Or, poor man's liquid nitrogen. I'm in college, but unfortunately no chem classes, nor do I have the money for a Dewar's of my own to have filled. I heard of this technique from a friend of a teacher's son's maid..or something, it was a while ago.
Full credit for this idea belongs to wbeaty over ar Youtube,http://www.youtube.com/watch?v=d11TFkeqbwY
I'm just the instrustables messenger;)