My first attempt at making mokume gane. I read from James Binnion’s blog that silver-copper mokume is self-destructing, so I only made this to test out the process and making the pattern.
The problem with this combination of metals is galvanic corrosion. Any ring made from base metal (copper, brass..) in contact with a noble metal (silver, gold..) will corrode, no matter how they’re joined (fused in mokume, soldered, riveted..). The two metals in a wet environment basically create a battery, the current flows from the more negative metal to the more positive one. Copper being the more positive metal in the copper silver pair will begin to dissolve every time it gets wet.
Even if the ring is entirely made of base metals, it will still happen. Base metals aren’t resistant to corrosion like noble metals are. Pairs entirely out of noble metals will still create a galvanic cell, but their resistance to corrosion prevents them from being dissolved when in contact with an electrolyte (water, sweat, lotion etc).
Any less than 50% gold or lower than sterling silver will corrode if paired with a more noble metal. So gold should also be at least 14k when used in mokume, 9k will corrode all the same if it’s joined to 14k or 18k. No matter how they’re joined, it will corrode. Not even a liner inside a ring will protect it. Something to consider when designing mixed metal pieces.
I guess it’s safe if the metals stay dry all the time, but how realistic is that when most pieces are always in contact with skin and the moisture on it alone will allow the process to occur.
Tons of useful info in James Binnion’s blog post with detailed pictures, worth the read for every jeweller.
Materials: Sterling silver, copper