Microscopic Analysis of Wall Painting Techniques: Laboratory Replicas and Romanesque Case Studies in Southern Switzerland

The identification of painting techniques is an important aspect of any research related to historical, artistic, and conservation issues in the field of wall paintings conservation. There are a variety of different methodological approaches that can be used to identify wall painting techniques. In this study, the application of optical (PLM) and electron (SEM-EDX) microscopy was explored as they are complementary analytical techniques commonly used for micro-stratigraphic analysis of painted surfaces. Five replicas were prepared according to the technical procedures reported in medieval historical treatises, and the pigment was applied at different time intervals in order to monitor the modifications at the interface between the ground and pictorial layer. The comparison of data from the replicas with samples from Romanesque wall paintings in churches in Southern Switzerland and Northern Lombardy (Italy) allowed for an evaluation of the reliability of the proposed methodology and for the interpretation of the painting techniques.