If you are silver soldering or brazing, the flux has formed a hard borax glass. There are chemicals such as Sparex that is used by jewelers to remove this. Sparex also has a compound that is either Sparex 1 or 2. I don't remember which is which. Soaking in water will also remove it. There is not easy way to clean it up that I can thick of. If it is all dark, perhaps it would be nice to just leave it dark. How about posting some pictures so we can see what you are talking about?
If you are silver soldering
If you are silver soldering or brazing, the flux has formed a hard borax glass. There are chemicals such as Sparex that is used by jewelers to remove this. Sparex also has a compound that is either Sparex 1 or 2. I don't remember which is which. Soaking in water will also remove it. There is not easy way to clean it up that I can thick of. If it is all dark, perhaps it would be nice to just leave it dark. How about posting some pictures so we can see what you are talking about?
marilyn