The Levi’s finishing process that creates a worn-in look using pumice stones is stonewashing.
In stonewashing, denim garments are washed with abrasive stones, commonly pumice, so friction removes some surface dye and softens the fabric. The result is a lighter, broken-in appearance that would otherwise take much longer to develop through ordinary wear.
Stonewashing is a finishing treatment, not a different type of cotton or a separate weave. Its effects can vary according to the stone size, washing time, temperature, chemicals, and garment construction. Industrial laundries later developed alternative methods, including enzyme washing and laser treatments.
The process became especially prominent in the late twentieth century as consumers sought jeans that looked worn from the first day. It also reduced the need for customers to break in very stiff raw denim themselves.