People use shakudo to be able color it with a patina that
produces a very nice black with purple undertones in it, Shakudo
without the patina looks just like copper.
I agree, Jim. Plus it naturally ages nicely from copper-coloured
to that dark colour over a period of months or years depending on
the kind of air you breathe. The Japanese use their trad radish
formulae but I torch-colour it to various colours, on the
understanding that it will slowly change with time. The torch
treatment just gets it to a reasonably deep colour to begin with.
Don’t think of shakudo as “merely a Japanese word for silly
man’s way to throw away gold or silly man’s way to make copper
sound expensive”. It’s a great metal - fine-grained and a delight
to file and draw. the traditional Japanese alloys are in a range
from 3% gold to 25% gold.
Melting any copper alloy is always a problem-rich area.
Oxidataion happens to the copper and it keeps those non-metallic
oxides inside. Try to avoid developing copper oxides, or have a
way to de-oxidise.
I melt it in a couple of ways - One; in that electric 'jug’
thing with a graphite crucible. Pouring from this into a steel
mold works ok, though the shakudo near the top of the mold is not
Two; the ‘Satsuo-Ando’ method that Douglas Frey referred to.
Pouring the metal through water into a specially prepared ingot
set-up made with a submerged cotton sling. In this case I heat
with a torch and often de-oxidise with phosphorus, depending on
how dirty it looks.
It’s a method I teach in my alloying workshops, and lately I’ve
just added to my resources some instructions from Bill Eisenburg
who was at an original Japanese water-pouring workshop.
Charles’ article is good. In part it reads:
Shakudo is the Japanese term for a low gold content alloy which
usually consists of between 2-7% gold and the rest copper.
Sometimes small amounts of other metals are added. The usual
alloy used and the one I’ve heard recommended most is a 3% gold
alloy/rest copper. Shakudo obtains a durable, purplish black
surface color when treated with a suitable solution. This is
used to best effect when the shakudo surface is combined with
inlays (mechanical or fusion) which then results in high
contrast pattern options. As with most Japanese metal coloring
methods the techniques are metallurgically based rather than
solution oriented; in the West we tend to use a myriad of
coloring solutions and limited number of alloys; in Japan there
are a limited number of coloring solutions and innumerable metal
alloys which react differently in the same solution. Over the
long haul the Japanese approach to my mind is the more sound one
as there is little change in the surface colors with time by
comparison with a Western often corrosion oriented coloring
solutions. There are for example over fifty types of silver
alloys in Japan which produce different shades of gray to white
when treated. Article by: Charles Lewton-Brain =A9 1995
B r i a n A d a m J e w e l l e r y E y e w e a r
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