Mokume-gane
Encyclopedia
is a mixed-metal laminate with distinctive layered patterns. Translating as burl
metal, the name was borrowed from one type of pattern created in the forging of swords and other edged weapons.
era, when the decline of the katana
industry forced artisans to create purely decorative items instead. The inventor, Denbei Shoami (1651–1728), 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-gane (wood-grain metal), and yosefuki.
The traditional components were relatively soft metallic elements and alloys (gold, 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 forged and carved to increase the pattern's complexity. To achieve a successful lamination using the traditional process required a highly skilled smith with a great deal of experience.
The modernized process typically uses a controlled atmosphere in a temperature controlled furnace. Mechanical aids such as a hydraulic press or torque plates (bolted clamps) are also typically used to apply compressive force on the billet during lamination and provide for the implementation of 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.
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 produced in small batches in a traditional process and is somewhat difficult to acquire outside Japan. There are some proposed substitute formulas (see rokusho
article.)
Traditionally a paste of ground daikon
radish is also used to prepare the work for the patina. The paste is applied immediately before the piece is boiled in the rokusho to protect the surface against tarnish and uneven coloring.
Shakudo can also be darkened by adding salt with ammonia in a plastic bag. The warmer the solution, the faster it will darken the metal.
Burl
A burl or bur or burr is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from dormant buds.A burl results from a tree undergoing some form of stress. It may be caused...
metal, the name was borrowed from one type of pattern created in the forging of swords and other edged weapons.
History
First made in 17th-century Japan, the mixed-metal was used only for sword fittings until the MeijiMeiji period
The , also known as the Meiji era, is a Japanese era which extended from September 1868 through July 1912. This period represents the first half of the Empire of Japan.- Meiji Restoration and the emperor :...
era, when the decline of the katana
Katana
A Japanese sword, or , is one of the traditional bladed weapons of Japan. There are several types of Japanese swords, according to size, field of application and method of manufacture.-Description:...
industry forced artisans to create purely decorative items instead. The inventor, Denbei Shoami (1651–1728), 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-gane (wood-grain metal), and yosefuki.
The traditional components were relatively soft metallic elements and alloys (gold, copper, silver, shakudo
Shakudo
Shakudō is a billon of gold and copper , mostly designed for its dark blue-purple patina. It was historically used in Japan to decorate katana fittings such as tsuba and kozuka...
, shibuichi
Shibuichi
is an alloy which can be patinated into a range of subtle muted shades of blue or green. Its name means "one-fourth" in Japanese and indicates the standard formulation of one part silver to three parts copper, though this may be varied according to the desired effect. A 5% silver / 95% copper alloy...
, and kuromido
Kuromido
Kuromido is an alloy of 99% copper and 1% metallic arsenic. It is most commonly used as one of the metals associated with mokume-gane....
) which would form liquid phase diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
bonds with one another without completely melting. After the original metal sheets were stacked and carefully heated, the solid billet
Billet (manufacturing)
Semi-finished casting products are intermediate castings produced in a foundry that need further processing before being a finished good. There are four types: ingots, billets, blooms, and slabs.-Ingot:...
of simple stripes could be forged and carved to increase the pattern's complexity. To achieve a successful lamination using the traditional process required a highly skilled smith with a great deal of experience.
The modernized process typically uses a controlled atmosphere in a temperature controlled furnace. Mechanical aids such as a hydraulic press or torque plates (bolted clamps) are also typically used to apply compressive force on the billet during lamination and provide for the implementation of lower temperature solid-state diffusion between the interleaved layers, allowing the inclusion of many nontraditional components such as titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
, platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
, iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...
, brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
, nickel silver
Nickel silver
Nickel silver, also known as German silver, Argentann, new silver, nickel brass, albata,, or alpacca, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver...
, and various colors of karat gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
including yellow, white, sage, and rose hues as well as sterling silver.
Coloring
To increase the contrast between the laminate layers many mokume-gane items are colored by the application of a patina (a controlled corrosion layer) to accentuate or even totally change the colors of the metal's surface. One example of a traditional Japanese patination is the use of rokusho. Rokusho is a complex copper verdigris compound produced specifically for use as a patina.To color the shakudo and gold, submerse the piece in boiling rokusho
Rokusho
is a traditional Japanese compound for inducing patination in decorative non-ferrous metals, especially several alloys which are nearly unknown outside Japan. Shakudō, an alloy of copper and gold, becomes dark blue-violet; shibuichi, an alloy of fine silver and copper in a higher percentage than...
, 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 produced in small batches in a traditional process and is somewhat difficult to acquire outside Japan. There are some proposed substitute formulas (see rokusho
Rokusho
is a traditional Japanese compound for inducing patination in decorative non-ferrous metals, especially several alloys which are nearly unknown outside Japan. Shakudō, an alloy of copper and gold, becomes dark blue-violet; shibuichi, an alloy of fine silver and copper in a higher percentage than...
article.)
Traditionally a paste of ground daikon
Daikon
Daikon , Raphanus sativus var. longipinnatus, also called White Radish, Japanese radish, Oriental radish, Chinese radish, lo bok and Mooli , is a mild flavoured, very large, white East Asian radish...
radish is also used to prepare the work for the patina. The paste is applied immediately before the piece is boiled in the rokusho to protect the surface against tarnish and uneven coloring.
Shakudo can also be darkened by adding salt with ammonia in a plastic bag. The warmer the solution, the faster it will darken the metal.
See also
- Pattern weldingPattern weldingPattern welding is the practice in sword and knife making of forming a blade of several metal pieces of differing composition that are forge-welded together and twisted and manipulated to form a pattern. Often called Damascus steel, blades forged in this manner often display bands of slightly...
- Mokume-gane titanium rings
- Damascus steelDamascus steelDamascus steel was a term used by several Western cultures from the Medieval period onward to describe a type of steel used in swordmaking from about 300 BCE to 1700 CE. These swords are characterized by distinctive patterns of banding and mottling reminiscent of flowing water...