Microscopic Structure

• Wool is the hair of sheep and like all protein fibers, including human hair, it is covered with scales that are directional. Clara Parkes in "The Knitter's Book of Yarn," suggests this demonstration: Run a fingernail over a strand of your hair from the scalp to the end, and then the other way. The resistance you feel on the second pass is because of the scales. In wool, these scales help to hold the fiber together so you can spin it into a durable yarn, says Parkes.
  
  

Features

• Fabric made from worsted wool, including hand knit sweaters, will feel warm and dry against your skin, even when wet, according to Parkes. This is because wool is hygroscopic and can absorb up to 30 percent of its weight in moisture. Worsted wool is also naturally flame retardant, which makes it a good choice for baby and firemen's blankets alike.
  
  

Fiber Length

• Sheep are sheared at least once a year, and the length of the sheared fiber is called the staple length. Different breeds of sheep produce different staple lengths, but they average between 2 inches for fine wools and 12 inches for long coarser wools. For worsted wools, according to Parkes. Manufacturers usually use long fiber wool because it wears better, and they can spin it with a lot of twist.
  
  

Fiber Preparation

• To create a worsted wool, manufacturers and hand spinners use combs to align the fibers and remove the short hairs. In "Spinning the Old Way," Priscilla A. Gibson-Roberts explains that combing also loosens the wool and makes the parallel fibers generally all the same length. This preparation allows the spinner to create the durable worsted wool yarn.
  
  

Spinning Technique

• Both manufacturers and hand spinners use the same method to spin a worsted wool. The technique is called a short draw, which means that the spinner drafts short sections of the combed wool, and then allows the twist into the drafted area. Lee Juvan demonstrates this technique for hand spinners in "Worsted Yarns and Worsted Spinning" on the Knitty website. With this worsted spinning technique, spinners can add a lot of twist to the wool, which makes it strong and durable.