A06_07

The application of radiocarbon dating of lead white in the study of polychrome stone sculptures

Sá S¹,  Hendriks L^2,3, Hajdas I³, Pombo Cardoso I¹

¹Department of Conservation and Restoration and LAQV–REQUIMTE, NOVA School of Science and Technology, 2829-516 Caparica, Portugal, ²School of Engineering and Architecture of Fribourg, HES-SO University of Applied Sciences and Arts Western Switzerland, Pérolles 80, CH-1700 Fribourg, Switzerland, ³Laboratory of Ion Beam Physics, ETH Zürich, Zurich, Switzerland

Polychrome sculpture was a foremost artistic expression in the Middle Ages proven by numbers and persistent production. However, studying the polychromy of these sculptures is extremely challenging as, frequently, these objects got their decoration periodically renovated, supposedly to hinder the poor preservation state of the previous polychromy or to answer to changes in artistic taste and style. Today, many polychrome sculptures present intricate surfaces as a result of the loss and degradation of paint material, of the consecutive reapplication of new paint layers over the centuries, and of the uneven removal of paint layers in past restoration interventions. Hence, the understanding and interpretation of these surfaces and the identification of the original polychromy is rather complex and requires assistance of different sources of information.

Unlike other cultural heritage objects, such as wooden sculptures or paintings on canvas, polychrome stone sculptures do not bear an organic substrate which may be radiocarbon dated. Providentially, lead white, which was recently put forward as novel proxy for artwork dating, is ubiquitous on the decoration of these sculptures. The present study¹ discusses the pioneering application of ¹⁴C analysis on paint samples from polychrome limestone sculptures by specifically targeting the lead white pigment and organic binder. The radiocarbon dating survey conducted on 16 Portuguese sculptures confirmed that some polychromies were produced within the medieval period while others were revised, hereby demonstrating the potential of the radiocarbon dating technique in the transdisciplinary approach used to study the complex paint stratigraphies found in medieval sculptures.

¹Published in https://doi.org/10.1038/s41598-021-91814-y