I recently watched a TikTok in which a man compares regular raw wool to superwash wool by submerging them in water to show how the former floated and the latter didn’t. The problem was he never explained why it mattered. While the comments devolved (as they always do) into arguments, I was left with a general “so what?” feeling.
That led me down a path of researching superwash wool. Superwash wool is a boon for knitters and crocheters who want to make projects that can withstand the agitation of a modern washing machine without felting, making the finished project much easier to care for.
We want to make cute blankets and sweaters for our babies (or babies we know) without burdening the busy parents with a handwash-only garment.
When my children were young and I hadn’t spent any time creating wool items, I admit, I would have given such a demanding gift away. I know what you’re thinking! All that work someone put in for you only to give it away?
Listen, when my three were little (and always playing in the dirt, might I add), laundry was a challenge even when everything could go straight into the wash. Many parents feel the same way.
So the advent of a process that makes some of the world’s softest natural fibers machine-washable is seemingly a godsend.
Seemingly.
The more time I’ve spent in the fiber community, the more I’ve come to learn that some people have big feelings about superwash. And most articles from fiber bloggers are opposed to the process (but don’t always cite their sources).
And here’s where the concerns come in…
Going from raw to superwash wool requires a chemical bath. This chlorine-Hercosett process flattens the fiber’s scales before it’s coated with a thin polyamide resin. We now have a machine-washable yarn with a silky sheen… and concerns about how the resulting product impacts human and environmental health.
But what does recent research actually say?
Is it as bad as people fear or did it suffer a fate similar to that of MSG?
Let’s explore.
Concern 1: “It’s coated in plastic, therefore no longer biodegradable.”
One of the main reasons so many fiber artists and other eco-conscious people who generally like to wear clothing have turned to natural fiber is because it is biodegradable. Unlike synthetics like polyester or acrylic, it will not go on to live forever in a landfill. And we’re all aware by now that the fashion industry is one of the world’s top polluters.
So by superwashing, have we just taken a beautiful, raw fiber and turned it into the very thing we’re avoiding?
Well, maybe not. In fact, research appears to lean the other way.
AgResearch-led studies confirm that both untreated and machine-washable wool readily biodegrade in marine environments, with machine-washable wool degrading at a faster rate than untreated wool fabrics.
A peer-reviewed study published in Water, Air, & Soil Pollution directly tested. Researchers compared the aquatic biodegradation behavior of unmodified wool, chlorine-Hercosett treated machine-washable wool and several synthetic fibers. They found both the treated and untreated wool biodegraded in marine environments, while the synthetics did not show comparable degradation.
The caveat: But alas, allow me to expand on that “maybe” above. While the science is still the science, I would be remiss if I didn’t highlight the following point. We are admittedly looking at research that was funded by wool-industry bodies, which have a vested interest in distancing wool from synthetic polluters. Again, that doesn’t mean it’s inaccurate or untrue – if I were a wool grower (which I hope to be one day), I’d want all my cards on the table too, so the public can shop with confidence. But I do think a fresh study from a truly independent source is in order. If you find one, please comment below!
Concern 2: “It’s coated in plastic, so it therefore sheds microplastics when washed!”
Again, what’s the point of paying more for natural materials that might impact our waterways in the same way as the more economical synthetics? We’re all just out here trying to survive and craft, dammit!
Once again – and with the same caveat from above – that doesn’t appear to be true.
The same AgResearch body of work addresses this specifically. Research found no evidence to support the idea that the Hercosett resin used in machine-washable wool treatment creates microplastic pollution. Woolmark clarifies how the resin is structured: microplastics form when solid plastic materials fragment into tiny pieces, but machine-washable wool doesn’t have a solid plastic layer to fragment as the treatment is integrated into the fiber surface.
Separately, the Water, Air, & Soil Pollution study demonstrated that wool not only biodegrades in marine environments but found no evidence that polyamide or Hercosett resin used in the machine-washable treatment forms microplastic pollution.
Concern 3: “The manufacturing process itself pollutes our waterways”
This one might be the least disputed concern… (But read to the end to receive a sprinkle of hope in the emerging innovations.)
The process uses tons of water along with hazardous substances that can lead to wastewater pollution.
Chlorine-based wool descaling is classified as generating AOX wastewater under the EU’s Industrial Emissions Directive framework, and European regulations made the process increasingly difficult to run domestically. We all know this can cause companies to go under or go overseas where regulations are weaker.
However, the issue is also driving genuine innovation: the EU-funded LIFE SUPERWOOL project developed plasma pre-treatment as a replacement for chlorine-Hercosett, resulting in a process that is AOX- and wastewater-free. Most recently, University of Leeds researchers recently demonstrated a rapid, chlorine-free method for removing wool’s hydrophobic lipid layer that also eliminates AOX formation entirely.
In sum…
Given the evidence we have so far, I would say superwash by itself isn’t the villain it’s been made out to be. Articles that claim this cite issues that are true of all fibers: chemical use and wastewater impacts and shipping pollution – raw wool is guilty of these too.
Awareness and voting with your dollar is key. The more we support companies doing it the right way, the more others will be forced to fall in line.
For crafters trying to shop smarter, labels admittedly won’t tell you much. “Machine washable” or “superwash” doesn’t specify which process was used, and common certifications like OEKO-TEX and RWS don’t address the shrink-resist treatment at all. Right now, GOTS is the one label that explicitly rules out chlorine at any stage. Until greener methods become standard, that’s the most reliable signal on the shelf.
Companies using GOTS-certified or chlorine-free machine-washable wool:
- Neighborhood Fiber Co. — Their Studio Merino line uses GOTS-certified organic, machine-washable merino sourced through their mill instead of the standard chlorine-Hercosett process.
- BC Garn (Semilla Organic) — Described as “soft wash treated (made machine washable without chlorine),” per Loop Knitting’s product listing.
- Find multiple GOTS-certified organic merino/cotton blends listed at Inspire a Mind.
- Rabbit Row Yarns — Sells an undyed worsted-weight GOTS-certified washable wool explicitly marketed as skipping the traditional superwash process.
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