Scientists burned their own papyrus to crack the code hidden in Vesuvius scrolls

Douglas Seiler rolled up a sheet of fresh papyrus, sealed it inside a steel container with almost no oxygen, and burned it in a furnace until it carbonized into something close to what Mount Vesuvius made of the Herculaneum library in 79 C.E. The point was not destruction for its own sake: the Berkeley SETI-affiliated researcher and a team spanning the National Institute of Standards and Technology and universities in three countries needed a scroll they were allowed to fail with, so they could test whether lead hidden in ancient ink might finally make its buried text visible.

Their results, published September 16 in the journal PLOS ONE, found that lead mixed into ink absorbs up to 25 times more X-rays than the carbonized papyrus around it, and that the difference shows up even at concentrations as low as 25 micrograms per square centimeter. About 1,800 Herculaneum scrolls and fragments survive today in collections across Italy, France, and England, most of them still too fragile to unroll physically and, until now, with no fast way to guess which ones might actually be readable inside.

A model scroll built specifically to be burned

The team could not experiment on an authentic Herculaneum scroll to test a new idea, so they built a stand-in. Using papyrus and reed pens sourced from Egypt and traditional Japanese lampblack ink, high school volunteers copied out passages from Star Wars, biblical texts, and television scripts onto fresh sheets. Seiler then carbonized the sheets the way the Roman volcano effectively had, in a low-oxygen furnace hot enough to blacken the papyrus without simply incinerating it, a process described in the team’s published paper.

The replica gave researchers something no real Herculaneum scroll could offer: a known text, written in a known ink, carbonized under conditions they controlled and could repeat. “The letters lit up like a Christmas tree,” Seiler said of the scans once lead was added to the mix, in an account of the project that also detailed how the model scrolls were made.

Lead nitrate turned an invisible letter into a bright one

Most carbon-based inks used in antiquity are made from soot, which is itself mostly carbon — nearly the same material as the carbonized papyrus it sits on, and close to invisible to standard imaging as a result. To test whether a different ink chemistry could break that stalemate, the team mixed measured amounts of lead nitrate into their lampblack ink at varying concentrations before writing.

The contrast the lead produced was not subtle. Because lead absorbs X-rays far more strongly than carbon, letters written with leaded ink appeared as bright marks against a dark background in both X-ray CT scans and X-ray fluorescence readings, the two imaging methods the team tested side by side. Detection held even at the lowest concentration tried, 25 micrograms per square centimeter, which the researchers described as the floor of what their equipment could measure rather than a hard physical limit.

A battery-scanning algorithm adapted from an unrelated NIST project

The imaging insight traces back to a project that had nothing to do with archaeology. NIST physicist Jake LaManna had supervised postdoctoral researcher Michael Cyrus Daugherty on software that virtually unrolls the tightly wound internal layers of lithium-ion batteries from X-ray CT scans, looking for manufacturing defects. LaManna recognized that a carbonized scroll, wound just as tightly, presented the same geometric problem in miniature.

Daugherty adapted the battery-unrolling code and tested it against the team’s furnace-made replicas before anyone tried it on genuine Herculaneum material. According to NIST’s own account of the collaboration, once Daugherty had working output, “he came back with examples of the scroll unrolled” within days of the first attempt — a turnaround that came from repurposing an existing tool rather than building new hardware for the problem.

Screening 1,800 scrolls before the next Vesuvius Challenge deadline

The practical payoff is triage. Instead of committing scarce synchrotron time to scanning every surviving Herculaneum scroll at high resolution, researchers can now run a handheld X-ray fluorescence scanner over each one first, flagging which contain lead and therefore have the best odds of yielding legible text once fully imaged. The lower-priority scrolls, written in ordinary carbon ink with little contrast to exploit, can wait.

That triage matters because the scrolls’ fate is tied to an active competition. The Vesuvius Challenge’s original $700,000 grand prize, which rewarded the first full digital reading of a Herculaneum scroll, was already claimed in 2023. A new $1 million grand prize covering 13 additional scrolls is open now, with a June 25, 2027 deadline for anyone who can render one of them fully readable — and a lead-detection scan, done in an afternoon with a handheld device, is now a plausible first step toward picking which of the 1,800 remaining scrolls is worth that effort.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.