Once woven, woolen cloth underwent a process of finishing known as “fulling” or walking, which entails washing and churning the finished cloth in a detergent in order to remove impurities and consolidate the fibers. Human urine, which contains ammonium salts, was a commonly used detergent. In cities, the fullers, like the dyers, were usually located in areas close to an abundant water source and in places in which the noxious fumes from the detergent were least offensive to other residents.