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How to Block Knitting and Crochet

Knowing how to block knitting and crochet is a crucial skill. Blocking may be the most important step in getting a professional-looking finish for your project. Here are some techniques and best practices for successful blocking.

purple crocheted shawl pinned out on black blocking boards, hand holding steamer head; How to Block Knitting and Crochet

While most projects will benefit from blocking, it’s important to do it right. Some crafters are afraid of blocking because they’ve heard blocking horror stories about someone killing a sweater. Blocking doesn’t have to be scary, but it does help to know what you are doing.  

This a big topic. What follows is an overview of blocking basic two-dimensional knitted and crocheted fabric. Projects worked in three dimensions or those with highly textured surfaces may be blocked a bit differently.

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What is blocking?

Blocking is a method of treating your finished knitted or crocheted fabric to set the stitches. It can even out irregularities. It makes it easier to work seams and edgings and it can even make minor size adjustments. Blocking can be done after a project is complete, but usually for best results you’ll want to do it before you assemble individual pieces. In other words, when knitting a sweater in pieces, block the front, back and sleeves separately, before sewing them together.

However, it shouldn’t be used to try to completely change the size of a piece. You need to do that from the beginning, by accurately determining your gauge and adjusting your hook or needle size to get the proper gauge!

Blocking Supplies

You’ll need a few simple supplies for successful blocking.

  • Yardstick or tape measure. I prefer a yardstick because it stays put and doesn’t require an extra hand or two.
  • Rustproof T-pins. Be SURE they are rustproof because you can’t get rust stains out of your fiber!
  • Blocking wires (optional). Not required, but they can make things SO much easier.
  • A steamer or steam iron for steam blocking. I prefer one with wheels to make it easier to move around a large table.
  • Plant mister for cold blocking
  • Water

In addition, you need a large, flat surface to work on. The ideal blocking surface has these characteristics:

  • Is large enough to hold the entire piece (or all the pieces) you need to block
  • Can withstand heat, moisture, and being stabbed with pins
  • Is colorfast, to avoid transferring color from the blocking service to your fabric
  • Can be left undisturbed while the fabric dries
  • Has a printed grid to aid in getting lines straight and dimensions correct
  • Is flexible in shape and easy to store

I’ve used many types of blocking surfaces successfully.

  • Ironing board – works well for small pieces like swatches.
  • Quilter’s Cut ‘N Press – also for small pieces. It’s more compact and easier to use than the ironing board.
  • Interlocking floor mats – not pretty, but large and inexpensive. These can be used in many different configurations and sizes. A better option might be a set of grid-printed blocking mats, like the ones from KnitIQ.
  • Large blocking board – made of three 24″ x 58″ Styrofoam panels in a cotton canvas casing. The panels unfold and create a surface that’s even larger than my dining room table. It’s great for blocking shawls and other large items. As far as I can tell, it’s no longer sold, but it wouldn’t be difficult to make.
  • Spare bed – covered with beach towels. It works surprisingly well. Just be sure to collect all the pins when you are finished!

The Importance of Pins, The Allure of Wires

At some point in the blocking process, you’ll be pinning your pieces to a flat surface. Depending on your blocking method, this will happen before or after the fabric gets wet. Make sure your pins are rustproof. Nothing is guaranteed to ruin a project faster than pins that will leave a permanent stain on your yarn!

If I’m not using blocking wires, I often use Knit Blockers from KnitPicks, which saves time over using individual pins

Blocking wires are not a necessity, but they make it so much easier and faster to block. You’ll use fewer pins, your edges will be straighter and your pointy bits pointier if you use blocking wires. I have two sets!

Eulerian Triangles Shawl pinned out on blocking board

Whether you are using pins, or a combination of pins and blocking wires, begin by securing the corners (if any) of your fabric. Use a yardstick or tape measure to ensure that the piece is the desired size from edge to edge and corner to corner. I prefer a yardstick because I can measure one-handed, and use the other hand to make adjustments. Make sure right-angle corners really are 90 degrees.

Here’s my Eulerian Triangles Shawl after blocking. I’m waiting for it to be cool and dry before removing the blocking wires.

Blocking can be used to make minor corrections to the finished size of a piece, but it’s not a substitute for making the piece the right size to start with. Don’t use blocking for that purpose!

Choose a Blocking Method

Proceed to add pins along each edge every 1 1/2-2″ [4 5 cm]. If you are using blocking wires, use enough pins to keep the wire straight where it should be straight.

If the fabric rolls, gently unroll it and use pins to keep it in place. If there are points or scallops, pin each one out individually. This is where a blocking wire comes in especially handy, as the wire can go through each point.

The blocking method you use will depend on the content of the yarn. Acrylic, cotton, wool, cotton, and other fibers each require different care. If your yarn is a blend of fibers, choose the method that is appropriate for the most delicate of the fibers. Wool and many other animal fibers can be steam blocked, cotton is often wet-blocked. With acrylic and other synthetic fibers, cold blocking is often the safest method.

Another consideration is the stitch pattern you used, and how aggressively the fabric needs to be blocked. Fabric with lots of openwork, for example, needs to be stretched to allow the holes to open up. If the fiber allows, wet blocking or steam blocking will be your best options for lace.

