Non-invasive Identification of the Pigments and Their Application on Theophilos Hatzimihail’s Easel Paintings

Theophilos Hatzimihail (1870–1934, Greek: Θeόφιλος Χατζημιχαήλ or Θeόφιλος Κeφαλάς), known simply as Theophilos, was a major folk painter of Neo-Hellenic Art. The main subjects of his works are Greek characters and the illustration of Greek traditional folklife and history. The objective of the present research work is the characterization of the pigments and their application on easel paintings of Theophilos Hatzimihail using a combined analytical methodology. For this purpose, four easel paintings (1927–1931) were studied, which are part of a large collection belonging to the Theophilos Museum in Varia, island of Lesvos, Greece. In-situ measurements were performed with the use of portable X-ray fluorescence (XRF) and VIS-NIR fiber optics diffuse reflectance spectroscopy (FORS) non-invasive techniques at multiple spots of various color impressions for the determination of the chemical elemental composition and the reflectance spectral characteristics of the pigments. Furthermore, limited, micro-samples (flakes) from the surfaces were collected and studied via the Fourier transform infrared spectroscopy (FTIR) non-destructive technique in the laboratory, in order to acquire detailed information on the molecular structure of the pigments and the binding media of the paintings as well as to assess the accuracy of analytical information that the combined non-invasive methodology of XRF and FORS techniques provide. The experimental results led to reliable conclusions concerning the identification of the pigments, the organic binding media, and the technique applied for the creation of the paintings. The results demonstrated the use of the following pigments: ultramarine, green earth with the form of celadonite and glauconite, minium, various earth pigments with the form of hematite and/or goethite (caput mortuum, ochres), lithopone, and/or zinc white, lead white, and white earths. Mixtures of these pigments are responsible for several color impressions and hues. Among the aforementioned pigments were used in the ground layer of the paintings. As for the binding media, the presence of organic materials is indicated, namely, oils possibly combined with resins (oil painting) as well as egg (tempera) or milk. The conclusions of this research work confirmed the applicability and efficiency of the combined use of XRF and FORS spectroscopic techniques as a non-invasive methodology for the identification of the pigments and their application used in works of art, while the FTIR non-destructive spectroscopic technique constitutes a valuable tool in order to identify the binding media.