Ground walnuts shells are a type of abrasive blast media used for cleaning. Typical substrates are metals, fiberglass, woods, plastics and stone. The walnut shells are ground to various sizes from coarse to extra fine depending on the application. The walnut shells are used in the same manner as typical blast media. Walnut shells are durable and can be re-used in many applications. Walnut shells can remove matter from surfaces without scratching or pitting underlying material.