Han blue
Composition and Properties of Han Blue
Han blue is a synthetic barium copper silicate with the chemical formula BaCuSi2O6. It is similar in composition, properties, and color to Egyptian blue (CaCuSi4O10). Recently, it has been discovered that it occurs naturally as the rare mineral Effenbergerite.The stability of this pigment is high and it is also resistant to high temperatures and it is lightfast as well.
Names
Chinese blueNamed after the Han Dynasty of Chinese emperors, the second imperial dynasty (206 B.C. until 220 AD).
Preparation of Han Blue
The pigment can be prepared by heating a mixture of either witherite (BaCO3) or barite (BaSO4), malachite (Cu2(CO3)(OH)2) and quartz (SiO2) in the presence of a lead salt (carbonate or oxide) to about 1000 °C. The lead salts serve as a catalyst for the chemical reaction and also facilitate the melting of the raw materials.
History of Use
Han blue was used in ancient and imperial China from the Western Zhou period (1045–771 BC) until the end of the Han dynasty (circa 220 AD).References(1) Berke, H. Chemistry in Ancient Times: The Development of Blue and Purple Pigments. Angewandte Chemie International Edition 41/14, 2483–2487, 2002.(2) Berke, Heinz (2007). “The Invention of Blue and Purple Pigments in Ancient Times”. ChemInform. 38 (19). doi:10.1002/chin.200719227Examples of use
