Layers of Beauty: Mokume Gane
Mokume gane jewelry is an art form whose origins stem, surprisingly, from the art of sword making. Renowned throughout Asia for superior swordsmithing, Japanese blade smiths in the 12th century discovered that by forging and folding steel, a stronger blade could be crafted. This technique of metal layering, performed with wrought iron and high-carbon steel, produced a metal laminate. Further manipulation of the layers led to the discovery that beautiful patterns could be brought to the surface. These patterns strongly resembled those found in nature, particularly in the growth patterns of trees, hence the moniker mokume gane, or “wood grain metal.”
This technique carried over into the realm of jewelry making. In fine jewelry, mokume gane is a painstaking process by which layers of precious metal, most often different colored gold alloys, such as rose, yellow, and white, are permanently joined through a process of diffusion or soldering, then rolled, hammered, carved, or punched to create an organic and attractive pattern. These precious metals are chosen for their metallurgical compatibility, as well as their visual contrast. Once the metals are fused together, the entire stack can be worked into a single piece.
In the process, the metals are carefully cleaned and stacked against each other in as few as eight or as many as twenty layers at a time. The layers are compressed in a hydraulic press or a vice, and then clamped securely between steel plates. Once clamped, the metals are heated in a kiln to the temperature at which the molecules begin to excite and travel. The heated metal expands, but the steel plates constrict the expansion, allowing the surfaces of the metal to migrate into each other. The heating process is difficult to execute and relies on precision for the outcome to be successful. The metal must reach the temperature where the surface begins to “sweat,” or verge on molten. If the metal does not reach this temperature, the diffusion bond will not occur. If heating surpasses the critical temperature, the metal will melt and the layers will not differentiate.
Once a laminate is successfully created, the stack is rolled thinly and the process is repeated, doubling the number of layers. Once the desired number of layers is achieved, the process of patterning begins. Jewelry artists may use a variety of patterning techniques, and each will yield a different result. Some of the most common mokume gane patterning techniques involve heat forging, cold forging, carving, and punching.
In heat forging, one end of the metal laminate is secured in a vise while the middle is heated with a torch. Heat will soften the metal, which then allows the jeweler to twist or bend the laminate by manipulating the opposite end with pliers. Heat forging can produce a loose or tight twist, depending on the intensity of the manipulation. This is a popular application in the formation of mokume gane wedding bands.
Cold forging is done with a hammer and anvil. The metal laminate can be folded over upon itself a number of times resulting in a wave pattern. Carving involves removal of metal either with a bur or graver. Carving the laminate gives the jeweler greater control over the pattern. The carved recesses are made level by hammering. The jeweler must take great care not to carve too deeply, otherwise the laminate may thin in places and holes may result.
Punching is done with chasing tools, dapping punches, or other tools that create a relief pattern. The laminate is secured in a pitch pot and the striking is done on what will become the reverse side of the finished piece. A series of bumps are made in the metal, and these bumps are filed off once the laminate is removed from the pitch. When the bumps are removed, the pattern is revealed.
After the pattern is revealed, mokume gane is then worked into a finished piece of jewelry. A mokume gane sheet is often mounted over a homogenous metal to add strength and durability. It is common to see mokume gane backed with a solid sheet of precious metal. Final finishing of mokume gane is done to bring out the textures and patterns, which can appear subtle. Using a corrosive is one way to achieve contrast between layers, as is selective oxidation or use of patinas. Care must be taken to protect certain layers from the corrosive or patina while exposing others. Wax is often used as a protector and the process of finishing mokume gane can be almost as complex and time consuming as creating it.
Organic, artistic, and appealing, mokume gane is a process that does not lend itself to mass production. While patterns may be repeated, there is something singular and extraordinary about each individual piece of mokume gane jewelry. Many hours of expertise go into each intriguing layer, and each layer is a testament to individual beauty.