Fireworks shower the skies with science | Science News for Students

Fireworks shower the skies with science

Putting on a 4th of July show also requires a lot of engineering and creativity
Jun 27, 2019 — 6:45 am EST

The displays that dazzle revelers on July 4th and many other holidays are the result of chemists and other researchers working to create and choreograph pyrotechnic theater in the night sky.

ProFilm4K/Creatas Video+/Getty Images

A dramatic fireworks display can be the highlight of a summer. It also can provide a feast for the senses. Bright colors delight the eye. Thunderous booms and whistles surprise the ear. If you’re close to the show, you can feel the pressure waves that ripple from each exploding shell. And folks downwind of the action can smell the burnt gunpowder that fueled each rocket — and perhaps even taste it in the air.

More than 14,000 fireworks displays light the night each 4th of July, according to the American Pyrotechnics Association. (Pyrotechnics is the art of making or displaying fireworks.) But Independence Day the isn’t the only time for such shows. New Year’s Eve is also a popular time for this colorful artistry. More and more often, even small celebrations, such as graduations, are going off with a bang. And then there are all of those sporting events and rock concerts. Altogether, pyrotechnic displays throughout the United States, last year, shot off more than 8.6 million kilograms (19 million pounds) of fireworks.

These days, there’s more to putting on a fireworks show than lighting a fuse and running for cover. Things can get really complicated — and quickly.

Large shows can run for many minutes and involve thousands of shells. Many have a musical soundtrack that plays on the radio while colorful bursts light up the sky. For such shows, timing is everything. So people who design these spectacles have to make sure that each shell explodes at just the right moment. They also have to consider how a show might look from different angles and locations. Then engineers and technicians have to build the electronic circuits to control the action.

But long before a show begins, people have to design the fireworks. At what height should each shell explode? How broad should the burst be? What color — or combination of hues — should each burst deliver? Answers to these and many other questions provide show designers with the outline for the pyrotechnic displays that become true crowd-pleasers.

The evolution of fireworks

a firework packet
Each streak of light emanating from a fireworks burst comes from a packet of chemicals (one shown) that contains fuel, an oxidizer and the metallic powders that provide color when they vaporize.
Fireworks by Grucci

Fireworks were probably invented in China more than 2,000 years ago. There, people found that when they tossed a bamboo stalk into a flame, it exploded. As air pockets in the bamboo overheated, they’d expand enough to shatter the stalk. The sudden bang would supposedly ward off evil spirits.

Centuries later, chemists added a crude type of gunpowder to these bamboo bomblets. That made the bangs bigger. Somewhere along the line, people found that adding metal powders and shavings to their mixtures made things sparkle. Later, they developed rockets by packing these materials into stiff paper tubes.

Modern-day fireworks are high-tech versions of those ancient Chinese devices. Today’s shells typically include some sort of fuel, often gunpowder. They also contain a chemical called an oxidizer. This helps the fuel burn more quickly. The shells also contain chemicals whose recipes include metals. Those metal-based compounds play a big part in determining the color of fireworks, explains Phil Grucci. He’s the owner of Fireworks by Grucci in Bellwood, N.Y. His family business has been operating for almost 170 years.

As a shell’s fuel explodes, it releases a sudden burst of heat. That energy, in turn, excites electrons orbiting metal atoms packed along with the fuel, Grucci explains. Excited electrons jump to a higher orbital. Soon, they’ll drop back to their original orbits again. At this point, the metal atoms emit a characteristic color of light.

Different chemicals produce different hues. For example, chemicals that contain barium give off a greenish light. Copper yields a blue light. This can be easily seen in an experiment that’s often a staple of high-school chemistry classes, says Grucci. A small wire is dipped into a powder and then thrust into a small flame. The color of the flame changes with the elements contained in the powder.

To come up with a new color for a firework, members of Grucci’s team, as well as the chemists they work with at other companies, do a version of that wire test. Now, however, these tests take place in bigger, better-funded labs.

Coming up with a new color can take a lot of time and involve a lot of trial and error. But by choosing and mixing chemicals in the right proportions, chemists can make a shell that will display almost any color imaginable, he notes.

three different colors of flames (orange, green, yellow-orange) occuring when exposed to different metal compounds
The various colors in fireworks (examples shown) are typically generated when metal-containing chemicals are vaporized.
Ian Redding/iStock/Getty Images Plus

And now for the physics

Fireworks displays depend on a lot of physics and engineering, notes Grucci.

