Senko-hanabi Traced by Successive Bursting Cascade of Molten Salt Droplets

From the Edo-period, a unique fragmentation cascade, the successive bursting of droplets, draws the ramifying sparks in a Japanese traditional sparkler, Senko-hanabi, depicting the fragile beauty. Involved potassium-salt droplets demonstrate nucleation without evaporation, while the thermal-decomposition supplies gas into a bubble following the thermal diffusion timescale. We specify the distinctions of Senko-hanabi from puffing/micro-explosion of multi-components volatile droplets and from bursting metal sparks rate-controlled by mass diffusion. But in the end, beyond the differences, we generally understand the underlying process of bursting droplet driven by a growth of internal bubble.