From Wood to Wood Charcoal: an Experimental Approach to Combustion

Abstract

The anthracological deposit as it appears in archaeological contexts is the result of successive taphonomic agents intervening at many stages from the gathering of wood, to combustion and post-depositional processes. These taphonomic agents constitute successive filters between the past vegetation and the charcoal studied. Therefore, the interpretation of charcoal remains should take into account the potential deformation between the anthracological spectra and initially burned wood.This paper presents the methodological issues and the first results of an experimental cycle whose aim was to study one of these taphonomic agents: the combustion process. Does combustion involve differential preservation of burned wood species? Does charcoal quantification reflect the real proportion of burned species? Is it necessary to define a correctional index for anthracological data?In order to answer these questions, 110 experiments were carried out under standardized laboratory conditions and more than 295,000 charcoals were studied. Such factors as wood density or temperatures are often considered to play an active role in the fragmentation process of charcoal during combustion. As expected, the results indicate a differential behaviour of species, but one which proved to be independent of the expected factors, tending to show that the parameters that interact in the combustion process are of different nature. These factors increase the difficulty of defining a correctional index. Nevertheless, it seems that the quantification of charcoal reflects in a satisfactory manner the initial proportion of each of the burned species.