How to Block Acrylic Yarn the Easy Way (in 3 Simple Steps!)

I’ve been blocking acrylic granny squares and garments ever since I started crocheting over a year ago, and it’s my favorite way to smooth out uneven stitches, even out the sides of my granny squares, and achieve an overall polished look.

As a general rule, steam blocking is the best way to block acrylic items and squares to specific measurements. To block, use T-pins or knit blockers to pin down the project to a foam mat. Then, use a steam iron and hover it a few inches away from the project, and let it rest overnight.

Now, I’ll lay out the three easy steps to block acrylic, and show you the before and after photos for the items I blocked, which include hexagons, squares, and even triangles!

here’s what I’m blocking today!

1. Gather materials: foam mats, pins, and steam iron.

There are only a few materials needed to steam block acrylic. You’ll need the following:

Foam blocking mats

These mats are usually square shaped, with interlocking edges that allow you to extend the total area of the mat in different configurations. Foam mats made specifically for blocking might include a grid with 1″ x 1″ squares, so that you can ensure that your project is completely square, triangular, or a specific dimension. Some mats might also include markings for circles, so that it’s possible to block mandalas and other large circular items.

However, if you’re willing to forego the grid, any kind of foam mats, especially those meant as floor mats for babies, are perfectly functional for blocking. The main purpose of the mats is to be able to insert pins through while also being waterproof during the steam blocking process.

This is the set that I use — though a little pricey, it includes nine mats total, a storage cube, as well as a box of T-pins for pinning. Normally I only use one or two squares, but I’ve used six or more for garments.

T-pins or knit blockers

To pin your project to the foam mats, you’ll need pins of some sort. At the most basic level, sewing pins will probably work in a pinch, but the most commonly used pins are T-pins.

T-pins are sturdy metal pins with a t shape at the top that make them easy to insert in foam mats and through knit fabric.

Knit blockers are several pins all embedded in a row, attached to a plastic handle. These are specifically made for blocking, since they can speed up the process of blocking large objects that might need many more T-pins. Although they aren’t necessary, they can be a worthwhile investment because of their efficiency and ease of use.

Steam iron

To steam iron your project after it has been pinned down, you’ll need either a handheld steam iron or a conventional iron with a steam function.

Both of these work the same way — there is a chamber for water, and a surface through which hot steam is pumped through.

I purchased this handheld steamer specifically for blocking, because it made it so much easier for me to hold for long periods of time, and also was able to be used for a longer duration. However, if you don’t want to shell out just yet, check your iron at home and see if it has a steam function — many of them do!

2. Pin project to mat to desired measurements.

After you’ve gathered your materials, the next step is to assemble your blocking mats until the area of the mat is larger than your project. For this example, I just used one mat since the granny squares and other shapes I was blocking all fit on it.

Pin your project down on the mat, making sure the edges are all flush with the lines and that after pinned, your project looks the way you want it to.

In the “before” photo, you can see that my granny squares and other shapes all have uneven sides and slightly curled edges. The triangle is particularly curled, with one corner that does not lie flat. The lace in the 12-sided mandala does not show particularly well, and each of the corners is not very defined.

I stretched out each piece slightly and pinned it down so that each of the sides were even and the corners defined, without a bulge in the middle. This also allowed the lace and gaps to show more clearly. the square out slightly and pinned it so that there was no bulge in the middle.

In general, blocking helps projects lie flat, become standardized shapes, show stitch definition more clearly, hold their shape, and all around look more professional!

3. Using a steam iron, hover it over the project.

The last step is to turn on your steam iron and hover it over the the surface of your project so that it releases steam onto the yarn. Doing so heats and relaxes the stitches into the shape that you just pinned it into. If you’re using a flat iron, do not touch the iron to the project, since it will melt. If you’re using a handheld steamer, try not to get too close to the yarn either.

I made a short video of me steaming the granny squares I made. You can see that I stay a few inches above the yarn at all times, and spend about a few seconds over each one. I can tell when I’m finished if I touch the yarn and it feels warm and a little denser than when I began.

It’s important that the yarn feels slightly hot because acrylic blocking relies on heat to relax the yarn. Acrylic is a synthetic materials made from plastic, so for the yarn to relax, it needs to be heated a little and then cooled.

Watch me steam block my granny squares!

After you finish going over the entire project, all you have to do is leave it for a few hours or overnight until it cools and dries. Afterwards, just remove the pins and your project should have smooth, even edges, in the exact shape that you pinned it in!

In the before and after picture, you can see that all all the squares have much more even edges without any curling. The most dramatic change is that of the triangle and the square on the top right. The 12-sided mandala’s lace is much more defined because it has been stretched out.

In case it looks a little like an illusion that the edges aren’t curling as much, check out this video I took after I finished blocking to see that the acrylic really does hold its shape.

And that’s it — your acrylic blocking is all done!

Commonly asked questions:

Is steam blocking acrylic permanent?

As a general rule, steam blocking acrylic is permanent. Acrylic yarn is spun out of plastic fibers, so applying heat gently will shape the yarn into a fixed shape. Once steam blocked, it can be washed and air dried without the fabric coming out of shape.

Can you block acrylic yarn?

Typically, acrylic yarn can be blocked through steam blocking. This method works because steam blocking uses heat to slightly melt and mold plastic fibers in acrylic yarn into the desired shape. Wet and spray blocking do not work because they do not apply heat, only water.

Should I block acrylic yarn?

As a general rule, acrylic projects that need to be a certain shape or measurement should be blocked. Blocking can show stitch definition and lace patterns more clearly, even out fabric, and uncurl the edges. Because of these benefits, it’s ideal to block squares, garments, mandalas, and shawls.

Should I kill acrylic yarn?

As a general rule, killing acrylic yarn is undesirable because it permanently eliminates elasticity and also melts the stitches together without a possibility of frogging. However, it can also make a project rigid and give it a shiny drape, so sometimes killing acrylic yarn can be intentional.

For a tutorial on how to kill acrylic yarn and before and after photos, check out this article on Moogly Blog here!

Can I wet block acrylic?

Wet blocking acrylic yarn is ineffective because acrylic yarn is constructed from plastic fibers that cannot be reshaped with water. Applying gentle heat by steam blocking is the only way to block acrylic projects into a specific shape since heat allows the plastic to settle in shape.

Can you iron acrylic yarn?

As a general rule, flat ironing acrylic yarn will melt the crochet fabric, also referred to as “killing” acrylic. To eliminatea wrinkles and uncurl edges, steam iron acrylic yarn without touching the iron to the yarn either with a handheld garment steamer or the steam function on a flat iron.