On the small scale, the size and shape of particles inside a shell affect how quickly they will burn. That, in turn, affects how long a burst’s glow lights up the sky. Also, as Chinese inventors long ago noted, slow-burning gunpowder doesn’t explode. Instead, it gives off gases that can provide thrust for a rocket if they’re forced through a nozzle.

a photo of the record-setting firework burst
A lot of engineering went into the design of this record-breaking shell, which rose more than 1,100 meters into the sky with a burst that spanned more than a kilometer.
Fireworks by Grucci

To design a fireworks shell that rises to a certain height before it blows up, there’s a lot of math and lab work to be done. For instance: How quickly does 1 kilogram (2.2 pounds) of a particular mixture of gunpowder burn? What volume of gas does it give off? (Those things can be measured in the lab.) How much weight can that lift? (That can be measured in a field test.) Together, those data can help engineers figure out how much gunpowder will be needed to send a 10-kilogram (22-pound) shell, say, up 500 meters (1,640 feet) into the air.

On larger scales, engineering challenges can be just as daunting. Consider the world-record-size shell that Grucci’s company recently developed. The projectile measured about 1.5 meters (5 feet) across and weighed a whopping 1,000 kilograms (1.1 U.S. tons). It was fired from a tube and rose to a height of more than 1,100 meters (3,600 feet) before it burst. When the shell exploded, its colorful display measured more than 1 kilometer (0.6 mile) across.

One challenge, says Grucci, was fine-tuning the strength of the shell’s outer casing, which was made of many layers of paper. For one thing, the casing had to be strong enough to survive the launch, he notes. (When the shell left its launch tube, it was traveling at a speed of 122 meters [400 feet] per second.) But the shell’s outer casing couldn’t be too strong or the shell wouldn’t burst open properly when it reached peak height, says Grucci. The engineers used computer software to estimate how shell casings of various thicknesses might stand up to the stresses of launch and explosion. At the same time, a different team was designing the steel tube needed to launch the shell. It ended up being 7 meters (23 feet) long. Designing and building it took his teams more than 10 months.

“Designing that shell was quite an interesting journey,” says Grucci. Near the end of the process, “all our math lined up,” he notes. And the team’s lab tests suggested that the shell would work, he adds. “But at some point in time you’ve just gotta build it and launch it.”

a photo of the record-breaking firework shell, Phil Grucci and his family
Fireworks maven Phil Grucci (second from left) and other family members also in the pyrotechnics business stand next to the record-breaking shell they designed, built and then fired from a steel tube that was 7 meters (23 feet) long.
Fireworks by Grucci

Many challenges remain to be tackled, says Grucci. He’d like to be able to reduce the amount of smoke that each shell produces. This might involve tweaking the ratio of fuel to oxidizer inside the shell. That, in turn, might lead to more complete burning of the chemicals inside the rockets. And needing smaller amounts of ingredients could greatly reduce overall costs. But there’s another reason to go smokeless, he notes. Smoke emitted by shells designed to burst at low altitude can obscure the view of fireworks exploding higher up.

Plus, Grucci would like to make his fireworks more ecofriendly. Smoke itself can be a problem, polluting the air. And many of today’s shell casings are no longer bamboo, but plastic. As the shells explode, they send a rain of little plastic bits falling all over the ground. “Greener” fireworks, he says, might house the rocket’s ingredients in polymers that are biodegradable. That way, the debris that falls to the ground might naturally break down over time.

Creativity reigns

A company that puts on only one or two fireworks shows per year probably wouldn’t earn much money. So it pays to diversify beyond staging shows on the 4th of July and New Year’s Eve. And many companies have done just that.

Among them is Pyrotecnico, based in New Castle, Pa. It stages some 3,000 shows across the United States each year, notes owner Stephen Vitale. The majority of those are small community celebrations. But the company also has staged events that range from a Super Bowl halftime spectacular to weddings (where, Vitale says, “Our fireworks are the icing on the cake”).

Fireworks are “obviously a visual business,” says Vitale. But shows, particularly the large ones, have really evolved in recent years. “About 50 percent of the shows we do are choreographed with a musical soundtrack,” he explains. “With music, crowds get more emotionally involved in the show.”

Turn down the volume! This fireworks display, in San Diego in 2012, was supposed to last 17 minutes. Instead all the fireworks discharged in less than one minute. The errror was blamed on the computer software controlling the show malfunctioning.
Dan Roy/YouTube

Making sure the soundtrack lines up with the bursting fireworks takes a lot of effort — and a lot of creativity. For each minute that a fireworks show lasts, his designers spend somewhere between 2 and 3 hours ahead of time getting the details right. They typically design the show using computer software. That software started out as an off-the-shelf program. Team members then tweaked the software to add new features. For instance, designers have to take into account how high a shell will fly, as well as how long it takes to reach that height and then burst to light the night sky.

