My mate's dad was a surgeon at the local hospital, and he was asked if he could get some dry ice for the chemistry teacher, so that she could show us its wonderful and interesting properties. Obviously we just had to keep a little for our own amusement, and armed with our new found knowledge of dry ice properties, we ventured to the dinner room. The recipe for fun consisted of a small lump of dry ice, dropped into a plastic cup of water containing a drop or two of washing up liquid. A slight delay...then VOOM!. Up came what can only be described as a tube of foam that grew ever bigger as the seconds went by. Great hilarity ensued. Over came the head honcho from the Kitchen staff to see what was going on. "err, I think this cup's a bit dirty" I said, and handed it to her. Even greater hilarity as she squealed in horror and ran with it held at arms length back towards the kitchen, with short lengths of foam tubing falling to the floor. Teachers and children united in laughter, whilst I felt it timely to make my exit.