Former research on ancient Egyptian mummies studied the composition of the black coating used in embalming and defined the "vanadyl porphyrins" as a basic compound of it.
A recent French study conducted by Paris Sciences et Lettres University, Lille University, and the Louvre Museum managed to determine two types of this compound found in the Dead Sea tar, and also spotted in the black coating used in mummies.
During a recent study published in the Journal of Magnetic Resonance Imaging (JMRI), the researchers used Electron Nuclear Double Resonance (ENDOR) and Hyperfine Sublevel CORrelation spectroscopy (HYSCORE) to examine the black coating detected in Louvre-based human and animal mummies dating to different eras between the Late Period to the Greco-Roman period.
The researchers found that the black coating consists in a complex and heterogeneous mixtures of conifer resins, wax, fat and oil with variable amounts of bitumen. Natural bitumen always contains traces of vanadyl porphyrin complexes.
Four types of vanadyl porphyrin complexes were identified from the analysis. Three types (referred to as VO-P1, VO-P2 and VO-P3) are present in natural bitumen from the Dead Sea, among which VO-P1 and VO-P2 are also present in black coatings of mummies, they explained.
According to the researchers, the absence of VO-P3 in mummies, which is replaced by another complex VO-P4, may be due to its transformation during preparation of the black matter for embalming. Analysis shows that bitumen and other natural substances are intimately mixed in these black coatings, with aggregate sizes of bitumen increasing with the bitumen content, but not exceeding a few nanometers.