Here's how your Fourth of July fireworks work

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How Do Fireworks Work?



As you gear up to watch fireworks this Fourth of July, you might wonder: How exactly do fireworks work?

How is it that there are fabulous, colorful explosions in the sky that come in different shapes and sizes?

Well, we're here to help you out. The short answer: It's a whole lot of chemical reactions happening all at once.

The explosion

Simply, a firework is a container (typically a tube or a ball shape) that holds explosives, hitched up to a time-delay fuse.

The explosives are where the fun happens. They typically contain little balls of colored explosives called "stars." These are filled with colors that blaze brightly in the sky, but only after a certain amount of time has passed. This is why fireworks can get up high in the sky before exploding into brilliance.

When the fuse gets low enough in the firework, it reacts with a bursting charge, which in turn lights the explosives that will disperse the stars. The ignited explosive creates a high-pressure gas that blows the colorful stars outward.

Here's what that looks like:

BI_Graphics_How fireworks workBusiness Insider

The colors

The colors that sparkle in the sky are chemical reactions happening right before your eyes.

Inside every star is an oxidizing agent, fuel, a certain metal that acts as the color, and a binder that holds it all together. The fuel and oxidizing agent are the parts responsible for the intense heat and gas of the explosion, according to the American Chemical Society.

But the coolest part are the metals that act as the colors. Some just heat up and cycle through red, orange, yellow, and white colors, depending how hot the explosion is. The heat makes the atoms inside the wire move faster and faster, causing the atoms to bump into each other more, which gives off light. If you can control the temperature of the firework, then you can pick the exact time you want that firework to be a certain color.

But more commonly, fireworks create light by letting off specific colors that depend based on what metals you add to the mix.

For a complete display, fireworks often mix different metals and metal salts to give you the vibrant, multicolored effects. Calcium salts will burn orange, while sodium salts will burn yellow.

And if you burn copper, it'll give off light that's blue-green.

The shape

Fascinated by that smiley face or oddly lopsided heart in the firework display? It's nothing more than some careful organization of the stars. If they're just spread randomly, they'll expand out evenly through the sky once they explode.

But, because the explosion will push the stars out in a predictable trajectory, it is possible to organize the stars in a particular pattern on the cardboard cylinder on the outside of the firework. This will create specific shapes.

The sound

No fireworks display would be complete without the ear-shattering booms that freak out dogs and resonate in our chest. That's caused by a sonic boom that happens as the gasses inside the firework expand faster than the speed of sound.

Throw all these explosives and awesome chemistry together and you get this

RELATED: See photos of incredible Fourth of July fireworks displays from years past

