How do fireworks — work?

How Do Fireworks Work?

Firecrackers are easy: Light the fuse and run. But most firework explosions are a bit more complex.

A Roman candle, for example, burns top-down through several layers of pyrotechnic charges called stars.

Their colors come from metallic powders: aluminum burns white. Copper gives fireworks a blue color. Lithium or strontium powder turns them red.

Mortar shells — the quintessential aerial fireworks you see in the big displays — require careful assembly beforehand.

See some of the best firework displays:

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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)
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 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)
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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The arrangement of stars determines what they look like when they burst midair. A circle-shaped pattern yields a circular firework. Star-shaped patterns give up star-shaped fireworks, and so on.

The timing of what explodes when and with what force can be controlled with precise fuses and thicker wrappings.

Even the noise they make can come down to what they're made of. Certain fuels, for example, can make flying fireworks sound like they're whistling.

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