Chemists have teamed up with conservationists at the Detroit Institute of the Arts and uncovered the composition of an unusual ceremonial mask in a story of discovery that brings together the ritual dances of the Banama people of Mali and the latest techniques in mass spectrometry.
Striking and somewhat terrifying, the Komo mask is a Smörgåsbord of strange materials, including horns and quills, fur and feathers – based upon skulls and wrapped with cloths. But that’s not all; encrusted on this mask is a mud-like material of unknown origin. Given that the Banama people were known to use blood in their rituals to symbolize power, museum specialists naturally asked – could the mask’s encrustation contain blood?
To answer this question, the chemists initially bombarded a sample from the mask with X-rays and found an abundance of iron, which was suggestive of blood. Next, using mass spectrometry, the chemists directly looked for the major protein found in blood - haemoglobin. Mass spectrometry works by first, destroying and breaking down the sample into tiny pieces of molecules or atoms. These make charged ions, which can be separated out depending on their size and charge. Every single protein has a unique signature; so mass spectrometry stands as a very powerful method in identifying unknown samples.
As the mask was probably 100 to 200 years old, it was unknown how the mass spectrometry signature of haemoglobin would change over time. Before destroying the precious sample from the mask the mass spectrometry approach had to be tested. The chemists were able to draw on another resource at the Eastern Michigan University; a long-term study of the binding agents used in rock paintings. Slides with drops of blood, bone marrow and egg made ten years ago, were stored either in the lab, outside and covered, or left outside completely exposed to the weather. On these samples, mass spectrometry revealed a distinct peak in the blood samples, which was missing from the other samples. This peak appeared even in blood samples that had been left unprotected outdoors.
Satisfied that their method could detect ‘old’ blood, the chemists tested a small flake of material from the Komo mask. The test only took two minutes to run and the result was very clear – the covering of the mask does indeed contain blood. By working together on this case museum specialists and chemists have shown how contemporary chemistry can be used to give new insight into cultural rituals that are centuries old.
Fraser D, DeRoo CS, Cody RB, Armitage RA. Analyst. 2013 Aug 21;138(16):4470-4. doi: 10.1039/c3an00633f. Characterization of blood in an encrustation on an African mask: spectroscopic and direct analysis in real time mass spectrometric identification of haem.