Teets,
Didn't use flour, but lycopodium (sp?) powder. Seem to remember it as having a tube coming out of the side with some poweder in it, a tealight candle in the bottom of the tin, shut tin lid then blow powder from tube into tin = BOOM. The experiment was preceeded by a video of a custard powder silo exploding. All about the energy in the powder and the powder/air mix.
But we digress
sw