Trace lead in ink makes writing stand out in X-ray scans of papyrus burned on purpose

Seiler's replicas come with an answer key. High school students copied passages from "Star Wars," the Bible and "The Outer Limits" onto papyrus from Egypt, using Egyptian reed pens and traditional Japanese lampblack ink ^[1]. Anyone reading the scans can check each character against what was actually written. A furnace burn of modern materials tests whether a lead signal survives carbonization. It does not reproduce a library buried under volcanic ash ^[9] or the nearly 2,000 years that followed ^[2].

Seiler reasoned that lead would absorb X-rays far more strongly than carbonized papyrus ^[13]. Software that virtually flattens the rolled sheets could then pick out the writing ^[13]. Lampblack is carbon, and so is burned papyrus. "They're having problems reading a lot of them because of the low contrast of carbon ink on carbon paper," Seiler said ^[2].

The 25-fold figure is a maximum. Lead absorbed "as much as" 25 times more X-rays than the burned papyrus around it ^[4], and the typical contrast across the test characters may be lower. The release does not give the lead concentrations tested or how contrast varied from letter to letter. Until it does, "extremely small amounts" ^[3] cannot be turned into a detection threshold to compare with real ink.

The replicas show that lead ink would stand out. Whether Herculaneum's scrolls contain it is a separate question. The surviving library holds about 1,800 items ^[12], and no one has yet searched it systematically for lead-based ink ^[7]. The release points to at least one earlier detection, in a fragment left over from the early attempts to open the scrolls physically ^[8]. "With lead in the ink, you would get a huge friggin' signature, so you really need to be looking for scrolls with lead in them," Seiler said ^[1].

I think the handheld result matters more to the collection than the CT contrast does. If the scanner reads ancient material the way it read the burned test scroll ^[5], ink chemistry becomes the first sort: screen the collection cheaply, then send the scrolls that test positive for lead to CT. That condition matters, because the detection was part of the replica study. Seiler puts the next step in the hands of whoever controls access. "We're relatively certain that if they start searching for lead, or they let us search for lead, it will help this whole process," he said ^[3].

The scrolls were discovered in 1752, and early attempts to unwind them often reduced them to ash until Italian authorities stopped the practice ^[10]. Every scroll that was successfully opened contained writing previously unknown to scholars, many of them works by the Epicurean philosopher Philodemus ^[11].