I've been curious for years what exactly this black mixture is comprised of. You can see in the picture a small firecracker whose contents I poured out: there's a red match head; a black powder which acts as both a fuse and a plug (it is not gunpowder); a grey flash powder which is the stuff that explodes; and ultimately the tube of the firecracker.
These firecrackers don't use visco fuses. This type of firecracker is popular in central and eastern Europe and China (they're all made in China actually) and you might not be familiar with it.
Anyway once you ignite the firecracker the black stuff starts burning slowly while releasing smoke and hardens inside the case as to provide compression so the flash powder can explode and not just fizz. There's clearly sulfur from the bad smelling smoke that comes out and there has to be some oxidizer but I think there must be something else too that makes it turn into a plug while it burns; I also don't know the proportions of the chemicals either. I can't find any information anywhere on the internet and I've searched everywhere. Does anyone know what this is? I can share more pictures.
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