I recently made a sterling pendant, a yin yang symbol. Today I noticed that where I sweat soldered the wire to the backplate (for the separation of the two sides in the design), there’s a green line where the solder joint is. Can anyone tell me why? Google won’t. lol.
You might have pickle residue or the copper may be turning things green. Background areas can remain moist longer and that might encourage discoloring as well. Hope this helps