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Once the conversation turns to superwash yarn it never seems to stop. There are loads of opinions and a lot of questions about how superwash yarns get super-fied.

The two yarns pictured throughout this post are both from O-Wool and both are 100% certified organic merino. The gorgeous golden yarn is O-Wool Merino Chunky in the shade Mustard Seed. The perfectly purple yarn is O-Wool O-Wash in the shade Blue Thistle. O-Wool uses a newer style of anti-shrink treatment on their fiber, one that is more environmentally friendly.

Why Do People Want Superwash?

First a couple answers on the why of superwash wool. Why do people want it?

A big reason is washability. I’ve made quite a few non-superwash baby gifts that ended up doll clothes, and socks that have been tossed accidentally in the washer and dryer that are now wee. Dyers and knitters also love the intense color produced by dyeing on superwash. Lots of folks also say that superwash yarns are softer; they are certainly smoother.

Only a very small percentage of the superwash produced in the United States goes to the hobby market (that’s us knitters).

Much of the US-made superwash wool goes to ready-to-wear fashion, and to the military for uniforms. Wool for military wear is praised for its durability, its suitability in a variety of climates, and its fire resistance. The superwash process makes it washable, and it makes the United States wool pool (a variety of sheep breeds mixed into one yarn) soft enough to wear. The military uses a lot of wool and helps keep wool farming viable in the United States.

What Exactly Is Superwash?

Superwash is a process that makes wool less susceptible to felting when it is washed and dried by machine. There are two ways most commonly used to make a superwash yarn. One is to strip or dull the scales of a fiber, then fill the irregularities left behind with a polymer to smooth the fiber. The other is to coat the fiber to suppress the scales. There are many scientists working on developing new ways of shrink-proofing wool. Most methods are the super secret, proprietary information of the companies and labs developing them.

Felting: It’s All About Scales

Each individual wool fiber is covered with tiny scales, like a snake’s skin. When these little suckers are agitated, literally, that’s how felting happens.

Felting needs moisture, friction, and sometimes a change in temperature.  In many cases that’s a partner who accidentally puts things in the dryer. Wool relaxes in water, even more if it’s warm or hot: the scales open like the hatch on the back of a car. Agitation makes the fibers scootch closer together so that the scales hang on to each other. As the fiber dries the scales slam shut, locking out the ability for fibers to move past each other and locking in the new shrunken size. Your beautiful knitwear is now smaller, stiffer, and not so soft. If you’ve ever knit and then felted a bag or slippers on purpose, you know exactly how much the felting experience can change knitting.

In the MDK Shop
Spectacular color on 100% superwash merino milled with 8 plies—making for durability without nylon. Your purchases support everything we publish here at MDK. Thanks!

Superwash and the Environment

There are environmental issues with many superwash processes, but not all superwash or anti-felting processes are the same. Different companies use different processes and chemicals, and different countries have different environmental regulations for their wool industry. The only way to know what process your favorite yarn company uses is to ask them.

While many yarn companies don’t know the process their suppliers use, some do, and a growing number are making it a priority to be aware and to choose supplies with the environment in mind. This is true about yarns processed in North America and the rest of the world.

For example, in most countries there are strict regulations on the cleanliness of water that gets dumped from any  industry, and there are companies that go beyond what the law requires to remove chemicals from their wastewater.

One of the most used methods to make a fiber superwash is to remove or reduce the scales on the fiber with chlorine, either as a gas or as a solution. Then the modified fibers are smoothed with a coat of a polymer.

Chlorine gas is the most toxic way to make superwash, both for the people working in the plants and the environment. A chlorine solution in water is less toxic to workers, and chlorine in this form can be filtered from wastewater.

The polymers used to smooth the fiber are made from different types of plastics. The type most commonly used is also used in paper processing. It’s a polymer that keeps paper from reverting to pulp when it gets wet.

