want the greater stretch running vertically. Better is two-way stretch, so the joint can expand the fabric in two direction, and even better is 4-way stretch, which allows the fabric to stretch to accommodate arbitrary expansion, such as approximate spheroidal features like knees and seat.

In reply to harold walmsley:

4-way materials stretch in spacetime. Behave like standard 3D-stretching materials, unless you climb at relativistic speeds like ueli Steck.

CB

In reply to harold walmsley:

I had a pair of six way stretch trousers once. Or was that my imagination!!

In reply to captain paranoia:

Surely if you have up-down and L-R stretch diagonal stretch is automatically provided by the combination of the two? Are there extra stretch mechanisms provided?

In reply to harold walmsley:

4-way stretch is not a marketing term. As stated above it means that the material stretches vertically, horizontally and in both diagonals. The diagonal stretch does not come from the combination of vertical and horizontal stretch. This material format is essential for pressure relieving cushions such as in wheelchairs as it prevents the cover material from hammocking over the underlying pressure cushion (eg memory foams and gels). Since this means the material can conform to 3D shapes I would imagine that it would work well in climbing clothing to reduce the restriction of movement.

In reply to Nicola:

There is probably a reasonable definition/guide in the latest edition of " textile terms and definitions" by the Textile Institute.Anybody got a copy ?

In reply to captain paranoia:

Surely most fabric stretches a bit on the bias (just double checked with a bit of cotton lawn)? To my mind it's the warp and weft stretch that make up the '4 way'.

In reply to Tall Clare:

Yes, woven fabrics do stretch slightly on the bias, which is why bias cut dresses hug the figure nicely. It's also why, twenty years ago, I considered modelling tent fabrics as a square grid mesh of four inelastic beams, jointed at the corners, and with springs across the diagonal corners. And why, when cutting panels for a tent, you can't simply try to achieve the best fit of panels from the roll, since you have to take into account the bias stretch on the way the tent behaves...

In a woven fabric, there's usually a bit more give in the weft direction, since the warp fibres are held tight in the loom, and the weft fibres are threaded through them, so end up having more slack. This give is used in cross grain designs.

But I think what I'd call four-way stretch is achieved by knitted, rather than woven fabrics. Since these are formed by loops of thread, rather than a rectilinear array, they can stretch in all directions more easily. That's why a lot of stretch soft shell fabrics are actually knits, rather than woven. And I suspect that coverings for foam seating that Nicola mentions is probably a knit, too.

As you know, I'm only an amateur at this stuff, and what little I know is down to observation, rather than formal study. So it's quite likely my understanding is wrong; looking up the MEC T3 hoody linked in a recent thread led me to a video by their clothing designer, and she seemed to use 'two-way stretch' to be in one direction, and 'four-way stretch' to mean two directions.

In reply to captain paranoia:


Found it again, but it was their 'materials developer':

youtube.com/watch?v=fNRM49dkJ_M&

In reply to harold walmsley:

Harold,

'Four way stretch' describes a material that is not only flexible across it's length and breadth but also can increase its depth. It will get thicker or thinner on demand. That is a condition for simple 'Three-way stretch'. For true 'Four way stretch' the material also has to be flexible in time. So your jeans (for example) will not only stretch as your thighs get fatter, they will stretch as you bend your knee. They will also get thicker and thinner as climatic conditions change. And, most essentially, they will last into the future.

It is believed that weaknesses in 'four way stretch' have led to the number of jeans one can see currently with rips and holes in them.

In reply to harold walmsley:

I found a more understandable description on another forum:

"One-way stretch means a fabric will stretch on the crossgrain (side to side) but won't recover. Jersey and interlock knits without lycra are a prime example.

Two-way stretch means a fabric stretches on the crossgrain and also recovers. Hence the "two" part - stretch and recover. Jersey knits with lycra are a good example.

Four-way stretch means a fabric stretches and recovers both on the cross and lengthwise grains. Nylon/lycra swimsuit fabrics are an example of a four-way stretch fabric.

Confusion however reigns when people don't understand the difference between one-way and two-way stretch fabric, and don't take the recovery of the fabric into account. It's not only about the stretch. It's also about the recovery.

One-way: stretch on the crossgrain, no recovery (no lycra)
Two way: stretch and recover on the crossgrain (contains lycra)
Four-way: Stretch and recover on both the crossgrain and lengthwise grains (contains lycra)"

In reply to harold walmsley:

I know Harold very well . Do not get into a discussion with him over this at your peril (and never ever ever ask him which is best;petrol or diesel?)

In reply to mark hounslea:


Neither... one *might* be 'better' than the other for some purpose but you can only have a comparative and not a superlative when comparing two? :-P

In reply to harold walmsley:

Surely if something stretches in one direction but doesn't return to it's previous state, it's effectively...erm...broken?

So, one-way stretch is stuff that you can stretch but doesn't go back, which is every material on the planet, apart from all the ones that do (which are two-way stretch).

I sounds to me like, to the layman:

One way stretch = not stretchy
Two way stretch = stretchy
Four way stretch = stretchy in two directions

In reply to harold walmsley:

Stretch with no recovery is want we call 'plastic deformation'.

Stretch with recovery to original dimensions is what we call 'elastic deformation'.

You don't need to add 'elastic' to a fabric to make it elastic (though it helps). Whilst fabrics relying on mechanical stretch only aren't perfectly elastic, neither are they perfectly plastic. Most knits will recover very close to their original dimensions, purely with mechanical stretch; a woollie pullie anyone? Note the comment in the Wiki link I posted earlier, about how much better knitted hose are than woven.

But I can see that those definitions of stretch have some merit when used to describe 'active stretch' fabrics that incororate genuinely elastic materials such as latex, Lycra or spandex.

In reply to mark hounslea:


I had noted apian sounds coming from brimless headgear...