Collection of 29 graphs of FTIR analyses of samples from combustion structures of Tossal de la Vila (La Serra d’en Galceran, Castellón) and Masies de Sant Miquel (Banyeres del Penedès, Tarragona, Spain).

FTIR Analyses have been carried out at the Archaeometry Laboratory of the Faculty of Geography and History, University of Barcelona. Specifically, for the preparation of the samples, a 2-tonne press, model SC-03940 Mini-Pellet Press from Teknokroma has been used, and to apply this technique, an iS5 spectrometer from Thermo Fisher Scientific.

The software used for the interpretation of the spectra was OMNIC and the mineral database used is available at the Kimmel Centre for Archaeological Science (Weizmann Institute of Sciences).

FTIR is a spectroscopic technique that obtains information on the molecular structures of crystalline and amorphous materials, as well as organic materials. It is based on the absorption of energy caused by the interaction between electromagnetic radiation and the material to be analysed; in this case, the interaction of the infrared with the analysed sediment. When clay is exposed to elevated temperatures, it is altered and becomes more disordered. The infrared spectra of clays exposed to high temperatures change depending on the type of clay, the temperature, and the length of exposure.