Pyrotechnological processes behind fire traces: Experimental archaeology for the interpretation of the archaeological record of Lugo di Grezzana

Several firing structures, fireplaces, ovens/kilns and firing-pits, related to the Fiorano culture (5500–4900 cal. B.C.) were found at the Early Neolithic site of Lugo di Grezzana (VR) in Valpantena (Italy). Hearths are heat alteration of substrate, which can be prepared or delimited; plastered surfaces hardened by fire are griddles or part of ovens/kilns; firing-pits are all characterised by deep rubefaction of the walls, a slightly-fired bottom (sometimes not fired at all) and large charred wooden boards just few centimetres above the bottom. There are also all those identifying elements of activities related to the use of fire: ash, charcoal, fired clay, burnt ecofacts and artefacts. In spite of superficial interpretations, it is difficult to define which processes led to the formation of such traces in the archaeological record and to relate them to a specific function. Dimensions of the pits and rubefaction of the walls could reflect several and/or long lasting firings as can be the case for pottery firing. The smallest ones could be used for other purposes. However, we cannot exclude that similar structures might have been used in a multifunctional way. The methodology we applied implements an experimental archaeology approach to test different hypotheses to better understand the complete firing process, and, in turn, through the comparison step by step of the results to the archaeological traces, to increase our knowledge of the archaeological formation processes. The several experimental actions have been enucleated and repeated, slightly changing them many times to see the effects to the record. The experimental work gave unexpected information about pyrotechnology, improving enormously our knowledge of the firing processes, confirmed by an archaemetric approach, through use of SEM-EDXS and FT-IR analyses on both archaeological and experimental samples of fired sediments and pottery. Experiments allowed us to observe the impact of a single vs several firings on a pit, the effects of a firing in reducing conditions and, moreover, what was the technology and arrangements that granted the preservation of charred wooden boards at the base of the pit. The firing-pits turned out to be the results of an advanced pyrotechnological complex which acted as a proper oven/kiln.