Make Your Own Shibuichi Clay
Shibuichi is an ancient Japanese alloy of copper and silver, with the percentage of silver ranging between 5% – 25%. There is a very informative article about this alloy in March 2010 issue of Art Jewelry Magazine by Lee Rumsey Haga, which I highly recommend.
I have been often asked about combining different metal clays together, so I decided to try. I made “Shibuichi clay” of 5% silver and 95% copper, using mixed Quick-fire copper and PMC Plus.
One way to measure is to use a scale. To make 10 grams of this type of Shibuichi clay, mix 0.5 grams silver clay with 9.5 grams copper clay.
If you don’t have a scale, roll the clays into layers of equal thickness. For example, roll each clay between two stacks of 4 cards.
Next, use a straw or a another cutter to cut one circle of silver and twenty circles of copper out of the layers.
To make an alloy with 15% silver, cut 3 circles of silver and 17 circles of copper.
To make an alloy with 25% silver, cut one circle of silver and 3 circles of copper (use a bigger cutter, of course).
Then mix the clay with your fingers, and roll it under the rolling pin over an over until you get a homogeneous color.
I pressed the clay against a texture with high relief.
I fired it with a torch for 6 minutes from the moment the binder had burnt off, and immediately dipped in water.
I found that torch-fired Shibuichi clay is stronger than torched-fired copper clay.
I also tried it in a kiln. Using my new firing method as described in my previous posting, I fired it for 1:00 hour at 1470°F (800°C) in my top loader kiln. In a front loader, fire at 1550°/843°C.
At this point, you can either start playing with patinas or, if you want to clean the piece first, dry it thoroughly on a warming surface.
Shibuichi is very receptive to patinas. Here are some examples:
Rust
Blue
Purple
Blue-green
Heat patina
The last example was done by gently heating with a torch and dipping in water when the desired color was achieved.
Since metal clay is so porous, you will need to apply the patina more than once. I placed the piece on my warming surface and applied it with a brush. At first the liquid was totally absorbed into the metal. With every further application the colors developed more and more. Sometimes they developed after I removed the piece from the warming surface and let it cool down.
When the color was achieved and the piece was dry, I sanded the high part of the relief, first with 220-grit sandpaper, then with 400 grit.
The patina can be sealed with lacquer spray or with sealers from the sources below.
Sources:
Rust, blue and green patinas are available from hardware stores, or from craft stores such as Blick and Michael’s. The series is called Sophisticated Finishes.
Another source is www.sculptnouveaux.com. They also have different sealers and their products come with full instructions.
