When fireworks were first created, it dates back over 1000 years in China, where they used gun powder to make the firework explode. Inside the firework are potassium nitrate and other chemicals that push it into the air, along with more gunpowder to set it off. Once it is in the air, it explodes creating beautiful images in the sky. Different colors are made by different metal salts such as Barium Nitrate, which gives off a green flame when burned. Another is Sodium nitrate which when burned it gives off a yellow flame, Sodium Carbonate that burns red, Copper Chloride that burns blue, and Calcium Chloride that is orange when burned. Let’s say you wanted a purple firework, you’d mix Copper Chloride and Sodium Carbonate in order to make that color. Fireworks have a delay because when the fuse is lit, it burns the powder outside the firework, then propels it into the air (lifting charge), after it’s in the air, the fuse inside ignites and explodes (bursting charge).

Info: Earthsky

pc: google 

featured image: google