Torch "bloom"

When I heat sheets of sterling I notice a change in color of the
surface as I move the flame. The colors range from copper color to
blues and other colors. The colors come and go as the flame moves.
Is this the silver oxidizing? I notice the effect most strikingly
when I have no flux on the silver such as when I am in the first
steps of reticulation and want to oxidize the surface. I have also
noticed it, but not as intensely, when I did have Pripps on the
silver and was trying to minimize oxidation. I am using a propane -
oxygen torch and try to keep a slight flicker of yellow in the torch
flame (hoping that means I have a reducing flame).

Mitch Adams

Mitch What You are observing is the different metals being oxidized
and or burnt off into the atmosphere…Green is copper blue would be
the silver. Ringman John Henry