Raman analysis of Gothic wall paintings in the apse of the Santiago Apóstol church in Alcazarén

In order to determine the mineral species used as pigments, an in situ non-destructive Raman spectroscopy study of the Gothic wall paintings in the Santiago Apóstol church in Alcazarén has been performed. Establishing the paint palette was challenged by the fact that these murals had undergone a restoration process in the 1980s. Bearing this in mind, the use of in situ Raman analysis was considered preferable to more aggressive conventional sampling techniques. The observed Raman spectra have been assigned to cinnabar, red lead, quartz, bone black, calcite and aragonite. Two variants of cinnabar with different crystallinities were alternatively used for the relevant figures and the decorative elements. Mixtures of cinnabar and red lead were used to obtain different orange tonalities. No spectral features from the pigments or the protective coatings that were used for the restoration process have been detected.