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.
Then the mokume gane billet was fired in a charcoal fired forge. This forge called a hodo. The hodo had a clay hearth set into the floor with an air blast supplied by a box bellows called a fuigo.
The intensity of the heat in the forge was controlled by the air blast from the fuigo. The billet was carefully heated to reach a uniform temperature low enough not to melt but hot enough to fuse. At this temperature the visible edges of the billet will exhibit a shine or flash. A sign that the alloy has reached the lower end of its melting range. The billet was quickly removed from the hodo and placed on the anvil and hammered to complete the bond.
Today some makers still use a charcoal or coal fired forge but many use gas fired or electric kilns to heat the metals for bonding. But the requirement for careful control of the heat is still of great importance. Skillful forging also must be mastered for a successful lamination.
Each metal in the billet has different characteristics, such as hardness, ductility and melting point. The bonding of these individual layers into a single billet with no cracks or voids is by far the hardest part of the process to master. It takes many attempts and many failures before someone begins to understand how to successfully bond a workable billet.
Once bonded the billet needs to be forged down to suitable size for the desired object.
Forging the billet
Once the layers have been successfully bonded the thickness of the lamiate must be reduced before patterning can begin.
The forging process can be done by hand hammering or other equipment like a rolling mill or press can be used to reduce its thickness. If there were any faults in the lamination process this is where they will most often show up. Normally if a fault is found the billet must be scrapped and the whole process begun again. A very frustrating experience.
Carving the billet
Traditionally mokume patterns were carved with small sharp chisels and a hammer do drive them through the metal. While some still use chisels other tools like rotary files called burs or drills are more often used to carve pattern today.
Typically multiple rounds of carving and forging are required to bring out the pattern in a piece of mokume gane. It is at this point that the artistry of the maker is shown, Even though the process of getting to this point is difficult to master it is in the carving of pattern that the beauty of mokume gane is brought out in the hands of a master artisan.
A skilled craftsman can then further work the billet to produce beautifully patterned objects like the Tsuba shown below. The skill and meticulous attention to detail of the craftsmen who developed mokume gane is breathtaking.
More Mokume Gane
For more on the history of mokume gane check out our history page.
And please go and look at some of the beautiful pieces we make using the mokume gane process like the ones below.