The definition of pottery used by ASTM is, "all fired ceramic wares that contain clay when formed, except technical, structural, and refractory products." Some archaeologists use a different understanding by excluding ceramic objects such as figurines which are made by similar processes, materials and the same people but are not vessels.
Pottery is made by forming a clay body into objects of a required shape and heating them to high temperatures in a kiln which removes all the water from the clay, which induces reactions that lead to permanent changes including increasing their strength and hardening and setting their shape. A clay body can be decorated before or after firing. Prior to some shaping processes, clay must be prepared. Kneading the clay helps to ensure even moisture content throughout the body. Air trapped within the clay body needs to be removed. This is called de-airing and can be accomplished by a machine called a vacuum pug or manually by wedging. Wedging can also help produce an even moisture content. Once a clay body has been kneaded and de-aired or wedged, it is shaped by a variety of techniques. After shaping it is dried and then fired.
Clay ware takes on varying physical characteristics during the making of pottery. Greenware refers to unfired objects. Clay bodies at this stage are in their most plastic form. They are soft and malleable. Hence they can be easily deformed by handling. Leather-hard refers to a clay body that has been dried partially. At this stage the clay object has approximately 15% moisture content. Clay bodies at this stage are very firm and only slightly pliable. Trimming and handle attachment often occurs at the leather-hard state. Bone-dry