Definition
Black catechu, derived from *Acacia catechu*, is a resinous extract used as a dye and astringent. It's created by boiling the wood of the acacia tree and then evaporating the water, leaving behind a dark, tarry substance. This substance is rich in tannins and has been used for centuries in tanning leather and dyeing fabrics. Consider it a natural multi-tool for crafts and medicine. It's a historical example of resourcefulness.