The nature of organic residue captured by the gypsum casings at the time of burial will provide valuable insight into the social and ritual practices of Roman Yorkshire.
There is archaeological evidence of the use of resins throughout history, before and after the Roman period. The Romans may have used resins for practical reasons, such as temporary preservation and to mask odours, as well as for ritual reasons including anointing shrouds to symbolise status, and to purify the body for the journey to the afterlife. Roman literature also describes the washing of the dead and the use of perfumes and oils in funerary practice which can serve as a powerful symbol of wealth and prestige. The choice of dyes in the fabrics used to dress the deceased, for example murex (Tyrian purple), further reflected an individual’s social status.
Chemical analysis is being used to determine the presence and nature of any remaining organic residues. Such chemical traces are complex, and so a holistic range of analytical techniques are employed. Field deployable Fibre Optic Reflectance Spectroscopy (FORS) is used first to examine the gypsum casings in situ at the Museums and museum stores. This non-destructive technique looks for organic signatures on the inorganic gypsum surface and for evidence of any dyes or stains on the fabric fragments or the gypsum casings. FORS is being used to identify strategic regions of the gypsum casings from which samples will be taken for further chemical analysis, thus providing an evidenced based approach for a minimally invasive exercise. Samples collected will be analysed in the Centre of Excellence in Mass Spectrometry by Gas and Liquid Chromatography (GC and LC) separation coupled to Mass Spectrometry (MS) detection.
Molecular signatures of any organic residues extracted from the gypsum will provide chemical fingerprints from which any resins, unguents or botanicals can be identified. Research by Brettell et al. 2015 provided the first evidence of resins used in gypsum burials in York, detecting resinous substances on three out of fifteen casings examined. In our wider study of 22 surviving casings, signatures for exotic resins, such as frankincense, or the non-exotic resins obtains from botanicals, such as pine, will reflect the presence and availability of these substances in Roman Yorkshire. Molecular signatures for dyes extracted from the gypsum or from fabric remains will allow the dye-substances to be identified.