Superwash wool is one of my favorite yarns to use for gifts, especially for babies. I love all the properties of wool but I worry about damage to my hand knit items during washing. Super wash wool is more resistant to damage during washing. What makes superwash wool so special?
Wool fibers have scales. With extremes in temperature and/or agitation, the scales bind the fibers together, resulting in felted wool. Sometimes this effect is desired, but many times it is not. The process of creating superwash yarn removes the scales with chemicals, or coats them with resin to prevent the scales from binding fibers together during washing. Inactiviation of these scales also results in the stretching sometimes seen when washing superwash items. The scales on the wool fibers that can cause felting, also help the final piece return to normal shape after wetting. Some superwash fibers do better when put in the dryer after washing. These fibers need the dryer heat to return the piece to its prewashed size. It’s best to check the yarn ball band for specific recommendations for your yarn. It is also best to make and block a gauge swatch when superwash wool. Since superwash wools tend to stretch during blocking/washing, you want to account for that stretch in your final knitted item. If your superwash fiber was created with resin, regular detergent can wash the resin away resulting in a felted wool piece. It is difficult to discover which process was used to create a specific superwash product. Therefore, it’s best to avoid regular detergent and use a wool wash in the washing machine even with superwash wool. I tend to still wash my superwash items by hand. However, I feel confident giving items made from superwash wool as gifts, knowing they won’t be ruined if they are run through the washing machine.