I spent today rolling out my three shibuichi ingots into useable sheet.
Above, I’m pickling the cast ingots in Sparex pickle. “Pickling” dissolves the dark oxides formed when the molten metal hits oxygen in the atmosphere. I use a small crockpot to keep the liquid hot, so it works faster. Three to four minutes per pickling cycle ought to do it.
Here is the ingot after the first round of rolling, and after I annealed it. Annealing is heating the shibuichi to glowing red – this softens the hardened metal. Shibuichi “work hardens” quite easily when being rolled (gets hard and brittle), and if I don’t anneal it pretty often, it will crack and ruin all my hard work. I’ll pickle the ingot again, followed by brushing to remove the dark oxides.
And above, the ingot has had several rounds of rolling, annealing,and pickling. Notice the crack developing at the top. Hopefully this crack won’t get too much worse as I continue rolling, lengthening and thinning the shibuichi. I’ll just have to take the crack into consideration when designing. I can probably get two to three small pendants from this piece.
Above, here is a magically computer-edited series of one of the other ingots. The red rectangle is a tracing of the original ingot, and each of the others is after a round of rolling, annealing,and pickling. Notice how each time lengthens the shibuichi sheet (thinning the sheet as it goes). Since the rolling mill tends to bend the sheet as it exits, I also forge the sheet flat on my anvil after most of the rounds of rolling. That explains the textured surface you can see on the three sheets on the right.
I noticed something interesting happening with the shibuichi I haven’t noticed before. The sheet on the right is how shibuichi appears after freshly brushing the surface. The sheet on the left is noticeably silver colored after pickling – I think this is “depletion gilding”. Depletion gilding is a jewelry technique where you can build up a pure silver surface in a silver alloy containing copper, by repeatedly burning the copper at the surface into an oxide layer, then pickling, which dissolves away the copper oxides, but leaves the silver. Just a cool thing I’ve never seen before, probably because I didn’t know enough to notice it!