Exploring Carolingian and Romanesque cycles: a study of the detached wall paintings from the Church of St. Johann in Müstair

Abstract Twenty-six fragment of wall paintings detached from the upper register of the Carolingian and Romanesque cycles of the church of St. John in Müstair (Switzerland) have been part of the Swiss National Museum collection since the beginning of the twentieth century. As some of these objects were in a critical state of conservation, a research project was launched to assess and document their conditions, and to gain knowledge about painting materials and execution techniques, in view of planning a conservation project. In a first phase, non-destructive analyses were carried out, using handheld XRF and portable FTIR spectroscopy; followed by the targeted collection of samples for detailed analysis in the laboratory. In parallel, similar investigations were carried out on the imprints left on the walls of the church’s attic. The results allowed the identification of the pigment palette and the execution technique. Besides earth pigments such as ochres, a lime-based white, probably bianco di San Giovanni , and limited amounts of lapis lazuli were used in both painting cycles. For the Carolingian cycle, Egyptian blue and mixtures of several lead-based pigments were also identified. In several instances, the deterioration of lead-based pigments resulted in shades of grey to black severely modifying the original appearance of the wall paintings. Additionally, both cycles have suffered from pigment alteration due to fire. The obtained results, together with iconographic considerations, allowed for an extended interpretation of possible original colour palette. Graphical Abstract