Everyone loves fireworks, except for small children and dogs, but what exactly goes into making the explosive and beautiful balls of fire?
Fireworks are a lot more than balls of explosive powder with a fuse. They are perfectly constructed chemical masterpieces used in celebrations all over the world. First, let’s look at how pyrotechnicians create various colors of fireworks.
Firework chemical reaction
When a firework explodes, it essentially is a chain reaction of chemical reactions that result in different shapes and colors in the sky. As you likely expected, the explosion creates heat that starts the burning of different chemicals packed within the shell. To make different colors, pyrotechnicians have to use different chemical compounds, some more dangerous than others.
These compounds are typically metal salts which burn specific colors. Compounds based on Sodium will burn different shades of yellow or orange, copper or barium salts will burn green or blue, and calcium or strontium make red shades. Combining these compounds in different layouts within the projectile will create different shapes.
For example, say you wanted to create a smiley face firework that had a yellow circle and blue eyes and mouth. Starting from the inside, you would pack the fuse, then the primer charge (we’ll get to this later), then lay out balls of barium in a smiley face (blue), then surround the perimeter of the shell with sodium balls to make the outer ring. All of this will be backed into a rigid spherical shell and launched into the air.
Now that we understand the chemical reactions behind a firework, let’s figure out how they are propelled and the explosions are initiated. There are four main parts that help to set off the firework: the stick, the fuse, the charge, and the effect.
How fireworks are propelled
The stick is essentially that, a long stick that protrudes out the end of the firework to make sure it shoots in the right direction. This helps show organizers arrange the fireworks and make sure the display goes according to plan. It also means that if you launch one yourself, you hopefully won’t fire it through your neighbor’s window.
The fuse is what is set off by the initial lighting of the firework. Fuses can be as simple as a piece of paper or as complex as electrically timed wires. Focusing in on the more complex electrically timed fuses, these are the kinds used in professional shows.
This allows a whole array of fireworks to be set off from one central computer sending signals to the individual fuses. These fuses burn for a predetermined amount of time then set off the main charge that launches the firework into the air. The fuse continues to burn while the charge is being expelled to eventually trigger the explosion of the shell which produces the effect of the firework.
The charge, as mentioned above, is basically a rocket that launches the entire shell into the air. It can accelerate shells to speeds greater than 300 miles per hour to reach altitudes above 1000 feet. Charges are typically made through a mixture of gunpowder and other minute chemicals. For fireworks that have extravagant tails as they are launched in the air, balls of chemicals mentioned above can be laced into the charge to create the effect.
The final explosive effect
The effect is the final destructive aspect of fireworks and is by far the most important. A firework without an effect is just a boring old rocket. This contains the chemicals mentioned before, the end of the fuse, and a primer to start the explosion. The effect is inside the main part of the shell, often called the head. The head is packed with the specific chemical design and explosives to cause the firework to go off. As the fuse burns through the charge, it sets off a primer that then ignites the main shell charge to explode the firework, starting the colorful chemical reactions.
The engineering behind fireworks is far more complex and dangerous than the processes make it seem. Only skilled pyrotechnicians can (safely) create fireworks of the magnitude needed to be impressive. While these fun festive devices may seem like toys, they are dangerous explosives that when used in the right way, can be fun displays of patriotism, celebration, or more.