Clay Culture: Blurred Lines

Close-up of the oil-spot glaze on an ancient Tenmoku teabowl. Photo: W.Li.

Art and science—seemingly so separate—are actually incredibly intertwined. Ceramics, for example, might have begun as an art, but science made art applicable. Likewise, art makes science relevant for those outside the lab.

The lines between art and science are further blurred by the work of an international team of researchers who believe a rare iron oxide found in ancient Chinese pottery could be critical in developing improved and inexpensive magnets for electronics.

Epsilon-phase iron oxide (-Fe2O3), first identified in 1934, was only fully characterized within the last 10 years. And despite modern technology, creating the rare compound has proved challenging. But a team of researchers, which includes several Lawrence Berkeley National Laboratory scientists, is helping to meet that challenge through the study of coveted Chinese pottery produced more than a thousand years ago.

Produced during the Song dynasty (960–1279 BCE) in southeast China’s Fujian Province, Jian blackwares, particularly the teabowls, are highly prized pieces of pottery. A combination of iron-rich clay, limestone, and wood ash, the pieces, also known by their Japanese name Tenmoku (temmoku or temoku), were fired, thousands at a time, to 2400°F (1315°C), in massive Jianyang kilns.

A modern replica of the famed Jian bowl. Photo: Z. Liu.

Original Jian bowls. Photo: Wikimedia Commons.

Jian wares, characterized by their famous black glaze, are equally well known for their brown (oil spot) and silver (hare’s fur) surface patterns. It was previously believed that the former contained only the mineral hematite (Fe2O3) and the latter crystallized from magnetite (Fe3O4).

Scientists analyzed the patterns using optical microscopy, electron microscopy, Raman spectroscopy, and synchrotron x-ray techniques. In studying the chemical composition and crystalline structure of the Jian glazes, they identified a small amount of highly metastable epsilon-phase iron oxide mixed with hematite in the hare’s fur patterns and a much larger presence with the magnetite in the oil spots.

According to a Berkeley news article, the discovery “could lead to an easier, more reliable synthesis (the production of chemical compounds by reaction from simpler materials) of epsilon-phase iron oxide, enabling better, cheaper magnetic materials including those used for data storage.”

Originally published on  Ceramic Tech Today,, May 20, 2014.

Art, Archaeology, and Conservation Science (AACS) is a division of The American Ceramic Society (ACerS.) To learn more about how a new collaboration between AACS and Potters Council (, a subsidiary of ACerS, is providing potters greater exposure to the connections between art and science, check out

Featured image: Close-up of the oil-spot glaze on an ancient Tenmoku teabowl. Photo: W. Li.


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