Multi-technique analysis of pigments on sandstone sculptures: Renaissance re-painting of a Roman relief

Abstract

The Antonine Wall was commissioned by the Roman Emperor Antoninus Pius around 142 CE and stretches for c. 60 km across the central belt of Scotland, marking the Empire’s most north-western frontier. This vanguard research reports on the materials referred to by Antiquarian sources as having been applied during the sixteenth century for the redecoration of an iconic Distance Sculpture that was once embedded into the mural barrier. Portable non-invasive technologies, including pXRF and in-situ microphotography were deployed. These techniques were further supplemented by micro-sampling for SEM/EDS, FTIR–ATR and microscopy of embedded cross-sections. The validity of applying these complementary techniques has been confirmed. They provide a comprehensive account of the polychromy present, including pigments that could have been applied during the Roman period and others that were only available from the fifteenth or sixteenth Centuries. The work has confirmed stratigraphic sequencing of the pigments which will, in due course, permit the digital reconstruction of how this Classical relief sculpture would have been adorned during the Renaissance.

Tracking Trajectories: Projecting Polychromy onto a Roman Relief from a Scottish Castle

“…To identify the pigments present as well as their sequence of application and chronology, the sculpture was subjected to intensive multi-technique analysis. This has been fully reported elsewhere [10], and a forthcoming programme of SEM/EDS on samples from all features will supplement that work. It is, however, useful to provide a brief summary of the methods used and the results to place the polychromy into context and to establish the palette used to depict the features present, all of which informed its digital reconstruction here.…”

“…Given its status as a chronological marker, this pigment demands more detailed consideration here (Figure 8). Taken together, the analytical results confirmed this blue to be smalt [10,57,58]. Commonly used from the late 15th-early 18th centuries, smalt is a vibrant blue derived from a potash silicate glass coloured with cobalt and often substituted for more expensive pigments [59] (p. 952), [60].…”

“…Thereafter, it was installed into its current position as an integral component of the museum's showcase exhibit "The Antonine Wall: Rome's Final Frontier". The sculpture retains visible traces of polychromy that permit a detailed exploration of one episode in its trajectory using cutting-edge, non-invasive technologies for in situ scientific analysis supplemented with micro-analytical techniques [10].…”

The Vindolanda Vessel: pXRF and Microphotography of an Enamel-Painted Roman Gladiator Glass

“…As a result, the application of in situ non-invasive analytical techniques in the field of heritage materials science has grown exponentially in recent years. PXRF and other analytical technologies [60], including Raman spectroscopy [50], Multi Spectral Imaging (MSI) [61,62] and Spectral Imaging [63], now make it possible to characterise materials used in the creation of some of the most exquisite artefacts from Antiquity, including Roman glass.…”

“…In-situ digital microphotography was, therefore, captured using a Dino-Lite Edge Digital Microscope (AM4515ZT) which provided powerful high-resolution images for detailed surface inspection (Figure 9). Dino-Lite instruments have been used to great effect for portable microscopy and image capture for a diverse range of archaeological artefacts including textiles [75], pigments on Classical statuary [60], metallurgy [76], ceramics [77], lithics [78], bone tools [79] and even close-range photogrammetry [80].…”