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 N'galama trees (Anogeissus leiocarpa). The clay contains a significant amount of iron (hydr)oxides, mainly akaganeite. It reacts with N'galama coating onto cotton to form black or brown colors. UV/Vis and IR spectroscopy indicated very similar behavior of N'galama 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.

Research Highlights
► Bogolan is a traditional dyeing technique of cotton tissue from Mali.
► It uses a leave extract from Anogeissus leiocarpa trees coating the cotton tissue.
► Clays with a high amount of iron (hydr)oxides are from the Niger River region.
► The dark color is due to the complexation of iron by tannins from the leave extract.
► The same process ensure the fixation of the clay mineral particles on cotton fibers.