Lead-based inks likely used as a drying agent on ancient Egyptian papyri

Detail of a medical treatise from the Tebtunis Temple Library with headings marked in red ink.
Enlarge / Detail of a medical treatise from the Tebtunis Temple Library with headings marked in red ink.

The Papyrus Carlsberg Collection

An international team of scientists used high-energy X-rays to analyze 12 fragments from ancient Egyptian papyri and found lead compounds in both red and black inks used. According to their recent paper, published in the Proceedings of the National Academy of Sciences, this is evidence that these compounds were added not for pigmentation but for their fast-drying properties, to prevent the ink from smearing as people wrote. Painters in 15th-century Europe used a similar technique when developing oil paints, but this study suggests ancient Egyptians discovered it 1,400 years earlier. So the practice may have been much more widespread than previously assumed.

“Our analyses of the inks on the papyri fragments from the unique Tebtunis Temple Library revealed previously unknown compositions of red and black inks, particularly iron-based and lead-based compounds,” said co-author Thomas Christiansen, an Egyptologist from the University of Copenhagen.

As I’ve written previously, synchrotron radiation is a thin beam of very high-intensity X-rays generated within a particle accelerator. Electrons are fired into a linear accelerator to boost their speeds and then injected into a storage ring. They zoom through the ring at near-light speed as a series of magnets bend and focus the electrons. In the process, they give off X-rays, which can then be focused down beamlines. This is useful for analyzing structure because in general, the shorter the wavelength used (and the higher the energy of the light), the finer the details one can image and/or analyze.

That’s what makes synchrotron radiation particularly useful for analyzing art and other priceless artifacts, among other applications. Back in 2008, European scientists used synchrotron radiation to reconstruct the hidden portrait of a peasant woman painted by Vincent van Gogh. The artist (known for re-using his canvases) had painted over it when he created 1887’s Patch of Grass. The synchrotron radiation excites the atoms on the canvas, which then emit X-rays of their own that can be picked up by a fluorescence detector. Each element in the painting has its own X-ray signature, so scientists can identify the distribution of each in the many layers of paint.

Last year, we reported on the work of a team of Dutch and French scientists who used high-energy X-rays to unlock Rembrandt’s secret recipe for his famous impasto technique, believed to be lost to history. Impasto (translated as “dough” or “mixture”) involves applying paint to the canvas in very thick layers. It’s usually done with oil paint because of the thick consistency and slow drying time, although it’s possible to add acrylic gels as a thickening agent to get a similar effect with acrylics. Rembrandt used it to represent folds in clothing or jewels, among other objects, in his paintings. The scientists discovered the presence of a mineral called plumbonacrite in the impasto layer—an uncommon element in paints from that period.

And earlier this year, we reported on

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Red and black ink from Egyptian papyri unveil ancient writing practices

Red and black ink from Egyptian papyri unveil ancient writing practices
Detail of a medical treatise (inv. P. Carlsberg 930) from the Tebtunis temple library with headings marked in red ink. Image credit: The Papyrus Carlsberg Collection. Credit: The Papyrus Carlsberg Collection.

Scientists led by the ESRF, the European Synchrotron, Grenoble, France and the University of Copenhagen, Denmark, have discovered the composition of red and black inks in ancient Egyptian papyri from circa 100-200 AD, leading to a number of hypotheses about writing practices. The analysis, based on synchrotron techniques, shows that lead was probably used as a dryer rather than as a pigment, similar to its usage in 15th-century Europe during the development of oil painting. They have published their results in PNAS.

In ancient Egypt, Egyptians used black ink for writing the main body of text, while red ink was often used to highlight headings, instructions or keywords. During the last decade, many scientific studies have been conducted to elucidate the invention and history of ink in ancient Egypt and in the Mediterranean cultures, for instance ancient Greece and Rome.

The scientists used the powerful X-rays of the ESRF to study the red and black ink in papyri from the Tebtunis temple library, the only large-scale institutional library known to have survived from ancient Egypt. The samples studied in this research project are exceptional, not only because they derive from the famous Tebtunis temple library, but also because the analysis includes as many as 12 ancient Egyptian papyrus fragments, all inscribed with red and black inks.

“By applying 21st century, state-of-the-art technology to reveal the hidden secrets of ancient ink technology, we are contributing to the unveiling the origin of writing practices,” explains Marine Cotte, scientist at the ESRF and co-corresponding author of the paper.

Red and black ink from Egyptian papyri unveil ancient writing practices
A papyrus fragment from a long astrological treatise (inv. P. Carlsberg 89) from the Tebtunis temple library and the ESRF X-ray fluorescence maps showing the distribution of iron (red) and lead (blue) in the red letters that write out the ancient Egyptian word for “star”. Image credit: The Papyrus Carlsberg Collection and the ESRF. Credit: The Papyrus Carlsberg Collection and the ESRF.

“Something very striking was that we found that lead was added to the ink mixture, not as a dye, but as a dryer of the ink, so that the ink would stay on the papyrus,” says Cotte. The researchers came to this conclusion because they did not find any other type of lead, like lead white or minium, which should be present if lead was used as a pigment. “The fact that the lead was not added as a pigment but as a dryer infers that the ink had quite a complex recipe and could not be made by just anyone,” adds Thomas Christiansen, Egyptologist from the University of Copenhagen and co-corresponding author .

A surprising fact is that the ink recipe can be related to paint practices developed many centuries later during the Renaissance. “In the XV Century, when artists rediscovered the oil painting in Europe, the challenge was to

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