In the middle of Egypt’s Sinai Desert stands a huge fortress. Its walls reach 18 meters (60 feet) high and enclose St. Catherine’s monastery. It is home to the world’s longest continuously operated library. For more than 1,500 years, monks have cared for the library’s priceless books and manuscripts.
The library is very remote. Surrounded by bare, brown mountains, it once took weeks by camel to reach St. Catherine’s. Today, visitors can fly in to the closest airport, in Sharm El Sheikh. But reaching the Greek Orthodox monastery still requires driving another three hours across the desert.
Many people find the trek well worth the effort, though. That is because this library’s collection is unlike any other. It includes more than 8,000 early printed books and at least 3,300 handwritten manuscripts. Many are one-of-a-kind — and that’s just what meets the eye.
Today, experts are visiting St. Catherine’s to take a closer look at its historic collection using modern science. By applying a new and powerful technique called spectral imaging, these scientists are slowly revealing something startling: the presence of even more ancient texts hidden within the library’s collection.
Elsewhere, scientists have been using spectral imaging to shine a new light on other important texts. These include drafts of the Declaration of Independence and Gettysburg Address.
Lucky scrape for science
Father Justin Sinaites, St. Catherine’s head librarian, has spent years photographing the monastery’s manuscripts. These images make the rare and ancient books available to a wider audience. It also protects and preserves the words those books contain against threats from outside the monastery’s walls.
For some of these texts, handwritten on specially treated animal skins called parchment, basic photography doesn’t provide the whole picture. That’s because these parchments aren’t just used; many have been reused.
Ancient scribes sometimes would recycle parchments, writing over freshly smoothed skins from which they had scraped any older writing. Lucky for science, reused parchments usually retain faint traces of any earlier writing. And with the help of technology, those missing words now can be retrieved.
At St. Catherine’s, visiting physicists and other experts are helping Father Justin to do just that. Early efforts by the team have begun revealing the undertexts — older writing masked by a topcoat of newer words. Initial estimates point to thousands of pages of hidden text in the volumes on St. Catherine’s library shelves. Undoubtedly, they hold countless secrets.
The experts are using spectral imaging to create multiple images of each manuscript page as it is illuminated under a succession of bands of light (colors). This technique can reveal words too faint or faded to decipher in full.
This is not the first time that researchers have used the technology to recover hidden words. Indeed, scientists working with a museum in Baltimore have found copies of works by Archimedes that no one had been able to clearly see and read in full. This mathematician and scientist lived in the Greek city of Syracuse roughly 22 centuries ago.
And experts at the Library of Congress also turned up something important recently. They found Thomas Jefferson wrote — and then erased — something while he was penning the Declaration of Independence. (Hint: It wasn’t a treasure map.)
Old-style book “recycling”
St. Catherine’s oldest books were created long before the era of paper and printing presses. Scribes hand copied each book, using parchment made from the skins of sheep, goats or other animals. Preparing parchment was hard work. So scribes would sometimes reuse the parchment from an existing book: It might have been an unneeded duplicate copy or a text that no one cared about anymore.
First, the scribes removed pages from their binding. Then they carefully scraped away the old inked text. Next, they penned the new words, sometimes writing at a 90-degree angle across any traces of the older lettering.
Over the years, visiting scholars and St. Catherine’s monks had identified more than 130 manuscripts containing such recycled skins. Librarians call an erased-and-then-reused manuscript a palimpsest (Pa LIMB sest). The term combines the Greek words for “again” and “rubbed smooth.” At St. Catherine’s, many palimpsests turned up in 1975. That’s when the monks opened a dusty, forgotten storage area that had been closed for centuries.
Undertexts in St. Catherine’s palimpsests could prove more interesting than the texts written atop them. That’s because older often means rare, if not downright unique. Yet in most cases, no one could decipher all, or sometimes even some, of the original penned words. They had all but vanished.
