Patented by the the Italian Candida Laundry company in 1986, the finish gave indigo jeans sharp contrasts. The process was achieved by soaking pumice stones in chlorine and letting these stones create contrast. 

Wet processors (laundries) try to make garments look worn or faded by scraping or rubbing the surface of the fabric causing abrasion. Pumice stones are most frequently used. (see stone washing)