A ceramic is a solid material comprising an inorganic compound of metal or metalloid and non-metal with ionic or covalent bonds. Common examples are earthenware, porcelain, and brick. The crystallinity of ceramic materials ranges from highly oriented to semi-crystalline, vitrified, and often completely amorphous (e.g., glasses). Most often, fired ceramics are either vitrified or semi-vitrified as is the case with earthenware, stoneware, and porcelain. Varying crystallinity and electron composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators (extensively researched in ceramic engineering). Artistic materials are inorganic, non-metallic materials produced using mixes of a metal and a nonmetal. Artistic materials may be crystalline or halfway crystalline. They are shaped by the activity of warmth and consequent cooling. Clay materials have a tendency to be solid, hardened, fragile, synthetically latent, and non-conduits of warmth and power, yet their properties differ broadly. For instance, porcelain is broadly used to make electrical covers, yet some ceramic mixes are superconductors.