How often do you need to re-block your knitting

Is blocking required every time you wash your hand-knitted projects? Find out here!

Let’s not dally around. Typically, blocking your knitting – so the act of soaking it in water for ~30min, stretching it out on a blocking board with pins, and letting it dry – is a one-time effort. It is a more or less irreversible process. However, that doesn’t mean you cannot use some tips and tricks to neaten up your knitted laundry every time you wash it.

The most important takeaway for you in this article is that blocking typically has two separate components: You submerge it in water AND stretch it.

Once you understand the difference, you will know exactly what is possible after washing a knitted garment one more time, and what not. Let’s take a look at the fine details together!

Part I: The magical reaction between wool and water

You’ve probably seen this before. The edges of your project in stockinette stitch are curling in. However, after blocking, the edges are more or less straight. I say more or less because you might have observed that, with time, they will gradually start to curl in again. So what is happening here?

Yarn is typically made from animal hair (think sheep wool, alpaca yarn, etc). So, first of all, we need to take a look at the chemical structure of hair. Various chemical bonds are responsible for the structure and form of hair. Among them are relatively weak hydrogen bonds. And these can be dissolved through water. As a result, the hairs become a little bit more maleable. However, as soon as the water evaporates, new hydrogen bonds are formed, and the hair becomes a bit more rigid one more time.

If you’ve ever received a blow-out, this is essentially the exact same process.

Now it’s important to note that there are also other, much stronger disulfide bonds in your hair. These are responsible for the overall structure of your hair, e.g., your curls. And these disulfide bonds cannot be weakened with water. You would need much harsher chemicals, like a perm.

And this is where we need to talk about ambient moisture. After your swatch has been blocked and is all dry, the humidity in the air will gradually dissolve the hydrogen bonds that locked down the shape. And in this moment of weakness, the stronger disulfide bonds prevail, making the individual hairs snap back into their original shape.

To give you a real-life example: No matter how well you straightened your hair, if the humidity is high and/or you sweat a bit, your hair will look all frizzy only minutes later. Or you might have noticed how a slightly worn-out sweater comes out of the washing machine a little bit shrunken.

Why? Sheep wool is very curly. Spinners would say it has a lot of crimp. As you wear it, and you may sweat a little bit, you can stretch out those curls. But as soon as you submerge it in water and there is no outside tension forcing the yarn in a different direction, the individual fibers all snap back into their original shape. That’s also why you say sheep wool is stretchy.

Your main takeaway as a knitter here is:

Every time you wash your knitted items, you can use this little bit of chemistry to neaten up your projects. Spread them out flat on a blocking board, use some choice pins or blocking combs, and get things back in shape. Make sure that all the seams, potential decrease/increase lines, and the edges are all symmetrical. And once your project is dry again, it will look that much neater.

On a personal note: I know this is a bit of extra effort. So, I don’t do this with every random plain vanilla sock I wash. However, for more important statement pieces like sweaters or so, I definitely go the extra mile. If I spent 50 hours knitting project and 200 USD on yarn, I definitely feel that 5 extra minutes of effort are more than worth it to get the most out of my initial investment.

Part II: Stretching your finished projects to open up the stitches

In the introduction, I mentioned that blocking also has a second component. As an experienced knitter, you are probably aware that you typically use pins to stretch your project out and keep it under tension as it dries.

If the project is a lace shawl, you might stretch things out a lot farther than if it’s some socks in 2×2 ribbing, but there is always this stretching component.

And this is where we need to look at a little bit of knitting mechanics. What are you actually doing when you stretch out your knitting, and what is the benefit?

Unlike with crochet, all stitches in a row of knitted fabric are interconnected. I can easily pull on one stitch, and it will steal yarn from the adjacent stitches. If I pull hard enough, I can potentially affect stitches even further down the line, and if one of your earrings has ever caught the yarn, you probably know what I am talking about.

Now, no matter how good a knitter you are, your stitches will never be completely uniform. One stitch might be slightly larger and one stitch slightly smaller. And as you stretch out your knitting and put the fabric under tension, you give those stitches the chance to balance out. The smaller stitch will steal some yarn from the bigger stitch, and your overall stitch definition will look much nicer.

But here’s the thing: More complicated stitches will create more friction. Think of a knit two together, where two stitches are basically lying on top of each other. The whole two loops are rubbing against each other, whereas two adjacent knit stitches barely touch each other.

Why is this important? Well, as you stretch out your knitting, these complicated stitches will often form knot-like structures. However, because the friction is so high, they will not open up again if you stretch your knitting in the other direction. On top of that, stitches will start to slightly felt together as you wear your garments, increasing the friction one more time.

As a result, blocking, or rather the act of stretching out your fabric, is pretty much irreversible. Once it’s stretched out, it stays stretched out.

This particularly applies to lace, where you will also create little yarn reservoirs between the stitches (but to a lesser extent also to knitting stitches, such as garter stitch, a lot of the edge stitches, etc.). And as you stretch out your knitting, this little bit of slack gets transferred to the loops of the stitches. But you can’t crumble up your knitting to let things ease back again.

You could, potentially, go into each and every single stitch individually with a fine knitting needle to reverse the process, but in real-life knitting and a lace shawl that has 50.000 stitches or more, that is not a feasible option.

Here is your main takeaway for this part:

Essentially, this means that as you lay out knitting on a flat surface after washing, there is no need to stretch it out anymore. In fact, I strongly advise against it as you only risk permanent damage.

Instead, I will only apply the lightest bit of tension. Just enough to ensure I get a smooth, unwrinkled surface but no more. I want my items to get back in shape, not create a new, stretchier shape.

I think the only possible exception to this rule is if you notice that your project just doesn’t fit well enough, yet. Maybe your sweater or your gloves are just a tiny bit too tight yet. And then, you can submerge it in water overnight to really loosen up the fibers and stretch it out a little bit further. But always remember, what you are doing will be more or less irreversible, and there’s almost nothing you can do to shrink an over-blocked sweater.

Anyway, I hope this helps you wash and block your projects. Let me know if you have any questions.