The traditional Hercosett superwash treatment is very effective. By superwash treating wool, the edges of the scales on each hair are removed and smoothed, so that they cannot catch together as well. This prevents shrinking and felting when the wool is washed in hot water or agitated. The treatment itself uses plenty of chlorine and is therefore of questionable environmental credentials.
After the advent of cotton and polyester fibres, and with the early washing machines, wool became seen as "too difficult" because, with life speeding up, everyone expected to wash everything in the machine and wool did not respond well to the heat and agitation. Hand washing was seen as a chore which took too long. So superwash treatment of wool was a break-through in terms of bringing back wool into popular usage.
But things have moved on now: washing machines have gentle wash cycles, which are needed for the more fragile fabrics of all types: not just wool, but silk, elastics and acrylics as well. I confess that I almost never wash by hand: all my pullovers, whether wool, silk or cashmere, go into the machine. They go on a wool cycle, low temperature or cold and I set the machine to rinse and hold. When ready (or when I remember), I then spin at no more than 1,000 rpm and take everything out immediately, shake, pull into shape if necessary and hang to dry. I am seriously allergic to ironing (gives me instant depression and rage - it was my family chore as a child!), so I almost never iron anything. So with care all wool is machine washable if not necessarily superwash and even superwash will not respond well to being boiled with the bedlinen!
So do we need superwash? People seem to think they need it for babies, but most of the stains they create require a bit of soaking anyway, or a bit of a rub with soap, so could then be put on a more gentle wash maybe?
The superwash process is also, of course, very large-scale, so Blacker Yarns and The Natural Fibre Company would not be able to use it. We do process superwash treated tops into yarns for some of our trade customers.
Interestingly, it is possible that the prevelance of super-wash goes hand-in-hand with the ubiquity of merino yarns. Merino felts like a dream (unless superwash treated of course). Some wools do not - smoother and lustre wools, alpaca and mohair are considerably harder to felt. Gotland seems to be an exception to this as it felts very easily despite being a lustre longwool (I defy you to felt Devon and Cornwall Longwool easily!). However, felting itself is interesting as some people seem to manage some fibres and not others and the results vary.
There is a new superwash treatment, called a plasma treatment, which uses high voltage electricity to obtain the same results as Hercosett. This has been developed in Germany and is approved for organic processing to Global Organic Textile Standards. So this is obviously environmentally more acceptable. However, I understand it can only be used to treat tops and not as part of the scouring process for greasy wool as with Hercosett. There is also a process using oxygen instead of chlorine - also able to be GOTS certified I understand.
So, if we want to use an environmentally friendly option, this is better, although there is still the option of just taking a little bit more care with untreated wool!
In the last Wovember month there was a very interesting article about the importance of superwash in saving the US wool processing industry as it was used for military uniforms, for example helmet linings, where wool's ability not to burn is of enormous value.
I am still researching this subject, for which there are no pictures! I would be interested in views - you can post them on Twitter @blackeryarns or on Facebook on the Blacker Yarns and Designs pages.