Abstract
The writing in carbonized Herculaneum scrolls, covered and preserved by the pyroclastic events of the Vesuvius in 79 AD, was recently revealed using X-ray phase-contrast tomography, without the need of unrolling the sensitive scrolls. Unfortunately, some of the text is difficult to read due to the interference of the papyrus fibers crossing the written text vertically and horizontally. Recently, lead was found as an elemental constituent in the writing, rendering the text more clearly readable when monitoring the lead X-ray fluorescence signal. Here, several hypotheses are postulated for the origin and state of lead in the papyrus writing. Multi-scale X-ray fluorescence micro-imaging, Monte Carlo quantification and X-ray absorption microspectroscopy experiments are used to provide additional information on the ink composition, in an attempt to determine the origin of the lead in the Herculaneum scrolls and validate the postulated hypotheses.
Highlights
The writing in carbonized Herculaneum scrolls, covered and preserved by the pyroclastic events of the Vesuvius in 79 AD, was recently revealed using X-ray phase-contrast tomography, without the need of unrolling the sensitive scrolls
Galena has been proposed as a pigment in black inks in Egyptian papyrus before[12], whereas minium (Pb22+Pb4+O4) has been reported as a red pigment in Roman writing13,14. -- Pb could originate from a binding medium in the ink: Pb compounds have been used extensively as dryers in paintings as they speed up the process of oil drying[15,16]
In order to have a good statistic record of X-ray fluorescence (XRF) data in and out of the ink, XRF 2D maps were acquired over the full surface of the samples, with a sub-millimetre beam
Summary
To be able to (dis)prove these hypotheses, two fragments (referred to as the “large” and “small” fragments) from unrolled scrolls were investigated. As detailed in Brun et al [submitted], the XRF map of Pb perfectly matches with the ink distribution (Fig. 1B) as the writing, faintly visible in Fig. 1A as well, is revealed From this map, two average XRF spectra were extracted, by summing the pixel spectra corresponding to i) the writing using K-means clustering[23] and visually comparing the clusters to the XRF distribution images, ii) the papyrus alone, excluding the written areas. In order to quantitatively determine the ink composition, XRF results were simulated by means of Monte Carlo calculations[24,25,26]. These simulations model all relevant photon-matter interactions, simulating the trajectories of a large number of photons originating from an X-ray source and undergoing interactions in the sample, to the point of possible detection in a detector. The main differences are attributed to the lack of simulation for X-rays below 1 keV25 and a slight underestimation of the generated pulse pile-up
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
