The convenience of machine washability in a natural fiber
by Jackie E-S
"Superwash" is a term generally applied to wool that has been treated to be machine washable and thereby resist shrinkage and felting.
You may have already discovered that wool shrinks and felts when subjected to a combination of moisture, sudden changes in temperature, and friction. This is because wool has microscopic scales that open up with moisture and heat, then grab and close up on each other with friction and changes in temperature. When the experience is unintentional, the result is not pleasant and is only partially reversible at best. However, if you are knitting with the intention of shrinking and felting, then you are in for loads of fun – just don't use superwash wool!
I have hand washed woolen articles, and even machine washed on delicate cycle, for years and years without adverse results. But it does require
more attention and time than just throwing in the machine wash with the rest of the clothes. Also, some wools naturally resist felting, and
densely knit or woven articles resist felting. However, if you really desire the convenience and ease of machine washing, such as for daily socks and baby items, then you certainly want to consider using superwash wool.
So, what makes wool superwash? As I understand it, there are two processes used to make wool machine washable. One is to coat the wool fibers with a plastic resin so that the scales are "glued down". The other removes the scales (which unfortunately also reduces the strength of the wool, as it is chemically destructive). Sometimes a combination of the two processes are used.
Which process is used on a wool yarn you might buy? Yarn labels do not specify. Is one better than the other? That is hard to say, because there
are just too many factors, preferences, and potential end-uses. If the yarn performs well for you and to your expectations, it does not matter.
If you don't know, make sure to ask your yarn shop or fellow knitters for their experience and recommendations. And even after that, sample for yourself to make sure!
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