Characterisation of lead carbonate white pigments submitted to AMS radiocarbon dating

The possibility of dating by radiocarbon lead carbonate, widely used as white pigment since ancient times, has been recently demonstrated. In this paper we tested two different samples processing procedures for the extraction of the carbon fraction from lead carbonate to be submitted to Accelerator Mass Spectrometry 14C dating. Samples with different origins were selected for this study: geological cerussite, modern sample produced by following ancient recipe and lead white used for restoration purposes. All the samples were characterised by using different techniques: X-Ray diffraction, X-Ray Fluorescence and Raman spectroscopy in order to highlight the chemical composition and identify the mineral phases. The 14C content was then measured by AMS in the carbon fraction extracted by acid hydrolysis or via thermal decomposition at different temperatures. Indeed, the selection of a proper temperature (500 °C) resulted in the possibility to get rid of the possible contamination from calcium carbonate. We also present the results obtained in the analysis of samples intentionally contaminated with 14C-free calcium carbonate and processed with the two different procedures.