The Byzantine Church of '40 Holy Martyrs' in Veliko Turnovo, Bulgaria: Pigments and Technique

The 'St. 40 Martyrs' church is the most famous medieval building in Veliko Turnovo, Bulgaria. It is located in Assenova mahala, just next to Tsarevets. It was built and its walls were painted during the reign of Bulgarian king Ivan Assen II after the victory against Epyrus despot Theodoros Comninos (1230 AD). It consists of two buildings - a six-column basilica and another, smaller building on its western wall, which was built later. During the presence of the Ottoman Turks, maybe until the first half of the 18th century, the church remained christian. When it was converted to a mosque, all the christian symbols in it were destroyed. The archeological researches on site were initiated in 1969. As it is clear, the 40 Martyrs church is a historical monument of culture with great significance. The church had murals, from the earlier period, but in the following years and especially during the Ottoman period, the church has suffered many and different destructions. Nevertheless, the very few pieces of murals that are rescued till nowadays provide important information for the technique and the pigments that were used on its wall paintings. In the present work, twelve series of samples from the wall paintings were studied in order to characterize the materials and the technique used for church iconography. The study was based on the micro-analytical techniques of the Fourier Transform Infrared micro-spectroscopy (μs-FTIR), the Optical Microscopy and the Scanning Electron Microscopy (SEM) coupled to an Energy Dispersive X-ray Spectrometer (EDS). In the FTIR spectra of all pigments the characteristic peaks of calcite were detected, confirming the use of fresco technique for the creation of murals. The combination of FTIR spectroscopy and SEM-EDS analysis, reveal the existence of lapis-lazuli for the blue color, green earth for the green color, cinnabar for the red color, calcite for the white color and carbon black for the black color. Moreover, in other chromatic layers, the presence of iron oxides (hematite and limonite) indicating the use of ochre for the yellow and red pigments, is identified. Finally, the surface of some samples was covered by a transparent and tensile material. This material was characterized by μs-FTIR spectroscopy as an organic substance, probably a natural resin that was used to protect the murals in the early ages.