A team of researchers from the European Synchrotron Radiation Facility (ESRF) in Grenoble, France and the University of Copenhagen, Denmark has managed to gain new insights into the nature of the inks that were used in ancient Egyptian papyri dating back to 100-200 AD, phys.org reports.
According to the media outlet, the scientists employed ESRF's X-rays in order to study the red and black ink in papyri from "the only large-scale institutional library known to have survived from ancient Egypt": the Tebtunis temple library.
"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," said Marine Cotte, scientist at the ESRF and co-corresponding author of the paper.
As Cotte explained, one of the discoveries they made was that lead was actually 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".
"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," Thomas Christiansen, Egyptologist from the University of Copenhagen and co-corresponding author, remarked.
The media outlet also notes that the recipe of the ink can apparently be related to "pain practices" that were developed during the Renaissance, centuries after the creation of the papyri in question.
"In the XV Century, when artists rediscovered oil painting in Europe, the challenge was to dry the oil in a reasonable amount of time," Cotte said. "Painters realised that some lead compounds could be used as efficient dryers."
And while scientists established that the red colour in the ink was produced by ochre, that pigment is "present as coarse particles" whereas the lead compounds are "diffused into papyrus cells, at the micrometer scale", thus producing "a coffee-ring effect around the iron particles, as if the letters were outlined".
"We think that lead must have been present in a finely ground and maybe in a soluble state and that when applied, big particles stayed in place, whilst the smaller ones 'diffused' around them," Cotte explained.