Copper produces blue sparks. Barium, also used in rat poison and glassmaking, makes green. A mix of strontium salts, lithium salts and other stuff makes red. Aluminum and titanium put the white stars in an aerial flag. Image credit: stockxpert
From Live Science:
Fireworks for the 4th of July are all about light, color and sound. But inside, there are some bizarre ingredients, from aluminum to Vaseline and even the stuff of rat poison.
An ancient mix of black powder, essentially gunpowder little changed from its invention in China a millennia ago, gets each rocket in the air by creating pressure in gas trapped in a tube, or mortar.
Two fuses are lit at once: one to ignite the black powder, and another that burns slower, creating a well-timed explosion high in the sky.
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