Simulation experiments for determining the use of ancient pottery vessels: The behaviour of epicuticular leaf wax during boiling of a leafy vegetable

Laboratory experiments were performed using replica ceramic jars to simulate ancient pottery vessel use. The aim of the study was to investigate the behaviour of lipids, specifically, epicuticular leaf wax components during the processing of foodstuffs in unglazed ceramic vessels to determine if the pattern of lipid accumulation in a vessel can be used as an indicator of the mode of use of individual vessels. Brassica (cabbage) leaves were boiled in replica jars and the ceramic fabric sampled from different parts of the vessel profiles. Leaf wax components were solvent-extracted from the fabric samples, and analysed by gas chromatography (GC) and GC/mass spectrometry (GC/MS) to determine their distributions and concentrations in different parts of the vessel profiles. The same lipid distributions were detected in the fabric of the replica jars as occurred in the wax of the Brassica leaves. The pattern of lipid accumulation observed in the experimental vessels, i.e. the relative concentrations of lipid at different points on the profile, was analogous to that seen in two ancient vessels which had been shown to contain Brassica leaf wax components. These results confirm that boiling a leafy vegetable in water results in mobilization of the epicuticular wax and its incorporation into the porous ceramic fabric. The boiling process is non-selective with respect to the major leaf wax components and leads to a characteristic distribution of lipid down the vessel profile, with higher concentrations in the upper parts and gradually lower concentrations towards the base. This provided the first experimental evidence for the actual mode of use of individual vessels based on the results of organic residue analyses. (C) 1997 Academic Press Limited