Hello everyone.
I decided to experiment with a Japanese copper alloy called Shibuichi. They mix I used was 75% copper, 25% silver. Over time it tarnished, which is to be expected due to its copper content, however the tarnish turned this really ugly gray. I tried burnishing with a brass brush and it turned shiny but didn’t get rid of the colour. Is this tarnish inevitable? What can I do to prevent it apart from laquers?
Shibuichi and shakudo are Japanese alloys which are meant to be colored via chemical processes. Leaving them in their polished form negates the point of the alloys.
Shibuichi can be colored in various shades of grays and blues. Shakudo is most often colored to a deep blue or blue/black similar to blued steel.
Many formulas for patination of these alloys have been published.
If you go to a Museum website and do a search for shibuichi and shakudo you will find many items that show the versatility of these alloys.
As an example, here is a tsuba (sword guard) made with shibuichi, shakudo, gold, silver and copper. The body of the tsuba is shibuichi which has been patinated to a rather lush blue.
https://www.metmuseum.org/art/collection/search/30053
Oh I see. I knew it was usually patinated but I didn’t think it was a sort of requirement for the alloy. That would explain the recent piece I made turning blue… it looks quite nice actually, I will experiment with patinas for Shibuichi. Thanks 
