When I put my gas tubes away after a run they usually light up when I
handle them.
I have 4 tubes that are clear glass about 15 inch long with neon sign type
electrodes. Judging by the color I am guessing that 2 are argon, and 1 is
neon, and the other neon and something else . They have no phosphor
inside. You can see the tubes in these videos.
http://www.youtube.com/watch?v=B7QW_a3oarA
http://www.youtube.com/watch?v=JLCr49Phum4
http://www.youtube.com/watch?v=b0u9GgT1sMg
The ionization may be caused by the discharge of surface charge when you
handle them .
I will try to get some video of this.
Jeff