Photo: Erik Kwakkel

Remember Dr. Erik Kwakkel? He’s the medieval book historian (from the Netherlands’ Leiden University) who brought us the delightfully distracted and cheeky doodles that medieval students scrawled in illuminated manuscripts. Now he’s back with a new discovery for ancient book nerds: X-rays of book bindings from the 15th to 18th centuries have uncovered fragments of manuscripts from 1,300 years ago hidden inside. More than that, these “stowaways from a distant past” (as Kwakkel calls them) are not only visible but actually legible.

As The Guardian explains, post-Middle Ages and during the rise of printing, bookbinders would chop up and recycle handmade books (seeing as the craft was now considered old-fashioned) and use the fragments to strengthen printed books. With this being such a common practice, Kwakkel estimates that one in five printed books from the early modern age contains these “hidden libraries.”

Using macro x-ray fluorescence spectrometry (MA-XRF), scientists and academics scan books (without having to damage them by removing the bookbinding) searching for traces of iron, copper, and zinc—the main elements in medieval inks. Professor Joris Dik (from the Delft University of Technology) and his team originally developed this technology to scan Old Master paintings in search of hidden layers; in 2011, they detected a previously undiscovered self-portrait by Rembrandt hidden beneath the layers of another work.

In applying this method to a 12th-century text, one of the biggest discoveries was fragments of the writings of Bede, the 8th-century monk and scholar—a.k.a. the Venerable Bede, a.k.a. “the Father of English history.” As the team is fine-tuning the process—for one, trying to shorten the scanning time from the current 24 hours per scan—they have plenty of goals in mind. Kwakkel hopes to find a piece of an ancient Bible, he explained, and there’s a lot of potential places it could be hiding: