The words mokume gane in Japanese (木目金) translate as wood grain metal. Mokume gane is a process of laminating sheets of metal then carving and forging that laminate to produce patterns that often resemble wood grain.
The Origins of Mokume Gane
Shoami Denbei (1651-1727) a master metal worker developed the mokume gane technique. His earliest work with mokume gane is from the early 1700’s.
TRADITIONAL JAPANESE MOKUME GANE PROCESS
Traditional mokume laminates were a combination of two or more different metals or alloys. Silver, gold, copper and the copper alloys shakudo, shibuichi and kuromi do were be the main choices for a mokume gane laminate. The finished objects almost always were patinated by immersing them in a rokushō patina solution which leaves silver and gold basically untouched and forms colors on the other metals in the piece.
The Japanese had several metals and alloys they would use in mokume gane billets. Along with gold and silver these other would patina to different colors. Copper: red, Kuromi do (1%-3% As – Cu): black, Shibuichi (2%-60% Ag-Cu): grey to chocolate with subtle green or blue tones and Shakudo (2%-6% Au-Cu): black with subtle blue or purple tone highlights. The Japanese referred to these colored metals as irogane.
PREPARING THE METALS
The metalsmith cast ingots of the metals for the mokume gane billet and forged them into sheets of the desired thickness. Then working these hand forged sheets with files, scrapers and abrasive stones develops absolutely smooth, flat surfaces on both sides of each sheet.. This preparation also removes surface oxides and foreign material from the metal.
Even today with commercially produced sheet readily available the cleaning and oxide removal extremely important to successful mokume gane lamination. This preparation takes time and requires attention to detail for a successful outcome.
In the traditional process, the sheets of the billet are stacked between two iron plates that are bound with heavy iron wire and folded iron sheet are used to hold the stack together during firing. Today it is more common to bolt together the plates of steel used to clamp the stack for firing.