Sunday, January 17, 2021

High-energy x-rays reveal the secrets of ancient Egyptian ink

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“By applying cutting edge 21st century technology to reveal the hidden secrets of ancient ink technology, we are helping to unravel the origin of writing practices,” said co-author Marine Cotte, scientist at ESRF.

These inks were typically made from soot and ocher, mixed with some kind of binder (usually gum arabic), and then hung in animal glue, vegetable oil, or vinegar. Then the mixture would be dried and pressed into granules so that the scribes could easily carry the inks with them. When they needed to use it, they mixed the dried lozenge with a little water, using the tip of a reed pen for the actual writing. In this sense, dyes were more akin to paints, in that they would be classified as pigments rather than colorants.

Cotte, Christiansen and their colleagues have previously studied the red, orange and pink inks used on 11 surviving fragments of several manuscripts found in two small caves in the so-called Tebtunis temple library, southwest of Cairo. This work revealed an unusual red ink based on a mixture of iron and lead compounds that had not been documented before, although there is a reference in Pliny. Natural History in mixing red ocher and lead white to obtain an orange-reddish pigment. It was generally used as a flesh color by Egyptian painters between 30 BCE and 400 AD, according to the authors, but had not been identified in ancient Egyptian papyri until their study.

For this last study, the team was interested in the analysis of the mineral compounds of the red and black inks of the fragments of papyrus of the temples, in particular the specific compounds of iron and lead. They used many synchrotron radiation techniques to probe the chemical composition, including X-ray micro-fluorescence, X-ray micro-diffraction, and micro-infrared spectroscopy. They found a complex mixture of lead phosphates, potassium lead sulfates, lead carboxylates and lead chlorides.

“The iron-based compounds in red inks are most likely ocher – a natural pigment of the earth – because iron has been found with aluminum and the mineral hematite, which are found in ocher, ” said co-author Sine Larsen, also from the University of Copenhagen, the results. “Lead compounds appear in both red and black inks, but since we did not identify any of the typical lead-based pigments used to color the ink, we suggest that this particular lead compound was used by scribes to dry ink rather than as pigment. “

Cotte et al. I think the temple priests probably did not make the inks themselves, given the complexity of the red ink in particular, which would have required specialist knowledge, and the considerable amount of raw materials that would have been required to make them.

The team also noted an unusual “coffee ring effect“in the red ink marks. The coffee ring effect occurs when a single liquid evaporates and the solids that had been dissolved in the liquid, such as coffee grounds, form a revealing ring. This happens because evaporation occurs faster at the edge than at the center. Any remaining liquid flows to the edge to fill in the gaps, carrying those solids with it. In this case, the red ocher pigment is present in coarse particles, which remained in place while the more finely ground soluble lead compounds diffused into the papyrus cells to create a ring effect, causing it to appear (at l ‘micrometric scale) as if the letters had been sketched.

“Advanced synchrotron-based microanalyses have provided us with invaluable knowledge about the preparation and composition of red and black inks in ancient Egypt and Rome 2,000 years ago,” says Christiansen. “And our results are supported by contemporary evidence of ink production facilities in ancient Egypt from a magical spell inscribed on a Greek alchemical papyrus, which dates to the third century AD. It refers to a red ink that was prepared inside a workshop.This papyrus was found in Thebes, and it may well have belonged to a priestly library like the papyri studied here, thus providing insight into some of the chemical arts applied by the Egyptian priests of the late Roman period. “

DOI: PNAS, 2020. 10.1073 / pnas.2004534117 (About DOIs).

This story originally appeared on Ars Technica.


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