Medieval Polychromy from Parisian Gothic Sculptures (1145-1250): Tracing Stone Preparation Techniques by Chemical Analyses and Radiocarbon Dating of Lead White

Abstract

This study presents a comprehensive analysis of preparatory layers of polychrome decoration of the portals of three major Parisian Gothic monuments dating from the mid-twelfth through the mid-thirteenth centuries: Saint-Germain-des-Prés church, Notre-Dame cathedral and the Sainte-Chapelle. Through a multi-analytical approach combining microscopy, spectroscopy, X-Ray diffraction, and radiocarbon dating, we characterized the composition and chronology of the preparatory layers.Microscopic and spectroscopic analyses reveal a consistent use of lead white as the primary component in preparatory layers across all monuments, with variations in minor materials. The Notre-Dame Last Judgment portal uniquely shows a two-layer system: a lead white base followed by yellow ochre, with evidence of environmental exposure between applications. The Sainte-Chapelle samples contain distinctive traces of minium mixed with lead white, while Saint-Germain-des-Prés and Notre-Dame's Sainte-Anne portal share similar compositions of lead white mixed with calcium carbonate and aluminosilicates.Radiocarbon dating of lead white provides unprecedented chronological evidence. The Sainte-Anne portal samples date to 1016-1158 AD, confirming the reuse of 12th-century elements. The Last Judgment portal samples yield dates of 1035-1164 AD, while Sainte-Chapelle samples date to 1027-1220 AD. Although these dates represent lead white pigment synthesis rather than application, they raise questions about sophisticated material supply networks as well as storage practices in medieval times.Thanks to the combination of analytical techniques implemented, this research has made it possible to identify different stone preparation techniques within the same building and the evidence of phased applications challenges previous assumptions about medieval workshop practices and construction site phases.

Keywords: (6)
Medieval polychromy, stone preparation technique, Gothic sculpture, radiocarbon dating, lead white, pigment