High temperature performance of two-layered ceramics and the implications for Roman crucibles: High temperature performance of two-layered ceramics and the implications for Roman crucibles

Roman metalworking crucibles are frequently characterised by an extra outer layer (EOL) of clay, applied to a pre‐formed vessel. Three‐point bending and standardised dead‐weight loading tests were conducted to determine the advantages offered by the EOL. Deformation and fracture behaviour, at temperatures up to 1,100°C, of two‐layer, monolithic, and tempered‐monolithic briquettes were compared. Measurements indicate that the two‐layer briquettes are more resistant to fracture at high‐temperatures: above 850°C they show more extensive plastically deformed regions than monolithic briquettes. The influence of temper is consistent with previous results: tempering causes quasi‐stable fracture and reduced fracture strength. Results suggest EOLs assisted in preventing catastrophic failure.