Why Knitting Stretches (and what to do about it)

posted March 25th, 2017

This is a sample from The Knitting School Newsletter that went out this morning. For complete content sign up for news in the side-bar.

All rights reserved. Copyright Helen Sharp 2017

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WHY KNITTING STRETCHES

(and what to do about it)

You probably know this already, but I’ll tell you anyway – knitting stretches.

Here’s why.

 

woven vs knit

Looking at the woven fabric you can see that each thread or yarn is already straight,

Unless it has some inherent elastic qualities, it has no potential to stretch.

Knitting, on the other hand, is composed of interconnecting loops. There is lots of possibility for it to stretch regardless of the inherent stretchiness of the yarn.

fig 14 - course_wise extensibility

Look at how far the loop can open up sideways (in a course-wise direction) – easily 2-3 times its width if it is really pulled.

It has less potential to stretch vertically (in a wale-wise), but still possibly double its relaxed state.

For this very reason, sweaters are usually made with the limited stretch of the wales (or stitches) placed vertically. Turning a sweater around and using the knit sideways gives much more potential for the garment to grow in length (and shrink in width).

wait_what just happened

 

The stretchiness of knitwear is what makes it comfortable to wear. It also means patterns for knitwear don’t have to be as precise as for woven fabric.

However, it is also why it is unpredictable.  In a way, knitwear is alive. It has a mind of its own, and yarn choice and stitch choice add to the unpredictability.

 

WHO’S THE BOSS?

Don’t let the knitting be the boss of you.  Learn how different stitches and different yarns behave and harness that power. A good designer will understand their fabrics and put them to work so the knit stretches where stretch is wanted hugs the body where that effect is desired. This can happen without any shaping, just by using the inherent quality of the yarn and fabric.  The first step -  pay attention to the fabrics you create – see how they behave and plan accordingly.  It is not just about their appearance.

Here’s a couple of examples.

rib relaxed and stretched

 

Ribs stretch more sideways. Looking at the rib from the top, we can see it has lots of potential to stretch and relax.

garter stitch stretches vertically

 

Garter-stitch stretches more vertically.  Looking at the fabric from the side, we can see that in a relaxed state, the courses form a zig-zag.  Once gravity is brought into play (the garment is worn) the fabric will start to straighten out and get longer.

 

 

ACCUMULATED WEIGHT
This brings me to a related subject – accumulated weight. The more fabric there is, the more it will weigh, the more it will stretch.

It is a fine art getting the garment length just right so that you end up with the sweater you want.

When I worked for design companies, the sweaters would come in from the factories and we would have a “fit review”.   A fit review is a meeting with the designer, the technical designer, maybe even the buyers would attend and the all-important fit model or models.

The fit model is a person whose measurements exactly correspond to the desired size/build of your ideal customer.  Different companies have different ideal sizes. Not just small, medium and large. One company’s medium might be quite different from another company’s medium.

In one company I worked at, we also ran petite and tall sizes, so the fit review had three models…but I digress.

The technical designer would measure the sweater flat to see how close the measurements corresponded to what we had asked for and then we looked at the garments on-body.

If we wanted a sweater to be, for example, 26″ long, it might measure exactly that flat, but on-body it may grow to 28″. If we took 2″ off the length to account for the accumulated weight, the sweater now weighs less and won’t drop so much.  Do you see the problem?  So, it became a bit of a guessing game to figure out the perfect length.

How should we approach this when making our own garments?  My advice is to make the tension swatch as large as you are able.  Measure it flat, and once you have calculated the correct tension, pin it to the wall or a vertical surface and let it hang out for a while. Then measure it again. If there is a significant difference, you can start the guessing game for the perfect length

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