There has been a bit of debate on social media this week about the merits of superwash wool vs untreated wool. I will say upfront that I sit right in the middle of this one, because each have their own merits and disadvantages, but it occurred to me that many of you might not even know that there is a difference or what it means. So here is my brief and (I hope) impartial description of each.
Much of the wool that one purchases these days, even if it is pure wool and not blended with acrylic, is what is called superwash wool. This means that it has been chemically treated – the scales on the wool eroded by acids and then coated in a synthetic resin. The main advantage of this process is that the wool is then machine washable, but it also makes the wool softer and gives it a drape which makes it great for shawls and such like. Also, which is great for those of us who enjoy the dying process, superwashed wool takes dye extremely well, allowing for bright and interesting colours.
There are downsides to superwashing wool, of course. One is that it carries some environmental risks – hazardous chemicals are used and a lot of water. It is also prone to stretching and not bouncing back into shape which can be annoying. The removal of the scales means that it is not quite as warm as untreated wool. Some people on social media have been claiming that the resin in which it is coated decays and leaves plastic particles, but this is not true and furthermore superwash wool is still biodegradable.
On consideration, quite a lot of the wool that I sell in the shop is superwash. Anything with a washing instruction allowing it to be washed in a machine – so the Bo Peep baby wool, the West Yorkshire Spinners Colour Lab and Signature 4ply, almost all the other sock yarns, Lang Merino 120 and other Lang ‘fashion’ yarns, my own hand dyed yarn, Malabrigo Rios and Sock, Knitting for Olive Merino. I would say, however, that I would not advise washing superwash wool at a higher temperature than 30 degrees and furthermore that the spin should be kept quite low. I have managed to felt superwash socks by not observing these basic rules.
Untreated wool is washed of course, carded or combed and spun. There are lots of upsides to untreated wool. No chemicals are used in its preparation (other than the dyes that are applied). The scales are left on the fibres and they help to trap air and make any garment warmer. It bounces back into shape after washing, does not hold smells and is excellent for use in colourwork and textured garments. It is still not brilliant for the environment – there are issues around the amount of water used to process all textiles and acid dyes are made from petroleum products. The major downside for many people is that it has to be handwashed, however not very often as untreated wool repels dirt and smells. And of course if you want to felt something, such as the Sailor Slippers I made recently, you can only use untreated wool!
The untreated wools in my shop include West Yorkshire Spinners Retreat Chunky and Super Chunky, Blue Faced Leicester, The Croft Aran. Also Hjertegarn’s Natur Uld, Frangipani for the gansey knitters, Jamieson & Smith and the John Arbon Textiles yarns that I stock (Devonia 4ply and Yarnadelic).
Manufacturers of yarn are working on creating superwash in a more eco friendly way, using enzymes instead of chemicals, but the process is in its infancy and I believe not many of these yarns are yet available. I will keep you updated.
I hope you found this useful and would be interested to hear your thoughts on the subject.