Always happy with an excuse to do some research, I dived into an online sea of opinions and information about superwash versus non-superwash wool, almost drowning in it. Here is a summary of what I found out:
Why would wool need superwash treatment at all?
Wool fibres have tiny open scales that interlock when friction is applied or when they come into contact with quickly changing water temperatures, leading to felting and shrinking. Superwash treatment can prevent that.
A controversial superwash treatment
The most commonly used method for shrink/felt-proofing wool by far is the chlorine-Hercosett process. After washing, but before spinning, the wool goes into a bath of diluted chlorine to dull the scales. And after that the scales are coated with a synthetic (polymer) resin to make them even smoother and prevent the wool from felting/shrinking. There is a lot of debate about this method:
- On the one hand: The chlorine-Hercosett method requires large quantities of water and produces an environmentally hazardous effluent. In some parts of the world this may lead to water pollution.
- On the other hand: Because of the strict waste water legislation in the EU and some other countries the effluent is treated to such an extent that only very clean water leaves the factory.
- Positive: This treatment prolongs the lifespan of items made from the wool.
- Question mark: Does the resin coating release micro pollutants when the wool is washed? Some producers say that the resin used is biodegradable and does not, but somehow I do not feel completely assured.
More environmentally friendly alternatives
- EXP, which stands for EX-Pollution, was developed by Schoeller. This method avoids pollutants altogether, but still uses extra water.
- Naturetexx Plasma, a treatment not using any water at all, but just air and electricity. The drawback is that it uses lots of electricity and there are questions about the durability of the wool treated in this way.
So, what is an environmentally conscious knitter to do?
It’s complicated – sigh! The labels don’t tell us much. They sometimes tell us that a yarn has been superwash treated, but not always. And they don’t tell us which treatment process was used. What we can do is this:
- Visit yarn manufacturers’ websites. Some of them give useful information about their production process.
- Look for yarns with the GOTS (Global Organic Textile Standard) label. Chlorine cannot be used in any stage of the production of these yarns.
- Remember that any superwash treatment makes knitted garments last longer, which is also sustainable, and may be necessary for items that need to be washed often, like baby things.
- Choose non-superwash yarns for items that do not need frequent washing. Some people say that non-superwash yarns have less saturated colours than superwash ones, but I find that hard to believe looking at these yarns from my nearest indie dyer.