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July 4th fireworks
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July 4th fireworks
WASHINGTON, DC - JULY 4: Spectators watch and take snapshots of the annual Independence Day fireworks display at the Washington Monument on July, 04, 2014 in Washington, DC. (Photo by Bill O'Leary/The Washington Post via Getty Images)
NEW YORK, NY - JULY 04: A view of the 38th Annual Macy's 4th Of July Fireworks from Brooklyn Bridge Park on July 4, 2014 in New York City. (Photo by Mark Sagliocco/Getty Images)
NEW YORK, NY - JULY 04: A general view of atmosphere during the 38th Annual Macy's 4th Of July Fireworks on July 4, 2014 in New York City as shot from the Brooklyn Bridge Park. (Photo by Brian Killian/WireImage)
Fireworks explode over the Philadelphia Museum of Art during an Independence Day celebration, Friday, July 4, 2014, in Philadelphia. (AP Photo/Matt Rourke)
Fireworks explode over the Philadelphia Museum of Art during an Independence Day celebration, Friday, July 4, 2014, in Philadelphia. (AP Photo/Matt Rourke)
NEW YORK, NY - JULY 04: Fireworks are set off at Liberty State Park during the ''Freedom & Fireworks Festival'' in Jersey City, New Jersey on July 4, 2014 as seen from New York City. The Macy's fireworks show returned to the East River for the first time since 2008. The United States marks 238 years as an independent nation as it celebrates the national holiday. (Photo by Michael Loccisano/Getty Images)
PHILADELPHIA, PA - JULY 04: A view of the fireworks during the 2014 Philly 4th Of July Jam on July 4, 2014 in Philadelphia, Pennsylvania. (Photo by Gilbert Carrasquillo/Getty Images)
PHILADELPHIA, PA - JULY 04: A view of the fireworks during the 2014 Philly 4th Of July Jam on July 4, 2014 in Philadelphia, Pennsylvania. (Photo by Gilbert Carrasquillo/Getty Images)
JERSEY CITY, NJ - JULY 04: Fireworks dazzle in the New Jersey skies as part of the Freedom & Fireworks Festival in Liberty State Park, NJ on July 4, 2014, where Budweiser also presented a $3 million donation to the Folds of Honor Foundation to benefit families of military killed or disabled in action. (Photo by Noam Galai/Getty Images for Budweiser)
JERSEY CITY, NJ - JULY 04: Fireworks dazzle in the New Jersey skies as part of the Freedom & Fireworks Festival in Liberty State Park, NJ on July 4, 2014, where Budweiser also presented a $3 million donation to the Folds of Honor Foundation to benefit families of military killed or disabled in action. (Photo by Noam Galai/Getty Images for Budweiser)
NEW YORK, NY - JULY 04: Fireworks are set off at Liberty State Park during the ''Freedom & Fireworks Festival'' in Jersey City, New Jersey on July 4, 2014 as seen from New York City. The Macy's fireworks show returned to the East River for the first time since 2008. The United States marks 238 years as an independent nation as it celebrates the national holiday. (Photo by Michael Loccisano/Getty Images)
PHILADELPHIA, PA - JULY 04: A view of the fireworks during the 2014 Philly 4th Of July Jam on July 4, 2014 in Philadelphia, Pennsylvania. (Photo by Gilbert Carrasquillo/Getty Images)
Fireworks light up the sky above the Brooklyn Bridge during Macy's Fourth of July fireworks show, Friday, July 4, 2014, in New York. (AP Photo/Mark Lennihan)
Fireworks light up the sky above the Brooklyn Bridge during Macy's Fourth of July fireworks show, Friday, July 4, 2014, in New York. (AP Photo/Mark Lennihan)
Fireworks light up the sky above the Brooklyn Bridge during Macy's Fourth of July fireworks show, Friday, July 4, 2014, in New York. (AP Photo/Mark Lennihan)
Fireworks illuminate the sky over the U.S. Capitol building and the Washington Monument during Fourth of July celebrations, on Friday, July 4, 2014, in Washington. (AP Photo/ Evan Vucci)
Fireworks illuminate the sky over the U.S. Capitol building and the Washington Monument during Fourth of July celebrations, on Friday, July 4, 2014, in Washington. (AP Photo/Evan Vucci)
Fireworks illuminate the sky over the U.S. Capitol building and the Washington Monument during Fourth of July celebrations, on Friday, July 4, 2014, in Washington. (AP Photo/ Evan Vucci)
Fireworks are seen from the Lincoln Memorial on the National Mall July 4, 2014 in Washington, DC. The United States celebrated its 1776 declaration of independence from colonial England. AFP PHOTO/Brendan SMIALOWSKI (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
Fireworks burst out over the US Capitol and the Washington Monument during Independence Day celebrations in Washington on July 4, 2014. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
People watch fireworks from the Lincoln Memorial on the National Mall July 4, 2014 in Washington, DC. The United States celebrated its 1776 declaration of independence from colonial England. AFP PHOTO/Brendan SMIALOWSKI (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
Fireworks burst out over the US and the Washington Monument during Independence Day celebrations in Washington on July 4, 2014. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
