Embalming as a Source of Contamination for Radiocarbon dating of Egyptian Mummies: On a New Chemical Protocol to Extract Bitumen

Abstract

Radiocarbon dating of Egyptian mummies could be challenged by embalming materials, especially bitumen which is attested in textual sources as being used during the Late Period. Six Egyptian mummies held at the Musée des Confluences in Lyon (France) have been radiocarbon dated, among which two embalmed mummies have given results older than expected, both on textile and organic material (flesh/skin). Radiocarbon dates’ ageing relates to the use of a radiocarbon depleted material that is not extracted by classical radiocarbon chemical pre-treatment. In this study, the presence of bitumen is corroborated by infrared spectroscopy analyses. The present paper describes the research we employed to extract bitumen from mummies’ linen wrappings. An experimental protocol has been developed and tested on modern linen textiles; it divides into four steps: textile soaking in bitumen – linen samples thermal degradation – extraction protocol – infrared analyses and radiocarbon dating at each step. Test-samples show that bitumen has been correctly extracted only on samples that have not been artificially aged, others remain radiocarbon depleted. Presently, the protocol is not efficient enough to be applied on archaeological samples. The difficulty does not rely on the bitumen present, but on the interactions developed between bitumen and linen fibres over time. Further perspectives and on-going research’s steps will also be described that enabled this study to restore these mummies to their chronological context.