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Shibuishi. Composition and production


#1

I need to make several sheets of Shibuishi and I do not know what to
do. I have two questions.

  1. How can I prevent that the copper becomes an unworkable lump of
    metal when melting the alloy? I do not feel easy about this, because
    I have no experience with melting copper.

  2. Which proportion should I use and why? Shibuishi consists of one
    part of silver and three parts of copper, but some goldsmiths use up
    to 50 per cent silver or go as low as 14 per cent silver.

On top of that, I just read in Ferguson that, due to the low solidus
point, the alloy may be difficult to solder. This bother me too,
because I want to use eutectic solder on it. Given this, what would
be the best proportion for me to use? Thank you.

Best wishes, Leach


#2

It sounds as if you have much to do. A lot you may need to research
yourself. But first… Why make it yourself? Are you indeed
interested in becoming proficient at alloying or is your interest in
designing and producing jewelry. Where should you put your energy
may be question #1.

As the next step you might purchase some Shibuichi in a variety of
formulations and see how they work and look. Does one fill your
needs better then another? There, your area of interest has been
greatly reduced in one step.

Bill
Bill, Deborah, Michele & Sharon


#3
Which proportion should I use and why? Shibuishi consists of one
part of silver and three parts of copper, but some goldsmiths use
up to 50 per cent silver or go as low as 14 per cent silver.

In my opinion you are approaching an area of - preference - on the
concentration or % of silver in your shibuichi.

(All of you moku-me experts can reserve your comments & or stop
reading now) When i took some classes from Marvin Jensen at the
Penland school, Marvin brought up the 14%-50% silver in the
shibuichi argument he then proceeded and proved to all of us that you
actually only NEED 4 % silver to make the alloy perform.

In my experience i found that it took a lot of heat to get that 4%
alloy to melt. After the ingot was formed into sheet it took a very
nice patina the way it was supposed to and looked as nice as the
higher silver % alloys that i have made in later years. In my
experience i have increased the silver content to make the alloy
easier to melt use less heat and fuel, (economy).

the higher % did not affect the coloration when the patina was
applied which is a completely different subject of the recipe for
ryokusho which i think has more influence on the final product than
whether to use the 14% to 50% concentration of silver in the alloy- :wink:

goo


#4

Copper isn’t a problem, just remember to load your crucible with the
low melt point metal first… if you’re using a furnace. Can’t help
you with torch melting, I don’t do that.

I think our Mokume expert would be the best to answer which alloy is
the best to use.

I was thinking about how to solder a mokume ring, because a line
would look horrible… even a faint one. I saw a demo by Rio Grande,
and they used their disc cutter, made a washer, then formed the
mokume onto a ring mandrel. There’d be no solder line, but I imagine
there would be some distortion to the pattern. Probably okay with a
random pattern, even a pool and eye, but a star pattern may look a
tad odd.

I’d be interested in some tips.

Regards Charles


#5

Hi Gustavo, Thanks. What you are saying about the 4 percent silver
is interesting enough. I made the shibuishi in the meantime, using 35
% silver and 65 % copper. I worked as usual, except that I made the
ingot much hotter than normal and I gave the crucible a good coating
of carbon. I did melt the silver first. The ingots are fine, but I
find them very hard to roll and for this reason alone, I would shy
away from this alloy in the future. The metal looks like silver, but
with a rose shine to it. It is quite attractive, but as it will
tarnish quickly, I need a think about a suitable patina.

Best, Leach


#6

I’ve done my share of japanese copper-based alloys and the
experience was good for me. For this sort of experimantation I favour
the Satsuo Ando method of pouring a small amount say 20g into a
cotton hammock immersed in steaming hot water. The resulting button
is a lovely smooth pebble-shape which has solidified in a reduced
atmosphere and which has no sharp edges needing filing. Ref:
Metalsmith magazine, Winter 1981 vol 1, no 2.

I highly recomend you read up on the Ag/Cu binary phase diagram and
try to understand the way the alloys melt and how most have a pasty
stage. Almost all the alloys share the same 779degC solidus. Which is
probably why someone said you’d have trouble soldering some of these
alloys with high-temp solders like Hard and the eutectic. By the time
you get to a solder flow temp in the high-770s degC the joint will be
starting to shimmer.

Phase diagram: http://matdl.org/repository/view/matdl:539

While you’re at this alloying lark you can be usefully employed
making your own eutectic solder at (from memory) Ag72/Cu28: it’s the
alloy that appears in the phase diagram right where the liquidus line
plunges down to meet the horizontal solidus line.

All the Ag/Cu alloys are useful in some way or other. Don’t expect
them all to be as ductile and malleable as sterling. That Ag35/Cu65
you made will be very springy, and therefore I’d recomend you saw a
piece off and make into pin wire. It’s better than stg at doing that
job and at least keeps the whole brooch within the silver family.

If you don’t like that 35/65 piece you’ll be able to recover the
silver by remelting and adding more sil or copper to make another
alloy.

Soon I bet you’ll be investigating the Shakudo alloys.

Brian
Auckland
New Zealand
www.adam.co.nz