We bet that this happened to you at least once in your life.
But who is really to blame?
Here we would like to clarify one point: It is never wool’s fault if a sweater shrinks. The human contribution to the end of your favorite garment is total.
So, after a ‘Mea Culpa’, read the reasons causing shrinking and felting:
With the effect of heat (i.e. hot air and water) and mechanical action, which promotes fiber shift (i.e. washing machine movements), fibers burst and bond to each other. That is why the garment becomes felted. The more valuable the wool is, the more the knitwear risks shrinking and felting. So when you say ‘the sweater has shrunk because of wool’s low quality’ the truth is exactly the opposite.
Even in the hopeless cases – for those who cannot refrain to put sweaters in the washing machine – there is hope! The market offers machine-washable yarns with an anti-felt finishing, which are less sensitive this kind of damages.
Another interesting point to consider is that felting, that is usually considered a problem, in the world of knitting is a feature obtained with the fulling process. (See the ‘The knitter’s tools’ article)
Fulling is simply an operation made on wool fabrics in order to give them special qualities of consistency, firmness, smoothness and softness. The result is technically obtained with simple water washings inside machines similar to washing machines, followed by a hot air drying process inside a special tumble, with variable temperatures up to 100°C.
Fulling also determines the knit’s hairiness. Even in this case water temperature and drying give the knit different features and levels of felting.