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Feather in Shibuichi and Shakudo

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Part of a recent sculpture, I chose to make this feather in shibuichi (40%silver/60% copper) and shakudo (4% gold/ 96% copper). Both of these alloys were made for me by Phillip Baldwin of Shining Wave Metals. I chose this alloy of shibuichi for patina reasons that will be explained later. The inlaid shakudo quill makes a striking contrast.

I modeled the feather from one from Jean's collection. Sadly I don't know what bird it's from. The first step was to draw the outline on the shibuichi. The outline went though some changes as the piece developed. The actual feather is seen in the two photos below being used as a drawing guide on the shibuchi.

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The next step was to saw the outline with a jeweler's saw, leaving some extra material for changing the design as things progressed.

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After filing the edges thinner and carving a center depression the quill was sawn from shakudo sheet. This needed then to be carefully filed to a taper.

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After the quill was shaped a channel was engraved to accept it, and the edge of this channel was raised with a punch along both sides. This raised bur will later be punched back down against the quill inlay to close any gap and to hold it in place.

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Because the ends of the quill inlay are somewhat vulnerable to snagging I silver-soldered both ends of the inlay to insure that it wouldn't be pulled up and out.

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The raised bur was then punched with a special footed punch to secure the inlaid quill and everything finished to 600 g with sandpaper.

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Guidelines for the engraved feathering were drawn then engraved at intervals to help in consistency.

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I proceeded to engrave by continually splitting each interval in half, and adding some anomalies to suggest a somewhat distressed, weathered look.

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When satisfied with the engraving the feather was polished with 800g silicon/carbide in a slurry with horsehair brush.

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One of the more challenging things to accomplish using Japanese non-ferrous alloys is achieving a gradual fade from one color to another. Inlaying separate distinct alloys for color differential, while very useful, leaves sharp boundaries. With shibuichi one way of achieving a fade is to enrich the surface with silver by repeated oxidizing and pickling(similar to depletion gilding), and then polish selected areas back to the original alloy. This can create a very pleasing, gradual fade from the lighter enriched area to the darker original alloy area.

The silver enriching works because when the surface is oxidized by heat and oxygen, it is mostly the copper that is oxidized, not so much the silver. When this layer of copper-oxides is removed by pickling in a weak acid it therefore increases the surface silver content and reduces the copper. This can be repeated to increase the silver layer to a degree. At a point the silver enrichment inhibits further copper oxides from forming.

The silver layer is thin enough so that by selective polishing the original alloy layer below can be revealed as one wants.

I have found this technique to work best with a fairly silver-rich alloy, say 40% silver/60% copper, as with this feather. This alloy has enough silver to enrich fairly easily with two or three cycles of oxidizing and pickling.

Enriching is done generally after a nearly final polish. I also needed to protect the shakudo quill from oxidizing by coating it and the nearby shibuichi with flux during the oxidation heating. This photo shows the flux coating and oxides resulting from heating(dull red in dark room).

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Showing the enriched areas after the oxides were pickled away. Much more silver apparent away from the quill and flux protected area. I subsequently engraved and polished some of the enriched area back to enhance the gradual fade from light to dark. I had purposely left the final engraving close to the quill unfinished as I knew I would be going over it again.

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After the final engraving and polishing the feather was patinated using the traditional niage process as found elsewhere in my tutorials.

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The actual length is 38mm (1.5 inches)

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