Superwashed wool is wool that is machine washable and, therefore, will not felt or shrink like untreated wool. Superwashed wool is made by exposing the fiber to a chlorine gas that erodes the scales and then it is coated in a plastic resin called Hercosett 125. One yard of our t-shirt fabric has .45 grams of resin, about half the weight of a raisin. The scouring mill has a EU Ecolabel Certificate and is Standard 100 by Oeko Tex.