Nothing to do with baking but to do with fireworks. Back in the early 1950s my father made his own fireworks for November 5th and got a supply of chemicals to make them including gunpowder . One of the fireworks he made was a catherine wheel but it was more squate than rounds. The result was that when he lit the fuse, there was a bang everytime the fire got to a corner
Of course, times have changed and making your own fireworks now would get you into extremely serious trouble.