How to Steam Block Acrylic Yarn

The last time we talked about blocking your knitting, we talked about wet blocking, which is great for natural fibers, but acrylic is essentially spun plastic, and simply getting it wet isn’t going to change anything fundamental about its shape or structure. So, let’s talk about steam blocking acrylic yarn.

You’ve just knit a cute acrylic scarf for your friend who is “allergic to wool”. You know you should block it, but you’ve heard that you can’t block acrylic. But you want the lace to look lacier, and the cables to look cable-ier. So what to do?

It’s time to steam block.

What is steam blocking?

Steam blocking is the best way to block acrylic yarn because the heat and moisture work together to relax the acrylic fibers. As they cool, they remain set in the position that you’ve pinned them in. Steam blocking is also great for pinning out blanket squares before attaching, and we’ll definitely talk about that more in a later post!

So what do I need to get started?

a photo of blocking boards, blocking wires, a steamer, pins, and a tape measure on a white table with a blue scarf on the top.

Foam Blocking Boards (Or foam floor mats)
Blocking Wires
Steel T-Pins
Tape Measure
An Iron with a steam setting, or a garment steamer. (I started this project with my garment steamer, and ended it with my steam iron, sorry about the inconsistency in the pictures)

(As an Amazon affiliate, I may receive a small commission from items you purchase through my links at no additional cost to you. I would never recommend something that I don’t love or wouldn’t use myself.)

Ok, I’ve gathered all my stuff. Now where do we start?

Click your blocking boards into the shape you need for your piece to fit. Make sure to leave growing room for your piece to stretch when you’re spreading it out. I left not quite enough room on the end of one side, but it ended up working out fine, but learn from my mistakes lol.

Take your finished piece and one of your blocking wires and begin to weave the wire along inside the longest edge. Choose a consistent amount of selvedge stitches–I usually do two stitches, but for whatever reason today, one and a half seemed to be about right. Move the wire from the front to the back every few rows or so, keeping to that selvedge stitch. Make sure to leave several stitches on either end of the wire to accommodate stretch.

When you approach the end of the wire, grab a second one, and thread it along the last inch or two of the first wire before continuing on. The overlap will just help you to keep it all as one edge, so it’s easier to keep it nice and straight. Take care at the corner to find the place where you’ll want your other wires to intersect.

Showing a blue scarf with the wires meeting in the center corner point.

Repeat along the other edges of your piece.

Now we come to the stretching.

Although, I don’t want you to think of it as “stretching” so much as a gentle spreading. More like shaping a pizza dough to a pan, less like pulling as hard as possible on your brother’s old Stretch Armstrong doll.

A blue triangle scarf, smoothed out and pinned

For this piece I began at the center top, and gently spread the scarf outward along the wires, pinning every 2 inches or so. I also pinned out the bottom corner, so that I could more easily eyeball the amount of spread the piece could accommodate. Then I moved down to the sides, where I began at the center point and again worked outward. I had some vertical rows of garter stitch in this piece, so I was trying to keep them parallel as much as possible.

Here’s where it gets painful.

For me. Learn from my mistakes, friends!

Remember how I said I started with the steamer? Well, once it came to a boil, it started spurting boiling water out of the head. All over the table, onto the floor, onto me. Genius that I am, I grabbed a towel, mopped up the floor and table, and then took the same towel and WHILE the steamer was on, wiped down the head–can you see where I went wrong?–and screamed. Because I scalded my stupid hand with boiling water and steam.

You can *JUST* see a puddle under the mat where the water was pooling before I decided to take a towel to the whole thing. This is pre-scald lol.

Ultimately I’m ok. A small little tender burn, with no blistering, but I’m aware that I’m really lucky and it could have been a lot worse, and I don’t want that for any of you, my friends. So DON’T touch the hot steamer head, or the iron to test it, as I’ve also known other people to do. I’m not sure what went wrong with the steamer. It’s not the first time I’ve used it, but it has been a while. I definitely didn’t fill it up over the max level line. I immediately unplugged it and set it aside, so I’ll take a look later, but it possibly has just exceeded its lifespan, and since the iron worked great, I’m not sure if I’ll replace it.

Ok, I won’t burn myself, I promise.

Perfect! Ok so what you’re going to do is get your iron to its steam setting (All I have to do on mine is turn it all the way up to its hottest setting) or get your steamer turned on, and once you have steam coming out we’re ready!

An iron hovering magically over a blue scarf. — This is such a cool shot and I couldn’t even see it when I took it, I was just clicking and praying haha.

Hovering 1/2″ or so above the piece, slowly move your iron back and forth across your piece. DO NOT touch your iron to your acrylic project unless you want melted plastic on your iron head. If you don’t trust your hand eye coordination enough to hover that low without touching, more passes from a slightly higher height is better than burning your beautiful creation. I move mine along as I would an iron on fabric–not super fast but not super slow. I passed over the project twice, then let it cool (which only takes a few minutes). Then I worried “is that enough” and I went back over for one more pass (which was probably overkill, but I’m Miss Anxiety, so…*insert shrug emoji here*).

Taking the pins out of the blue scarf — The cool thing about using T-pins is that you can just go along, scooping them up in a big row without having to keep reaching over for the box a million times!

Once it cooled for a second time, I took some pins away from the center corner to see if there was any rebound. There wasn’t, so it decided it was good! I removed all the pins, and then whooshed the wires out, and then voila! It was done! Now it has beautiful drape, and the eyelets have opened up a bit more, and because of the garter stitch, it still retains a fair amount of bounce. I’m super happy with how it came out!

A blue triangle scarf hanging on a grey picket fence with blue sky and clouds in the background

FAQ

How much did it change?

The beginning measurements on my piece were 57″ long and 13″ wide at the center. The finished measurements were 71″ long and 17″ wide at the center. So it grew quite a bit!

What pattern is this?

Lacy Baktus by Terhi Montonen, a currently free pattern. It calls for a fingering weight, but I knit it in a worsted and think it came out great!

What yarn is this?

Lion Brand Mandala Ombre in color 204BS Harmony

How hard is this project?

If you can cast on, knit, yarn over, k2tog, and cast off, you’ll be all set. If you can’t “read” your knitting, keep a small pad beside you so you can check off which row you’re on. (It’s an 8 row repeat).