May 20, 2020 5 min read 1 Comment
Last week, Claire dove into the world of single-flock yarn - beautiful, small batch fibres. Today, I'll be looking at something that is a lot more easily found: superwash yarn. More specifically, why exactly is it that superwash yarn is not sustainable?
To answer that, let's take a little step back and revisit what 'superwash' actually is:
Superwash yarn and fibre (yes, there's also superwash fibre for the spinners out there!) has undergone an additional processing step after it's been spun to make it shrink-resistant and therefore machine-washable.
Wool shrinks because it felts: The tiny scales that contribute to so much of the awesomeness of wool (They trap air to keep you warm! They increase the surface area of the fibre so that it can hold more water!) have a strong tendency to link arms when rubbed against each other. As they hold on to each other, the fibre becomes smaller and smaller, denser and denser - it felts.
So to make yarn machine-washable, you have to get rid of the scales. There are - generally - two ways to do this: You can either strip the scales off the fibre, or you can coat it in something to flatten the scales.
The most common superwash process - used forapprox. 75% of all superwash-treated wool- is theChlorine-Hercosett process which combines both techniques. As a first step, the fibre is chlorinated, i.e. treated with chlorine gas or a chlorine solution, to get rid of the natural 18-MEA (18-methyl eicosanoic acid, a fatty acid that helps to repel water) coating the fibre and to etch away the edges of the scales. In the second step, a polyamide-epichlorohydrin resin - more commonly known as Hercosett 125 - is applied to the fibre.
The removal of 18-MEA and the edges of the scales helps with the distribution of the resin; the application of the resin creates the 'superwash' coat that helps prevent felting and shrinkage. The resin itself is a type of plastic which is why you'll also find superwash yarn described as 'plastic-coated'.
The yarn that comes out of this process has a few distinct advantages:
It's machine-washable: This one is by now obvious: Because the yarn has gone through the superwash process, it can be washed in the machine or by hand at higher temperatures and wrung out without fear of shrinking or felting.
It takes dye beautifully: All of you will know the beautiful deep colors or speckled goodness that indie-dyers are able to achieve on superwash yarns. This happens because superwash yarns can absorb more dye than non-superwash yarns due to the de-scaling and smooth resin-coated surface!
It's very soft: The removal of the scales and coating of the fibre in resin results in a much smoother and therefore softer surface than most non-superwash yarns can offer.
It also has a range of disadvantages:
It's not elastic: If you've knit a sweater in superwash yarn, you will have noticed that it's not easy to coax it back into shape when it's been washed. This is because the yarn itself loses much of its elasticity - its 'springiness', if you will, it's ability to hold and spring back into the shape you intended it to - as the individual fibres are not able to cling to each other anymore.
It's not warm: The scales on untreated wool fibre trap air, and air equals warmth. They are the reason your woollens keep you warm even on the coldest days, and when you remove them, you also remove the yarn's potential to warm you.
It doesn't repel water: If you've gotten into a rain shower with only a (non-superwash) sweater on, you might have noticed that you don't get as wet as fast, right? Wool has natural water-repellent properties, and as you remove both the chemical and physical ones (hello 18-MEA from up above! hello scales!) during the superwash process, a superwash yarn won't repel water as well as an untreated one.
In addition to these mostly fabric-related disadvantages, let's talk about the proverbial bull in a china shop here: Superwash yarns are not sustainable. Full stop.
It uses hazardous chemicals: Both the chlorine and the chemicals used to create the polyamide-epichlorohydrin resin are highly toxic. In addition, during the chlorination process, the chlorine reacts with the carbon-based (i.e. organic) compounds present in wool, creating adsorbable organohalogens (AOX), another group of toxins. The production process itself has the risk of exposing employees to these toxic chemicals, and the wastewater resulting from it contains extremely high levels of AOX. (So much so that most wastewater treatment facilities in the US don't accept it.)
It uses more water and energy: If you make a yarn superwash, you add in another process step in the - already pretty long - production chain of yarn. More process steps = more water and energy used in the entire process.
It sheds microplastic:If you've knit a pair of socks in superwash yarn, and you've washed them quite often, you might notice that the smooth coating wears off. The plastic that covers the yarn's surface slowly but surely detaches itself from it and gets washed down the drain as microplastic particles.
It's not biodegradable: Well, it's wool coated in plastic. Wool itself is beautifully compostable, but with the plastic coating on top, it's not anymore. As with all plastics, it can take a long - a very long - time to degrade, shedding harmful chemicals and polluting the environment until then.
To sum it up: The traditional superwash process used by most superwash yarns is not sustainable at all. It uses highly harmful chemicals, is potentially unsafe for the workers, definitely unsafe for the environment, and results in a non-biodegradable product that might sit on our earth for the foreseeable future.
This might sound counterintuitive now, but: don't throw it away! It's already been produced, so throwing it out - maybe even in the trash - would just create more waste. Instead, use it to create something beautiful or give it to someone who might do so. Using up what we have is a cornerstone of sustainability!
Glad that you asked! I'll be taking a look at alternative superwash processes that have been developed over the last years next week to see if there are any superwash-like options that are more sustainable. I'd love to invite you to check back in next Wednesday for that post!
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