Characterization of the Chloroform-Based Pretreatment Method for 14C Dating of Restored Wooden Samples

At INFN-LABEC (Florence, Italy), a new pretreatment for radiocarbon dating based on chloroform has been recently set up. This method aims to remove the synthetic resins used for artwork restoration, which otherwise could alter the original 14C content. The present study characterizes the efficiency of the process when applied to wood. We have verified whether the effectiveness of the pretreatment depends on the number of extractions in chloroform. We prepared samples by applying different volumes of Paraloid B-72®, one of the most widespread products used in restoration, on poplar wood of known age. Contaminated samples were artificially aged in a climatic chamber. A fraction from each sample was collected before any treatment and after respectively 1, 2, 3, and 4 extractions in chloroform, and 14C dating by AMS, the resin appears to be already removed after the first two extractions. Furthermore, the extracted mixtures of chloroform and possible removed Paraloid were measured by FTIR spectroscopy, the results of which confirmed the 14C results. The efficiency of the pretreatment was also verified on historical wooden materials that had been previously restored. In these cases, a higher number of extractions is required, suggesting a careful approach when dealing with “real” artworks.