One order of fine silver didn't handle the same as my other orders.
Whenever I tried to fuse it (using a tabletop kiln and butane
torch), something would bubble up on the surface and either
crystalize or turn black. Fine silver is not supposed to discolor
under heat. Sterling does discolor, but this didn't behave like
sterling, either, as it discolored only where the torch was used and
not over the entire piece.
Just in case it was sterling, I called Rio Grande to see if I
ordered the wrong stuff, but that wasn't the problem. Since it was
only a half ounce, they very kindly offered to replace it.
The new wire works just fine, which supports my belief that there
was something different about the first batch of silver.
Should I expect silver to vary significantly from batch to batch? It
seems to me that refiners take a small leap of faith when they
accept silver for recycling, and that the less recycled material in
a batch of silver, the better the quality.