Painting the Ancient World

Crystallochemical Characterisation of Pigments and Minerals in Ancient Written Artefacts

2022–2025

RFA19

Figure 1: Raman spectrum of a Babylonian cylinder seal (#1920.0056) dated around the 2nd millennium BCE, where the characteristic Raman peaks of talc (peaks shaded in blue) and hematite (peaks shaded in red) can be observed. The photo of the analysed cylinder seal can be seen as an insert in the plot, whereas the figure is after Aspiotis et al. (2023).

The main objective of this project is the non-destructive determination of the crystallochemical characteristics of the mineral phases comprising pigments found on rock-based writing supports and of cultural-heritage objects, for instance of a series of old Babylonian cylinder seals belonging to the collection of Museum für Kunst und Gewerbe, Hamburg (MKG) dated between 3200 and 400 BCE. For this purpose, the chemical and structural properties of colour and weathering-related products on rock-based inscriptions and their writing supports, as well as on other objects from two different localities of the Hellenistic and Imperial Greece and Asia Minor are going to be comprehensively analysed. So far, Fourier-transform infrared (FTIR) reflection and near-infrared (NIR) spectroscopic analyses revealed that several earth pigments were used for colouring marble statues and epigraphic stele of the Classical-Hellenistic period and of wall paintings of the Byzantine period. The most remarkable finding was that the traces of red colour on the neck and feet of a female marble statuette (Classical-Hellenistic period) can be assigned to different pigments.

Further analytical techniques such as X-ray fluorescence (XRF) and Raman spectroscopy are applied, since the latter has already been proven to detect differences in the weathering-related products between inscribed and non-inscribed areas of the same specimen (see Aspiotis et al., 2021; EJM, 33, 189-202). In addition, the potential of micro-spatially offset Raman spectroscopy to study non-invasively the chemical and structural composition of subsurface layers in painted and/or restored rock-based written artefacts is explored to elucidate the artefact conservational history and provenance.

The second part of this project is dedicated to the development of quantitative relationships between the crystal chemistry and Raman scattering selected subgroups of layered silicates, present in cultural-heritage objects, by following the already established methodology for biotite (see Aspiotis et al., 2022; EJM, 34, 573-590), serpentine-group minerals and talc (see Aspiotis et al., 2023; JRS, 34, 1502-1516). Here the applicability of the proposed method has been demonstrated for material profiling of two representative rock-based cultural-heritage objects, particularly of Late-antiquity inscribed gems and old Babylonian cylinder seals (Figure 1) of the 2nd millennium BCE from the MKG collection. Overall, the knowledge of the chemistry and structure of mineral groups present in common cultural-heritage objects and pigments, may advance provenance studies and reveal peculiar characteristics of societies. Therefore, they are key-factors in studying coloured inscriptions, their rock-based writing supports, as well as the origin and conservational history of a coloured object.

People

Project lead: Stylianos Aspiotis