Rokusho

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Rokusho is a traditional Japanese compound for inducing patination in decorative non-ferrous metals, especially several alloys which are nearly unknown outside Japan. Shakudo becomes dark blue-violet, shibuichi misty aqua, and kuromido dark coppery black; rokusho was generally used to patinate all types of mokume-gane as well. Although other patination agents can be used on these metals, some artisans prefer to maintain tradition despite the unavailability of premixed rokusho outside Japan.

Several different formulas have been proposed to replicate the commercial product:

• In a container made of glass, porcelain, or copper, dissolve 6g copper acetate, 2g calcium carbonate, and 2g sodium hydroxide in 150ml water. After a week, siphon or decant the clear liquid from the top; just before use, add another 2g copper sulfate.

• Dissolve 4g copper acetate, 1g copper nitrate, 1g cupric chloride, and 4g copper sulfate in 1L distilled water.

• Dissolve 60g copper acetate and 60g copper sulfate in a 2L solution of white vinegar diluted 5-12% with water.

Application of Rokusho:

1. Finish all forming, soldering, etc. Coloring is the last process in finishing a piece of metal work.

2. Remove all firescale before the piece is to be colored. Boil the piece in water to remove any surface grease and oils if it has been buffed, or use a commercially available cleaner. Fantastik is a good grease remover. Clean in a strong pickle solution.

3. Construct a scaffold for suspending the piece with a copper-wire harness in a pot of boiling rokusho. The piece may need to be raised and removed several times.

4. Bring the rokusho liquid to a boil in a large copper pan or Corning ware. Do not use stainless, aluminum, steel, brass, bronze, or enameled steel. Work under good ventilation.

5. At some point, the piece should be coated with finely-grated or blenderized daikon, although different sets of instructions disagree whether this should take place before or after the rokusho bath. If beforehand, then apply the daikon by itself; if afterward, dilute the daikon with five parts water and use the resulting slurry as a wash.

6. To the boiling rokusho solution, add the wire-harnessed piece and keep it in motion without allowing it to rest on the bottom. After ten minutes, remove it and rinse as indicated in the next step. Do not allow the surface to dry out, which will cause spotting.

7. If daikon was applied before dipping, submerge the piece in water to wash all particulates from its surface. Otherwise, apply the diluted daikon slurry at this stage, rubbing it gently into the surface with gloves, followed by a similar rub with baking soda before rinsing the surface clean with water.

8. Repeat steps 5-7 several times until the coloration is achieved. It usually takes 30 minutes to one hour.

9. After coloration, coat with Renaissance Wax and buff with a soft cloth. Lacquer can also be used as a protective coating.