Newer, more environmentally friendly methods of creating superwash are being developed and used in several different countries. I’ve read about some scientists experimenting with heat, and others working on a coating that biodegrades quickly, making the shrink resistance temporary. All of this work is industrial and secret.

One environmentally friendly method is used by O-Wool. They use a natural (and proprietary) polymer to coat the fiber to keep scales from interlocking. They do not remove or reduce scales, but only smooth them down—like using pomade on unruly hair.

Their O-Wash superwash yarn acts just like any other superwash I’ve used. It washes beautifully, and feels just as smooth and slinky.

A Closer Look at Merino and Superwash Merino

These two yarns are close enough in gauge to be interchangeable in most projects, the Merino Chunky is 15 stitches to four inches, and the O-Wash Chunky is 16 stitches to four inches. It’s hard to find merino and superwash merino close to the same gauge from the same company, so it’s a real treat to be able to compare these kissing cousins in detail.

I talked about how superwash yarns behave in my first superwash post, but here, with a regular and a shrink-proofed merino side by side, you get a visual to help connect all the words.

Just at a glance I can see how dissimilar they are. It’s not the first time I wish I could hand you yarn to touch through the screen, or just invite you all over to my house to touch all of the yarns. Hang on, let me turn on the espresso machine.

Looking at skeins and swatches is one thing, but looking at two strands side by side really shows how the regular merino (gold) is matte and velvety looking, and the superwash merino (purple) is smoother.  The texture of each yarn is completely different from the other, even though they are made of the same fiber. The smoothness of the superwash comes from the trapping and smoothing of the scales in the O-Wash process. Considering these two yarns in strands, I know I would choose my yarn based on the texture I wanted in my knitting: smooth or velveteen fuzzy.

The two yarns are constructed differently. Superwash merino usually has more plies and more ply twist than untreated merino to compensate for the structure lost when the fiber’s scales are removed or suppressed. Superwash needs more plies and and ply twist to help control the body of the yarn. Untreated merino yarn has structure with fewer plies and less twist.

Both the hand and the grist are different. We talked about the drape of superwash in the last post. Part of what contributes to the swing and sway is the density of the yarn, or my friend and yours: grist.

Looking at the swatches stacked both in stockinette and garter stitch, we see that the superwash swatch wants to drape. I just placed the superwash swatch on top of the regular merino swatch in both photos, and both times the superwash swatch molded itself around the edge of the plain merino swatch like a sleepy kitten.

Any of the processes used to make a yarn superwash will restrict the fiber scales, smoothing them to keep the fibers sliding by each other no matter what. Altering the scales eliminates some air (and space) between the fibers and plies of yarn, making the yarn more dense and less elastic. Superwash treatment can affect the weight of  a knitting project.

Checking in with Auntie Grist, if I made a 1,ooo yard sweater out of the regular merino it would weigh 1.3 pounds. In superwash merino the same yardage would weigh 1.8 pounds.

There’s a lot to think about! See you next time, yarn explorers.

About The Author

Jillian Moreno spins, knits and weaves just so she can touch all of the fibers. She wrote the book Yarnitecture: A Knitter’s Guide to Spinning: Building Exactly the Yarn You Want so she could use all of the fiber words. Keep up with her exploits at


  • Thank u so much for this as I have been in a dilemma over superwash. Having made several sweaters with both types I must say I enjoy wearing superwash more than untreated wool. I was a staunch no chemical person with my wool for years but finally realized many items I didn’t wear as often due to needing another garment under them so they sat ina drawer more than being worn. Or the thought of finding a place to dry a sweater etc was too much to think about. The final straw that broke the camels back was when I made my grown daughter a lovely long cardigan with beautiful wool from Quince and Co only to have her disappointed she couldn’t wear it without something under it as it was uncomfortable next to her skin. She wears it in cooler months and now to find a place to dry a long cardigan?? It will be dry cleaned, and sitting around not being worn as often as my daughter envisioned.

