Open flame is fine and all and you can get very beatiful colors, but I have a couple questions: I know that when people temper knives they often use a kitchen oven, there the metal turns different colors as the rest rises, yet, because of the controlled heat, it is a consistent color throughout the peice, would I be safe to assume this is the same for copper? What are all the colors copper can turn to because of heat?
I am trying to make a chart for copper coloring via controlled heat and time, just like those made for tempering steel so any info would be awsome!