Lime is used in Chinese porcelain glazes. Lime is prepared by heating limestone, marble, chalk or shells (calcium) to 540 entigrade. The process is called calcining. Lime is used in plaster, mortar, and cement to form durable aggregates. When calcium carbonate is heated, carbon dioxide is driven off leaving anhydrous calcium oxide or quicklime. When quicklime is soaked in water, it is changed to calcium hydroxide or slaked lime. Slaked lime that is dried and ground to a fine powder is called hydrated lime.