Senko Hanabi

These are a type of handheld sparkler that date back to at least the early 1900's in Japan. Older versions of them were closer in construction to modern western sparklers where a thin stick was coated in a composition and dried. These days they're more often constructed from a small amount of the composition powder tightly rolled in a strip of tissue paper with a long tail of paper functioning as the handle.

The end of the tissue paper near the composition is lit and the flame quickly ignites all of the composition. Then a ball of molton slag forms on the end, believed to be composed of carbon particles trapped in potassium sulfide. As the slag bubbles tiny explosions erupt in all directions forming a quiet and elegant display of fractal branches of sparks.

Composition

The composition of senko hanabi these days is a variant on the typical black powder formula but with a higher sulfur content. The increased sulfur facilitates the formation of the molton potassium sulfide slag that the sparks are emitted from.

In his book "Fireworks: The Art, Science, and Technique", Takeo Shimizu suggests that the optimal amount of the composition per sparkler is about 0.09 grams (90mg). This small lump of powder is rolled tighly in tissue paper with one end being twisted into a long tail to form a handle.