X-rays Reveal Text on Scorched Herculaneum Scrolls

Close up photograph of Herculaneum Papyrus scroll Herc.Paris.4, an (almost) entire rolled-up scroll / E. Brun
Janet Fang 20 Jan 2015, 23:16

When Mount Vesuvius erupted in 79 AD, it buried several seaside Roman cities including Pompeii and Herculaneum, preserving them under thick volcanic material for many centuries. In the 1750s, hundreds of ancient, handwritten papyrus scrolls were discovered on shelves in the library of Villa dei Papiri in Herculaneum—the only library to have survived from the classical world. But the hot volcanic gas had carbonized the documents, making them too fragile and brittle to unravel. Attempts to read the scrolls have only led to further damage, until now. Using a non-invasive imaging technique, researchers have managed to decipher some of the text in two scorched scrolls. The findings were published in Nature Communications this week.

In antiquity, the most common writing materials were sheets of papyrus and black, carbon-based ink. But after the 320-degree-Celsius blast of gas, it became almost impossible to distinguish the blackened papyrus scroll from the black charcoal ink used to write on it. And because they both absorb X-rays weakly, efforts to read the rolled-up scrolls using X-ray computed tomography (XCT), a common tool used in medicine, were limited. 

Now, an international team of researchers led by Vito Mocella from the Italian National Research Council has successfully used a technique called “X-ray phase contrast tomography” (XPCT) to differentiate the ink from the burnt papyrus, despite their similar chemical compositions. XPCT exploits the differences in the phase—a measure of how fast light or other types of radiation spreads through the substances—of the papyrus and the ink that sits on it. This enhances the contrast between the two, making it possible to discriminate modifications hidden inside the scrolls. 

Using high-energy X-ray beams at the European Synchrotron in Grenoble, France, the team examined two of the six Herculaneum scrolls that were presented as gifts to Premier Consul Napoleon Bonaparte in 1802: One is a fragment of an unrolled scroll, and the other is an entire rolled-up scroll (pictured in the two images above). 

The researches were able to reconstruct the complete 24-letter Greek alphabet from the rolled-up scroll. And so far, they’ve been able to decipher two words from the unrolled scroll fragment: PIPTOIE (pi-iota-pi-tau- omicron-iota-epsilon) on top and EIPOI (epsilon-iota-pi-omicron-iota) just below it. These previously unreadable sequences were interpreted as the Greek words meaning "would fall" and "would say," respectively. They're pictured below to the right.

“At least we know there are techniques able to read inside the papyri, finally,” Mocella tells New York Times. Their attempt opens up new opportunities to read many of the still-rolled-up Herculaneum scrolls from the villa belonging to Roman statesman Calpurnius Piso Caesoninus (Julius Caesar's father-in-law), as well as other works thought to have been lost for the last couple millennia. "Next spring we have an allowance to spend more time at the Grenoble synchrotron, where we can test a number of approaches and try to discern the exact chemical composition of the ink,” Mocella tells Smithsonian. “That will help us improve the energy setting of the beam for our scan."

The handwriting style, they found, is similar to that on another (unrolled) Herculaneum papyrus document written by the Epicurean philosopher Philodemus—suggesting the scroll they examined was written by the same author, during the second quarter of the first century BC. 

Images: E. Brun (top), D. Delattre © Bibliothèque de l'Institut de France (middle), Mocella et al. Nature Communications (bottom)

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