Northwestern scientists go high-tech to uncover the secret hidden on top of a 16th century book

Researchers at Northwestern University used non-destructive analytical techniques to examine the "ghost images" on top of a 16th century book. (Center of Scientific Studies in the Arts/Northwestern University)

By Catherine Chen

Researchers at Northwestern University are relighting lost history by identifying “ghost” texts on a degraded manuscript used as the cover of a book printed in Italy in the early 16th century.

The book, “Works and Days,” was originally written by Greek poet Hesiod in the 8th century B.C. Northwestern has a copy of the book, printed in 1537 in Venice. The book is bound in parchment with text on the parchment’s inner surface. The outer surface of the manuscript was degraded after centuries of use, and the images of the text inside became visible to the naked eyes.

Although they could see the text, researchers couldn’t identify specific words with human eyes, said Marc Walton, senior scientist at the Center for Scientific Studies in the Arts at Northwestern University (NU-ACCESS).

To uncover the writing, researchers at NU-ACCESS used two non-destructive analytical techniques, X-ray fluorescence and multispectral imaging, to make the texts legible.

X-ray fluorescence reveals the presence of different elements on a sample. Different elements have different energy levels and have unique peaks in the imaging software. Researchers tracked iron at the surface of the manuscript, because the iron gall ink was the standard writing and drawing ink in Europe in the late Middle Ages.

Researchers took the book to Cornell University based in Ithaca, New York, to use the Cornell High Energy Synchrotron Source (CHESS). This extremely focused and intense X-Ray source can speed up the process of deciphering.

Another technique used to examine the book is multispectral imaging. It is a technique that can visually enhance the contrast between the writing and the parchment.

“We have a camera that is capable of seeing wavelengths every two nanometers between 400 nanometers to 900 nanometers, from the ultraviolet into the infrared. It gives us an opportunity to see what wavelengths are actually penetrating the structure and reflecting back to the camera to be able to look at variation, tone and contrast,” Walton said.

Multispectral imaging has proven to be effective in examining historic documents. In a study done by researchers at the Walters Art Museum in Baltimore, Maryland, about 15 years ago, multispectral imaging was used to successfully reveal some erased texts in a 10th century manuscript found in a 13th century prayer book.

“Our approach was to do several different techniques [and] use the book as a laboratory to be able to test out our different methods of looking through a scattering media,” Walton said.

The project was initiated by an NU librarian who was interested in book binding styles of the 15th century. But after Works and Days was found at NU’s Special Collections Library, researchers began to be curious about the “ghost images” of texts.

The book has been checked out by students and faculty until the 1960s. It has severe deterioration on top and requires delicate care. Emeline Pouyet, the leading scientist of the project, said they avoid to open the book and further fragilize the book and the manuscript.

Tonia Grafakos, chief conservator at Northwestern University Library, said special collection items are stored in a stable environment. The temperature is controlled at 60 degrees Fahrenheit and the relative humidity is kept at about 40 percent.

“By keeping the storage environment at a steady rate, we are trying to preserve them for the longest possible time for future researchers,” Grafakos said.

Pouyet said one of the biggest challenges of the project is “the object itself,” due to the delicacy of the ancient book. Researchers were careful about the moving of the book and the order of the analyzing techniques.

Researchers integrated the images retrieved by the two techniques and got an overall image of the manuscript. Results were sent to language and religious studies experts at Northwestern to identify the context.

The text proved to be a Roman Law code with notes in the margin commenting on the interpretation of the legal contexts. It was a routine practice in the Middle Ages that law scholars wrote annotations of Roman Law between the lines. The discussion of  “legal glossator” scholars was primarily academic rather than practical at first. After the 14th century, scholars began to seek ways to apply Roman law to the practical legal needs of the day.

Walton said finding the results was a joint effort of interdisciplinary collaboration. Computer scientists helped with the modality of the imaging techniques. Conservation scientists like Pouyet steered the scientific process. Librarians preserved and transported the book. Finally, medieval historians interpreted the results.

Two possibilities emerged on why the manuscript was used as a book cover. One reason is economics, that the book owner simply wanted to avoid extra expenditure in covering the book. The other is that the owner wanted to hide the manuscript, as the book was published just prior to the reinstatement of the Inquisition in Venice, a time when religious and political texts were being destroyed.

“It’s a detective story,” Walton said. “We are revealing something that has not been seen for 500 years.”

Photo at top: Researchers at Northwestern University used non-destructive analytical techniques to examine the “ghost images” on top of a 16th century book. (Center for Scientific Studies in the Arts/Northwestern University)