More than 1,600 scientists from all over the world use the Stanford Synchrotron Radiation Lightsourse (SSRL) at SLAC National Accelerator Laboratory each year for research that spurs advances in medicine, energy production, environmental cleanup, nanotechnology and new materials. And now, a multidisciplinary team has used the machine’s acceleratordriven X-rays to reveal the hidden text of a medical manuscript written on parchment in the sixth century and then overwritten with religious text some 500 years later.

This type of manuscript is a palimpsest, a parchment reused by scraping off the original text and writing new text on top of it. The original words are from a medical text by the Greek doctor Galen, while the overwritten religious text contains psalms composed for the days of the week. Both works were written in ancient Syriac.

The palimpsest first turned up in Germany in the early 1900s, and research indicates it was originally from St. Catherine’s Monastery on the Sinai Peninsula. For nearly a decade, a multidisciplinary team of technical experts, scientists and scholars used advanced multispectral imaging and digital processing techniques to study Galen’s original text but were not able to reveal all of the hidden text, which was thoroughly scrubbed off in some sections.

An SSRL team led by SLAC distinguished staff scientist Uwe Bergmann, in collaboration with Stanford University Libraries and R.B. Toth Associates, used SSRL’s high-powered X-ray beams to scan each page and converted them to high-resolution TIFF and jpeg files that will be posted online for scholars to study the unseen Galen undertext. It took the team about 10 hours for each of the 26 pages.

The images, according to the team, show minute variations in the ink used to write characters and words on the page. The ink in the newer religious text and the residual ink from the scraped-off hidden text respond to the X-ray beam in slightly different ways, allowing scientists to tell them apart. The technique builds upon a decade of work, including research with the same beamline to image the Archimedes palimpsest in 2006, as well as the imaging of fossils, archeological artifacts and other manuscripts.