(34 kb
jpg) The first shows
the components unassembled, 
(32 kb jpg) and
the second shows
the components assembled for the
demonstration,
before the cover is placed over the large coffee can. 
Dust Explosion (1.1
MB, quicktime, 58 sec) Dust
Explosion (1.6 MB, microsoft avi, 16 sec) Dust
Combustion (1.3 MB, microsoft avi, 9 sec)
(34 kb
jpg) The first shows
the components unassembled,
(32 kb jpg) and
the second shows
the components assembled for the
demonstration,
before the cover is placed over the large coffee can.
The fuel, in this case commercial cornstarch, is placed into a small container. After this container is placed inside the large coffee can, the small container is connected to an external tube through the side wall of the coffee can. A burning candle is placed inside the coffee can and the can is sealed. When the cornstrach is dispersed as a finely divided powder by blowing through the tube, the dust is ignited by the candle. The pressure buildup caused by the rapid accumulation of the gaseous combustion products causes the lid of the coffee can to be blown off.
(C6H10O5)n + 6n O2 --> 6n CO2 + 5n H2O.
The explosive effect results from the increase in pressure due to confinement of the rapidly produced gaseous combustion products; notice the 11n moles of gaseous products compared with only 6n moles of gaseous reactants. The same reaction can be made to occur, albeit much more slowly, when a small pile of cornstarch is placed on the table and ignited with a match or butane lighter. The significant increase in the reaction rate when the fuel is dispersed as a fine powder occurs because the increase in the exposed surface area of the fine dust particles allows more of the fuel to interact with the oxidizer (in this case air).