Then modern technology came to the rescue. Digital techniques to fully recover undertext have existed for only a decade or two. The monks allowed a group of scientists who could provide the special lighting, camera systems and skills needed to apply spectral imaging to hunt for erased words.
Spectral imaging involves taking a large series of photographs while shining different colors of light onto the palimpsests. The colors include the red, blue and green visible to our eyes, as well as others, such as infrared and ultraviolet, which are not visible. If the experts have selected the appropriate colors, the photographs will reveal highlights of the faint impressions or ink residues that trace out individual letters and words.
“One of the things that attracts me to this work is the sense of discovery,” says Michael Toth. He’s a systems engineer who helps manage the project. “You are seeing things that haven’t been seen — sometimes for a millennium,” he notes. As a systems engineer, Toth’s job is to look at the project’s big picture and make sure all the pieces are in place, including the right experts, cameras and data-storage devices.
In the right light . . .
Various groups around the world use spectral imaging. The trick to revealing hidden words is not only to select the right color of light, Toth explains, but also to use that light in clever combinations with new digital technologies. And sometimes how the words were written can introduce novel challenges.
For instance, the researchers who teamed up to work on the Archimedes text in Baltimore had to work out some special techniques for probing palimpsests. The efforts proved successful, revealing portions of books written by the ancient mathematician (who died about 212 B.C.).
Father Justin heard about this project and arranged to meet with Toth’s team. He wanted to find out whether their new technology might also work on the palimpsests at St. Catherine’s.
The team knew it would not be easy. There were so many pages to image and, eventually, huge amounts of data to manage. Moreover, the group would have to install all of its equipment at the remote monastery because St. Catherine’s books shouldn’t be moved outside the library. Clearly, this project would be costly. But the team was up for the challenge.
Soon after, Michael Phelps agreed to lead this new project. An expert on ancient Biblical manuscripts, he is the executive director of the Early Manuscripts Electronic Library in Rolling Hills Estates, Calif. Phelps got the monastery’s permission to begin tests in Egypt during the fall of 2009. He also arranged for a five-year, $2.1 million grant from a British organization called the Arcadia Fund to finance the hunt for St. Catherine’s hidden texts.
Bringing CSI tech to Egypt
The team had to lug almost all the equipment they needed with them on that first trip to St. Catherine’s. And that’s where it has stayed. As for the precious manuscripts the experts came to probe, they are so fragile that only Father Justin gets to handle them. He turns each page, bringing in new manuscripts when it’s time.
His monastery also helped by supplying its manuscript “cradle.” Ancient manuscripts are so fragile they should never be opened flat on a table. Instead, a bound manuscript should be opened only partway. The special cradle supports the book as its pages are turned. Resembling a tilted-back metal chair, the cradle has a mechanical arm that gently and ever so carefully inserts a wedge below each page to be photographed. This helps prevent other pages of the manuscript from showing through.
The team employs more than a dozen different light configurations to probe each page. Sometimes, lights placed above the text work best. Other times, it helps to place the lights below or to one side of a page.
Certain lights have proven quite useful because of a phenomenon known as fluorescence. Living or once-living materials often fluoresce. If you shine certain wavelengths of blue or ultraviolet light on fluorescent materials, including parchment, the light doesn’t reflect back in the original wavelength (or color). Instead, the page absorbs some of that light and then re-emits it in a different color. Using filters to block out certain colors of light, the analysts photograph only the shifted wavelengths of light re-emitted by a page.
That’s the same basic process often depicted in TV dramas, where technicians scouring a crime scene for clues put on yellow glasses and shine a special “black light” — ultraviolet light — to look for traces of blood. They will glow as they fluoresce.
Turning stains into words
With manuscripts created using ink on parchment, the undertext can block enough of the fluorescence. That creates a strong contrast between each relatively dark letter and the light parchment. It also makes the words readable even on pages where, to the unaided eye, there’s no visible undertext.
