Ok so here's something I've been wondering about...
Ignoring the extremes of mixture... what about the "blue cone"? It has different shades of blue even a greenish one. Any place you know of that talks about what the color means?
Acetylene is easy as pie, even hooking up propane to an Oxy-torch doesn't make the mixture "cut and dried" like the acetylene does. You get shades of blue and green with no "feather" etc.
Hmmm... maybe need to ask this on the welding NG? :) Oooo a cross-post? :) I like cross posts like that, it's almost like having a visiting speaker come to your club, but better somehow.
Alvin in AZ