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Beyond Gold and Platinum: Mokume Gane
15 August 2005
James Binnion © 2004
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In
many ways the “ultimate” noble metal that one might consider for jewelry
isn't gold or platinum but their slightly tan colored cousin iridium. With
the possible exception of osmium (which is smelly and toxic) it’s the
rarest non-radioactive element in the earth’s crust -- several times more
so than either gold or platinum. It’s even more chemically incorruptible
than the other two, it’s heavier (17% denser than gold and 6% denser than
platinum), and it’s much more scratch-resistant. There’s also the
additional mystique that most if not all of the iridium we mine comes from
meteorite impacts and is therefore extraterrestrial.
Unfortunately no one
has come up with a way to work with it economically, mainly due to its
absurdly high melting point and its glassy brittleness. The first artisan
to tame iridium will surely take the world by the tail. But in the
meantime there’s a metalworking specialty that’s just as interesting if
not more so called mokume gane (mo-KOO-may GAH-nay) which involves bonding
as many as thirty alternating layers of differently colored metals;
twisting, stretching, or otherwise heavily deforming the resulting mass;
and then carving it into rings and such that display a riotously swirling
agate- or woodgrain-like surface. Japanese metalworker Denbei Shoami
(1651-1728) invented mokume gane to make ornamental handles for samurai
swords. Metals used include silver; gold and differing hues of it such as
rose, white, and green; shakudo (an alloy of 96% copper and 4% gold that
develops a blue-black patina); kuromi-do (copper with a smidgen of
arsenic); shibuichi (a pink copper/silver alloy); and various alloys of
titanium and tungsten that can involve iron, nickel and molybdenum. They
sandwich these layers and heat them to a temperature, which chemists call
a eutectic, that’s hot enough to cause the atoms to jostle and intermingle
at the layer boundaries yet not so great as to melt the stack into an
undifferentiated blob. It’s unquestionably a high art and something not
everyone can pull off. Currently the best known mokume gane master appears
to be Norio Tamagawa, whose family has worked the field for nine
generations. You can Google the term yourself to find some good sources,
but one of the most visible and accomplished is clearly James Binnion at
www.mokume-gane.com.
© Peter Blinn 2005
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