Researchers aiming to read carbonized papyrus scrolls from the ancient Roman city of Herculaneum without destroying them have found that adding lead to ancient ink creates a massive X-ray signature, according to a study published Sept. 16 in the journal PLOS ONE. Douglas Seiler, an affiliate of Berkeley SETI, led the research team by burning custom-made replica scrolls in a high-temperature furnace to mimic the catastrophic eruption of Mount Vesuvius in 79 C.E.
Replicating Vesuvius in a Home Laboratory to Test X-Ray CT Imaging
Seiler went to extraordinary lengths to recreate the ancient catastrophe that preserved the Villa of the Papyri library, obtaining papyrus and reed pens from Egypt and traditional lampblack ink from Japan. He paid high school students to write passages from “Star Wars,” the Bible, and a quote from the 1960s science fiction television show “The Outer Limits” onto the papyrus sheets. Seiler then rolled up the inscribed papyrus, sealed it inside a container, and burned it in a high-temperature home furnace until it transformed into thoroughly carbonized husks.
The experiment targeted a major hurdle in modern archaeology: how to read more than 1,800 surviving Herculaneum scrolls and fragments held in Italy, France, and England without physically unrolling them. Unwinding the brittle, carbonized rolls manually often reduces them to black dust, as happened during disastrous early attempts following their 1752 discovery. Seiler reasoned that if ancient scribes used lead-bearing ink, that heavy metal would absorb X-rays far more strongly than the surrounding carbonized papyrus, allowing computer algorithms to virtually flatten the tightly rolled layers.
Lead in Ink Creates a Massive X-Ray Signature on Scans
Working with retired Berkeley chemists David Kreimer and Elena Kreimer, Seiler mixed measured quantities of lead nitrate into lampblack ink to create varying lead concentrations. After burning these modern models, the team partnered with Jake LaManna, a physicist at the National Institute of Standards and Technology (NIST) Center for Neutron Research, to produce three-dimensional CT scans using laboratory X-ray sources.
The results showed that lead absorbed up to 25 times more X-rays than the burned papyrus surrounding it. The X-ray CT scans and handheld X-ray fluorescence scanners easily detected leaded ink at concentrations as low as 25 micrograms per square centimeter. “If you look at the images, the letters lit up like a Christmas tree,” Seiler said. He noted that researchers struggling with the low contrast of carbon ink on carbon papyrus should now prioritize searching for scrolls with lead-containing ink, calling the strategy “the Holy Grail.”
Pro Tip: Archaeologists can screen ancient scrolls using an inexpensive handheld X-ray fluorescence scanner before committing them to high-resolution X-ray CT imaging, safely prioritizing the most promising candidates.
Adapting Battery Algorithms and AI to Decipher Ancient Greek Texts
To virtually unroll the scanned model scrolls, NIST postdoctoral fellow Michael Cyrus Daugherty adapted software originally developed to map the internal “jelly rolls” of lithium-ion batteries. By tweaking his code to follow the uneven and changing thickness along the length of a papyrus scroll, Daugherty quickly generated digital flat versions of the text.
In 2024, artificial intelligence helped researchers recover 15 complete columns of an Epicurean philosophical work by Philodemus about perception and pleasure. In 2026, Seales’ team decoded portions of a damaged scroll known as PHerc. 1667, which discusses Stoic philosophy and may date back to the second or third century B.C.E. Leah Packard-Grams, a Berkeley archaeology graduate student and papyrologist who consulted on Seiler’s project, emphasized the immense stakes for the field, stating, “The value in this project is practically unquantifiable. The stakes are the largest in the history of Greek literature.”
Did You Know? The Herculaneum library is the only known intact library to survive from antiquity, housing books directly from Roman intellectual circles rather than later medieval copies.
Frequently Asked Questions
What caused the preservation of the Herculaneum scrolls?
When Mount Vesuvius erupted in 79 C.E., volcanic ash overwhelmed the ancient Roman city of Herculaneum and carbonized more than a thousand papyrus scrolls into fragile, charred remains rather than destroying them completely.
How does lead in the ink help researchers read burned scrolls?
Lead absorbs up to 25 times more X-rays than the surrounding charred papyrus. This stark contrast makes the written characters stand out brightly during X-ray CT scanning, allowing computer algorithms to map the letters without physically opening the brittle scrolls.
Have scientists found lead in actual Herculaneum scrolls yet?
While researchers have not yet carried out a systematic search across the entire collection, at least one previous researcher detected lead in the ink of a fragment left over from early physical unrolling attempts.
Who authored the new study on replica scrolls?
Douglas Seiler is a researcher on the study, published Sept. 16 in PLOS ONE.
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