In embossing, sheets of soft, malleable metals, such as gold, silver, lead, or copper, are hammered over designed forms (matrices) of wood and other materials, heated for malleability (tempered), and hammered again until they assume the intended form. Large, complex sculptures are created in parts and later assembled with the help of fasteners (rivets) and soldering, or by fusing them together. Some small parts can be cast as well. Artists employ chiseling and sometimes chemically coat the surface with gold, or gilding.