In the past stone wash jeans were actually made with pumice stones. There were many drawbacks to using stones which include damage to the fabric and costs associated with the machinery used. It is now done by biostoning with the fungus Trichoderma reesei . The fungus produces cellulolytic enzymes that helps degrade the cotton material. The enzymes are cellulases and hemicelulases. These enzymes bind to the exposed cellulose on the outer cotton fiber wall (dyed fabric/indigo) and the molecular bonds are broken while the interior are left unbroken. It changes the surface of the jeans without destroying the makeup of the fabric. This allows for endless creative works!!! And at a fraction of the cost of using pumice stones.
Li X., Chang S.H., Liu R. (2018) Industrial Applications of Cellulases and Hemicellulases. In: Fang X., Qu Y. (eds) Fungal Cellulolytic Enzymes.