I understood this topic has already been discussed. But I know someone worked it out, so maybe it worth to discuss it again here.
My understanding is that the rhodium layer is burned to black by soldering work, that’s the key problem.
I tried to either polish the rhodium first or polish the black layer after torch work, only problem is those places under small stones, I can reach there.
Currently I’m doing a silver plating in the last step to cover up the dark spot under these small stones. It kind of work, but I’m wondering if anyone has a better idea.