A range of dyestuffs, which are formulated within the fibre by combining two components. The production of an insoluble azo compound on a substrate by interaction of a diazotized amine (azoic diazo component) and a coupling component (azoic coupling component). Also known as ice colours because of the necessity of lowering the temperature during processing. Traditionally used in the production of African prints, they have been superseded by other dyestuffs and become uneconomic, their use having declined.