The glass-melting crucibles of Derrière Sairoche (1699–1714 AD, Ct. Bern, Switzerland): a petrological approach

Forty-three sherds of crucible found in the pre-industrial (1699–1714 AD) forest glassworks of Derrière Sairoche (Ct. Bern, Switzerland) were studied in order to determine the nature of raw materials and the technological aspects of their production and use. The samples were analysed using optical microscopy, XRD, XRF, UV–VIS spectrometry and SEM/EDS.The crucibles were produced with local natural clayey sand and fired in two steps. After preliminary firing in a low-temperature furnace (800–1000 °C), the crucibles were brought to temperatures up to 1500 °C within the glass-melting furnace, before adding the glass batch. Using the structural order of cristobalite as an archaeothermometer, temperatures between 1370 and 1500 °C were estimated. The crucible surface shows corrosion by glass and furnace gases. Connections between glassmaking and crucible production are emphasised by this study.