Science of Fireworks

Every year on the Fourth of July, fireworks light up the usually explosion-less sky with bursts of brilliance, color, and, much to dogs’ chagrin, titanic booms.

Fireworks have been around for a long time; they are not an invention of the last few hundred years. The ancient Chinese invented them during the seventh century, and they have since been used to elicit wonder and awe from audiences all around the world.

How They Work

Firework creation is a process with many steps and safety precautions. Fireworks are essentially rockets that are encased in a cardboard ball or tube that has been filled with gunpowder and little balls of elements (perchlorate and black powder with binding and coloring agents) called ‘stars.’ The gunpowder and the stars are what create the bright colors and explosions commonly associated with fireworks.

To create a firework, the assembler creates the stars first. The stars are hard balls that vary in size and weight and are made up of different elements. Different elements give off different colors when they burn. For example, strontium nitrate burns red and barium nitrate burns green. Other colors are more difficult to get and sometimes require a mix of elements. The assembler must form the stars out of the appropriate elements to get a desired color. The pattern of assembly inside the cardboard case has to be carefully thought out as well. Both the weight and the size have to be considered when placing the stars in their case. If the assembler doesn’t particularly care where the stars explode out to, the stars can just be dumped into their casing; however, if the stars need to explode in a certain pattern, like a circle, the stars must be placed, and sometimes even glued, into a certain order to get the desired shape.

Once the stars are placed in their casing, the casing is filled with gunpowder. After the stars and gunpowder are in place, the rocket is attached with a slow-burning fuse inside. The assembler must time the slow-burning fuse precisely so the firework explodes in the air at the correct time. Once the fuse hits the gunpowder, the gunpowder explodes and flings out the stars that then burn and glow.

Making fireworks is a complicated process and takes a long time to get the timing exactly right. If, for example, the slow-burning wick is too short or long, the firework will explode too soon or late, potentially injuring people.

And last, but not least, the firework is attached to a rocket and placed in a launch tube. The main wick is lit and the firework flies up into the air, eventually exploding into red, white, and blue in time to patriotic music.

-Mackenzie Brown, College of Physical and Mathematical Sciences


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