In the beginning of the 20th century, commercially available blue pigments consisted mainly of Ultramarine blue, Prussian blue, Indigo derivatives and some azo derivatives. Unfortunately none of these had the desired qualities demanded by the colour industry. Most of these pigments had poor chemical resistance, unsatisfactory acid and/or alkali resistance, insufficient light fastness and poor sublimation fastness. The colour chemists in those days were in need of a cheap and durable pigment that could fill the bluish region of the colour space. The discovery of copper phthalocyanine blue provided them with a satisfactory solution to their problems. Phthalocyanine pigments proved to be outstanding organic pigments because of their incredible resistance to chemical attack, good fastness to heat and light, combined with brightness and cleanliness of shade - all the qualities sought by the colour industry.