Yes! Certain styles of mokume ring can be sized, within limits. But not all jewelers are able to size a mokume ring. As a general rule, the only person really qualified to size a mokume ring is the one who made it in the first place. Sizing mokume is not like sizing any other kind of precious metal ring. No matter the skill level of the jeweler, if they have not had years of experience with the mokume there can be problems.
Mokume starts as a stack of precious metal sheets containing different colored alloys, usually between 2 to 5 colors. Each of these metal alloys has a different set of characteristics – melting point, rate of work hardening, amount the metal can be worked before tearing, temperature at which is can be annealed to soften the metal again. When you fuse these metals together using diffusion bonding other strange things begin to happen. Without getting into the metallurgy, the bonded layer between the metals can have a lower melting point than the surrounding parent metals.
When a soldering alloy is also introduced into a cut seam, which happens all the time in normal ring sizing, there can be a cascade effect along the diffusion bond at low soldering temperatures. When this happens the colors in the ring melt together into a muddy new alloy that we lovingly refer to as mokumelt. The ring is basically ruined at this point.
Let me be clear – when soldering rings, even the low temperatures are still very high, over 1000 degrees in most cases. Your mokume ring is perfectly safe at any temperature you will expose it to.
Another common sizing method on standard rings is to use a ring stretcher. But the metals in mokume each expand at a different rate, which causes stress between the layers and can tear or shatter the ring if it is taken too far without proper annealing in between stretching.
Here again, the stresses involved with stretching rings are hundreds of pounds per square inch. If you ever subject your ring to that kind of force I’m much more worried about your hand than the ring.
So the first choice is to always take the ring back to the store where it was purchased. If that is not possible please feel free to drop us an email and we will figure out the best way to make your ring a comfortable fit again.
Our mokume rings can be sized, in general, up or down 1.5 sizes. There are exceptions to this – stone setting being one of those. And there may be options to take certain rings farther up or down if needed.
As always, if you have any questions or concerns please drop us an email.