A new FTIR spectrophotometric method for estimating the firing temperature of ceramic bronze-casting moulds from the Houma foundry, China

Abstract

The ceramic piece-mould casting technology is a unique feature of ancient Chinese bronze production. Firing temperature was undoubtedly one of the important elements in mould production. However, firing temperatures determined by existing analytical techniques are controversial. This study establishes an innovative new FTIR spectrophotometric method to estimate the firing temperature of ceramic moulds. In the clay-containing material the absorbance ratio of clay’s SiO stretching peak to quartz’ (A1030/A1082) can divide the firing temperatures into three groups: below 500 °C, between 500 °C and 800 °C, and above 800 °C. The ratio is negatively correlated with firing temperature at 500–800 °C, enabling firing temperature at this range to be better estimated. This finding was applied to the measurement of firing temperatures of ceramic bronze-casting moulds from three Chinese Bronze Age foundries: Houma, Anyang and Yaoheyuan. It was found that the Houma moulds were generally fired at above 800 °C, the Anyang moulds fired at a wide range from below 500 °C to above 800 °C, and the Yaoheyuan moulds fired at below 500 °C, indicating chronological development and regional difference in mould production during the Chinese Bronze Age (c.18th–5th century BCE).