special type of pigment consisting of an organic soluble colouring matter combined more or less definitely with an inorganic base or carrier, an organic pigment produced by the interaction of an oil-soluble organic dye, a precipitant, and an absorptive inorganic substrate. Insoluble in water., pigments formed by the interaction of dyestuffs and 'bases' or 'carriers', which are generally metallic salts, oxides or hydroxides. The formation of insoluble lakes in fibres, which are being dyed, is known as mordanting, the hydroxides of aluminium, chromium and iron generally being employed as mordants.