Abstract
Sparkling fireworks are composed of black powder containing no metal wrapped in a twisted paper. The fireworks have their unique beauty. However, physics behind the beauty of sparkling fireworks is a 400-year mystery. There are four seasons in a life of the fireworks, and the beautiful streaks of light scatter from the fireball with soothing sounds in the mid seasons. By the high-speed visualization, we have elucidated that the beautiful streaks of light, which result from a tiny droplet reacting with surrounding oxygen, are produced by bursting bubbles on the fireball. Unsteady temperature measurement are also carried out by two color temperature radiometry method. It is clarified that fireball temperature is decided by the melting points of K2S and K2CO3, and highest droplet temperature is determined by melting point of K2SO4. As the production mechanism of the light streaks as pine-like needles, the microexplosion due to gas generation inside the droplet can be an essential phenomenon.
