John Dwight's Crucibles
In 1672 the alchemist and potter, John Dwight, was granted a patent, in which he stated that he had “discovered the Mistery of Transparent Earthen Ware, commonly knowne by the Names of Porcelaine or China and Persian ware, as also the Misterie of the Stone Ware vulgarly called Cologne ware….”. Dwight was able to establish a successful salt glazed stoneware production and his white wares (“porcelain”), while not truly equivalent to oriental porcelain, were arguably the most advanced ceramics in Britain at the time.
Contemporary texts suggest that Dwight also made crucibles comparable to the highly regarded Hessian wares from Germany. Crucibles are required to withstand conditions more extreme than virtually any other ceramic, and we have examined samples excavated from Dwight’s pottery in Fulham to determine how they were made and if they were indeed as successful as those from Hesse.
We have examined Dwight’s wares using petrography, SEM-EDXA, EPMA and XRD. Hessian wares were more aluminous and developed extensive mullite, so are likely to have been stronger and dimensionally stable to higher temperatures than Dwight’s crucibles. However, it is unclear if this was significant for most practical purposes.
The addition of glass to vitrify refractory ceramic clay in Britain appears to have been an innovation by Dwight. Transmission of the practice is traced through the early eighteenth century. It was widely used in in architectural stoneware and in porcelain of the mid-eighteenth century and later, and it is suggested that this trajectory originates in the practice of Dwight.
- Martinon-Torres M, Freestone I C, Hunt A and Rehren Th (2008) Mass-produced crucibles in Medieval Europe: manufacture and material properties. Journal of the American Ceramic Society 91, 2071-2074
- Accademia Nazionale dei Lincei