Superwash Wool: What you need to know to make the choice

sheep in the long grasswool-fiber

Each individual hair on a sheep has small scales that can open and close in response to heat and moisture. Before these hairs have been sheared off, the scales help regulate the sheep’s body temperature and repel moisture away from the sheep’s skin. They serve the same function after the hairs have been sheared off the sheep and turned into  yarn. The scales make wool “breathe,” which helps to regulate temperature and repel moisture away from the skin underneath.

Microscopic_Fiber_ComparisonThese scales are responsible for the “scratchy” feeling of natural wool.  The finer the wool, the smaller the scales, which means the finer the wool the softer it is to the touch. If you think you’re allergic to wool, you’re probably not, since wool is one of the most hypoallergenic materials we make clothes from. But some folks have fine textured skin that is more sensitive to even microscopic irritants…like wool scales. 

felting-600x263These scales are also what make wool felt. The scales open up in the presence of moisture and heat. Agitating hot, wet wool tangles these scales together. This in turn pulls the hairs more closely together…which, in turn, tangles the scales more tightly together…which, in turn…you get the idea. The hairs get so tightly drawn together that the overall area will shrink 25-30% in both directions, while, at the same time, it gets thicker and denser. Then when the heat and moisture are gone, the scales close a bit and become bonded together forever, or near enough. Thus, felt.

Some of us do this on purpose to make felt. We knit or crochet or weave wool larger than we think we want it, then subject it to moisture, heat and agitation in order to shrink and thicken it. But we’ve all also had the experience of throwing something into the washer and dryer accidentally and ruining a beloved wooly object.

If only someone would invent a way to make wool impervious to the felting process. If only we could neutralize those pesky scales that make felting possible. If only…  But wait!  There is such an invention. It’s called The Superwash Process.

1930sPermMachineHow many of you are old enough to remember the permanent waves of the 1940’s, or the 1960’s, or the 1980’s? They stripped away the top layer of each hair and chemically weakened the hair so it could be made flat instead of round. Thus, curls. The superwash process is similar. Manufacturers take raw wool and soak it in a vat of a chlorine based solution. (If you want to know more about the chemistry, you can look at the sites listed in the foot notes below.) This solution chemically burns off the tiny, delicate edges of the scales, leaving them even tinier and very blunt. After rinsing off the chlorine solution, they then soak the wool in a vat of polymer resin. Polymer resin is a generic category and includes chemical compounds such as nylon, and is similar to the resins added to the “wax” they put on your car at the car wash. It means plastic, and it slicks down what remains of the burned off scales so they can’t tangle with their fellows. Thus, superwash.

wool_series_kroycmt_superwash_top_processing_strong_style_color_b82220_equipment_strongThe result is a wool that can withstand exposure to heat, moisture and agitation without shrinking or felting. Superwash wool is also silkier to the touch, as there are no more protruding scales to prickle against skin. The smoother surface appears more lustrous than untreated wool. It also results in a wool that does not “breathe” the same way untreated wool does. Without those scales, superwash wool doesn’t regulate temperature or repel moisture the way untreated wool does. It also doesn’t last forever. 

As I said above, a polymer resin is a kind of plastic, and will melt and deteriorate when exposed to heat. That means every time you toss your superwash wooly objects in the dryer, you are shortening the life of the resin coasting. Polymer resins will also get worn away with friction over time. This will either leave the stumps of the scales poking out, or pull the scales completely off, leaving a roughened surface on the core of the hairs. Your superwash wooly objects will have a longer, prettier shelf life if you treat them delicately.  Wash them on gentle cycle in cool water, and don’t put them in the dryer.


Superwash wool seem like a great alternative to unprocessed wool. But remember that it has its own vulnerabilities and requires its own kind of special care. There are folks who have concerns about how the plastics, including polyamide, in our clothing may be affecting our health. So you may want to think about that as well and weigh convenience, durability and comfort when shopping for yarn for your next project.


Written by mim

mim

One Comment on “Superwash Wool: What you need to know to make the choice

  1. RE: Superwash wool vs. blends

    OK, you’ve certainly aroused my attention this morning! Although I have a deep commitment to using only ‘natural’ fibers, especially when knitting for my grandchildren and because of my concerns over the health and environmental effects of all the chemicals we come in contact with, nevertheless, I had not researched the process required to create ‘superwash’ wool. I have been blindly trusting!

    I thank you for this eye-opening information, although it’s now created a new dilemma I will have to take into consideration. It seems that either choice is going to involve synthetic/chemical/oil-based components, so the question is, which one is environmentally worse in the making, and which one contains the greatest residue that the wearer will come in contact with. Although I understand the desirability of easy care, I personally don’t want synthetics in my wool. I only use superwash or blended yarns when I know the relative involved won’t be diligent in hand-washing a garment, so this doesn’t effect most of my yarn choices, but still, I now hesitate. Cascade’s yarns have always been wonderful to work with. They hold up well in children’s garments and you can hardly beat the color selection or price. Although I personally dislike the feel of blended yarns like Vintage, I’m not the wearer of this fiber blend so maybe that factor doesn’t matter. Much to ponder as my Christmas knitting gets any further underway! My personal preference is to use regular Cascade and double strand it with some alpaca lace to add some softness for those of tender years and skin. I just finished a ‘pumpkin’ hat this way and its hard to put down!

    On a related note, some people are allergic to wool. I have three family members who suffer this misfortune and they are a challenge to knit for. My mother couldn’t even sit next to me at the dinner table if I was wearing wool, because she would break out in hives. Growing up in the 1930s when her only other choices were cotton or linen (requiring great care and a lot of ironing), you can’t imagine her joy when synthetic clothing was finally invented and she could wear warm winter clothing! And when my brother was a bit miserable his freshman year in college, due to the change from Colorado’s sunny, arid climate to the damp and gloomy autumn in St. Louis, I made him a wonderful wool flannel shirt to cheer him up. He wore that shirt every single day as he was ill throughout the entire winter and it gave him such a feeling of comfort. Until, spring allergy testing revealed that he is very allergic to wool and once he quit wearing the shirt, he got well! The next year I sent him a crock pot and all my best soup recipes. On the other hand, I have a granddaughter who breaks out in a rash whenever she wears acrylic or polyester, and wearing those fibers makes me immediately break out in a sweat and quickly feel like I’m suffocating. The bottom line is that we are each greatly blessed to have the choices available to us today!

    Again, thanks for the information, the intellectual challenge, and for helping us all be better informed consumers and knitters!

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