vat dye: a water-insoluble dye that is applied by reducing the dye to an alkaline form, applying the dye, then regenerating the insoluble dye by oxidation in the material; used for dyeing cotton
material: the tangible substance that goes into the makeup of a physical object
alkali metal: any of the monovalent metals of group I of the periodic table (lithium or sodium or potassium or rubidium or cesium or francium)