I remember watching a demo in 8th grade chemistry wherein the teacher poured some liquid into a beaker that was about a quarter full of ordinary white sugar. Within seconds, an enormous black stalk grew out of the sugar/liquid mixture. It got so tall the teacher had to hold it with tongs to keep it from toppling over. I think it eventually reached a height of about a half meter.
What was the liquid, and what was the experiment meant to demonstrate?