Great diagram, huh?
Note that it is mostly shades of blue – there should be minimal yellow or orange (indicating that there is adequate air/oxygen) but the flame should not begin to separate from the burner (indicating too much). There should be no smoke or soot from such a flame. The hottest location is just above the inner cone. With soda-lime glass, once the glass is hot enough to work, the flame will take on a yellow color due to the sodium ions in the glass. With the air/oxygen supply cut off, the flame will be long and yellow and may produce black smoke and soot. This will be the proper temperature for the annealing step. Note: Where you have control of the air/oxygen supply as with a professional glass working torch (or Oxy-Acetyline welder, for that matter), light it up by first opening just the gas supply a small amount and then adding air/oxygen and adjusting gas flow after the flame is lit. Shut down in the reverse sequence. This avoids unsightly pops, bangs, and other explosive behavior.
