Mokume Gane was invented in Japan in the 17th century to adorn samurai swords and means “wood grain metal” in Japanese. Making mokume gane is exacting & time-consuming and requires skills & equipment outside the usual range of jewelry-making techniques, some more akin to blacksmithing, so not many jewellers practise the art today.
It is essentially the process of fusing many layers of contrasting non-ferrous metal sheets so that they become a solid block or billet. The billet can then be patterned and made in to rods or sheet metal with the charateristic grainy, layered mokume patterns.
I most often make the mokume billet into sheet to use in my jewelry. To begin the process I clean, stack and clamp the sheets tightly between two steel plates. The clamped block is then heated until the separate sheets fuse together.