We have established scientific basis for a new, non-destructive methodology for dating ancient Egyptian papyri based on Raman spectroscopy. Egypt’s dry climate has preserved thousands of handwritten documents which provide insight into ancient cultures, but most of these manuscripts are not dated. Currently, the only scientific method for estimating the date is radiocarbon dating, which is destructive and cannot be used to date the ink separate from the support. In contrast, micro-Raman spectroscopy, a non-destructive light scattering technique, can distinguish physical and chemical properties of materials. We discovered, for a study of well-dated ancient Egyptian papyri covering the date range from 300BCE to 900CE, the Raman spectra (25-40 measurements per manuscript) of black ink all show the spectrum of carbon black characterized by two broad features, the G- and D-bands indicative of crystalline and amorphous carbon. The G-band, 1585cm-1, is a Raman allowed transition arising from the E2g in-plane vibration of sp2-bonded carbon. The D-band at ~1350cm-1 is a forbidden Raman transition that occurs when the lattice symmetry is broken due to disorder, vacancies, crystalline edges, etc. We observed the spectra exhibit systematic change as a function of manuscript date, unexpected given these papyri span 1,200 years and the fact that each manuscript has a unique provenance, archeological, and storage history. We conclude Egyptian black ink pigments were manufactured using similar processes over this time-period. We attribute the systematic changes in Raman spectrum to two concurrent oxidation processes: slow oxidation of crystalline carbon and faster oxidation of amorphous carbon. Oxidative degradation proceeds over time altering the Raman response of the material, providing a direct experimental indicator for manuscript age. This research establishes the basis for a simple, rapid, non-destructive method for dating ancient manuscripts from Egypt as well as the ability to differentiate between modern forgeries and authentic ancient manuscripts.

Characterizing the age of ancient Egyptian manuscripts through micro-Raman spectroscopy

251st National Meeting (2016)

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