Chemical Composition and Micro Morphology of Golden Laminae in the Wall Painting “La Maestà” by Simone Martini: A Study by Optical Microscopy, XRD, FESEM-EDS and ToF-SIMS

The chemical characterization of gilding decorations in works of art is fundamental in order to elucidate the techniques and materials used by the artists. In the present work we investigated by a combination of bulk and surface sensitive methods the composition and micro stratigraphy of the gilding laminae in the wall painting of the 14th century “La Maesta”, the masterpiece of Simone Martini. The aim of this study was to determine the composition of the gilding leaves and of the adhesive organic materials used to glue the metallic decorations to the wall painting. Due to the altered state of the samples we could not univocally identify the nature of the adhesive materials. Time of flight secondary ion mass spectrometry measurements showed that the gilding layers consisted of a gold leaf which was laid either directly on a preparation layer or on a tin lamina. The high sensitivity of ToF-SIMS and its spatial resolution allowed us to find traces of silver in the gold leaves and in the tin laminae which were not revealed by energy dispersive X-ray analysis.