Knit Tips: Sweater Growth

If you’ve ever blocked a hand-knit sweater and ended up with super long sleeves or more length in the body than you planned for, you’ve probably had this thought:

How do you know how much it’s going to grow when you block it?

That’s a great question, and while it’s not a simple answer, there are a few ways to predict – and plan for – growth. It comes down to three things:

  1. Washability
  2. Fiber Content
  3. Stitch pattern/texture

Let’s start with washability. Superwash yarns naturally grow more (usually significantly more) in both length and width than non-superwash.

Why does superwash grow SO MUCH?

Superwash yarns are processed to remove the outer scales of the fiber. The removal of outer scales makes yarn smoother and softer; two qualities that can be quite appealing. These outer scales are what cause animal fiber to felt (think: major shrinkage) when introduced to hot water and friction, and are often the reason we might refer to a fiber as “itchy” or “crunchy”. (Personally, I love crunchy wool.)

Here’s the thing: the outer scales of animal fiber serve a purpose, and it’s worth considering their role in your finished product. These scales work together to keep your stitches where you left them, optimistically holding each other up while gravity works against them. They also create a smokescreen – for lack of a better word – that hides inconsistent stitches by blooming slightly when blocked, masking light unevenness.

Without the outer scales intact, yarn is noticeably softer – but the stitches become less collaborative. With nothing to hold onto they lose their ability to maintain their shape and are unable to work together in the same way that untreated animal fiber can. Superwash wool often enhances stitch definition (yay!), but at the same time, can affect the ability for those stitches to hold their shape, and – most frustratingly – shows off inconsistency (boo!).

When it comes to most sweater knitting I love a non-superwash wool if you/the recipient can handle the feel of it. It will hold its shape and wear better over time. (A note for seamless sweaters: sticky wool can really help with maintaining shape and fit.) And, since the garment won’t grow excessively, you can more easily predict the outcome for your sweaters. Keep in mind that not all animal fibers are the same, though, and they don’t all behave like wool; if you’ve ever knit a sweater with baby alpaca, you know what I mean. To learn more about various fibers and their attributes, I highly recommend Clara Parkes’ book The Knitter’s Book of Yarn.

If you want to knit a sweater with superwash yarn (and – truth be told – sometimes that’s the way to go, especially if itchy yarns bother you), be sure to keep in mind that it’s going to grow in length when you block it.  — And you WILL block it, right? Of course, you will. How much it will grow depends on an infinite number of factors (keep reading to learn a few of them), but I find that the body and sleeves usually grow several inches in length when using superwash wool vs. untreated wool. This means you’ll want to stop at least 2 inches (if not more) BEFORE the finished length you’re hoping to achieve.

Last but not least, I can’t talk about superwash yarn without a caveat: Remember that “superwash” doesn’t mean you can really throw it in the washer and dryer without consequence. Sure, your garment won’t felt (in theory), but it might still shrink a bit and can lose its shape. No matter what yarn you use I recommend hand washing and laying flat to dry for best results.

What else makes your knitting projects grow?

Fiber Content

Some fibers lend themselves to structure, and some lend themselves to drape. Silk, alpaca and bamboo – while excellent for drape – can lead to extra growth in your project. Regardless of washability, when slippery fibers are involved growth is inevitable. Even if your yarn only has 10 or 20% silk, you’ll see a difference in growth versus a fiber without it.

Last but not least:

Stitch Patterns

Every student I’ve ever had has heard me say, “The eyelet giveth and the cable taketh away.” Stitch patterns with lots of eyelets (i.e. lace and mesh designs) will grow in length. Period. If you combine a lace or eyelet pattern with a slippery or superwash yarn, growth will be enhanced. Keep in mind that this isn’t necessarily a bad thing; a good pattern will employ these characteristics as a design element, which is why it’s important to stay within the fiber family of the yarn the pattern recommends; it’s an easy way to make sure you’ll get similar results. It helps to know ahead of time that growth is expected so you can prepare accordingly.

Cables, however, work like a good support bra; those stitches aren’t going anywhere. Cables draw the fabric in width-wise and maintain their partnership with the fabric around them. You can expect less growth when cables or heavy texture are involved. The more textured stitches, the more secure the fabric tends to be (stranded colorwork can also be of assistance here). There are exceptions to every rule, but in general, texture works against gravity.

Let’s talk about a few variations

Q: What happens if you combine cables with slippery yarn?

A: The cables will help prevent some of the growth you would normally see in a superwash or slippery yarn, but they won’t prevent all of it. When considering how long to knit your project, consider what proportion of the garment includes cables. The more cables or heavy texture (i.e. twisted stitches, mosaic, etc…) the more it will counteract growth.

Q: What happens if you combine eyelets with crunchy, non-superwash wool?

A: Much the same as with the previous example, pairing elements with opposite characteristics will help to moderate your results. Crunchy wool sticks together better than slippery wool, so eyelets/lace in a natural wool will experience slightly less growth.

Q: What if you combine eyelets with slippery/superwash yarn?

A: GROWTH. So much growth. Prepare yourself for multiple inches of extra length. I once had a customer who knit my As The Crow Flies wrap (eyelets!) with a superwash silk blend yarn (slippery!) and it grew nearly 10 inches (25 cm) with blocking.

Q: What happens if you combine cables with sticky/crunchy wool?

A: Minimal, if any, growth. This combination is the closest thing you can get to a guarantee when it comes to guessing how long your sweater and sleeves will be after blocking. Every garment relaxes with wet blocking, so at least some growth (1 in/2.5 cm) is fairly standard, but with this combination of fiber and texture, you’d not likely see any additional growth beyond that.

In conclusion

In case you haven’t noticed, figuring out how much your garment will grow can be a bit of a guessing game. As with anything, though, the more you do it, the better you’ll get at predicting results. When I dive into a sweater project, I keep the characteristics of the fiber and the stitches in mind as I go, making sure I compensate for growth (or lack thereof) in determining the length of my project.

The best part? It’s always fixable. Adding or removing length after blocking has never killed anyone (that I know of). Be brave, darling knitter. Be brave.

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