Berkeley researchers burned new scrolls to learn how to read ancient ones

A team working out of UC Berkeley reported on Wednesday, Sept. 16, that traces of lead in ancient ink make the writing on burned papyrus scrolls readable by X-ray, with no need to unroll them. The paper ran in the journal PLOS ONE.

The scrolls at stake are not in Berkeley. About 1,800 of them and their fragments survive from the Villa of the Papyri at Herculaneum, the Italian town that Mount Vesuvius buried in 79 C.E. The ash cooked that library into carbon. It is the only intact library known from the ancient world, and most of it has never been read.

Douglas Seiler, an affiliate of Berkeley SETI, rebuilt the problem from scratch. He sourced papyrus and reed pens from Egypt and lampblack ink from Japan. With help from retired Berkeley chemists David Kreimer and Elena Kreimer, he spiked the ink with calibrated amounts of lead nitrate. High school students and the children of friends wrote out passages in it: lines from Star Wars, the Bible and the 1960s series The Outer Limits. Then he rolled the scrolls, sealed them in a nearly airless steel container and burned them in a furnace.

The point was contrast. Carbon ink on carbon paper is close to invisible to a scanner, which is why the Herculaneum scrolls have been so hard to decipher. Lead is not invisible. It absorbs up to 25 times the X-rays that charred papyrus absorbs.

Jake LaManna, a physicist at the National Institute of Standards and Technology in Gaithersburg, Maryland, rotated one of the burned scrolls in an X-ray beam and recorded thousands of slices. A NIST postdoctoral researcher, Michael Cyrus Daugherty, had already written a program to virtually unroll the jelly-roll interiors of lithium-ion batteries. With a few changes, it unrolled a scroll.

"If you look at the images, the letters light up like a Christmas tree," Seiler said.

Lead concentrations as low as 25 micrograms per square centimeter showed up, both on the laboratory X-ray CT rig and on an inexpensive handheld X-ray fluorescence scanner. The handheld result is the practical one: it gives conservators a cheap way to sort which scrolls are worth a full scan.

The Berkeley end of the work is not only Seiler's. Leah Packard-Grams, an archaeology graduate student who translates papyri at the Bancroft Library's Center for the Tebtunis Papyri, ran a handheld scanner over fragments excavated for the university 126 years ago in Egypt. Scrolls inscribed after the first century C.E. turned out to carry lead, copper or both in their ink.

"The value in this project is practically unquantifiable," Packard-Grams said. "The stakes are the largest in the history of Greek literature."

What is still open: nobody has systematically searched the Herculaneum scrolls for lead. Only a few have been virtually unrolled and read, and none of those were tested for leaded ink.