Wool Wiki

Wool straight off a sheep contains a high level of grease which contains valuable lanolin, as well as dirt, dead skin, sweat residue, and vegetable matter. This state is known as “grease wool” or “wool in the grease”. Before the wool can be used for commercial purposes it must be scoured, or cleaned. Scouring may be as simple as a bath in warm water, or a complicated industrial process using detergent and alkali.

Via: The New Shelton Wet / Dry  LINK