Moa Shooter, the reason I chose that expression was to preempt a pedant saying that, for example, a sawdust pile might go to flame after smouldering ignition from a cigarette end. Clearly in such a case the wood dust is entirely unprocessed. Hence the caveat about bulk. As you will probably know, there is an interplay in bulk heating scenarios in which the density of the charring material produces a balance point at which sufficient oxygen diffuses into the pile but sufficient overlying insulation is present to maintain the char. It is for this reason that fires in woodmill sawdust piles, or bulk cargoes in ship holds, can appear to have burnt preferentially in a defined layer within the pile. Once there is sufficient heat present to sustain charring in upper layers, the surface of the pile can transition to flaming. The interesting aspect of your demo is therefore, that such a small quantity of powder transitioned to flame. Again, thanks for sharing.