Spectroscopic investigation of Cappadocia proto-Byzantine paintings

Abstract

The present contribution focuses the attention on the mural paintings of two among the oldest Cappadocia churches, belonging to the group of “proto-Byzantine paintings.” These materials have never been extensively investigated before and represent a starting point of paramount importance to understand the evolution of both materials and techniques during the ages in this extraordinary region of central Turkey. Specifically, among the several investigated churches and after the synergic work of art historians, conservators, and scientists, we selected the church of St. John the Baptist at Çavuşin, whose architectural structure is dated back to fifth–sixth century, and Church nr. 5 (Süslü church, sixth–ninth century) in Güllü Dere. A limited but exhaustive number of samples was carefully selected and then collected during the on-site campaign in Cappadocia. Samples were investigated with a multianalytical approach by using cross-section examination, X-ray fluorescence spectroscopy (XRF), Fourier-transform infrared (FT-IR), and micro-Raman spectroscopy to characterize materials, execution technique, and conservation state. The wall paintings in the church of St. John the Baptist are characterized by the presence of superimposed or adjacent layers ascribable to different historical periods, as it occurs in many of the Cappadocia churches. Their discrimination has been based on the mortar/ground layer. Pigments have been successfully identified and are mainly based on iron earths and ochres; the presence of gypsum and anhydrite, oxalates, and organic materials have been highlighted on the surface, thus suggesting alteration processes. The church nr. 5 at Güllü Dere shows a unique pictorial phase. Pigments are applied on a gypsum based ground layer and exhibit alteration patterns being made of lead based compounds, such as lead oxides and carbonates. A peculiarity of this church is the presence of anatase, detected in correspondence of red and yellow areas of the samples.