Doctoral defence: Jan-Michael Cayme „Organic-inorganic interactions in experimental and archaeological ceramics“

On 10 February at 14:15, Jan-Michael Cayme will defend his thesis „Organic-inorganic interactions in experimental and archaeological ceramics“.

Supervisors:

Associate Professor Ester Oras, University of Tartu

Associate Professor Signe Vahur, University of Tartu

Professor Ivo Leito, University of Tartu

Oponent:

Dr. Léa Drieu, PhD Université Côte ďAzur-National Centre for Scientific Research (CNRS), France

Summary:
Archaeological pottery is a good reservoir of organic residues, that can be used to trace the original parent molecules from which these residues originated. Based on this chemical information, key archaeological questions about the diets of past communities, their technological practices, trade networks, and survival strategies can be answered. Chemical information can be obtained from pottery through a method called organic residue analysis, which employs various analytical chemistry techniques to identify and quantify organic residues in the material. Despite significant progress in identifying organic residues in archaeological pottery over the years, the mechanism underlying the retention of these molecules within the clay matrix remains poorly understood. Two primary factors are known to influence this retention: the adsorption of organic compounds within the pores of clay, which effectively shields them from the harsh environmental conditions during burial, thus preserving them, and the role of the minerals in the clay pottery itself. The contribution of this doctoral thesis provides baseline quantitative data on how mineral composition of clays influences the formation of micro- and mesopores. This was achieved through the use of experimental replicate clay briquettes made from mixtures of different clay types, temper, and fired at different temperatures. Some of these briquettes were tested for the recovery of simple fatty acids (C16:0 and C18:1). Quantitative analysis with gas chromatography-mass spectrometry (GC-MS) proved that the temper and degradation by heating significantly affect its recovery. Furthermore, an alternative method for quantifying mineral components in clays using attenuated total reflection Fourier transform infrared (ATR-FT-IR) was also employed. These findings were applied to archeological pottery from a 12th to 13th century AD burial site at Kukruse, Estonia, and found to be consistent with the results of the clay briquettes, proving that the mineralogical composition greatly affects the recovery of lipids.