Ceramic is any clay that has been fired or baked. Pottery refers specifically to ceramic vessels like mugs, jugs, bowls and plates. People have been making ceramic objects for at least 29,000 years (Venus of Dolni Vestonice figurine)[i] and the earliest evidence of pottery has been found in the Hunan Province of Southern China (18,300 BP). The oldest pottery made in North America is referred to as Stallings Island pottery (4500 BP) and has been found on archaeological sites in the Southeastern US.

Clays are fine-grained earthy sedimentary deposits, created from the disintegration of rocks, that become malleable when mixed with water.[ii] Clay particles absorb water. When moistened water does not become a part of the chemical make-up of the clay particles, instead water is weakly bonded to the surface and edges of the clay particles creating a malleable material. Because of the weak bond, water can be removed from clays at relatively low temperatures. Baking clay changes its chemical makeup. When clay is baked between 450 to 600 degrees Celsius (842 and 1112 degrees Fahrenheit) the water within the molecular structure of clay burns off and it undergoes an irreversible chemical change. This irreversible loss of the water content in the clay makes a durable ceramic that is no longer malleable. Firing clay at higher temperatures creates a vitrified, or glass-like, ceramic ware.[iii]

Ceramicists categorize pottery by the temperatures they are fired at and the qualities of the paste.

• Earthenwares– the lowest fired pottery that is semi-porous and unvitrified
• Stonewares– high fired pottery that is partially to fully vitrified and non-porous
• Porcelain– very high fired kaolin clays that are completely vitrified and at least partially translucent

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[i] D.W. Zimmerman, M.P. Yuhas, and P. Meyers, Thermoluminescence dating of Upper Paleolithic fired clay from Dolni Vestonice, Archaeometry 13(1):53-57.

[ii] Prudence M. Rice, Pottery Analysis: A Sourcebook (The University of Chicago Press, Chicago, IL, 1987), 36,54.

[iii] Rice, “Pottery Analysis”, 54-55, 80-82,87,103-104.