Aside from the basic 25% silver to 75% copper mix, combinations as divergent as 5% silver to 95% copper are also marketed as "shibuichi". A wide range of colours can be achieved using the whole range of alloy compositions, even above 50% silver, e.g. 90% copper and 10% silver for a dark grey and down to 70% copper and 30% silver for lighter greys.
|name (JA)||Ag : Cu, +Au||Note mentioned colors are after patination|
|Shibuichi||25 : 75||Dark grey, has a trace of gold|
|60 : 40, +1||Shiro is White in JA
lighter grey, harder, lower melting temp
|40 : 60, +1||Ue is Upper in JA
|30 : 70, +1||Nami is Regular in JA
lighter than Shibuichi
|23 : 77, +1||Darker than Shibuichi|
Kuro is black in Japanese. Kuro-Shibuichi is different from others in the table. Kuro-Shibuichi is mixture of Shibuichi (40%) and "Shakudō (60%) with additional 1% of gold. The proportion is roughly 9.9% silver, 87.3% copper, and 2.8% gold. Kuro-Shibuich will develop black patina which is different from the black patina of Shakudo.
It is a common misconception that both copper and silver oxides form, but in fact a detailed study has shown that only copper oxides are formed on the copper rich regions of the material's microstructure, while the silver rich regions are left largely untouched.["citation needed]
The first official mention of the material is from the early 18th century, in documents from the State Mint, though it is believed to have existed before that. For most of its history, shibuichi was mostly used to ornament various fittings for "katana until the "Meiji reforms, when most swordmakers began to make purely decorative objects instead. The material is often used in "mokume-gane combinations. Similar alloys have been used elsewhere but the use of shibuichi to achieve different colored patinas appears to have remained nearly unknown outside Japan, until recent interest from artisans in the West.
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