Mechanism of traditional Bogolan dyeing technique with clay on cotton fabric

Bogolan is a traditional dyeing technique, deeply rooted in Mali. It uses local clays from Niger River region and a leave extract from Nʹgalama trees (Anogeissus leiocarpa). The clay contains a significant amount of iron (hydr)oxides, mainly akaganeite. It reacts with Nʹgalama coating onto cotton to form black or brown colors. UV/Vis and IR spectroscopy indicated very similar behavior of Nʹgalama leaves extract and carboxylic aromatic acids, mainly ellagic or gallic acids, which form dark colored complexes with iron. Since iron (hydr)oxides are coated on clay mineral particles, they contribute to the fixation of the clay mineral particles and also cause the dark color. X-ray diffraction of oriented tissue and SEM observations confirmed the presence of clay particles attached on the fiber surface.