Neat :-) I can understand their excitement. I've discussed the dangers of combustion with students, and we also did the paint-can thing :-) Lots of fun, very spectacular. We used smaller cans though and small candles. The lid flies sky high with those. With a shorter tube you can even do some lycopodium fire-breathing that's more safe than any guides you see with liquids. For anyone looking into buying Lycopodium powder: It's spectacular, relatively safe, but always do keep some water, a fire extinguisher and a fire blanket nearby. It's still fire.