Evaluation of archeothermometric methods in pottery using electron paramagnetic resonance spectra of iron

Abstract

Knowing the techniques mastered by ancestors in their production of pottery can help understand their habits and skills, therefore increasing the understanding about their culture. In this work, we study pottery from an archeological site located in the city of Campos dos Goytacazes, state of Rio de Janeiro, Brazil, in order to appraise the firing temperature, atmosphere and time during pottery production. For this purpose, electron paramagnetic resonance spectroscopy (EPR) is used to analyze the signals of iron (Fe3+). Methods for obtaining the firing temperature were assessed, comparing archeological pottery with clay and changes caused by heat treatment in archeological pottery. In addition, potteries were prepared in laboratory, finding changes in the EPR spectra resulting from changes in the parameters of pottery making. The observation of colors profiles can provide information about temperature, time and firing atmosphere, but it is not accurate. From these findings, it was considered that the archeological pottery studied were prepared in a single firing, at temperatures up to 650°C in an open pit firing with semi-oxidizing atmosphere during a short time of approximately 0.5h.