Saturday, 9 July 2011

Can acrylic be blocked?
(a tutorial of sorts)

The short answer is "yes" but not in the same way as natural fibres.

Natural fibres are generally "wet" blocked. For some people, this means spraying their finished knitting and gently stretching easing it to the correct size. For others, blocking means thoroughly wetting the item, removing some of the excess water and then pinning it and easing it to the desired size and shape.

Acrylic is designed to be washed in the machine and (sometimes) tumble dried and still retain its shape! Therefore wetting it to block it and expecting it to retain its new shape is futile. It will just think it's getting a bath and retain its original shape when dry.

Acrylic is a form of plastic. It is created and moulded into various shapes under heat. Have you ever accidentally put a plastic container near a heat source and have it melt on you? Heat will change the shape of acrylic and after it cools it will forever hold that shape.

Acrylic yarn is simply plastic fibres spun together. Heated, they can be moulded to take on new shapes (Ooo, this sentence gives me an idea). But if you bring acrylic yarn into contact with a heat source, the yarn will melt.

So, what heat source do most of us have that will not melt acrylic fibres?


There are, of course, several ways to create steam but for me the easiest way to block acrylic is with my steam iron.

Here is my process:

1. Fill the iron with as much water as it can contain and put it on maximum heat and steam.

2. Pin your item to the size and shape you want. In my case, it was a 25cm (10 inch) square. Pin the corners first

...then the centres of each of the sides. Make sure the centre is in the middle - in this case 12.5cm (5 inches).

Press it gently with your hands to get the shape you want and ensure that it is flat.

3. Hold the iron about 2 centimetres (approximately three quarters of an inch) from the item for about 10 seconds then move the iron to another part of the item and steam there for ten seconds, etc. I hold the iron at an angle because I have discovered that a) steam is hot and it hurts and b) steam goes straight up so if I hold the iron at an angle my hand is protected!

 I go all over the item again a second time, just to be sure. For my 10 inch square that meant 10 seconds at the top (horizontally), 10 seconds across the centre (horizontally) and 10 seconds at the bottom (horizontall) followed by 10 seconds on the left then 10 second down the centre then 10 seconds on the right (one minute of steaming) - then repeat all that again (two minutes of steaming).

Do not let the iron touch the knitting - the acrylic will melt on your iron and, besides making an awful mess on your iron and ironing board cover, it smells terrible! (no, I haven't tried it but I did once burn acrylic while dyeing in the microwave - I left a metal paper clip attached!!)

4. Let the item cool before removing it from your blocking surface (I pin straight into my ironing board).

So, here is one of my pinwheel blocks - unblocked.

And here it is after blocking (notice there are no pins holding it in shape).

Does it retain its shape after blocking? Well, let's find out.

Here is the square scrunched up after blocking.
Here is the square un-scrunched.
Neat, huh?

Come back tomorrow to see what happened to these blocks next!


  1. I usually sew my acrylic yarn projects together without blocking, toss in the washer on gentle and then the dryer on low heat and consider it blocked! My very first sweater for myself I got too close while blocking and melted it smack in the middle of the front-ruined before I ever got to wear it! A lesson long remembered!
    This is going to be a great blanket-if you are blocking, does it mean you are finished knitting all the blocks or just getting some done ahead of time?!

  2. Can you tell me why a scarf I am knitting has become wider at the beginning as I go along and if I block it will it go back to the original size?

    1. Pam, I'd love to help you but you left me no email address and it appears you don't have a blog either. If you get this, please contact me again with your contact details.


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