Mokume-gane

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Mokume-gane ring
Mokume-gane ring

Mokume is a mixed-metal laminate with distinctive layered patterns. Literally translating as "wood eye (i.e., burl) metal", the name was borrowed from one type of pattern welding used to forge katana blades. As another recent variation, has also been used to describe similarly-patterned laminations among different colors of polymer art clay.

First made in 17th-century Japan, the mixed-metal was used only for sword fittings until the Meiji era, when the decline of the katana industry forced artisans to create purely decorative items instead. The inventor, Denbei Shoami, initially called his product "guri bori" for its simplest form's resemblance to "guri", a type of carved lacquerwork with alternating layers of red and black. Other historical names for it were kasumi-uchi (cloud metal), itame-gaine (wood-grain metal), and yosefuki. (Pijanowski & Pijanowski, 2001)

The traditional components were relatively soft metallic elements and alloys - copper, silver, shakudo, shibuichi, and kuromido - which would form liquid phase diffusion bonds with one another without completely melting. After the original metal sheets were stacked and carefully heated, the solid billet of simple stripes could be hammered flat and folded to increase the pattern's complexity.

The modernized process typically uses a hydraulic press, which can apply far more force than hand-forging and induce lower temperature solid-state diffusion between the interleaved layers, allowing the inclusion of many nontraditional components such as titanium, platinum, iron, bronze, brass, nickel silver, and various colors of karat gold including yellow, white, sage, and rose hues as well as sterling silver. (Binnion & Chaix, 2002)

Contents

[edit] A semi-traditional small-batch billet making method

The metal surfaces must be slightly roughened but absolutely clean without any dust, dirt, grease, or other contaminants. Prepare two steel torque plates by painting their inner surfaces with yellow ochre or Scalex to prevent them from adhering to the billet. Handling the clean metal sheets only by their edges, stack them together between the torque plates, which should be sandwiched tight around them with corner bolts, clamps, or wire.

Wrap the torqued sandwich inside a thin steel sheet (no thicker than 28 gauge or 0.40 mm) or a stainless steel foil bag, also enclosing some charcoal to get rid of any oxygen. Put the entire thing in a preheated furnace and bake for three to twelve hours, keeping the temperature 50 to 100 degrees Fahrenheit (25 to 55 degrees Celsius) below the lowest melting point in the stack.

When ready, remove the billet from the furnace, steel wrap, and torque plates. Strike while the billet is hot. A billet with silver in it must be forged at 'black heat', or when the billet isn't glowing red. Cool the forged billet and saw about 1/8 to 1/4 of an inch (about 5 mm) off the edges of the billet to prevent stress-cracking. Reheat the billet with a torch and continue forging. At this point you can start pattern development using burrs, drills, files, punches, chisels, and mills. Anneal with borax often. (Pijanowski & Pijanowski, 2001)


[edit] Coloring

To color the shakudo and gold, submerse the piece in boiling rokusho, and hold there - agitating constantly - until it reaches the desired color. Rokusho colors shakudo a black-purple. The more gold is in the alloy the more purple it turns. Rokusho is made in Japan and cannot be found in the United States. Rokusho is a solution of 6 g cupric acetate, 1.5 g copper sulphate, table salt in 1 L of distilled water.

Some people used a paste made of ground daikon radish. The recipe is the following; 1 part Daikon radish to 5 parts water, ground with a mortar and pestle.

The paste is applied immediately before the piece is boiled in the rokusho to protect the surface against tarnish and uneven coloring. After the coloring process is over, the finished piece is waxed. (Pijanowski & Pijanowski, 2001)

[edit] References

[edit] External links



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