Have you ever had a piece of metal absolutely refuse to melt? Or
rather, it appears to have melted, but it doesn’t ball up. It’s as
though there is an outer skin holding back the molten metal.
This has happened several times with sterling wire (16ga) that I am
using to make chain clasps. The ends of the wire need to be melted
until they ball up. I held the end in a propane flame for what
seemed like a long time, but it never flowed or balled up. I could
tell that it was melted below the surface, though, because the wire
got skinnier about 3/8" from the end. Eventually it broke off at the
skinny part–but the broken-off part was still the same shape!
I had applied Prip’s flux to the wire before heating it. Could this
have created a skin of some sort, or increased the surface tension
so the metal couldn’t flow?