Metallic ink revealed in Herculaneum papyri

" Civilization -- or at the very least, human history -- depends on the use of papyrus " remarked the Roman antiquarian Pliny the Elder in his Natural History. A rigorous scientific study of writing is of fundamental importance for the historical understanding of ancient societies. The Herculaneum papyri, discovered between 1752 and 1754 and carbonised during the eruption of Mount Vesuvius in 79 AD, is of main importance. It constitutes the only complete library ever discovered dating from Antiquity and containing unique examples of philosophical texts unkown to scholars.

Until now it was assumed that the ink used for Greek and Roman manuscripts was carbon-based and that metal was only introduced to ink from the 4th Century AD. In his Natural History, Pliny the Elder describes the carbon-based ink used in Antiquity, which was obtained from smoke from wood burnt in furnaces without any deliberate addition of metal. The only known use of metallic ink before this period was for the writing of secret messages in the 2nd Century BC. From around 420 AD, a metallic iron-gall mixture was elaborated and adopted as a new writing ink for parchments. Thereafter metallic inks became the standard for parchments in late Antiquity and for most of the Middle Ages.

The international team of scientists from the ESRF, INSERM, Grenoble Alpes University, CNRS (France), the University of Ghent (Belgium), CNR (Italy), discovered metallic ink in the two fragments of papyrus from the Herculaneum library. By combining several synchrotron X-ray techniques (multi-scale X-ray fluorescence micro-imaging on ID21 beamline, X-ray diffraction on ID11, and X-ray absorption near edge structure on BM26), the scientists determined that the ink contained fairly high concentration of lead. Their studies also proved that the high concentration of metal could not be attributed to lead contamination of water or from a copper inkpot or a bronze container.

A change of paradigm for the history of writing

The findings of this research modify our knowledge of the history of writing and push back by several centuries the introduction of metal into ink. The research also opens promising paths of exploration to reveal the contents of the undisclosed Herculaneum scrolls and for other archaeological discoveries, through an optimizing choice of imaging technique to be used and the wavelengths to be selected.