Keith Knox is an imaging specialist who works on palimpsest analysis as an extra job (his regular job is working with images at the U.S. Air Force Research Laboratory in Maui, Hawaii). Knox created a computer program to analyze the fluorescence given off when palimpsest pages are lighted. His program can take images of pages where only the overtext is visible and compare it against images of pages where the undertext is visible. Then the program subtracts out the overtext. This enhances the undertext.
“Ultraviolet light does a remarkably good job of turning the characters from stains into letters that you can read,” explains Knox.
Most times, anyway. The researchers do hit obstacles. For instance, at times over the centuries, an undertext’s ink may have eaten into that soft material on the fleshy side of a parchment page. This complicates the light’s ability to reveal undertext.
Ever inventive, the research team has tested all types of lighting. And one new scheme solved that problem.
One spectral scientist, Bill Christens-Barry, added lights to the wedge of the manuscript cradle inserted beneath each page. Then the researchers measured how much light from the wedge shone through a page. Called transmission imaging, no one had ever tried this with palimpsests. But it worked well. It allowed the bonus light to shine through where the old ink had eaten into a parchment page. And that bonus light highlighted the undertext.
In other cases, where some undertext letters were hard to read, shining one or more colors of visible lights revealed the hidden words.
Scribes usually created the manuscripts using iron gall ink. As it breaks down over time, the ink’s color changes slightly. That gives older undertexts a slightly different hue from any overtext. The difference in colors between the two inks makes each respond a bit differently to each color of light. If the undertext was a little redder, for example, it would show up better under red light.
Those differences can be so slight that the eye would never pick them out in a photo. But special software not only can pick out the differences, but also magnify them.
“It’s brand new science,” explains Knox. And it takes trial and error “to find what might work.”
During its first trip to Egypt in 2009, the research team worked on just a few sample pages from several different manuscripts. The work was hard, but it easily turned up interesting undertext. Knox compares the group’s work to hunting for treasures on a beach littered with jewels: “There are so many gems that wherever you put your hand down you’re going to be pulling up something really fantastic.”
Still, it took a while to confirm the value of these literary gems. That’s because the imaging specialists can’t tell right away what they are uncovering. Their job is to highlight once-hidden words and photograph them. While these scientists can read light spectra, they can’t read all the ancient languages, such as Georgian and Caucasian Albanian, used to write the manuscripts. So they must send digital photos of the revealed words to ancient-language specialists around the world.
These scholars have already translated bits of undertext. The snippets included passages written in nine different languages, including classical Arabic and ancient Greek. Some words came from languages that have since died out completely, such as Syriac.
The undertext in one manuscript appears to be at least 1,200 years old. It offers medical information about the importance of diet to health.It’s likely to be at least 500 years older than any other book of its type known. And “we’re only just beginning,” notes Claudia Rapp. A medieval-text specialist from the University of Vienna in Austria, she leads the group of language scholars analyzing St. Catherine’s undertexts.
There’s also more to the work than just finding and translating buried words. Studying the palimpsests also helps the scientists better understand what the world was like 1,000 years ago or more. These manuscripts tell us which ideas people back then considered important enough to write down — and save. Similarly, the manuscripts reveal which texts were common enough, or had so little value, that they could be erased and not missed. “One thing about St. Catherine’s is that it’s a time capsule,” says Phelps.
The main imaging team, including American and Greek researchers, has made four trips to Egypt. Now that the equipment is in place, two Greek members are making additional trips by themselves. Over the next several years, the researchers hope to finish imaging all of the palimpsest pages. They’ve already taken more than 60,000 photos. These represent 2,000 manuscript pages from 25 palimpsests. Another four times that many palimpsests still await analysis. Curiosity about what will be revealed next continues to motivate everyone involved.
The same basic spectral imaging techniques can uncover text hidden within more recently created documents too. In 2010, for instance, Toth’s group worked with the Library of Congress to set up a system for studying documents, including some that are extremely important to American history. These included original copies of the Gettysburg Address. Toth even noticed that in the right light, a smudged thumbprint showed up on one copy. It may have been left by its author: Abraham Lincoln.
