Polychromy on the Antonine Wall Distance Sculptures: Non-destructive Identification of Pigments on Roman Reliefs

Abstract

ABSTRACTNon-destructive analytical techniques are now widely and successfully employed in the fields of materials science and conservation. Portable X-ray fluorescence (pXRF) and portable Raman spectrometry have proven particularly valuable for the rapidin-situanalysis of samples, but their applicability for the analysis of archaeological artefacts for which survival of surface treatments can be negatively impacted by post-depositional processes has been underexplored. Roman relief-sculpted monumental inscriptions from the Antonine Wall, commonly referred to as ‘Distance Slabs’, have offered an excellent opportunity to deploy these non-destructive techniques to determine whether they were originally adorned with pigments and, if so, to identify the colours used. This is a revolutionary approach to identifying colours on ancient sandstone sculpture that transforms our understanding of these unique monuments. Elemental composition analysis by pXRF has confirmed evidence for pigments and this is supported by the Raman results, making it possible to develop and reconstruct a palette of colours that originally brought these monuments to life in vibrant polychrome. The research offers a new methodology for identifying pigments on sandstone sculpture and opens new avenues for investigating other classes of material culture alongside the development of bespoke analytical equipment.