A Study of the Pigments and Cohesive Colour Layers of the Paintings in a Church from the Tenth to Thirteenth Centuries on the Plateau of Eski-Kermen
In 2018-2019, the excavations of an aisleless church dated from the tenth to thirteenth centuries and located in quarter II on the territory of a provincial Byzantine town atop of the plateau of Eski-Kermen discovered fragments of wall-plaster with polychrome painting. There are several shades of green, two shades of red, white (beige), yellow (ochre), and grey-brown colours. This paper presents the results of studies of the colour layer, determines pigments and cohesive colour components, and uncovers the features of the painting technique applied to the walls of the church. Four groups of samples were selected for the study featuring: 1 - white, 2 - yellow, 3 - red, and 4 - green colours. The elemental composition of the colour layer was studied by scanning electron microscopy combined with energy-dispersive X-ray microanalysis (SEM/EDX). The phase constitution of the samples was investigated by X-ray powder diffraction (XRD) method with the use of diffractometers operated in a transmission mode at the Kurchatov synchrotron radiation source. The chemical composition of colour layers was studied by infrared spectroscopy, and the study of cohesive colour materials was carried out by gas chromatography with mass spectrometry (GC/MS). The elemental composition and phase constitution of the white colour indicated the use of lime whitewash. Yellow ochre (goethite) was used as yellow colour. Red colour features the presence of hematite typical for the group of pigments united under the name of red soils. However, the discovery of 1% goethite typical for yellow ochres in the phase constitution of one sample allows the possibility that burnt yellow ochre was used as a red pigment. The green colour was green soil (glauconite and celadonite). It should be noted that none of the examined samples of red pigment contained traces of vermilion, which occurred in ancient paintings in the Crimea and was typical for Byzantine wall-paintings. In all the samples of pigments contained a significant degree of calcite (36-98%), possibly due to the presence of particles of undercolour in the measured samples of wall paintings, or diluting the pigment with lime water for the making of wall-painting featuring fresco technique. The use of the latter technique is also indicated by the presence of white lime colour. The traces of cohesive component in the form of fish glue and protein products from chicken eggs found in the red and green paint samples also suggests the use of the dry painting technique. Therefore, there are reasons to suppose that the painting of the quarter church of Eski-Kermen used two techniques, fresco and dry plaster paintings.