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.
The Blue Room (Picasso)
The painting was investigated by several scientific methods in 2017. The investigation revealed the hidden portrait described below and the identity of the pigments used in both paintings. Picasso employed a wide palette of vivid pigments such as vermilion, viridian, chrome yellow, and cadmium yellow. He used predominantly Prussian blue for the blue areas.