Knitty: little purls of wisdom

To Block or Not to Block

I’m talking about handspun, not knitting.

I know many spinners that like to block their wool yarn under tension, some under a lot of tension – milk jugs filled with waters, pounds of tension.

They use it to offset extra twist they have in their yarn either in singles or plied yarn. Sometimes lots of extra twist. I’ve heard spinners say that they’re fixing their yarn by setting in under weighted tension. It may be a temporary fix, but depending on the the amount of twist and the end project it can cause even more problems.

I almost never block my wool yarns (silk and cotton are a different story) to reduce twist. Why? Even when my yarns look mostly straight and even, the twist is still hiding in there. If I knit with blocked yarn and then wet or steam block my project, I get a nasty surprise.

To make sure what I think happens with reactivating twist actually happens, I did some quick experiments with a couple of different wools. I used commercially prepped top dyed by Cjkoho designs, some BFL and some Corriedale cross.


I spun singles from both yarns with a crazy amount of over twist. I didn’t measure. I put my drive band on the smallest whorl on my regular Lendrum head and treadled like a mad woman. I used an extreme amount of twist to have a lot of contrast in the before and afters of my experiment. I used the same amount of twist , same whorl, same treadle count for both yarns.

I saved a bit of each yarn and set the rest under weighted tension. I soaked both yarns in hot water then hung them with weight. I used a gallon milk jug, half full of water. It pulled my singles taut and stretched them as they dried.

After they dried my yarn was straight or at least straightish. Before I blocked it, both yarns felt stiff due to extra twist and after blocking they also felt lifeless. In my BFL sample there were spots that were perfectly straight and spots that still had little coils of twist. Since the BFL is a longer stapled fiber than the Corrie-Cross it doesn’t need as much twist as the Corrie Cross to hold together as yarn. By using the same amount of over twist with both fibers, the same whorl and the same number of treadles, the BFL yarn has a twistier reaction, leaving me with coils even after blocking.


I knit my singles yarns into two small stockinette swatches for each breed. I didn’t block them. Both samples are pretty flat and straight, though a close look at the individual stitches shows they are resisting the block. If you look at the left leg of my stitches in both swatches, they are anything but orderly.

The second swatches I soaked in water and let the twist reactivate. Both the Corrie cross and the BFL swatches curled up like dry fall leaves. I wouldn’t want this to happen with something I’ve spent time knitting, especially something like a sweater.

I’ve shown an extreme amount of overtwist, but even a moderate amount of overtwist would skew knitting when the twist is reactivated. Reactivating the twist also reverses the stretch that happened in the finishing, changing the yardage.

The only knitting instance that it might be ok to finish this way, depending on the amount of over twist is in lace knitting, or any type of knitting that would get a hard, thoroughly pinned out block., something that mimics the setting under tension scenario.

There are knitters who love the look of over twisted yarns, but they plan for it. Kathryn Alexander has designed many gorgeous things utilizing over twist as an element, she calls her yarns energized singles. She plans in advance for her over twist creating rhythm and motion in her pieces and usually uses fresh singles in her work.

What about plied yarn? Funny you should ask because I did the same experiment with 2-ply yarn. I spun regular singles that would easily ply to balance as a 2-ply, maybe a 45-degree twist angle. Then I over-plied until I made many pigtails in the plying. I blocked both yarns with the same hot soak and tensioned with a half full milk jug. The resulting yarns, don’t look nearly as distressed as the singles, though they feel every bit as wiry. There aren’t any pigtails left in the yarns after blocking.

Like the singles yarn I knit 2 swatches out of each plied yarn. I left one alone and soaked the second in hot water. The swatches that were left plain don’t show as much distress in the stitches as the singles swatches. But the right legs of the stitches in both swatches aren’t quite uniform. The BFL swatch over all does not want to align, it’s biasing to the left.

The swatches that were dunked had a bigger reaction than the singles swatches that were soaked. These, especially the BFL swatch looks like crumpled paper.

The original twist reactivating in a plied yarn is more extreme because there is more than one single in play and 2-ply yarns already tend to push away from each other. Both of those things bring more potential motion to the yarn, creating this wild rumpus in the swatch.

After doing these experiments I’m even more adamant about not setting my yarn under tension or weight unless I have a special plan for it. If I find myself with yarn that has too much twist I’ll use different ways of pulling the twist out, like running it the opposite direction through my wheel, rather than subject it to harsh finishing.


Jillian Moreno is the editor of Knittyspin. She's on the Editorial Advisory board for PLY Magazine. She lives in a house packed with fiber and books.

Be warned, she's a morning person and is disgustingly chipper before 9 am.