// ARS TECHNICA — MONDO
Scientists unlock secrets of ancient Egyptian materials with proteomics
Analysis revealed seed proteins from sesame and moringa, which held religious and symbolic significance.
The precise composition of ancient Egyptian paints, binders, adhesives, and similar materials used to make artifacts is largely unknown, in part because a full analysis would require taking samples that would damage those valuable artifacts. The development of cutting-edge, non-destructive techniques has been helping to unlock those secrets, aiding conservation efforts.
Most recently, researchers have used mass spectrometry-based proteomics to analyze the glues and adhesives in a broad set of Egyptian artifacts, according to a new paper published in the journal Science Advances. They found plenty of expected sources, such as animal collagens and egg proteins, but also plant proteins, specifically from sesame and drumstick tree (moringa) cereals.
As previously reported, the ancient Egyptians had a highly formalized (and easily recognizable) painting style, and there has been considerable interest in gaining insights into the specific pigments and painting techniques employed. Common pigments included hematite and realgar for red; goethite and orpiment for yellow; Egyptian blue; Egyptian green; carbon-based black; and calcite, gypsum, anhydrite, and huntite for white. (Just last year, Washington State University researchers were able to re-create Egyptian blue by mixing together silicon dioxide, copper, calcium, and sodium carbonate in varying proportions and heating them at very high temperatures akin to those of ancient kilns.)
Many pigments available to ancient Egyptian artists have elemental markers detectable by X-ray fluorescence imaging. Macro-XRF imaging in particular has previously been used (in combination with hyperspectral imaging) to study a Greco-Roman painted funerary portrait from the second century CE, as well as to determine the remnants of color on marble at Delphi in Greece. In 2023, scientists used a portable MA-XRF imaging device to study ancient Egyptian paintings, part of a broader project investigating tomb chapels in the Theban Necropolis.
Mass spectrometry-based proteomics is a relative newcomer to the field and is capable of providing a thorough and very detailed characterization of any protein residues present in a given sample, as well as any accumulated damage. The technique is so sensitive that less sample material is needed compared to other methods. And unlike, say, gas chromatography-mass spectrometry, it’s also capable of characterizing all proteins present in a sample (regardless of the complexity of the mixture), rather than being narrowly targeted to predefined proteins.
In 2023, scientists used this approach to discover that beer byproducts were popular canvas primers for artists of the Danish Golden Age. And earlier this year, we reported on the identification of proteins from fingerprints of Renaissance people rifling through the pages of medical manuals, revealing more about how people constructed hands-on knowledge in that period.
For this latest study, the authors took tiny samples from several Egyptian artifacts housed in different collections in Sweden, the UK, and Denmark, dating between 1425 BCE to 400 CE. These included painted wooden coffins, wall painting fragments from a tomb, painted plaster used to make a mummy bust, and painted limestone architectural elements. In addition to those samples, the team also analyzed blank negative control samples and examined the chemical damage to all detected proteins in order to exclude the possibility of laboratory contamination from the final results.
The results confirmed that ancient Egyptians frequently used cow glue, as well as collagens derived from sheep, goats, horses, donkeys, and antelope. Those materials were most likely prepared by boiling animal skin and connective tissue. These weren’t just found in adhesive samples, but also in samples of paint and ground layers, suggesting that Egyptians chose their materials bas