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Article © MAIL User: Drax


Target metals: Copper, Brass, Bronze
Target colors: Red-brown

Rokusho is a Japanese concoction for adding patinas on metals. This article will only cover the effects on copper alloys, which it turns a red-brown. However, rokusho can also be used on 'shaku-do', an alloy of copper and gold, and this will turn it purple; it can also be used on 'shibu-ichi', a silver-pink alloy of copper and silver that will turn it a light gray. Some of the information here comes from The Complete Metalsmith by Tim McCreight, and other parts come from various sources on the web.

Outside of Japan, most of us don't have access to sources of rokusho, so we have to make our own. Various approximations for this exist, and here is one of those recipes:

3 parts copper acetate
1 part sodium hydroxide (lye)
1 parts calcium carbonate (chalk)

Add these three solids to a solution of water (around 250mLs) and stir. Only the lye will dissolve, the others are pretty insoluble in water; the solid will be a light blue. Let this stand for 1 week (it may darken over this time). After 1 week, pour off the water and collect the wet solid left over.

To make the mixture that will color the copper items, mix:

5g rokusho (see above)
5g copper sulfate
1L water

Method of use: Bring this mixture to a boil and submerge the piece to color in the boiling water for at least an hour. The Japanese traditionally applied a mix of chopped daikon radish to the piece before submerging; this is theorized to help prevent uneven coloring, but I did not attempt this.

My first attempts at this left only a slightly darker metal on both the brass and the bronze. I'll have to keep trying at this one.

The picture shows a bronze ring on the left, a brass ring on the right, and their "rokusho-ed" versions below.

Image: dab_cb_rokusho1.jpg

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