Imprimir Republish


Lights on the past

Sophisticated analysis techniques reveal writing from papyruses and deteriorated documents

Images in ultraviolet or infrared are throwing light on unintelligible passages from Egyptian papyruses more than 2 thousand years old and are bringing to the surface lost works by great classical authors, such as Sophocles, Euripides and Hesiod. X-rays are making it possible to get to know better the mathematical theories of Archimedes contained in murky and difficult to understand copies, made in the 10th century, from parts of the original writings. Chemical and spectrometry analyses reveal the composition of the pigments used in the 15th century by Johannes Gutenberg to illustrate the first book made with movable type, the Bible. As can be seen, the most varied technologies are today at the service of the study of ancient texts, filling in information gaps hitherto inaccessible to the most acute exegetes.

At Oxford University, British researchers are using a method created by NASA for use in its satellites in the visualization of planets and celestial objects, multispectral imaging, as an ally in the work of studying the texts of the Oxyrhynchus project. This is a collection of 400 thousand fragments of manuscripts written by classical authors from Greece and Rome found at the end of the 19th century in the remains of the ancient Egyptian city of Oxyrhynchus. The papyruses, which, according to some scholars, may expand by 20% the quantity of classical texts, remained a long time in contact with the soil, amidst all kinds of garbage, in particular glass, and became dark and illegible in some passages. The contrast was lost between the pigment used in the writing and the background of the papyruses, which had darkened too much.

Multispectral imagining consists of producing a succession of images, in different wavelengths, of the object under study. In this way, one of the images, or a juxtaposition of some of them, can make passages of the analyzed material leap into sight that until then were invisible. “In general, there isn’t a magic wavelength that makes all the ancient writings appear”, says engineer Gregory Bearman, from NASA’s Jet Propulsion Lab, who, at the beginning of the 1990’s, had the idea of employing the technique in archeological studies. “Everything depends on the state of the document and on what has happened to it in the course of time.”

Passages from the ‘Dead Sea Manuscripts’, a set of 850 texts about 2 thousand years old found in caves in Israel between 1947 and 1956, were the first ancient texts on which multispectral imaging was employed with success. Next, the method was tested on texts from Pompeii that were buried and scorched by the eruption of the volcano Vesuvius in 79 BC. Carbonized material, as from Pompeii, and non-carbonized writings, like those from the Oxyrhynchus project, usually reveal hidden details when submitted to different wavelengths. According to Dirk Obbink, a specialist in papyruses and Greek literature at Oxford, some passages of the documents rescued from the most ancient city of Egypt became legible after images were generated in ultraviolet. In others, infrared achieved better results.

The crux of the matter
To decipher a transcription from the Middle Ages of the original works of Archimedes (287 to – 212 BC), unpublished passages from his work Method of mechanical theorems, which fell victim to different kinds of damages and adulterations in the course of the last millennium, physicists from the American university of Stanford, in California, were afforded the assistance of images generated by X-rays. A major part of the untoward alterations suffered by the parchments, such as their scraping and reuse as a support for the text of a religious book in the 13th century, had already been overcome with the adoption of other techniques. But it remained to get round the latest aggression suffered by the documents, now in the 20thy century, when modern writing was added to the top of some pages, hiding parts of the ancient texts. Generating X-ray images overcame this hindmost obstacle. This was because the exposure to radiation highlighted the ferrous pigments of the original manuscripts, to the detriment of the modern ink used to alter the parchments, according to an article in mid April from the news service of Nature magazine.

Talking about paint, a group of European and American researchers determined, for the first time, the main types of pigment used to draw the figures that adorn seven of the so-called Gutenberg Bibles, published in the 15th century. Besides resorting to chemical analyses, they used in their detective work Raman spectroscopy, a noninvasive method in which a laser lighted up the pages and a special sensor read the pattern of light generated. The origin of seven colors was determined precisely, and of two in an approximate way.

The light red is derived from cinnabar (mercury ore). The yellow comes from compounds with lead and tin. The black originates from carbon, and the white, from calcium carbonate. The blue derives from the use of azurite, a kind of copper carbonate. The olive green, from malachite, another copper carbonate. The dark green from copper ethanoate (verdigris). Of an uncertain origin, the golden tones seem to come from gold itself, and the reds from pigments extracted from plants or insects. “The study of the paints represents a first important step of an appropriate policy for conserving and preserving old works of art”, says one of the authors of the study, Gregory D. Smith, from Buffalo State College, in the United States. Made known to the public at large in April, the complete study of the pigments of the Gutenberg Bibles will be published in the June 1 issue of the American magazine Analytical Chemistry.