Grain Silo explosion: A cloud of power is ignited and blows lid off of can.

Lycopodium powder is put on a square of paper which is then placed on top of a funnel connected to a rubber hose. The funnel is inside a coffee can, next to a lit candle. A plastic lid is placed on top of the can. Blowing on the hose tosses the powder into the air. The candle flame ignites the cloud of powder, and the lit pops off the can. This effect can be observed with any fine powder and is the reason why grain silos sometimes explode when fine particles are disturbed and create space at interstitial spaces.
UCB Index: 
C+70+90
Demo Diagram: 

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Comments

The coffee can is stored in Pimentel in 54-2. It works best with a holder that is about half the radius of the funnel. I've built one and stored it with the apparatus. When you set it up use the general utility blocks to hold the coffee can up and put a couple of weights in the coffee can to stabilize it if the instructor blows particularly vigorously. Knock out any leftover Lycopodium powder before you insert a lit candle or attempt to light a candle inside of the apparatus. Stress to the instructor that the candle should only be lit half a minute or so before the demo is performed or else the rising heat will melt the lid of the coffee can before the oxygen is depleted. Also stress that, although this should be a perfectly safe demo, it does result in a column of flame rising up from the middle of the coffee can so standing away from it is well advised. The tube provided for the instructor to blow into is very long for this reason.