Is Superwash Yarn Environmentally Sustainable?

Many times I've said that shiny superwash merino singles are my favorite yarn to work with. In the past few months I've begun thinking about the sustainability of the so-called luxury yarns. I'm the world's laziest hand washer and will chuck just about anything in the washing machine. But does everything have to be machine-washable? How often do you need to wash shawls, for example? Does luxury have to mean environmentally harmful? The next two weeks I'm delving deeper into superwash yarns: what are they, how are they produced, what's the environmental impact of superwash treatments and, more importantly, are there sustainable alternatives?

​What is Superwash? To understand what superwash means and why superwash treatments are used, you have to understand the structure of the wool fiber itself. The surface of wool fibers are covered in tiny scales. Heat, moisture, and friction cause these scales to open up like pine cones.

If you've ever felted anything — on purpose or by accident! — you already know where this is headed. Heat, moisture, and friction are the elements that are needed for wool to felt. Felting happens when the scales on wool fibers open up, grab onto each other, and are then permanently locked in place in this new configuration. Felting is a natural but sometimes unwanted property of the wool fiber. Superwash treatment is used to prevent wool from felting in the washing machine.

Mechanism of felting shrinkage of wool (Hassan & Carr 2019)

There are two ways to prevent felting from happening. One method is de-scaling, that is, removing the scales so that the surface of the fiber becomes smooth and has nothing to grab with. The second is gluing the scales shut so that they won’t open up when wool is washed in hot water. The industry standard for superwash treatment, called the chlorine-Hercosett process, uses a combination of the two methods. Approximately 75% of all superwash wool is produced using this method. 5 Reasons Superwash Yarn is Harmful for the Environment So why exactly is superwash treatment harmful for the environment? Some reasons have to do with the process itself, some with its side and after effects. #1. Harmful chemicals are used in the process The Hercosett treatment uses hazardous chemicals in both the de-scaling and coating steps of the process. To remove the scales, wool fiber is exposed to chlorine that basically eats away the scales so that they can no longer grab onto each other. The coating step is no better: the raw materials used in the production of the polymer resin that the wool is coated with are also highly toxic. #2. Toxins end up in waste water When chlorine reacts with organic compounds (such as wool) it creates toxins that end up in the waste water. Not only are these toxins lethal to humans even in tiny concentrations, there is so much of these chlorinated chemicals in the water that the use of the Hercosett process is restricted in developed countries. #3. High carbon footprint from back-and-forth shipping For these reasons, wool is often exported overseas to countries with less strict environmental regulations. It is then transported back to the originating country — or perhaps shipped to yet another country — for further processing steps such as spinning or dyeing. Although greenhouse gas emissions of transportation is estimated to be a fraction of that of fiber processing, all of this back-and-forth shipping of wool increases the carbon footprint of the final product. These so-called outsourced emissions also distort calculations to see if global efforts to reduce carbon dioxide emissions are actually paying off. #4. Monitoring that environmental regulations are upheld is difficult Shipping the wool to be processed overseas has other problems as well. The further away the production gets from the originating country, the harder it is to ensure that international standards when it comes to environmental regulations, labor laws, or human rights are upheld. There have been occasions when an entire river in China has been turned red because of either dye dumping or other pollutants in the water. #5. It’s covered in plastic The superwash yarn you buy from the yarn store might not contain any poisonous residue even if harsh and dangerous chemicals are used in the process. But the substance used to glue down the wool scales is polymer resin — basically a form plastic. (This is why you often see that subtle shine on superwash yarns.) Because of this resin coating, superwash yarn is not biodegradable, that is, it cannot be composted. ​​

The harsh truth about superwash yarn is that the widely-used industry standard for superwash treatment is NOT eco-friendly nor sustainable. Luckily there are other options. In next week’s blog post I’m going to discuss what these alternatives are and where you can find them.

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