Effect of conservation treatments on radiocarbon ages of wood

Abstract

The efficiency of the standard radiocarbon pretreatment in removing contamination from carbon introduced by wood conservation treatments was tested. Seven consolidated waterlogged wood samples from well-dated archaeological sites in Switzerland were chosen for preparation and AMS analysis. Conservation material included materials frequently used in the second half of the 20th century such as Arigal C, Polyethylene glycol, Ethanol-Ether, and sucrose. Seven treatment methods were applied to chosen samples and the AMS analysis were compared to the expected age. A positive offset is observed between the archaeological age and the radiocarbon age for most standard cleaning procedures, thus highlighting the necessity for the identification of the components present in the samples prior to treatment. Fourier transform infrared spectra obtained on some of the remaining material indicate the presence of the contaminants in the cleaned material. Our results highlight the importance of sampling exclusively conservation-free material and monitoring sample purity using Fourier transform infrared spectroscopy.