Hi Question: Did you alloy the metal yourself? If you did it may be
possible that the metals were not completely mixed.
If the problem is in the metal, then the best solution is to make a
new ring. You will feel better about your work and your customer will
gain a tremendous amount of respect for you because you stood by your
workmanship.
It is a good thing to keep in mind that this is a craft that is all
about striving to achieve perfection. When I looked at your design I
could see that your were really trying to create a unique and
beautiful piece. If you have to make this ring over you won’t just be
solving the problem of the stain you will be taking one more step
towards reaching your goal as a goldsmith.
Ted Curtis