How Fireworks Work
An aerial firework is normally formed as a shell that consists of four parts:
- Container - Usually pasted paper and string formed into a cylinder
- Stars - Spheres, cubes or cylinders of a sparkler-like composition
- Bursting charge - Firecracker-like charge at the center of the shell
- Fuse - Provides a time delay so the shell explodes at the right altitude
Located just below the shell is a small cylinder that contains the lifting charge.
The shell is launched from a mortar. The mortar might be a short, steel pipe with a lifting charge of black powder that explodes in the pipe to launch the shell. When the lifting charge fires to launch the shell, it lights the shell’s fuse. The shell’s fuse burns while the shell rises to its correct altitude, and then ignites the bursting charge so it explodes.
A simple shell used in an aerial fireworks display. The blue balls are the stars, and the gray is black powder. The powder is packed into the center tube, which is the bursting charge. It is also sprinkled between the stars to help ignite them.
Simple shells consist of a paper tube filled with stars and black powder. Stars come in all shapes and sizes, but you can imagine a simple star as something like sparkler compound formed into a ball the size of a pea or a dime. The stars are poured into the tube and then surrounded by black powder. When the fuse burns into the shell, it ignites the bursting charge, causing the shell to explode. The explosion ignites the outside of the stars, which begin to burn with bright showers of sparks. Since the explosion throws the stars in all directions, you get the huge sphere of sparkling light that is so familiar at fireworks displays.
Read on for more about multibreak shells and fireworks displays.