Highly textured fabric like cables, ribbing and bobbles may not react well to too much steam. There are nuanced ways to deal with these textured stitches, but that will be the focus of a future blog post.

Always practice your blocking method on a swatch or two before trying it on your finished project!

Wet Blocking

Wet blocking is appropriate for cotton, silk, and wool, as well as for any fiber that can get completely wet.

To wet block, fully immerse your fabric in water, either by washing it or simply by putting it in a sink. Allow the water to fully soak the fabric. Gently squeeze out the water – don’t twist or wring – and pin the pieces to shape on the blocking surface.

Wait until it dries completely before removing the pins. Obviously, this is the most time-consuming blocking method. It’s hard to be patient and wait for that yarn to dry, especially in humid climes.

Steam Blocking

Steam Blocking a Crocheted Shawl

Steam blocking works well for wool and most animal fibers. Be careful, however, of using it on fibers that can be damaged by heat.

Begin by pinning your pieces to the blocking surface. Use a steam iron or steamer that’s shooting out plenty of steam. Hover the surface of the iron or steamer over the fabric, about 1.5 – 2″ [4 – 5 cm] from the surface. Never touch the iron to the fabric! You are using the moisture from the warm steam to do its work, not the heat from the iron.

Get the fabric warm and damp with the steam, then allow it to dry completely. When the fabric is cool and dry to the touch, remove the pins.

Cold Blocking

Cold blocking is the safest method to use with acrylic yarns, which can be damaged beyond repair with too much heat.

Pin your pieces to the blocking surface. Use a plant mister to spray water over the fabric, taking care to dampen the entire fabric thoroughly. Allow it to dry completely before removing the pins.

Killing Acrylic Yarn

How to Block Acrylic Yarn

Did you know that you can kill yarn? Yes, that’s an official term for an actual thing. It happens when you use too much heat on an acrylic fiber — such as when you press a hot iron onto acrylic yarn. This causes the fibers to melt together and changes the characteristics of the fabric permanently. It can’t be undone.

Despite my warnings to you not to steam block acrylic yarn, I confess that often do. I always always always practice on a swatch first. I’m very careful to use as low a heat as possible and to hover the steamer (or iron) above the fabric. I watch carefully to make sure I’m not killing anything. I understand the consequences of failure. So if you decide you want to steam block your acrylic yarns, that’s up to you. Your mileage may vary. You didn’t hear it here.

More About Blocking

I could write another thousand words on blocking. Or teach an entire three-hour class. In other words, there’s a lot to learn! Just remember: tailor your blocking techniques to the project, the fiber, the stitch pattern and the finished use of the project. Some projects (like amigurumi) don’t need to be blocked at all, while others demand it.

Ask your questions about blocking in the comments.

Now that you know how to block knitting and crochet, go forth and practice what you’ve learned. Your projects will thank you!

20 thoughts on “How to Block Knitting and Crochet”

  1. Excellent tutorial Edie! I will be sure to share this with my students when they are afraid to try blocking for the first time.

  2. This is wonderful Edie, thank you! It will be an wonderful resource to give my students.
    I use Knit Blockers & love them! They have a neat feature that I recently learned, and it’s wonderful for scarves. There are small holes in the corners of the pins for attaching thread that is run through the edge of the fabric. You can then pull your edges straight. Works wonderfully!

  3. I read that you can use, and I have used a spray bottle to mist and a hair dryer to steam block acrylic. I personally like it better than the iron (as it is harder to “kill” it). and yes that’s cause I got to close with the iron before I did a little more research. Just another option.

  4. Carlene Braithwaite

    Thanks for this Wondering. When making squares for an Afghan – which will be joined later, do you recommend blocking each square before you join or blocking after.


  5. If they are separate pieces, then I’ll usually block each individually. However, I usually work join-as-you-go, and block when the whole thing is complete.

  6. Hi! This is a great tutorial on blocking my projects. The only question I have is about blocking 100% acrylic yarn. Can it be wet blocked if I use cold water, or is cold blocking with a most bottle the best way to go? Thank you!

  7. Yes, you can use cool or warm water to wet block acrylic. Just squeeze out the excess water by hand first.

  8. No. No matter what type of blocking method you use or what type of fiber you have, washing it undoes the blocking.

  9. Thank you for the tutorial. Very helpful! What is your suggested blocking method for 60% cotton/40% acrylic yarn?

  10. I’ve steam blocked many times with great success. Mostly scarves and baby blankets. Now I have a full size afghan. Obviously, I can’t block it on my ironing board or kitchen table because of the size. How do you recommend I block it?

  11. Can you do a few bits at a time, with the rest supported by a chair so the weight doesn’t pull down? I have a bunch of foam boards (play mat thingies) that fit together and could support a full afghan on a bed, so I can do a whole one at once, as long as I am willing to give up the top of my bed for a while.

  12. I usually steam-block with the iron, but always put wet gause in between, over the knitting. Lisa’s idea with hair dryer seems maybe even safer.

  13. I would probably carefully steam block it. However, I’d want to test the blocking method on my swatch first, just to check that it doesn’t ruin the fabric. If it doesn’t work, then spritzing with water and letting it dry would be the safest.

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