Refutata per ignem: The Evidence for the Use of Thermal Analysis in 17th century European Ceramic Innovation

Refutata per ignem: The Evidence for the Use of Thermal Analysis in Seventeenth-century European Ceramic Innovation

Morgan Wesley

This Working Group project explored evidence for the use of thermal analysis in seventeenth-century European ceramic innovation. While the interaction of clay and fire in the kiln is integral to the ceramic process, the seventeenth century saw the inclusion of a new permutation of that elemental relationship. In the quest to develop European porcelain, alchemical laboratory practice was deployed towards the exploration of Chinese porcelain's properties. A critical component of this approach was the new application of fire towards the material analysis of imported prototypes. This fusion of alchemical processes and craft knowledge was integral in laying the foundations for the successful commercialization of European porcelain.

John Dwight of Fulham and Ehrenfried Walther von Tschirnhaus of Saxony were the first to employ thermal analysis into their ceramic experimentation. This evolution was born in the halls of the academy, initially devoid of exposure to the practice of the pottery workshop. Dwight was a self-described "chymist," trained in Robert Boyle's Oxford laboratory, while Tschirnhaus was a natural philosopher, educated in Leiden. In their pursuit of the secret of porcelain, the workshop and the laboratory were necessarily synonymous—the techniques of one discipline informing and enriching the other. By using thermal analysis in a manner consistent with the chymical literature of Jan Baptista van Helmont, Francis Bacon, and Johann Rudolf Glauber, both men aligned their craft practices with chymical theory.

While previous literature on porcelain innovation has given cursory attention to experimentation on Chinese ceramic bodies, specific discussion of the importance of thermal analysis as an empirical approach has been lacking. Evidence for Dwight's employment of thermal analysis toward identifying liquefaction temperatures and the thermal resistance of Chinese glazes appears in the archeological record. Excavations of his Fulham pottery, conducted in the 1970s, revealed the existence of re-fired Chinese sherds, several with Dwight's test glazes applied. More focused on the specific melting temperatures of Chinese porcelains and other ceramic bodies, Tschirnhaus actively published his findings in the journal Acta Eruditorium over the period between 1687 and 1696, along with increasingly sophisticated plans for the high temperature burning lenses he developed.

This chymical approach defined the separation of European porcelain's materiality from its Chinese counterparts. Basing the development of ceramic bodies on the information gained from prototype objects, Dwight and Tschirnhaus's productions support the view that no direct transfer of technology occurred between East and West during the critical period at the end of the seventeenth century. Instead the process of analysis and innovation was tied to the application of techniques extrinsic to European ceramic tradition, drawn fundamentally from alchemy. Of these methods, thermal analysis must be viewed as pivotal in the creation of distinct European porcelains.