What is Machine Washable Yarn?

At times we want to make a project with machine washable wool.  Socks, baby clothes, and items for children come to mind.  But which machine washable wool do we choose and what exactly does machine washable mean?

My Sister Knits
Cestari machine washable Traditional collection, not superwash

Superwash yarns

Usually machine washable wool means superwash wool. One of the reasons superwash wool is appealing is that it takes dye beautifully, creating bold vibrant colors.  Another is that it can be machine washed on cold.  Plus, it won’t pill or shrink.

machine washable yarn
Superwash yarns

However, wool that has been superwashed comes with drawbacks.  The superwash process itself, mostly done in China, changes wool from a natural product to a manufactured one.  The outer surface of wool fiber is made up of scales.  These scales can ‘grab’ onto each other and cause shrinkage when agitated, such as in a washing machine.

When wool is superwashed, these scales are removed.  The first step is done by exposing the wool to chlorine gas or being bathed in a chlorine based acid bath.  Then, once the scales are removed, what is left is sealed with a polymer coating.  This plastic polymere coating, Hercosett 125, contains epichlorohydrin which is classified by several international health research agencies as a probably or likely carcinogen in humans.

The resulting superwashed wool lacks the breathable, moisture wicking, and fire retardant properties of wool due to the plastic coating.  The fabric is also likely to stretch out of shape after washing because the scales are gone.

These are all important points to take into consideration when choosing a superwash yarn.

Cestari yarn to the rescue!

superwash yarn
Cestari Vermont yarn is lightly processed and is machine washable!

My Sister Knits now carries a line of yarn that is machine washable wool without being superwashed!  Cestari yarn can be washed in the machine using the gentle, wool, or hand wash cycle using cold water.  Francis Chester, founder of Cestari yarn, emphasizes that the water temperature must be cold!  He and his family have been washing their yarn this way since the 1960s and it doesn’t shrink or pill.  Plus, their wool is grown in the US and processed at their farm in Virginia and never leaves the United States!

We want you to know that if the superwash process is of concern to you, we have alternatives!


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