The researchers measured three embalming-residue samples from two Egyptian crocodile skulls using infrared spectroscopy, ultrahigh-resolution FTICR mass spectrometry, and GC-MS. FTICR MS assigned 3,169–6,944 molecular formulae and revealed oxidized pine-resin fingerprints; GC-MS structurally identified 109 compounds overall and additionally detected bitumen biomarkers. Combining the methods supported pine resin, beeswax, fats/oils and bitumen in the residues. Formula matches alone are tentative identifications, and the resin changes reflect heating and/or ageing rather than a uniquely determin

Archaeochemistry / Egyptian crocodile mummies

A dark crust on an ancient crocodile skull holds thousands of molecular clues. Read the ingredients. Follow their transformation.

AI-generated conceptual illustration. The downward H/C arrows indicate hydrogen loss; the interactive plot below uses H/C increasing upward.

Musée des Confluences, Lyon, France From a crocodile-mummy collection radiocarbon dated to 400 BCE–200 CE .

What is hidden in the residue?

A biomarker is a molecule whose chemical features point back to a material. Different instruments uncover different kinds of clues. Switch the method to see the evidence change.

Analytical bench / read the evidence

Formula clues: resin, wax and fats

Precisely measured molecular masses yield thousands of formulas. Matching these formulas to known biomarkers suggests the ingredients.

The strongest signal in sample 1840 b matches an oxidized resin molecule: 7-oxodehydroabietic acid. Fragmentation of another oxidized resin ion supports the resin assignment.

1840 b · 3,169 assigned formulae. Mostly embalming material, with little bone contribution.

Share of assigned formulae, not ingredient proportions. CHO: carbon, hydrogen, oxygen; N: nitrogen; S: sulfur.

Choose a family to read its molecular clues. Nodes and motion are schematic; the formula counts and class shares are measured.

A fingerprint and an identification

FTICR MS assigns molecular formulas with simpler sample preparation and reaches higher-mass compounds. A formula lists atoms; it does not uniquely identify a structure. GC-MS separates compounds and checks characteristic fragments, identifying 109 compounds across the study.

The sample carries more than balm

Sample 1840 a has a much larger share of nitrogen-bearing formulas, consistent with degraded bone proteins. Infrared spectroscopy also detects bone phosphate. The collection is largely from Esna, Egypt; some specimens have unknown provenance.

The resin has a second story.

An ingredient changes as it is heated and ages. Comparing the ancient balm with fresh pine resin reveals a fingerprint richer in oxidized molecules. Follow the atom changes to see how the clues move.

Van Krevelen diagram / ratios from molecular formulas

Abietic acid

O/C 0.10 · H/C 1.50. This formula matches the strongest ion signal in the fresh pine resin. Move through the pathway to inspect chemical change.

Measured contrast / fresh & ancient

In the ancient sample, 7-oxodehydroabietic acid gives the strongest signal. The changed pattern is consistent with heating and/or ageing .

Values from supplementary Table S1, normalized to the strongest ion. Ion intensity is not an ingredient percentage. Tap a signal to inspect its formula.

Materials hold chemical memories.

Combining methods brings two histories into view: the materials people used, and the chemical changes those materials underwent. Thousands of formula assignments can provide a rapid fingerprint of a residue; targeted measurements connect that fingerprint to recognizable ingredients.

This approach can help researchers read organic remains in cultural heritage and assess their state of chemical degradation.

Unravelling the Egyptian embalming materials by a multi-method approach comprising high-resolution mass spectrometry

Jasmine Hertzog, Hitomi Fujii, Rugilė Žostautaitė, Agnès Lattuati-Derieux, Pascale Richardin, Vincent Carré, Frédéric Aubriet and Philippe Schmitt-Kopplin. Journal of Archaeological Science: Reports 48, 103861 (2023). DOI: 10.1016/j.jasrep.2023.103861.

Visual & data credits. Original interactive diagrams based on the paper’s Figures 2–3 and supplementary Tables S1–S3 and Figures S4–S6. Formula counts, class shares, formulas, ion masses and selected relative intensities are reported measurements. Constellation positions and motion are schematic.

Illustration. AI-generated conceptual illustration. The accepted manuscript is © 2023, published by Elsevier under the Elsevier user license. Original paper figures are not reproduced.

AI-generated conceptual illustration. Downward H/C arrows indicate hydrogen loss; H/C increases upward in the interactive scientific plot.