The sights and sounds of each explosion are the result of several chemical reactions – oxidations and reductions – taking place within the firework as it ascends into the sky. Oxidizers produce the oxygen required to burn the mixture of reducing agents and to excite the atoms of the light-emitting compounds.
Simple Chemical Reactions in Fireworks. The amazing colors in exploding fireworks come from chemical reactions triggered by heat. Combustion propels fireworks into the air while oxidization provides the oxygen needed to excite the metal compounds in fireworks.
Traditionally, gunpowder used in fireworks was made of 75 percent potassium nitrate (also called saltpeter) mixed with 15 percent charcoal and 10 percent sulfur; modern fireworks sometimes use other mixtures (such as sulfurless powder with extra potassium nitrate) or other chemicals instead.