Absorption edge sensitive radiography and tomography of Egyptian Papyri

Abstract

In the Egyptian Museum and Papyrus Collection, Berlin, a multitude of papyrus manuscripts are stored. Papyri found on Elephantine island are of special interest. No other settlement in Egypt has been so well documented through texts over four millennia. However, 80% of the Elephantine texts are yet to be documented and published. As part of the “Elephantine” project, funded by an ERC starting grant, we attempt to gain access to hidden text. Most of the fragments are very fragile, deformed, with some rolled or folded. Papyri from the Old and Middle Kingdom were typically written with carbon ink. Consequently, these fragments show no absorption sensitivity for hard X-rays. Also, other inks have been used in those times. If small traces of high-Z elements, like Fe or Pb, are found, absorption may be sensitive enough for radiography and tomography to distinguish between writing and base material. We sorted out suitable fragments and papyrus packages by X-ray fluorescence mapping. When promising high-Z elements were detected, absorption tomography was applied using micro-CT laboratory systems or synchrotron X-rays at the BAMline at BESSY II. The sensitivity can be enhanced by element-sensitive absorption edge imaging, where transmission data taken above and below the edge are compared. This technique was applied at the absorption edges of the elements known to be used as ink and pigment material – Iron, Antimony and Lead. These X-ray results were complemented by Fourier-transform infrared spectroscopy (FT-IR) measurements showing that the lead is found in the form of lead carboxylate. In the future, the presented methodology will be applied to folded or rolled papyri, allowing for analysis of the text without manually opening the fragments.

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