In a sense, Vitale says, a fireworks show is like staging a play. “In the first scene, you grab the audience’s attention. After starting out strong, you program in a series of ‘Wow!’ moments,” he points out. “Then, you end with a bang!”

Designing the succession of bursts in a computer allows planners to visualize how a potential show will look. It also gives the company a way to preview the show. Designers can view via computer what the show would look like from any location in the area and from any angle. The team can then tweak the display as needed.

The opportunity to be creative attracts a lot of people to the field, says Vitale. “People get to be their own designer and choreographer, or direct their own play or movie,” he notes. It’s a very satisfying business, he adds. “We try to make a difference every day — to put a smile on people’s faces.”

Diversity pays

Pyro Spectaculars by Souza is based in Rialto, Calif. It stages shows at all scales. On the small end, they might run a show at graduations that lasts only a minute or two, says Jim Souza. He’s the company’s president and creative director. On the big end, they’ve orchestrated a 25-minute fireworks show shot from four river barges and the 580-meter-long Brooklyn Bridge in New York City. That spectacle sent up about 50,000 shells and other devices. Each year on the 4th of July alone, Souza’s company stages about 400 shows.

fireworks blasting off the Brooklyn Bridge and an inset photo of workers setting up the fireworks
A large fireworks show, such as one staged from New York City’s Brooklyn Bridge (main image), may take dozens of people a couple of weeks to set up.
Pyro Spectaculars by Souza

When his designers put together a show, they start by creating what Souza terms “a script.” From that, they map out what sort of shells they’d like to use and how high those shells should burst. They also, among other things, decide where each shell should be fired from. In the virtual model that the designers create, events are precisely timed, Souza notes — “usually down to the tenth of a second.” They also work closely with clients to make sure that any musical soundtrack triggers “excitement, enjoyment and a lot of emotion,” he adds.

a photo of a person at a control panel for a fireworks show
Many fireworks shows are synchronized with a musical soundtrack and are designed to start with the push of a button.
Pyro Spectaculars by Souza

Souza has 60 full-time employees at 10 offices around the world. His teams also work with hundreds of technicians that have many different specialties. In the United States, these technicians usually are certified by local or state authorities. To be certified in California, for example, the technicians must go through a training program, take a detailed test and have two years of job experience.

Besides being trained in safety, the technicians have to be handy with tools and keenly creative. These are the workers who turn the designers’ visions into a reality. Some design and assemble the circuits that control when shells get fired. Others design and build the brackets that hold fireworks at a particular angle so that the shells will fly off and burst at the proper locations and heights. Yet other technicians may have to hang off the sides of skyscrapers and bridges to install brackets and wiring.

More than 50 people helped set up the fireworks show that lit up the Brooklyn Bridge, notes Souza. It took two weeks to set up a show that was over in less than half an hour.

Like all fireworks firms, Souza’s company has to abide by state and local environmental rules. One recent challenge has been a need to reduce their use of chemicals called perchlorates (Per-KLOR-aytes). If some of those oxidizers are left over when a shell explodes, they can drop into waterways or onto soil and affect animals and plants living or growing there. Not only that, they can be harmful to human health. Among other problems, they can reduce the production of hormones in the thyroid gland.  

So, there’s plenty of challenges for people to address, both in the near term and into the future. The fireworks industry relies on many types of experts, says Grucci. In the end, one of the biggest challenges may be meeting customer expectations. To make a “seamless performance,” he says, “chemistry, engineering and artwork all have to come together.” 

Learn about the chemistry of fireworks from John Conkling of Washington College in Chestertown, Md. You can trust this guy as he’s literally written the book on making fireworks (a textbook, that is).
Reactions/American Chemical Society/YouTube

Power Words

(more about Power Words)

angle     The space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet.

atom     The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.

barium     An abundant, silvery-white metal that can be founds in air, water and soils across the planet. From there it often enters foods, such as fish, nuts and certain plants.

biodegrade     (adj. biodegradable) To break down, based on the activity of microbes, into simpler materials. This usually occurs in the presence of water, sunlight or other conditions that help nurture those organisms.

casing     (n.) Some structure that encloses the potentially fragile working parts of a device, such as a cellular phone. It affords those internal parts protection by fully covering, or encasing, them. (in food science) The outer skin or material used to hold — or encase — the meat and other ingredients used to make a sausage.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemistry     The field of science that deals with the composition, structure and properties of substances and how they interact. Scientists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances. (about compounds) Chemistry also is used as a term to refer to the recipe of a compound, the way it’s produced or some of its properties. People who work in this field are known as chemists.

choreograph     (n. choreography) The process of planning or designing each step in a complicated performance (be it dance, ice skating or the movements across the stage in some play). Or it can be setting the controls to set the role of each participant in some precision operation (such as battlefield plan of attack or marching band’s half-time display). The person who does this planning is known as a choreographer.

