Sheep's wool is the most frequently used pile material in a Turkish rug because it is soft, durable, easy to work with and not too expensive. It is less susceptible to dirt than cotton, does not react electrostatically, and insulates against both heat and cold. This combination of characteristics is not found in other natural fibers. Wool comes from the coats of sheep. Natural wool comes in colors of white, brown, fawn, yellow and gray, which are sometimes used directly without going through a dyeing process. Sheep's wool also takes dyes well. Traditionally, wool used for Turkish carpets is spun by hand. Before the yarn can be used for weaving, several strands have to be twisted together for additional strength.