OPPS Watch out! Tips about Firing Sterling Silver Metal Clay with Stones!

I have an update about the last blog where I fired the sterling silver ring inside the fiber blanket.

What I have found is that the fiber blanket fumed brown soot on all my stones! Notice the brown in the fiber blanket around the ring.
It washes off the tops of the stone, but it is on the under-side of the stones too! This makes them look dull and hazy!
I fired the ring again, this time buried in the charcoal and only went up to 1400F. It did help burn off the soot but a lot of it is still there under the stones making them dull.

I will try putting it into an ultra sonic cleaner and then steam blasting them to see it that cleans it off the back of the stones.