Dr. Keith Knox, technical advisor for the Space Surveillance Systems Branch of the Air Force Research Laboratory in Kihei, has been involved in an extraordinary project. For more than 20 years, in his spare time, Dr. Knox has worked with independent scientific groups that travel to different parts of the world to recover writing on ancient documents.
"Multispectral imaging, one of the techniques used for observing the sky, can also uncover the erased texts of ancient manuscripts," said Dr. Knox, whose expertise in this field has recently taken him to St. Catherine's Monastery in the Sinai Desert.
In the sixth century, Byzantine Roman Emperor Justinian the First built St. Catherine's Monastery at the foot of Mount Sinai, the mountain where Moses received the Ten Commandments. The monastery, now a UNESCO World Heritage Site, encloses the Chapel of the Burning Bush, the site where Moses was appointed by God to lead the Israelites out of Egypt and into Canaan.
“In our manipulation of the digital images, we use these different spectral responses to separate the two writings and enhance the erased writing, making it easier for the scholars to read,” said Dr. Knox. In this view, the ordinary visible text appears in black, while the more ancient erased text written in Greek appears in a blue-gray color.
Photo: Copyright St. Catherine’s Monastery, used with permission.
Dr. Knox was recruited with an international team of scientists to assist the Sinai Palimpsests Project. This program is part of a long-term effort of the monastery librarian, Father Justin Sinaites, to document the manuscript treasures under his care. Michael Phelps, executive director of the Early Manuscripts Electronic Library in Los Angeles, heads the program in cooperation with His Eminence Archbishop Damianos of Sinai and with the support of Arcadia, a London-based foundation.
Father Justin had been working to digitize the monastery's huge manuscript collection using standard photography for about 10 years, until the time came to develop a more comprehensive plan to explore the vast collection of hidden words.
"The monastery library preserves the second-largest collection of early codices and manuscripts in the world, outnumbered only by the Vatican Library," said Dr. Knox.
"What we are after is the overwritten text from centuries earlier, which had been scraped away to recycle the parchment," Dr. Knox said.
Pages with such erased texts are known as palimpsests.
Because writing material was very expensive in ancient days, frugal medieval scribes would sometimes scrape an old manuscript to remove the ink and write new text in place of the old. Many manuscripts of historic importance are difficult to read because the text has been accidentally defaced or deliberately erased.
"In either case, information about the previous content may still exist, even if it is invisible to the human eye," said Dr. Knox.
In 1992, Dr. Knox and colleagues at the Rochester Institute of Technology in New York started analyzing old texts on papyrus scrolls using simple imaging software.
"I realized that techniques we had developed to enhance images in photocopiers would work to recover writing on the ancient documents," he said.
Lately, Dr. Knox's group has been studying manuscripts written on parchment, the cleaned and dried skin of a sheep or goat.
"Centuries later, the erased ink on the parchment palimpsests begins to darken and becomes partly visible as faint stains," he said.
The team's job is to capture digital images of the parchment leaves.
"Later, we manipulate the image files to enhance the erased writing, while simultaneously suppressing the overwritten text," Dr. Knox explained. "We then provide these enhanced images to the scholars who read and interpret the erased writing."
Various modern imaging technologies can be applied to the problem of reading erased text in manuscripts that may have historical and cultural significance.
"The technical heart of the St. Catherine's project involves spectral imaging over many wavelengths from the ultraviolet through visible light to near-infrared," explained Dr. Knox.
The equipment used to scan the palimpsests is designed both to transmit light through the parchment and to shine light on to the surface in order to record the digital image. The largest source of data is ultraviolet irradiation, which makes traces of ancient ink fluoresce blue.
Computer programs combine all the spectral data, using special algorithms to make the overt top-text disappear as far as possible while enhancing the appearance of the under-text.
"St. Catherine's holds 120 known palimpsests that contain classical, Christian and Jewish texts in Greek, Syriac, Georgian, Armenian, Arabic and other languages," said Dr. Knox.
Some of the documents date from the fourth through the seventh centuries. However, the writing hidden underneath their visible texts is even older.
"Only a few of these palimpsests have been extensively studied," he said.
The Sinai Palimpsests Project is advancing both our historical understanding of the recovered texts and our scientific understanding of the multispectral techniques needed to read them.
"The information we uncover will assist libraries around the world to design methods to make the erased texts legible again," Dr. Knox said.
As a scientist, Dr. Knox relishes the quest of working on old manuscripts.
"It is a chance to discover something that has been hidden for centuries and would otherwise be lost to the world," he said. "To make a discovery of that magnitude is a thrill beyond measure!"