The last step of the knitting process is blocking because stitches can get clumped together and edges can roll inwards. Blocking straightens the stitches out for a more professional look. But it takes time, so is blocking really worth it?
And how permanent is blocking? Natural fibers will retain their shape after being blocked until they get wet or re-blocked. Blocking synthetic fibers, such as acrylic, is not permanent. However, it is possible to “kill” acrylic by melting the fibers, which is permanent.
When you take the time to knit or crochet a project, you want the best result possible. Blocking is an important step that ensures you are rewarded for the time investment. Wouldn’t it be nice to know what to expect when you block?
Effect of Blocking Different Fibers
For those of you who are not aware of what blocking is, let me cover that quickly. Blocking is the final step of knitting that uses water or steam to even out the stitches and set the finished size. The type of fiber used will give different results after blocking due to the unique properties of each fiber.
Natural fibers are commonplace in knitting projects. Natural fibers can be made from animals or plants. Animal fibers include, but are not limited to wool, mohair, cashmere, alpaca, silk and merino. Plant based fibers include bamboo, cotton, and hemp.
Many animal fibers have a unique structure. Take wool for instance. Wool has an outer layer of scales on the fiber, which can give the scratchy feel. But when wool is knitted up, the scales work together to keep the stitches where you want them. This is especially important in blocking.
When you block a project made from animal fibers, the fabric can be stretched to the dimensions you want. After the fabric dries, the stitches remain in their blocked place due to the structure of the fiber, i.e. the outer scales. The fabric will remain that shape until water is reintroduced.
When water is reintroduced, the fabric will go back to its original shape. Wool has a lot of memory, meaning it will spring back after being stretched. Other fibers have less memory and will remain closer to the blocked shape, while others can have a tendency to stretch too much.
There is also a chemically treated version of animal fibers which are referred to as “superwash”. In the manufacturing process, the outer scales of the fiber are removed, which yields a smoother and softer yarn. Superwash fibers are also supposed to be machine washable. Thus their popularity. But without those outer scales, the fibers cannot hold their shape as well. They are more prone to gradually grow in size over time, even after blocking.
Plant based fibers have a different composition than animal fibers. They will react differently when blocked. Cotton for instance is very inelastic, it has no memory. You can permanently stretch the cotton too far if you’re not careful.
There are also fibers that are man-made which include polyester and acrylic. These synthetic fibers do not react to blocking the same was as natural fibers. They will typically spring back to their original form shortly after blocking. Blocking will only remain permanent if you “kill” the synthetic fibers.
As you can see, every type of fiber will react differently to blocking. And there are certain blocking methods that work best on different fibers.
Blocking Methods
There are three basic blocking methods. Each method works best on certain fibers. There is no “best blocking method” that works for every yarn. That is why blocking your swatches at the beginning is so important! You need to see if the method you used worked, and how your fabric reacted.
Let me quickly give you a run down of what the three methods of blocking are before I get into best practices for each type of fiber.
Wet blocking: The swatch/project is fully submerged in water. Excess water is pressed out with a towel. The swatch/project is shaped and pinned into place. Then let it completely dry.
*When completing the wet blocking method, be careful not to stretch the fabric too much. Many fibers get weaker when they are wet and can be susceptible to stretching too far. If this happens, the fibers will not be able to go back to its previous shape.
Spray blocking: The swatch/project is pinned to the correct size. Then with a spray bottle, spritz the fabric until damp. You can use your fingers to help shape and soften the stitches. Let it completely dry.
Steam blocking: The swatch/project is shaped and pinned to size before adding steam. Then with an iron or a steamer, run the steam above the fabric. Use your hands to press the steam into the fabric and help shape it.
The following table is a list of suggestions for best practices on blocking different fibers. These are based on my own experiences and the experiences of others.
| Fiber Content | Blocking Method | Notes |
| Wool | Wet blocking | Wet blocking can add length to your project. |
| Alpaca | Spray blocking | Has a tendency to stretch when wet. Wet blocking could accidentally stretch the fabric too much. |
| Merino | Wet or spray blocking | Wet blocking is best if there is cabling involved. |
| Cotton | Steam block | Cotton is inelastic and can get overstretched with water. |
| Linen | Wet blocking | Linen strengthens with water. |
| Acrylic | Steam or Spray blocking | Careful not to add too much heat or you will make the fiber limp and shapeless. |
How Often to Block
Blocking should be done for nearly every project. It must be done for clothing items and shawls. But, some blankets, scarves and hats won’t be affected by not blocking.
Always be on the safe side and make a gauge swatch and block it before starting on your project. This will save you a lot of headache when you get to the end. You will know exactly what size to expect.
Take the time at the end to block every project for a more professional look, and to sew seams together effortlessly. You may say you don’t have the materials or the space or the time to wait for it to dry. No matter the excuse, I believe in you. Trust me, it is worth your time and effort.
I would also like to point out that since blocking is not permanent for every project, there will come a time when your sweater goes back to its previous shape after washing. This is especially true of natural fibers. When this happens, stretch the wet piece out, shape it back to the dimensions you want and let it dry flat. Done. It will be ready for wear again.
Reasons to Block
There are several reasons to block your finished knit projects. I compiled a short list to help motivate you to block on your next project.
- Shapes the sweater to the correct dimensions every time.
- To achieve clean, straight edges for a professional look.
- To have straight edges that are easy to seam together.
- To “kill” the acrylic. I’ve heard this is best for shawls when you want a lot of drape.
- Some fabrics are rough before blocking, but through the blocking process get softer.