  Oxy-hydrogen flame. 
OK, I don't really have an eternal hydrogen flame burning as a sample in my collection.  This particular flame burned for about half an hour in my shop, while I was photographing it rotating on a very slow turntable.  Click the turntable icon to see the resulting rotating image.  The flame is coming out of a very, very small torch, made for the jewelry industry.  In half an hour of operation it uses only about 2 cubic feet of hydrogen, and that's with the biggest of the 5 tips it comes with.  The holes in the smaller tips are so tiny they have to use laser-drilled sapphire inserts in the tips. 
Source: Claudin Welding Supply 
Contributor: Theodore Gray 
Acquired: 8 May, 2005 
Price: $2 
Size: 4" 
Purity: 99%
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