How Does a Firecracker Work?
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Introduction
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Many celebrations, such as the Fourth of July, New Year's and the Chinese New Year, are not complete without scores of fireworks and firecrackers going off everywhere. Fireworks signify independence and excitement, and also continuously evolve to form beautiful pieces of artwork in the sky. However, even the most complicated firework started with the concept of a simple firecracker.
Elements
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Firecrackers start with three main substances: 75 percent is made up of potassium nitrate, 15 percent is made up of carbon (charcoal) and 10 percent is made up of sulfur. These substances--in these proportions--create a powerful chemical reaction when a heat source (usually fire) is introduced. This chemical reaction is the explosion you see with most firecrackers.
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The Wrapping
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The wrapping is an integral part of the firecracker's reaction. The wrapping allows the chemical reaction to build up pressure. The pressure beneath the wrapper is what allows the firecracker to build up enough energy to explode. The wrapper is also responsible for the cracking sound as the paper is ripped open during the explosion.
The Reaction
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When the fuse is lit, the fire (or the catalyst) makes its way to the substance wrapped inside the firecracker. The carbon acts as a fuel for the ignition process, while the potassium nitrate (the oxidizer) reacts with the sulfur and carbon. As these substances react, they form nitrogen and carbon dioxide gasses. The substances also react with the external air to create energy. As the reaction occurs, the gasses expand until the wrapper can no longer hold them. When the wrapper bursts, it causes a simultaneous release of energy, making an explosion as well as the cracking sound of the paper breaking.
Pyrotechnics
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Modern pyrotechnics take the basic form of a firecracker and expand it to not only make the explosions larger, but also to create colors, designs and effects. Pyrotechnics still use a modified form of a firecracker called a bursting tube. This bursting tube is then surrounded by black powder and specialized chemicals that are packed into small balls like a bullet. When the bursting tube ignites, it explodes and ignites the gunpowder. The explosion forces the small balls of chemicals out and ignites them in the process. The color of the firework depends on what types of chemicals are inside the balls. Certain chemicals can also cause the twinkling, sparkling and spinning effects that are often seen in fireworks shows. To create patterns in the sky, the balls can also be arranged inside the fireworks' shell to create specific shapes when the shell explodes in the sky.
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Resources
- Photo Credit frontierfireworks.com
