Researchers burned their own scrolls to prove Herculaneum’s ink can still be seen

Lead absorbs as much as 25 times more X-rays than the burned papyrus around it, and that single ratio is what a team at the University of California, Berkeley set out to prove by burning scrolls of their own. Led by Douglas Seiler, an affiliate of Berkeley SETI, the researchers wrote on fresh papyrus with ink spiked with measured amounts of lead, charred the rolls, and then asked whether a scanner could still find the writing.

It could, down to 25 micrograms of lead per square centimetre.

Replica papyrus, lampblack and a low-oxygen furnace

The replica scrolls were built to mimic what Mount Vesuvius did in 79 CE. According to the Berkeley News release, Seiler used authentic Egyptian papyrus and Japanese lampblack ink, mixed with lead at known concentrations, and had high school students write passages from Star Wars, the Bible and The Outer Limits on the sheets. He then carbonized the scrolls in a low-oxygen chamber, the condition that preserved the Herculaneum rolls as charcoal instead of letting them burn to ash.

The reason to burn scrolls of their own is control. With an original Herculaneum scroll nobody knows exactly what is in the ink or how much, so any scan result is ambiguous. A replica written with a recipe of known lead content, charred under conditions meant to match the ancient ones, gives the team a ground truth: they know where the writing is, what it says and how much lead lies under each letter, and can check each scanner against it. Students writing passages familiar to the researchers made the test legible, since an unrolled replica either spells the text back or does not.

The team also included physicist Jake LaManna of the National Institute of Standards and Technology, who produced the CT scans, postdoctoral fellow Michael Cyrus Daugherty and papyrologist Leah Packard-Grams. The results appear in PLOS ONE, published on 16 September 2026.

CT, fluorescence and the 25-microgram floor

Because the lead was added in known amounts, the experiment could measure how little ink a scanner can see. ScienceDaily’s repost of the university release says the scans detected ink containing as little as 25 micrograms of lead per square centimetre using both X-ray CT and X-ray fluorescence, and quotes the paper: lead absorbed as much as 25 times more X-rays than the burned papyrus around it, causing the writing to stand out dramatically.

LaManna’s CT scans made the letters show, Seiler said, like a Christmas tree lit up, and a handheld X-ray fluorescence scanner could identify lead ink directly. Seiler’s own summary of the point was blunter: with lead in the ink, a scanner would get a huge signature, which makes identification much simpler. A computer algorithm then virtually unrolled the digitised replicas, revealing legible text without any physical opening.

The two techniques answer different questions. CT builds a three-dimensional picture in which the letters can be traced through the layers of a rolled scroll, while fluorescence reports which elements sit at a given spot, so a lead signature can be confirmed even before the writing is reconstructed. Together they make a detection that does not rest on one instrument.

Fluorescence matters because it is portable. The CT work in this study needed LaManna’s laboratory scanner; a handheld unit can screen a scroll’s surface quickly and show whether lead is present before anyone commits to heavier scanning.

Which scrolls this helps

The Villa of the Papyri at Herculaneum yielded what the release calls the only known intact library to survive from antiquity, about 1,800 scrolls and fragments by ScienceDaily’s count. Most were written in carbon-based ink, which is nearly invisible to X-rays because it is chemically close to the charred papyrus beneath it, and that similarity is why reading them has been so hard.

Some scrolls are different. As the Wikipedia article on the papyri notes, some were written with ink containing lead, and in 2016 synchrotron radiation detected metallic ink traces on certain scrolls. The Berkeley experiment does not show that every scroll carries lead ink. What it adds is a measured threshold for how much lead a scanner needs to see, so a scroll showing a lead signature can be flagged and the rest set aside for other methods. It is a screening result for the library.

The result lands in a field that has moved quickly. The Vesuvius Challenge, which uses X-ray tomography and machine learning to read scrolls without opening them, says PHerc. 1667 in 2026 became the first Herculaneum scroll virtually unwrapped and read end to end, and lists 45 scrolls and fragments scanned so far, with one fully read. Seiler’s team supplies the physics that tells those readers where a scroll is likely to give up its text.

What remains to be measured is how much lead the ancient inks actually hold; the replicas fix the detection limit at 25 micrograms per square centimetre, and the real scrolls still have to be compared against that number.

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

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