Kuromidō
Kuromidō ( Japanese 黒 味 銅 , Kuromidō ; often also written Kuromi-do) is a traditional Japanese metal alloy that has been used since the 12th century for the color design of decorations on swords or jewelry. It has a dark brown to black color and consists of 99% copper and 1% metallic arsenic . Like many copper alloys , Kuromidō was created as a substitute for precious metals because they were lacking and they caused high costs, both due to the low occurrence of precious metals on the Japanese islands.
Because of its arsenic content, Kuromidō must be processed under special safety precautions as it is toxic . In addition, the goldsmith / silversmith must weigh in advance to what extent the patinated metals are skin-friendly.
Even today it is still used in the mokume-gane forging technique, albeit very rarely. In Germany, the Mokume Gane artists have completely renounced the use of Kuromidō since 2005.