Other Asian innovations, like paper and gunpowder, have a clear record of dissemination to Europe, with artifacts and record-keeping that trace their travel westward along routes of trade and conquest. Printing doesn’t have that kind of paper trail, says Valerie Hansen, a professor of Chinese history at Yale University. There is no evidence that European printers saw the fruits of Asian printing, like money or pamphlets, and then tried to reverse engineer the processes that made them—though it’s plausible, given increasing contact between east and west in the 13th and 14th centuries.

A close look at both printing technologies has also revealed more differences than similarities: different inks (oil-based in Europe versus water-based in Asia) and different processes to create the metal types, which stamp ink into the page. In the 14th century, when Jikji was printed, Korean printers were widely using a method called sandcasting to produce types, which involves filling molds lined with compressed sand. To create their movable type, Europeans swapped sand for metal. One of the benefits was that, unlike sand, these metal molds could be reused, allowing the types for individual letters to be mass produced. This is one factor thought to have helped the printing press spread so quickly in Europe.

That innovation has long been traced back to Gutenberg’s workshop. But in the early 2000s, in front of a packed house at a literary club in New York City, a pair of Princeton researchers outlined a startling theory: Perhaps Gutenberg’s creations represented less of a singular technological triumph than people had previously thought.

Their analysis focused on subtle imperfections in the text. If a metal mold had been used to create the types, each letter—say, all the letter a’s on a page—should be the same. But a mathematical analysis revealed that there were differences in the letters. The researchers hypothesized that the patterns were more in line with sandcasting. Not everyone agrees with that interpretation, but since then, there has been more evidence in its favor. As a way of kicking off a deeper study of Gutenberg’s methods for the Jikji project, Silverman asked Jonathan Thornton, a retired librarian and craftsman at the State University of New York at Buffalo, to see whether he could recreate the typographic flaws using sandcasting techniques in his own workshop. Lo and behold, it appeared to work.

The use of sandcasting doesn’t definitively link the two traditions—various forms of the technique were common in both Asia and Europe at the time—but it’s yet another example of how the two traditions are slightly closer than people think. It would so also mean that the metal mold, with its regular, replicable type, likely came later, and suggest that the printing press was a more gradual development than a sudden arrival on the scene. “It turns out we don’t know very much about Gutenberg, this guy who we’ve all said modernity hinges on,” Silverman says.

Mining objects with X-rays isn’t a new method. A Gutenberg Bible had been analyzed in the 1980s at a much less powerful particle accelerator at the University of California, Davis. But the Stanford synchrotron is far more sensitive, expanding the range of the elements and the level of detail it can see, says Mike Toth, an imaging expert who frequently works with ancient objects. These X-rays are often used to explore what can’t be seen—such as in cases where a document is rolled up and can’t be unfurled, or to check whether a hidden painting was covered up by another artist to save canvas. If it’s known that a covered-up ink or pigment is made of, say, iron, and the ink that covers it isn’t, the X-ray imaging can reveal it by isolating that element.