  • After growing up with sheep and shearing sheep, washing fleece, spinning wool and knitting handspun …. I have to admit that now, as an adult … I LOVE superwash! I’ve done my time with wool and felting … now when I knit with superwash, I don’t care that my 5yo kid tosses their jumper into the washing machine as it never shrinks!

  • Another fabulous article by Jillian! Very informative.

  • I do appreciate your addressing the environmental concerns. Thank you!

  • That’s nice to call it drapy instead of droopy! I am so seduced by the superwash colors but then end up frustrated when it doesn’t have the bounce and body of non-superwash wool. That thing where it stands away from my skin just a little and gives me breathing space? I love that about wool. Anyway – this description will help me predict what the different yarns will do so thank you!

  • Wow! Thank you so much. This is a lot to digest, but so very helpful. With a big family and friends to knit for, I want them to enjoy wearing the knits and not worry about care of them. Mindful of the processes to. Who says knitting is just an art? Obviously it is a science too; the whole enchilada!

  • I simply and wholeheartedly appreciate your posts. So science-y, thorough, and thoughtful. Thank you.

  • What a great explanation- especially regarding the grist involved and drapiness of superwash. Thank you!

  • I’m such a nerd that I love these articles. I am a very tactile person. If the hand doesn’t feel right, back it goes. So why is the combination of merino wool and cotton so washable and delightful to work with…i.e. Spud and Chloe worsted weight. The price is high but the quality is worth the price ?

  • Once again, a fascinating article! It just reminds me of how much I DON’T know about yarn! Thank you!

  • I thought all polymers were plastics. Don’t they all break down eventually and end up in the environment as pollution?

    • Polymer mostly just means that the component pieces repeat, but the component pieces don’t have to be plastics. I went to a talk last week when the chemist speaking referred to proteins as polymers … I was just as surprised as you!

  • great article. However, it doesn’t quite address what I find so very frustrating about super wash wool. (I won’t use it). The articles made from super wash won’t block. When wet, the garment stretches out beyond any reasonable “shapability,” leaving you with a garment made for a giant. I cannot reshape it, even to proper measurements, and instead of blocking a shape, I end up throwing the garment in the dryer, only to have it come out exactly as it came off the needles — good or bad. How I love the tweaking that is possible with wet wool, or steam, and the ability to shape (either stretching or pinching) the individual areas of a sweater or dress or skirt. Give me old fashioned wool every single time!

  • Thank you for another very informative article. Many years ago, when I started knitting I stocked up on super wash wool. I was enamoured with the colours, soft touch and washability. Plus, my lys was pretty much filled with super wash wool. Now, I’m more aware of the intrinsic qualities of super wash and regular wool thanks in large part to knowledge gained from articles written by experts such as yourself.

  • Wow, interesting article. I did realize that superwash processing is not super environmentally friendly, but alternative “wools” made from plastic are not a good alternative. Superwash has made it great for me to wear wool. Growing up, I could never wear wool because it would make me have a rash and sometimes welts. Don’t get me started on mohair and angora! That gives me hives! I’m so happy to have superwash in my life and I am glad they’re making waves in discovering new ways to make it more friendly to the planet!

  • Where is the scratch and sniff app when you need it!!! Lots of good info here and only reinforces why I don’t superwash except for baby items. It grows and grows

  • I heard superwash eventually loses it’s superwash proerties. Is that true? Does it depend on which process was used?

    Also it seems using non-superwash or only organic superwash might be much better for the environment. Is that true. Knitters should be made aware of this if it is.

    I find superwash grows a lot. That’s one of the many reasons I try to stay away from it for anything but shawls ir socks. Even tho I habdwash all my knit stuff regardless.

  • Great article. Now I’ve just got to find out what happens in Australia.

  • Thank you for this informative article. It answered most of my questions about superwash processed yarn. Thank you for sharing it and increasing my understanding about wool. I will be a more thoughtful knitter.


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