Revealing metallic ink in Herculaneum papyri

Abstract

Writing on paper is essential to civilization, as Pliny the Elder remarks in his Natural History, when he describes the various types of papyri, the method of manufacturing them, and all that concerns writing materials in the mid-first century AD. For this reason, a rigorous scientific study of writing is of fundamental importance for the historical understanding of ancient societies. We show that metallic ink was used several centuries earlier than previously thought. In particular, we found strong evidence that lead was intentionally used in the ink of Herculaneum papyri and discuss the possible existence of ruled lines traced on the papyrus texture. In addition, the metallic concentrations found in these fragments deliver important information in view of optimizing future computed tomography (CT) experiments on still-unrolled Herculaneum scrolls to improve the readability of texts in the only surviving ancient Greco-Roman library.

Keywords: Herculaneum papyri; metallic ink; paleography; papyrology; ruled lines.

Fig. 1.

Comparison of visible light photographs (A and D), infrared microscopy images (B and E), and lead distribution maps obtained by XRF (C and F) for both of the examined Herculaneum papyrus fragments. XRF maps were normalized by the incident flux and are in arbitrary units.

Fig. 2.

Micro-XRF images of elemental distributions at low resolution (Left, 50-µm beam and mesh scan step size) and high resolution in the red frame (10-µm beam and mesh scan step size) and at very high resolution in the green frame (1-µm beam and mesh scan step size). Maps were normalized to the incident flux and are in arbitrary units.

Fig. 3.

XRF and XRD maps obtained for the larger fragment. (A) Si XRF maps for the recto of the sample and (D) for its verso, (B and E) Pb XRF maps, (C) XRD cristobalite map superposed on the Pb XRF map, and (F) XRD cristobalite map on the portion of the sample defined by the red region of interest in C. The maps are normalized to the incident flux and are in arbitrary units.

Fig. 4.

Close-up in the microscopic IR image of the smaller fragment (A and B) and of the larger one (C and D). The close-up areas are labeled by red rectangles, and the ruled lines are indicated by yellow arrows.

Fig. 5.

XRF maps of the three papyrus fragments: Si maps (A–C) and P maps (D–F). The larger fragment is shown in A and D, the papyrus sheet carbonized at 200 °C in vacuum is shown in B and E, and a fresh (modern) papyrus sheet is shown in C and F.