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Question How do fireworks work?


Fireworks are explosions of numerous small pellets of black powder called stars. The main ingredient in fireworks is black powder, which explodes when ignited (lit on fire). In addition to black powder, firework stars contain different chemicals or metals to create certain colors. The stars are intentionally arranged to create various firework shapes or images.

July 4th fireworks, Washington, DC. Carol M. Highsmith, photographer, 2007. Prints & Photographs Division, Library of Congress

The fireworks we enjoy at large celebrations are called aerials. To assemble aerial fireworks, trained professionals called pyrotechnicians first make stars by mixing black powder with different chemicals or metals. When reacting with heat from exploding black powder, the chosen additive produces a certain color. For instance, mixing copper into a star will produce a blue firework. The stars are then arranged inside a cardboard or plastic container called a shell. How the pellets are arranged within the shell determines the shape of the firework. Lastly, fuses are attached to or embedded within the shell and everything is wrapped in paper.

The Great bridge – Fire-works and illumination, from the Brooklyn side. Drawn by Charles Graham, 1883. Prints & Photographs Division,  Library of Congress

Pyrotechnicians don’t just make the fireworks; they also supervise every aspect of firework shows. It can take several days to several weeks designing, preparing, and setting up a 20 minute show. To set up an aerial fireworks display, pyrotechnicians prepare the launch site with short metal pipes called mortars. Each shell is placed in a mortar on top of more black powder called the lift charge. The professionals then attach one end of a wire fuse to the lift charge. The other end of the wire fuse is connected to a control panel. When prompted by a computer or trained operator, the panel sends an electric jolt to the shell which ignites the lift charge to create an explosion. This explosion launches the shell into the air and lights the shell’s fuse. When the lit fuse reaches the stars in the shell, they explode into the air in the designed shape. The heat from these explosions reacts with the chemicals mixed within each star, and we see the vivid colors and shapes of the fireworks in the nighttime sky.

Fireworks over Houston, Texas. Carol M. Highsmith, photographer, between 1980-2006. Prints & Photographs Division,  Library of Congress

Pyrotechnicians carefully measure black powder, chemicals, fuses and other supplies to build fireworks that work properly. These professionals make precise calculations to ensure that each firework projects to the correct altitude (height) and explodes at the right time and in the right location. The next time you enjoy an aerial fireworks show hopefully you can appreciate the exact science that becomes a beautiful celebration of chemistry and physics.

Fireworks Sanderson & Lanergan, pyrotechnists. Prints & Photographs Division,  Library of Congress

Published: 11/19/2019. Author: Science Reference Section, Library of Congress

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