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.
Blue
In Egypt blue was associated with the sky and with divinity. The Egyptian god Amun could make his skin blue so that he could fly, invisible, across the sky. Blue could also protect against evil; many people around the Mediterranean still wear a blue amulet, representing the eye of God, to protect them from misfortune. Blue glass was manufactured in Mesopotamia and Egypt as early as 2500 BC, using the same copper ingredients as Egyptian blue pigment. They also added cobalt, which produced a deeper blue, the same blue produced in the Middle Ages in the stained glass windows of the cathedrals of Saint-Denis and Chartres. The Ishtar Gate of ancient Babylon (604–562 BC) was decorated with deep blue glazed bricks used as a background for pictures of lions, dragons and aurochs.