Felted Wool

Boiled wool/felt yardage is created commercially by first weaving or knitting wool fibers resulting in a fabric of uniform thickness. The material may either be dyed first or left natural, with or without design and embellishment. Then "boiled" and agitated in hot water and suds which shrinks the fabric without the use of chemicals. The result is a tighter and more dense material, usually shrinking anywhere from twenty to fifty percent. Wool that has been boiled/felted is thought to be warmer, more durable, and windproof depending on the degree of felting. Increased felting creates a denser but thinner felt and vice versa. (Wikipedia)