K1P1 Ribbing Quest: The Big Knit Stitch Question

My quest continues! If you are just joining me, this post is number three in a series about k1p1 ribbing-- the investigation started with a comparison of attractive (and elusive) k1p1 ribbing and ugly k1p1 ribbing (which seems to be the only kind I can produce). In my second post I looked closely at the characteristics of knitted fabric and how it behaves, and I left off with this picture:

And a question: why are the knit stitches in k1p1 ribbing so much bigger and more untidy than those in stockinette, keeping yarn, knitting technique, and needle size the same? When the knits and purls alternate with each row, or when they alternate both vertically and horizontally as in seed stitch, the stitches remain neat and orderly. But line the knits up vertically between two columns of purl stitches and all hell breaks loose. Why?

My first thought looking at the two swatches side by side is that surely there must me more yarn in those bigger stitches-- seems logical, right? This is easy to test. I knit each swatch with the same number of stitches and rows, I even carefully clipped the yarn tails to equal lengths, so if one swatch used more yarn, it should weigh more. Well I threw each one on my digital scale and they weigh exactly the same. Meaning that there is the SAME amount of yarn in each swatch! So much for that idea.

If there isn't more yarn in those bigger stitches, what accounts for the size difference? What's going on in the fabric? While I was thinking about this I held each swatch up in a sunny window so that I could better see the spaces in and around the stitches. I immediately observed something very striking-- take a look at each swatch in silhouette:

Notice the difference? The spaces between and inside the stitches of the ribbed fabric are much bigger than those in the stockinette fabric. Not only that but the yarn plies in the ribbing stitches look looser and airier-- the ribbed swatch is overall less opaque. The same effect happens in stockinette when I use a MUCH larger needle-- I have been using a size US 5/3.75mm, here's the same yarn knit on a size US 10/6.0mm:

So much more air space! And see how the plies look more open in the bigger stitches? The same thing is happening in the knit stitches of the ribbing sample-- there is more space for the yarn to expand and for the plies to separate in the stitches. There isn't more yarn in those big stitches-- there's more air! But why?

I have sort of a hypothesis-- otherwise I probably wouldn't be wasting my time and yours with this business! Stockinette fabric has less air because the stitches hold each other together better. It has more structural integrity. Each stitch supports the others next to it, the plies of the yarn are held together more firmly and the stitches sit closer to their neighbors. Stockinette can be made to look airier and looser when knit on very large needles, but when knit at a normal gauge it is much denser than ribbing. Garter stitch and seed stitch are also denser, so there can be some alternation of knits and purls without compromising the integrity of the fabric-- it is only when the knits and purls are lined up vertically into columns that the fabric starts to become unstable. Ribbed fabric has more elasticity, but it lacks the structure and cohesiveness to hold the stitches tightly, so the stitches appear larger and looser though they have same amount of yarn per stitch as stockinette.

What causes this instability? Bear with me here because it's about to get even nerdier. This problem of enlarged stitches happens in other ribbed fabrics-- many knitters find that the left knit column in any type of ribbing turns out loose and uneven. You can see it here in k2p2 ribbing:

It is the same on both sides of the fabric-- so both the second knit stitch and the first purl stitch in a k2p2 sequence are loose. Here's what's going on between the stitches:

There are two columns of large holes and two columns of small ones-- the first knit and the second purl in the k2p2 sequence behave just like stitches in stockinette fabric! These stitches are held tightly while the others are loose and airy. It doesn't seem to matter if a stitch is knitted or purled but the transition between them does. The enlarged stitches are on either side of a knit-to-purl transition. The stitches on either side of the purl-to-knit transition are "normal." Why?

While I was pondering this I thought about mirror knitting, where a knitter moves stitches from the right needle to the left as they works across the row-- many left-handed knitters find it more natural to work this way than the more common left-to-right stitching direction. Thus mirror knitters approach the knit-to-purl transition in k2p2 ribbing from the right, rather than the left. If it is in fact the knit-to-purl transition that is destabilizing the fabric in ribbing, mirror knitters might have a different problem-- enlarged right knit columns. I had a friend who knit this way, and I wish she was still around to ask-- in the spirit of dauntless scientific inquiry (which I think she would appreciate) I resorted to stalking the project pages of other mirror knitters on Ravelry, looking for k2p2 ribbing (creepy, right?). Sure enough, some of these knitters have enlarged right knit columns in their k2p2 ribbing!

To bring it all back home: the transition from knit to purl-- no matter which direction you are working-- seems to lead to enlarged stitches on either side of it. And in k1p1 this transition is happening every other stitch! Why does this transition alter the stability of the fabric? And can anything be done about it? At this point in the inquiry I'm not sure but I will take a stab at it in my next post!

I hope if you are reading and enjoying this series you will leave me a comment-- What do you think about my hypothesis so far? Have you tried to improve your ribbing? What has worked for you?