Saturday, April 8, 2017

The what and why of ribbing

Back in January I promised more posts on k1p1 ribbing and I'm finally getting around to it! Yay! This started as a side quest/distraction from my green sweater odyssey-- to recap: I became obsessed with getting the folded neckband of my sweater to look just right, and after about eight attempts I decided there must be something special/diabolical about k1p1 ribbing. So the side quest became a kind of exorcism! 😈  I have been knitting many swatches and learning a ton and finding new little threads of inquiry to follow all the time. I'm not sure it's possible to tie this all "research" together into a neat package, but I want to share what I have so far!

The first question I want to tackle: what is ribbing and why is it... what it is? I really never thought about this until I started trying to make my k1p1 ribbing LOOK better-- when I learned to knit, I just made stitches, and then began following patterns. Knitted fabric wasn't really a mystery to me until I started asking questions about it!

Down to basics: all knitted fabric starts with knit and purl stitches, of course, and when you look closely you see that knits and purls are just different faces of the same stitch! (Do you remember the moment when you first realized this? Mind blowing.) I am enthralled by the variety that arises from just this one stitch, by a loop pulled through another loop. The fundamental knitting choice is the direction the loop is pulled from-- back to front for a knit, front to back for a purl-- and from there we build an almost infinite number of stitch patterns with different characteristics and behavior!

Take, for example these four swatches:

They all have the same number of stitches, and three out of the four were made with the same number of knits and purls. But they all act very differently!

So what makes ribbing ribbing?

It is composed of knits and purls alternating horizontally but stratified vertically. I'm mainly interested in k1p1 fabric, but ribbing can have any multiple of knits and purls in these vertical columns as long as they are strictly separated-- k2p2, k3p2, k1p3 and so on... Any intrusion of knits into the purl columns or vice versa changes the fabric's nature, which is elastic-- like any knitted fabric in can stretch, but ribbing can grip and cling and gather. This is because it actually contracts in the horizontal dimension when it is relaxed. You can see that it is much narrower than the stockinette swatch with the same number of stitches:

But what makes ribbing elastic? Different knitted fabrics behave in characteristic ways, but why? When you stretch a piece of ribbed fabric horizontally, it will snap back when released (how readily it does this varies depending on other factors, but that is another thread of inquiry!) There seems to be energy in the fabric-- maybe from the twist in the fibers making up the yarn? maybe from the path the yarn takes as it moves through the stitches across the row? maybe both?-- and the placement of the knits and purls in relation to each other determines how this energy will make the fabric look and act.

If you align all the knits on one side of the fabric and all the purls on the other side, you get stockinette fabric, which (famously, maddeningly) curls vertically toward the purl side and horizontally toward the knit side:

The energy in the fabric is unbalanced somehow, hence the curling. Other fabrics lay flat-- think of garter stitch, which is generally made by knitting all the stitches back and forth.

When viewed from one face of the fabric garter stitch alternates one row of knit stitches with one row of purl stitches-- this can be hard to see until you stretch the fabric vertically:

The same number of rows of stockinette stitch makes a much longer fabric:

Yet garter stitch is wider-- I wonder why?

Garter stitch lays flat but contracts vertically-- the purl bumps come forward and the knits recede. This also happens when you make a single row of purl across the knit face of a stockinette fabric-- the fabric makes a kind of horizontal fold at the line of the purl stitches. But the opposite of happens when you make a vertical column of purl stitches in stockinette-- the purls recede into the fabric rather than coming forward. Weird!

In seed stitch and its variations (moss stitch, double moss stitch, etc), the knits and purls alternate both horizontally and vertically, and the fabric is both flat and relatively expansive-- it has more rows per inch than stockinette, but fewer than garter stitch.

These stitch patterns are more efficient in terms of fabric dimension than garter stitch or ribbing and more balanced than stockinette-- but they don't have as much elasticity as ribbing or garter stitch.

In ribbing, the knits and purls line up in columns. Ribbed fabric lies flat but contracts horizontally. Just as garter stitch forms horizontal folds where the purl bumps come forward, k1p1 ribbing forms vertical folds where the purl columns recede between the knit columns, like the bellows of an accordion. And just as garter stitch can be stretched vertically to reveal the knit stitches, ribbing can be stretched horizontally to reveal the purls, and the energy of the fabric causes it to return to its contracted state. Elasticity!

We take advantage of this property of ribbing to make our garments more fitted and resilient at their borders-- but something becomes very obvious about ribbing when it is right next to stockinette stitch:

The knit stitches in the k1p1 ribbing are MUCH bigger than the knit stitches in stockinette-- both of these swatches were made on the same size needle. The knits also look very different-- loose but also flattened and squarish:

Why is that? Are these two phenomena-- the larger stitch size and the unsightly, ladder-y stitch appearance-- related? More on this and other questions soon!


  1. Yeay! I'm glad to see part two of the exploration of ribbing (and what you've come up with so far is fascinating, thank you!)

    I hate swatching, so I also commend your patience. :)

    1. I'm so glad you came back! I love finding people who enjoy my knitting nerdery :)

    2. Thank you! And I'm learning so much about the various fabrics from what you're posting here, so it's wonderful!