THE ANCIENT STORY
Japanese craftsman Denbei Shoami (1651-1728) is credited with the invention of Mokume Gane for embellishing samurai weapons and hilts. The process was only used in sword making until the 19th century. Changes in Japan’s political and social structure in the late 1800s saw the collapse of the caste system dominated by the samurai warriors. They were no longer allowed to carry their katana (sword) in public so demand for these arms decreased. Metalsmiths then began transferring their skills to create more artistic products.
THE MODERN STORY
The husband and wife team of Eugene Michael Pijanowski and Hiroko Sato Pijanowski brought Mokume Gane to the United States in the early 1970s. They learned the technique from ninth generation metalsmith Norio Tamagawa. Watch a video with Hiroko and Gene demonstrating the Mokume Gane technique.
Today, Mokume Gane jewelry, flatware, hollowware and art objects are created by layering precious and semi-precious metals such as Gold, Platinum, Palladium, Sterling Silver and Copper. The layers are bonded and deformed by rolling, forging, and twisting. A combination of techniques including punches, chiseling, carving, and surface abrasion exposes the beauty of the work: the unique layering of these metals. A Mokume Gane artisan can make an unlimited number of distinct patterns with no two being precisely the same.
THE PROCESS
Alloy sheets of varying thickness are purchased, including karat Gold, Sterling Silver, Palladium-enhanced Sterling Silver, Platinum and Palladium. We will bond these precious metal alloy sheets together in order to form your Mokume Gane billet. The precious metal alloy sheets are inspected and then cleaned in order to remove any dirt or grease. Then, the alloy sheets are stacked and placed in the cavity of a punch and die assembly that is made from high-temperature aircraft engine alloys. In turn, this assembly is placed between two other high-temperature alloy plates and is bolted together using 50 tons of pressure. This entire assembly is called the TEMTP system.
The stacked alloy sheets are bonded by firing the TEMTP system in a kiln. First, the TEMTP system is placed in a stainless steel bag filled with charcoal which forms a protective atmosphere. The assembly is loaded into the kiln and heated to between 1375F and 1425F for 4 to 5 hours. In most cases, The TEMTP assembly is allowed to cool overnight, but in some cases, the TEMTP is quenched immediately after firing in order to avoid the formation of undesirable brittle phases. The resulting bonded stack of alloy sheets is called a billet.
The Mokume Gane billet is hot-forged at high temperatures and pressures using a proprietary process. When the billet has been flattened to half its original thickness, a portion is cut off with a jeweler’s saw. Then, the Mokume Gane rod is annealed and cold-rolled into a series of progressively smaller square cross-sections. The final dimensions of the square cross-sections vary between 3.75mm and 5.5mm. Rods with a 3.75mm square cross-section are used to make Mokume Gane bands between 4mm and 5mm wide. Rods with a 5.5mm square cross-section are used to make Mokume Gane bands between 6mm and 8mm wide. The entire process that starts with flattening the billet requires 10 to 12 individual forging, annealing, and rolling operations until the final square cross-section achieved.
The Mokume Gane rod is twisted in a multi-step process. This process of twisting with annealing in between is repeated 4 to 8 times until the desired number of twists is achieved. Ultimately, the rod will have between 10 and 15 twists along its length. At this point, the rod is rolled into a square shape. Then, the rod is either hand-forged or pressed (using a hydraulic press under approximately 25 to 50 tons of pressure) in order to achieve the desired starting rectangular shape, width, and thickness.
The Mokume Gane rod is ready to be patterned through a metal removal process. We use high-speed steel burs attached to high-speed flex shaft driven by a permanent magnet motor. After the preliminary metal removal, the rod is again forged followed by additional metal removal. This process of metal removal and rolling with annealing in between is repeated 3 to 4 times until the desired pattern is achieved.
The patterned rectangular Mokume Gane rod is rolled to the final length and thickness. A flat ring blank is cut. The ends of the ring blank are brought together and soldered.
GETTING STONED
For flush set diamond or other gemstones a hole is drilled through the surface of the ring at the appropriate location. A setting tool is used to form a seat in the hole on which the gemstone will sit. The gemstone is placed in the hole and is pressed onto the seat. A special tool is used to move a small amount of metal over the top edge of the gemstone all the way around; this action sets the gemstone in place. As a final step, the edges of the hole are cleaned up. Multiple flush set gemstones can be placed on a ring.
For channel set diamonds or other gemstones a groove on the surface of the ring using high-speed cutting tools. A seat is formed within the groove on which the gemstones will sit. Preliminary cleaning of the groove is performed to ensure uniformity. Then, the gemstones are set in the groove and pushed against the seat. A special tool is used to move a small amount of metal over the top edge of the gemstones; this action sets the gemstones in place. As a final step, the edges of the groove are cleaned up.
