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Red copper


#1

We’ve been using the red copper process for some years now, as
accents to jewellery and also in larger copper pieces. It appears
to be a reduced copper oxide (potters recognize the colour from
raku glazes), but like raku is fairly unpredictable.

We heat the piece using propane/oxygen, with a flame that is
just starting to reduce (a hint of yellow, too much yellow and
the flame is not hot enough). Holding the piece can be tricky, as
tweezers will leave an unoxidized part to the surface. If the
piece has a drilled hole, suspend it on stainless steel wire in
the flame. Heat to a bright red heat, even approaching orange
heat, and quench in boiling water (or water that has just been
boiled) with only a moment’s hesitation. The piece sits in the
water in a bubble of water vapour for a few seconds, before it
rumbles furiously and cools down. The hot water can splash, so be
careful. When it works well you get a beautiful crimson colour.

The variables, which we are still learning to control, seem to
be: 1. how hot the metal is (orange heat works great but the
copper can start to melt) 2. how long the piece is exposed to air
before you quench it (one to three seconds)and 3. how hot the
water is. The metal should be polished and clean (grease-free)
before starting. Potential problems? The temperatures needed are
higher than the annealing temperature of copper, so any
work-hardening will be gone, and annealed copper is very soft.
It’s also pretty unpredictable. Some days it just doesn’t seem to
work well as well as others.The oxide is remarkably durable but
can be dissolved with acid (pickle, or skin acids) so it needs a
protective lacquer, spray or wax. In jewellery, you need to
design the copper piece so that it is away from skin: perhaps a
silver hoop around a copper disc, or a silver bezel to hold a
copper shape. Hope this is useful.

Andrew

Goss Design Studio http://www.makersgallery.com/goss/
Owen Sound, Ontario, Canada
email @Goss_Design


#2

Thank you all for regarding my red copper question.
They were all very helpful.

Here is another method I learned from my japanese friend.

You need something called “rokusho” which, according to
McCreight’s book, you can make by mixing 3 parts cooper acetate,
1 part sodium hydroxide, 1 part calcium carbonate - mix them up,
let it settle for a week and gently pour off the liquid on the
top. Another thing you need is “umeboshi” (pronounced
oo-meh-bo-shee) . This is pickled japanese plum and if you
live in big cities like NY or LA, you can buy it at a japanese
supermarket like “Yaohan”, or maybe in korean or chinese grocery
store. If not, you could try health food store that carries
exotic food from the orient.

Now, mix same amount of rokusho and copper sulfate ( 3 to 5 gm)
in about 1 liter of water. ( The amount of water is not
important. It only makes the reaction time longer or shorter)
Put the solution and umeboshi in copper or glass container and
bring it to boil. Careful not to break the skin of the umeboshi
open! Clean your piece with baking soda, dip it in grated
raddish. Reason for raddish, I don’t know. But everybody’s very
specific about this. Put it in the solution, let it simmer for
1/2 to 1 hour. The piece should not be touching the wall of the
container. Copper part of your piece should turn red, while gold
and silver remain the same. You could do the same without
umeboshi, too. In this case copper turns brownish red, which is
also very beautiful.

Ako