Tripod vessel with lid, Maya culture, Mexico or Guatemala, c. 4th-5th century, hand-built ceramic with incised decoration and burnished slip, Honolulu Museum of Art, accession 4183.1A pot by Maria Martinez, approximately 1945, at the de Young Museum in San Francisco
Burnishing is a form of pottery treatment in which the surface of the pot is polished, using a hard smooth surface such as a wooden or bone spatula, smooth stones, plastic, or even glass bulbs, while it still is in a leathery 'green' state, i.e., before firing.[1]