Scientists have found a promising way to recover lost texts buried inside the Herculaneum scrolls, ancient manuscripts that turned to charcoal when Mount Vesuvius erupted nearly 2,000 years ago.
A study published in the journal PLOS One found that scrolls containing a number of Greek philosophical texts, written with lead-based ink, are far easier to scan and read than those written with plain carbon ink. That difference could help researchers decide which rolled-up scrolls are worth the costly effort of scanning.
The Herculaneum scrolls were discovered in 1752 at the Villa of the Papyri near Naples, Italy, buried under volcanic ash since the eruption in A.D. 79. They make up the only known complete library to survive from the ancient world, holding mostly philosophical writings by ancient Greek philosophers, Philodemus of Gadara and Epicurus. Hundreds of the scrolls remain rolled up because they are too brittle to open by hand without falling apart.
Why ancient ink nearly vanishes under X-ray scans
In recent years, a research effort called the Vesuvius Challenge, led by Brent Seales and Seth Parker, has used detailed X-ray scans and artificial intelligence to digitally unroll and read some of these scrolls without ever touching them.
That work is difficult because the carbon-based ink used by ancient scribes looks almost identical to the burnt papyrus itself under an X-ray, leaving the writing nearly invisible.
Earlier research had shown that some Herculaneum fragments contain lead in their ink. Lead blocks X-rays far more strongly than carbon, making any lettering with it much easier to spot. To test how useful that difference could be, a team led by Douglas Seiler built its own practice scroll from modern Egyptian papyrus.
The ink was mixed with lead nitrate to match lead levels found in real ancient fragments, and the scroll was then baked in a low-oxygen furnace to recreate the extreme heat of the volcanic eruption.
Lead-spiked ink recreates Herculaneum scrolls to trace lost texts
Researchers then scanned the burnt model at the National Institute of Standards and Technology and digitally unrolled it with custom software.
Without any extra computer enhancement, they could clearly make out the words “the children of” on the unrolled surface. Lead remained detectable even at concentrations as low as 25 micrograms per square centimeter, the smallest amount tested.
The team also found that a handheld scanner, a cheaper and far more portable tool than the large research facilities normally used for this kind of imaging, could detect lead through the outer surface of the burnt scroll without opening it.
That result points to a practical way of checking real Herculaneum scrolls for lead before committing them to expensive imaging, helping direct attention toward the lost texts most likely to be recovered.
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