Han violet (pigment)

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Han violet or Han purple , Chinese violet or Chinese purple is a modern term for a synthetic violet barium copper silicate , which has been identified as a pigment in China since the War of the States . The original name of the pigment is unknown.

Han violet is the only violet pigment of antiquity. It is also a pre-industrial inorganic synthetic pigment.

history

Wall painting in a tomb in Zhucun 朱村, Henan Province ; Painted with Han Blue and Han Purple pigments, around 220 BC. Chr.

Han violet is a pigment that has been identified in China since the Warring States Period (475 BC – 221 BC). It peaked in use in the Han Dynasty (206 BC – 220 AD), when most evidence of Han violet could be made. This is where the name Han violet comes from. Most of the evidence is found in the painting of ceramics, the most famous example being the color version of the terracotta army of Qin Shihuangdi , the first emperor of China . The terms Chinese violet and Chinese purple also used refer to the fact that pigment was used even before the Han dynasty. After the end of the Han dynasty, the once popular pigment suddenly disappears.

Han-Violett was only rediscovered in 1992 on an object that can be assigned temporally and geographically.

Manufacturing

Han violet is a violet barium copper silicate that does not occur naturally. It was invented by Chinese alchemists through chemical experimentation .

No contemporary sources exist for the manufacture of the pigment, so the exact manufacturing process is not known. In any case, it is very complex and difficult. It also requires technical knowledge and experience.

The most likely method of manufacture requires a barium mineral such as barite , a copper mineral such as malachite or azurite, and sand containing quartz. In addition, Han Violet often also contains lead , presumably as a flux to lower the manufacturing temperature. These raw materials are crushed, mixed and heated in the oven at a constant temperature. The Han violet appears after 10 to 24 hours. If this is heated further, you get Han blue . The Han violet was then presumably traded in octagonal pigment sticks, which were then pulverized before use.

The production of the Han violet is therefore very similar to the production of the Egyptian blue . A widespread theory therefore says that the technology for making Egyptian blue came to China via the Silk Road , where it led to the invention of Han blue and Han violet. However, this is unlikely, as no Egyptian blue has yet been detected in China. In addition, long-distance trade via the Silk Road did not come into being until the 2nd century BC. BC and thus long after the invention of Han blue to its peak. Furthermore, there is no reason why the Chinese should have replaced the cheaper components of Egyptian blue with the more expensive components of Han blue and Han violet.

Composition and structure

Han violet is a barium copper silicate with the formula BaCuSi 2 O 6 . There are three other stable phases of barium copper silicate known: Han blue and two other unnamed compounds.

Han violet consists mainly of plate-shaped angular particles or their fragments. These are mostly octagonal, but also square or, more rarely, hexagonal. Their size is usually 6–32 μ , but can rarely reach up to 45 μ. Han violet usually also contains blue particles. However, these are stronger and darker than those of the related Han blue.

Modern products differ from antique ones in their particle size and shape. In addition, they show a strong pleochroism , which is not found in the ancient pigment.

Han violet fades when exposed to acid.

literature

  • H. Anthamatten, C. Cataneo, G. Kremer: Color Pigments - Dyes - Color Stories. Winterthur Trade Museum. Alataverlag, Elsau 2010, ISBN 978-3-033-02349-9 , p. 34.
  • N. Eastaugh, V. Walsh, T. Chaplin, R. Siddall: The Pigments Compendium - A Dictionary of Historical Pigments. Elsevier Butterworth - Heinemann, Oxford 2004, ISBN 0-7506-5749-9 .
  • H. Berke, HG Wiedemann: The Cemistry and Fabrication of the Anthropogenic Pigments Chinese Blue and Purple in Ancient China. In: East Asian Science Technology and Medicine. Vol. 17, Tübingen 2000, pp. 94-119.
  • H. Berke: The Invention of Purple Pigments in Ancient Times. In: Chemical Society Reviews. Volume 36, No. 1, The Royal Society of Chemistry. London 2007, pp. 15-30.
  • F. Delamare: Blue Pigments - 5000 Years of Art and Industry . Archetype Publications, London 2013, ISBN 978-1-904982-37-1 .
  • EW FitzHugh, LA Zycherman: An Early Man-Made Blue Pigment from China - Barium Copper Silicate. In: Studies in Conservation. Vol. 28, No. 1, London February 1983, pp. 15-23.
  • EW FitzHugh, LA Zycherman: A Purple Barium Copper Silicate from Early China. In: Studies in Conservation. Vol. 37, IIC, London 1992, pp. 145-154.