A Comparative Study of Extractable Lipids in the Shards and Surface Residues of Ceramic Vessels from Neolithic and Roman Iron Age Settlements

In this Chapter lipids extracted from charred and non-charred surface residues are quantitatively compared to lipids absorbed into the ceramic material of the vessel. The emphasis is on ceramic vessels originating from Uitgeest-Groot Dorregeest, but charred surface residues from other Roman Iron Age settlements and from Neolithic sites were analysed for comparison using Gas Chromatography and Gas Chromatography Mass Spectrometry. Both the total yield of extractable lipids and the relative lipid composition of the extracts were studied quantitatively. Three indices were formulated and used as tentative, comparative measures for the state of preservation of the various samples (i.e. degree of saturation of fatty acids; the degree of hydrolysis; and the proportion of odd carbon number fatty acids). The results show considerable variation in composition and preservation between different types of samples. Surface residues clearly contain a more intact acylglycerol profile than lipids extracted from the ceramic fabric of the vessel. These differences are probably caused by repetitive heating of the absorbed lipids inside the vessel wall. The refractory nature of charred materials is proposed to be an additional important factor in the high degree of preservation of lipids in surface residues.