Pilot study on the lipid residues in the clay core of Lost-wax process

Abstract

The debate on whether lost-wax casting was used to make some exquisite bronze vessels during the Eastern Zhou period (8th-3rd centuries BCE) raises an important issue, that is how to identify the use of lost-wax casting in the archaeological record. This paper proposes a method based on the analysis of lipid residue in clay molds, assuming that the use of lost-wax casting technique might have left some lipid residue in clay materials involved. A series of simulation experiments were carried out in order to investigate the absorption behavior and chemical changes of beeswax during a casting process. The results show that a considerable amount of wax was absorbed by the clay core and underwent various chemical changes under the high temperature condition during the heating and pouring processes. It has been revealed that characteristic biomarkers of beeswax such as 14- and 15-hydroxypalmitic acids can sustain a low temperature heating (<100℃) while certain components including different acids and aldehydes retained when the heating temperature were kept between 100 and 300℃. However, when the heating temperature exceeded 400℃, no lipid components were detected in the clay mold and molds. This preliminary experimental work indicates some potential of the proposed method in exploring an effective way of identifying the use of lost-wax casting via analyzing organic residues that clay core may have absorbed and retained under certain circumstances.