Fourth of July is coming up and it got me thinking about what goes into all of the amazing fireworks displays that we see every year to celebrate so many holidays all around the world. I’ve always been fascinated by fireworks and how cool they look exploding up in the sky in different colors and shapes, especially when they are perfectly timed with the music. It all combines together to make for a really magical experience. Read on to learn all about the history, engineering, art, and science of fireworks.
The History of Fireworks
Fireworks themselves have been around for centuries and they are believed to have started in ancient China as a way of scaring off evil spirits. Back then, they were really simple and made of bamboo stalks that would explode when they were thrown into a fire. Later on, a Chinese alchemist figured out how to make the first gunpowder using potassium nitrate, sulfur and charcoal. He apparently decided it was a good idea to pour it into the bamboo tubes and throw it in the fire. Needless to say, it made quite a bang, and thus, the first man-made fireworks began. (Please don’t do that at home)
Since then, fireworks have progressed to include various colors and shapes. Today even computers are part of the fun! Computers synchronize the displays to music and trigger the explosions remotely at the right moment and at exactly the right location.
Licensed pyrotechnicians, or firework technicians, go through lots of training and have a good understanding of chemistry, physics, and creativity, in order to create dazzling light, shows that captivate the public.
How are Fireworks made?
The firework itself is made up of these main parts:
- the aerial shell, which holds everything together and is usually shaped like a ball or cylinder. This contains a fuse that burns slowly and is measured out to reach the explosive at a certain time when the shell is in the sky
- the explosive, or gunpowder, which is at the end of the fuse inside the shell. This reacts to create an explosion when heated and causes the components inside the shell to ignite and be pushed outward
- the â€œstars,â€ which are explosive pellets that can be covered with different metals and burn a bit slower to create the colored points of light we see in the sky
The shell gets put into a tube in the ground (a mortar) in order to guide it in the correct angle. A slow-burning fuse gets lit up which leads to a small packed portion of black powder propellant underneath the shell. Once it’s lit, the momentum of the burning powder launches the firework high into the sky really quickly. Meanwhile, a shorter pre-measured fuse inside the shell is burning until the firework reaches the right height. Then, the gunpowder inside the shell ignites safely up in the air, lighting the â€œstarsâ€ outward in a pattern, causing them to burn off and create the amazing light patterns we see from the ground. In a well-made firework, the components of the stars completely burn off before they ever reach the ground. In modern computerized fireworks displays, the fireworks are detonated using electric matches, or e-matches, which contain a compound that ignites quickly when heated using a wire coil. These are triggered remotely using controllers with switches that can even set off multiple batches of fireworks at once.
The Science of Fireworks
But how do they create the different colors? The â€œstars,â€ or explosive pellets, contain a few components to make that happen. They are composed of metal salts that naturally react and change different colors when they are ignited. They also contain fuel as well as a chemical that provides oxygen for combustion in order to feed that fuel. This also makes it last longer and creates cool cascading effects as they burn. Plus, there is also a compound that can make some colors brighter (by adding chlorine), as well as a chemical that binds all of these parts together.
Here is a handy guide to remind you which metal salts create which colors. Now you can shout out the appropriate metals that correspond to the colors you see in a fireworks display. Wait, am I the only one who does this? Itâ€™s totally normal, right?
RED: Strontium salts
ORANGE: Calcium salts, charcoal or iron
YELLOW: Sodium salts
GREEN: Barium salts
BLUE: Copper salts
PURPLE: Copper and Strontium salts
WHITE/SILVER: Aluminum or Magnesium powder
You’ve probably also seen that some fireworks create cool shapes like smiley faces, hearts, stars, and even Mickey Mouse. This takes careful planning and packing the exploding stars in a certain way into the desired pattern on a piece of card inside the shell. When the shell explodes, it pushes the stars outward in that shape.
Pyrotechnicians can even control when the explosions happen in order to choreograph a fireworks display so that it is timed to happen during certain parts of a music track or show. This is all based on knowing how much energy is released during an explosion (thermodynamics) and also knowing how fast that energy gets released (kinetics). They measure the velocity, launch angle, speed and even air resistance in order to pinpoint exactly where the shells will travel and when they will explode so they can time it just right to the beat of the music.
You have to admit that fireworks are really cool, and there is obviously a lot of time, science, math and creativity that goes along with creating those amazing displays. Not to mention safety concerns…you are dealing with explosives, after all!
You’ve probably also seen and held sparklers, which look like miniature little fireworks in your hand. Fireworks are basically controlled explosions in the sky. But, unlike fireworks, sparklers are made to burn over a longer period of time (about a minute). The components behind a sparkler are similar: they contain a metal fuel, an oxidizer to feed the fuel, and something to bind it all together onto that wire. Sparklers can also contain those same metal salts to create different colors. The ones you typically see are white with some orange sparks, which means they contain a mixture of aluminum, magnesium and iron (hint: look at our handy color chart).
We do not condone the use of fireworks for home use. Leave it to the professionals! And we strongly urge you to use caution (and adult supervision) even if you’re just holding a sparkler. They can get really hot and you should always use appropriate safety measures if you are near any explosives.
We hope this has helped you understand a little more about fireworks and that you can appreciate the hard work that goes into creating them the next time you see these magical (*ahem*…totally scientific) explosions of colors.
Here is a fun explanation and demonstration of the chemistry behind fireworks from an expert:
Want to learn more about how to become a pyrotechnician? Hereâ€™s a quick overview to give you a sense of the kind of training involved.
To learn more about other STEM careers, check out Smore Magazine for ages 8+. and to get the little ones excited about science and science experiments check out Lil Smore
-Written by Julie Nagy, Assistant Editor, Smore Magazine