When you had oxygen, you get a small hot flame that works for gold
but is not so good for silver.
Just for balance, let me say that I have two torches, an acet/air
Smith and an acet/oxy Meco. I use mostly silver. I much prefer the
hotter, more concentrated Meco flame, and see no reason that it is
not so good for silver. I used the Smith for years, and it is a
perfectly good set-up, I just find the Meco more versatile. To me,
the hotter flame seems all the more helpful with silver, which
quickly conducts heat away, than with gold, which allows the heat to
build up where you aim the torch.