How do you test a theory on how to decipher a priceless archaeological artifact? According to a team of researchers, you pay children to make fake versions of it.
A team of scientists has proposed a new approach to reading the famous Herculaneum scrolls: 2,000-year-old texts that are impossible to unroll because Mount Vesuvius burnt them to a crisp in 79 BCE. They suggest looking for lead in the ink. In a study published yesterday in the journal PLOS ONE, the team writes that even small amounts of lead in the ink make letters highly detectable to X-ray CT (an imaging technique).
“If we know that the Herculaneum papyri have lead in them—some of them do, some of them don’t—then when they take the CT scan, they can scan it with a sensitivity for the element lead and we can see where the ink is,” Leah Packard-Grams, a papyrologist at the University of California, Berkeley, who consulted for the research, explained in a statement. “As you unroll it, you can map the letters a lot more clearly.”
An ancient intact library
When Mount Vesuvius erupted, it both triggered the most infamous ancient tragedy and, in Herculaneum, preserved today’s only known intact library from antiquity. The caveat is that all of the library’s ancient scrolls are completely carbonized. After they were discovered in 1751, “experts” tried to physically unroll them but mostly ended up with piles of ashes. Only this past summer did researchers manage to virtually unroll and read an entire Herculaneaum scroll, but they didn’t leverage the potential presence of lead.
“With lead in the ink, you would get a huge friggin’ signature, so you really need to be looking for scrolls with lead in them,” said Douglas Seiler, co-author of the study and a retired inventor. “They’re having problems reading a lot of them because of the low contrast of carbon ink on carbon paper,” he added, presumably referring to other scientists working on the scrolls. “We’re relatively certain that if they start searching for lead, or they let us search for lead, it will help this whole process. This is the Holy Grail.”
To test out this theory, Seiler made his own crunchy Herculaneum scroll with papyrus and reed pens from Egypt and traditional lampblack ink from Japan. He paid high school students to write on the papyrus with inks of various lead concentrations, rolled it up, stuck it in a low-oxygen semi-sealed steel container, and put the container in a high-temperature furnace.
The team then conducted a 3D X-ray CT scan of this barbecued Herculaneum scroll imitation. Lead absorbs more X-rays than the surrounding papyrus, so the ink appeared bright in the resulting 3D computer model. A 3D model of a burned scroll is still illegible, however, and so the team used a computer algorithm to virtually unroll the scroll and display the text, including excerpts from the Bible as well as Star Wars.
Unquantifiable value
The team that produced the first reading of a complete Herculaneum scroll a few months ago followed a similar process, but as mentioned previously, they weren’t looking for leaded ink. Researchers have previously discovered leaded ink in two Herculaneum scroll fragments, but no one has ever thoroughly searched the Herculaneum scrolls for it.
On this front, Seiler and his colleagues demonstrated that a cheap handheld X-ray fluorescence scanner (a technique to identify elements in materials) can pinpoint leaded ink in a charred scroll. They found that even ink with a low lead concentration was easily spotted by both X-ray CT and X-ray fluorescence.
“The value in this project is practically unquantifiable,” said Packard-Grams. “Doug had a really great idea scientifically with creating a model,” she added. “If you hurt a model, it’s fine. If you hurt a 2,300-year-old ancient artifact, you’ll have a bunch of archeologists ready to jump you.”
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