Cobalt blue
Cobalt blue in impure forms had long been used in Chinese porcelain, but it was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard in 1802. Commercial production began in France in 1807. The first recorded use of "cobalt blue" as a color name in English was in 1777. The leading world manufacturer of cobalt blue in the 19th century was Benjamin Wegner's Norwegian company Blaafarveværket ("blue colour works" in Dano-Norwegian). Germany was also famous for production, especially the blue colour works ("Blaufarbenwerke") in the Ore Mountains of Saxony.
Monochrome painting
The next exhibition, 'Proposte Monochrome, Epoca Blu' (Proposition Monochrome; Blue Epoch) at the Gallery Apollinaire, Milan, (January 1957), featured 11 identical blue canvases, using ultramarine pigment suspended in a synthetic resin 'Rhodopas'. Discovered with the help of Edouard Adam, a Parisian paint dealer, the effect was to retain the brilliance of the pigment which tended to become dull when suspended in linseed oil. Klein later patented this recipe to maintain the "authenticity of the pure idea." This colour, reminiscent of the lapis lazuli used to paint the Madonna's robes in medieval paintings, was to become famous as 'International Klein Blue' (IKB). The paintings were attached to poles placed 20 cm away from the walls to increase their spatial ambiguities.