Tom, The hydrogen/oxygen flame is not as hard to see as you would
think. i suppose there are some impurities that cause it to be seen.
Perhaps it's even because as the burning gases hit the atmosphere,
right then and there the impurities enter in somehow and show up. It
definitely can be seen when you look for it. You know how you can
even see heat in the summer radiating up off hot pavement into the
atmosphere. It's much more apparent than that though. Annette