iets meer informatie over hummers,bron:
www.pyrouniverse.com.
Humming fireworks consist of a thick walled tube filled with powder and capped off at either ends with clay. A small hole is drilled in the side at such an angle that when the composition is ignited, the thrust spins the device around rapidly on its axis. During each revolution, there is a brief period of time when the thrust hole (the source of sound) is pointed towards the observer. The rapid increase/decrease of sound pitch created by the spinning tube results in a continuous noise that we perceive as humming. Hummers can be placed in shells, or used by themselves (such as Ground Bloom Flowers).
en nog een collectiefoto'tje met deze cake.