circuit     A network that transmits electrical signals. In the body, nerve cells create circuits that relay electrical signals to the brain. In electronics, wires typically route those signals to activate some mechanical, computational or other function.

compound     (often used as a synonym for chemical) A compound is a substance formed when two or more chemical elements unite (bond) in fixed proportions. For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.

copper     A metallic chemical element in the same family as silver and gold. Because it is a good conductor of electricity, it is widely used in electronic devices.

daunting     A description for something that is intimidating and which seems hard to imagine in detail such that you can figure out how to cope with, master or achieve it.

debris     Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.

diversity     A broad spectrum of similar items, ideas or people.

electron     A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.

engineering     The field of research that uses math and science to solve practical problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

evolution     (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. Or the term can refer to changes that occur as some natural progression within the non-living world (such as computer chips evolving to smaller devices which operate at an ever faster speed).

excite     (in chemistry and physics) To transfer energy to one or more outer electrons in an atom. They remain in this higher energy state until they shed the extra energy through the emission of some type of radiation, such as light.

fuel     Any material that will release energy during a controlled chemical or nuclear reaction.

fuse     (v.) To merge two things together, often along some seam. (n.) Some cord, tube or other material that can burn and eventually ignite an explosive. Or an electrical device that breaks an electrical circuit when it overheats, thus preventing electrical wires from getting hot enough to cause a fire.

gland     A cell, a group of cells or an organ that produces and discharges a substance (or “secretion”) for use elsewhere in the body or in a body cavity, or for elimination from the body.

green     (in chemistry and environmental science) An adjective to describe products and processes that will pose little or no harm to living things or the environment.

hormone     (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.

hue     A color or shade of some color.

lift     An upward force on an object. It may occur when an object (such as a balloon) is filled with a gas that weighs less than air; it can also result when a low-pressure area occurs above an object (such as an airplane wing).

model     A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.

nozzle     A round spout or slot at the end of a pipe, hose or tube. Nozzles are typically used to control the flow of a jet of some high-pressure liquid or gas.

orbit     The curved path of a celestial object or spacecraft around a star, planet or moon. One complete circuit around a celestial body.

orbital      Adjective for something relating to orbits. (in chemistry and subatomic physics) The pattern(s) of electrons (and their density) that form(s) within an atom or molecule.

oxidizer     A substance that yields oxygen, resulting in the combustion of another material, such as a fuel.

perchlorate     This naturally occurring chemical is a potentially cancer-causing component of certain jet fuels, explosives and fertilizers. In animals, this pollutant can perturb levels of thyroid hormones. It also appears capable of acting like an androgen (a male sex hormone).

physics     The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study that emerged later, is a more accurate way of explaining the motions and behavior of matter. A scientist who works in such areas is known as a physicist.

plastic     Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.

polymer     A substance made from long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).

pressure wave     (in geoscience) A type of wave that moves through materials in a manner similar to the movement of sound through air. That is, it jiggles the material back and forth along the same line as the path of the wave. Moreover, unlike other types of seismic waves, these can travel through more than just solids. They also can move through liquids and gases. 

proportion     The amount of a certain component of a mixture relative to other components. For example, if a bag contains 2 apples and 3 oranges, the proportion of apples to oranges in the bag is 2 to 3.

pyrotechnics     A term for fireworks.

range     The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which variation in values is possible. Also, the distance within which something can be reached or perceived.

ratio     The relationship between two numbers or amounts. When written out, the numbers usually are separated by a colon, such as a 50:50. That would mean that for every 50 units of one thing (on the left) there would also be 50 units of another thing (represented by the number on the right).

rocket     Something propelled into the air or through space, sometimes as a weapon of war. A rocket usually is lofted by the release of exhaust gases as some fuel burns. (v.) Something that flings into space at high speed as if fueled by combustion.

shell     The protective, hard outer covering of mollusk or crustacean, such as a mussel or crab. (in munitions) An explosive bullet, bomb, grenade or other projectile.

software     The mathematical instructions that direct a computer’s hardware, including its processor, to perform certain operations.

thrust     A force that makes an object move forward.

thyroid     A gland in the neck that releases hormones, which play a pivotal role in directing development and metabolism (the use of food as fuel). The gland is relatively small, with two lobes separated by a bridge-like structure. Some therefore refer to its shape as resembling a butterfly.

virtual     Being almost like something. An object or concept that is virtually real would be almost true or real — but not quite. The term often is used to refer to something that has been modeled — by or accomplished by — a computer using numbers, not by using real-world parts. So a virtual motor would be one that could be seen on a computer screen and tested by computer programming (but it wouldn’t be a three-dimensional device made from metal).

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