Hi, currently I also do some experiments with NaOH, just looking for info here and found this topic. About a year ago, I also disassembled fireworks, so that silvery stuff in your fireworks that reacts with NaOH is probably an alkali metal, like strontium or lithium or more likely aluminum. These guys are famous for their shiny look, how they react with bases like NaOH, and for making fireworks light up in different colors. The black stuff left behind? That could be an oxide. As for the gas, it might be hydrogen or something with sulfur in it. If you're still not sure, I'd say hit the books or read some online materials like https://edubirdie.com/docs/harvard-university/chem-40-inorganic-chemistry you're never too old to learn, trust me! Just remember to be careful when messing around with chemicals and stick to the safety rules. It is better to be more careful with flammable substances (unfortunately, I know this from my own experience) But I think in general it's a problem to find information about it on the Internet, because fireworks are easily accessible and therefore become a great material for research