One researcher at the Library of Congress also discovered that when writing the Declaration of Independence, Thomas Jefferson substituted the word “citizens” for another word he had first written and then erased. Spectral analysis revealed the undertext. It shows that Jefferson had originally written the word “subjects.”
The freedom that Jefferson and his fellow patriots were proclaiming with this document meant they would no longer offer allegiance to a faraway British king. And that is why he erased the word. These Americans would no longer be subject to the king.
The Library of Congress — the nation’s premier library — now has a long list of other documents it’s planning to probe with spectral imaging.
One of the more unusual challenges that Toth, Knox and their fellow researchers have confronted is a diary kept by David Livingstone. While traveling through Africa in the mid-1870s, this famous Scottish missionary and explorer ran out of paper and ink. To keep his account going, Livingstone began writing on old newspapers using ink he fashioned from local berries. He later copied passages into other diaries. Historians had assumed his original penned thoughts were lost.
But spectral imaging brought them back.
The handwriting on the ancient newsprint was faint. The spectral-research team also had trouble finding what light would make the berry’s ink readable. Then the scientists realized that infrared light would reveal only the newspaper print — but not the handwriting. By using other colors of light, both were visible. With a computer, they processed those pages and subtracted out the newspaper text as it showed up under infrared light. When they were done, two years ago, “Handwriting was the only thing left,” explains Knox.” So, “for the first time in 140 years we were able to read what Livingstone had written” — and in his own hand.
The team continues to find plenty of new challenges. For instance, while working at Harvard University in 2013, a librarian suggested the experts probe some pages. Herman Melville had penned notes into the margin of a book about whales he was studying while writing his famous novel, Moby Dick. The researchers went to work. So far, however, they have yet to make out all of what Melville wrote.
Most people think of science as discovering things that were not known before. But with all of these projects — from Livingstone’s diary to St. Catherine’s palimpsests — the definition of discovery is somewhat different. The hidden words were once known. It is just that they’ve been lost. So librarians are recruiting scientists to regain knowledge from that lost past. And to Knox, “Discovering something that was lost in history is a real thrill.”
electromagnetic wave Waves of energy found in various sizes that can include everything from radio waves to visible light to X-rays.
fluoresce Absorbing light in one color and re-emitting in another. That re-emitted light is known as fluorescence.
manuscript A handwritten book or document.
medieval Having to do with the Middle Ages, which lasted from about the 5th to 15th centuries.
overtext The newer, visible text of a palimpsest.
parchment The treated skin of an animal used as a writing surface.
palimpsest A manuscript whose original writing has been erased to make room for other writings.
spectral imaging Collecting very detailed images of something under different types or colors of light.
systems engineering This field applies research to manage all aspects of solving some major technical problem. That “problem” could be the development of a new machine or even a large solar- or nuclear-power plant. Sometimes the scale will be far smaller, such as the creation of computer chips and the computer programming instructions required to use them. Systems engineers take a big-picture view to consider every aspect of a project. This includes everything from the people, materials and financing that will be needed to the environmental impacts of some system, the work that is needed, and the expected lifetime of its many parts.
undertext The scraped away earlier text of a palimpsest.
wavelength The distance between the peaks in a wave.
Word find (click here to enlarge for printing)
S. Gaidos. “Cool Jobs: The science of secrets.” Science News for Students. Oct. 31, 2012.
S. Ornes. “Crime-solving camera.” Science News for Students. Aug. 31, 2012.
S. Ornes. “Fish eyes go green.” Science News for Students. Jan. 25, 2012.
Teachers' questions: Questions for The ultimate wordfind puzzle
Explore the history of St. Catherine’s monastery by visiting its official website.
Read more about how spectral imaging revealed an important change to the Declaration of Independence on the website of the Library of Congress.