In virtually all societies there are hierarchies of materials; expensive materials are often copied in cheaper ones. Silverware provided a model for many Chinese porcelains, with potters often imitating metalwork features, such as stepped handles and faceted vessel sides. Emulation of silverwork stimulated several technical innovations in porcelain manufacture, including the use of molding, the firing of bowls on their rims, and the stacking of wares in tiers in the kilns.