Chemical characterization and origin of dyes used in the manufacture of Beninese cultural heritage objects

Abstract

Six objects of Beninese cultural heritage provided by African and Confluences museums of Lyon (France) were the focus of this study. The characterization of colored compounds was achieved using: microchemical tests, Fourier transform infrared spectroscopy and liquid chromatography coupled to a photodiode array detector. The main results reflect the presence of organic compounds like indigotin, 2‐hydroxynaphthoquinone, and mineral ions such as Al3+, S2−, Na+, and Fe3+. Dyes were identified from Philenoptera cyanescens (Yoruba indigo) and Lawsonia inermis L. (henna); pigments were identified as laundry blue, Prussian blue, and iron oxides. All of these data therefore make possible the conservation and the restoration of these objects while maintaining their visual and functional integrity.