MIAMI, FL - JULY 04: Spectators watch a 4th of July fireworks display over downtown Miami from Watson Island on July 4, 2014 in Miami, Florida.The United States marks 238 years as an independent nation as it celebrates the national holiday. (Photo by Joe Raedle/Getty Images)
MIAMI, FL - JULY 04: Spectators watch a 4th of July fireworks display over downtown Miami from Watson Island on July 4, 2014 in Miami, Florida.The United States marks 238 years as an independent nation as it celebrates the national holiday. (Photo by Joe Raedle/Getty Images)
Fireworks are seen from the Lincoln Memorial on the National Mall July 4, 2014 in Washington, DC. The United States celebrated its 1776 declaration of independence from colonial England. AFP PHOTO/Brendan SMIALOWSKI (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
MIAMI, FL - JULY 04: Spectators watch a 4th of July fireworks display over downtown Miami from Watson Island on July 4, 2014 in Miami, Florida.The United States marks 238 years as an independent nation as it celebrates the national holiday. (Photo by Joe Raedle/Getty Images)
Fireworks erupt over U.S. Cellular Field after the Chicago White Sox played the Seattle Mariners in a baseball game on Friday, July 4, 2014, in Chicago. (AP Photo/Andrew A. Nelles)
Fireworks erupt over U.S. Cellular Field after the Chicago White Sox played the Seattle Mariners in a baseball game on Friday, July 4, 2014, in Chicago. (AP Photo/Andrew A. Nelles)
Fireworks erupt over U.S. Cellular Field after the Chicago White Sox played the Seattle Mariners in a baseball game on Friday, July 4, 2014, in Chicago. (AP Photo/Andrew A. Nelles)
Fireworks erupt over U.S. Cellular Field after the Chicago White Sox played the Seattle Mariners in a baseball game on Friday, July 4, 2014, in Chicago. (AP Photo/Andrew A. Nelles)
Fireworks explode beside the White House marking Independence Day celebrations in Washington, Friday, July 4, 2014. (AP Photo/Charles Dharapak)
Louis Celli of Montgomery Village, Md., carries his 18-month-old grandson Jayden on his shoulders to watch the fireworks in front of the White House marking Independence Day celebrations in Washington, Friday, July 4, 2014. (AP Photo/Charles Dharapak)
Fireworks light up the lower Manhattan skyline during Macy's Fourth of July fireworks show, Friday, July 4, 2014, in New York. (AP Photo/John Minchillo)
Fireworks light up the lower Manhattan skyline during Macy's Annual Fourth of July fireworks show, Friday, July 4, 2014, in New York. (AP Photo/John Minchillo)
Fireworks light up the lower Manhattan skyline during Macy's Fourth of July fireworks show, Friday, July 4, 2014, in New York. (AP Photo/John Minchillo)
Fireworks explode over the Philadelphia Museum of Art during an Independence Day celebration, Friday, July 4, 2014, in Philadelphia. (AP Photo/Matt Rourke)
Fireworks explode over the Philadelphia Museum of Art during an Independence Day celebration, Friday, July 4, 2014, in Philadelphia. (AP Photo/Matt Rourke)
Fireworks explode over the Philadelphia Museum of Art during an Independence Day celebration, Friday, July 4, 2014, in Philadelphia. (AP Photo/Matt Rourke)
This aerial photo shows a Fourth of July fireworks celebration over the Mississippi River in New Orleans, Friday, July 4, 2014. (Photo/Gerald Herbert)
This aerial photo shows a Fourth of July fireworks celebration over the Mississippi River in New Orleans, Friday, July 4, 2014. (Photo/Gerald Herbert)
The Macy's 4th of July Fireworks are viewed from The Circle Line Cruise Ship in the Lower New York Bay on Friday, July 4, 2014 in New York City. (Photo by Brad Barket/Invision/AP)
This aerial photo, shows a Fourth of July fireworks celebration over the Mississippi River in New Orleans, Friday, July 4, 2014. (AP Photo/Gerald Herbert)
WASHINGTON, DC - JULY 4: Reece Newhouse, 13, of Seattle, Washington watches the Independence Day fireworks with his brother Jonah, 17, left, and mother Russann, right, at the Lincoln Memorial in Washington Friday July 4, 2014. (Photo by J. Lawler Duggan/For The Washington Post via Getty Images)
WASHINGTON, DC - JULY 04: Fireworks display during PBS's 2014 A CAPITOL FOURTH at U.S. Capitol, West Lawn on July 4, 2014 in Washington, DC. (Photo by Paul Morigi/Getty Images for Capital Concerts)
NEW YORK, NY - JULY 04: Fireworks overlooking the Brooklyn Bridge at the 38th Annual Macy's 4th Of July Fireworks on July 4, 2014 in New York City. (Photo by Bobby Bank/WireImage)
NEW YORK, NY - JULY 04: A general view of fireworks during the 38th Annual Macy's 4th Of July Fireworks at the South Street Seaport on July 4, 2014 in New York City. (Photo by Mychal Watts/WireImage)
NEW YORK, NY - JULY 04: Fireworks overlooking the Brooklyn Bridge at the 38th Annual Macy's 4th Of July Fireworks on July 4, 2014 in New York City. (Photo by Bobby Bank/WireImage)
NEW YORK, NY - JULY 04: A general view of atmosphere during the 38th Annual Macy's 4th Of July Fireworks on July 4, 2014 in New York City as shot from the Brooklyn Bridge Park. (Photo by Brian Killian/WireImage)
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Jennifer Welsh contributed to an earlier version of this article.

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