Epigraphy is traditionally defined as the study of writings inscribed on durable materials. The vast majority of these are engraved on stone. Other materials also inscribed include bronze, potsherds (ostraca), walls (graffiti), and portable objects, such as vases, amphorae, tiles, tesserae, gems, weights, and measures. The field of epigraphy also includes texts painted on newly made pottery prior to firing, as well as pottery and bricks impressed with stamps. This wide range of materials distinguishes epigraphy from the fields of papyrology and numismatics.