Making Shibuichi part 1

Since I’ve spent the last week working on my web site format change, my wife is making me get serious about starting a new knife, so I have to make some shibuichi ingots for the knife handle scales. Shibuichi is an ancient Japanese precious bronze art alloy, typically made of 75% copper and 25% silver. It comes out as kind of a hard pinky bronze, which will patinate to a dark grayish color. Although it is a somewhat expensive alloy, it engraves and carves really nicely. I probably used an ounce of silver in the ingots I made today (about $35 worth).

Here I’m weighing out the copper scraps for a single ingot on my little electronic scale. Once I have the amount of copper I want, I’ll figure out how much silver I need to add (in the white lid at the bottom of the photo).

Above is the equipment I’m using to create the shibuichi alloy, melt it and cast it into a small, thin ingot. From the left is my oxy/acetylene torch, here just burning acetylene (no oxygen) – very smoky, and used like this to put a layer of soot on my ingot mold, the little black assembly at the top of the image. The soot will keep the shibuichi from soldering itself to the mold. Also in the picture is a small melting crucible, a container of borax flux for cleaning the scuzz off the melted metal, and the flint striker to light the torch.

Here you can see the crucible and assembled ingot mold. In this melt I’m going to use up a little extra bit of shibuichi and some scrap. Since shibuichi is so expensive, I collect all my scrap for re-use. This ingot I’ll probably use for a couple of small pendants. I cast my own shibuichi because it’s the only way I can get the thicknesses I need for knife scales, and commercially available thin sheet shibuichi costs about $30 per square inch. This much commercial shibuichi in 16 guage thickness would probably cost about $100.

Above, I’ve cast the ingot and opened the ingot mold. The shibuichi is the copper colored rectangle in the sooty mold at the top.

And here are the three ingots I cast today, two 25% silver shibuichi ingots, and one about 20% from the scraps I had on hand, since some of the scraps were 15% shibuichi and I estimated…

I’ll eventually put the ingots I cast today through a rolling mill to lengthen them and make them the proper thickness for my knife scales.