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How do fireworks work?

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Quick answer

Fireworks work by burning a chemical mixture that produces hot gas and light. A lift charge launches the shell, a fuse delays the burst, and then a burst charge explodes, igniting stars that contain metal salts. These salts emit specific colors when heated, creating the colorful display.

Fireworks work by burning a packed mixture of fuel and oxidizer, which rapidly produces hot gas and light. Metal salts added to the mixture emit specific colors when heated, creating the visible explosion.

Step by step

  1. A lift charge at the bottom of the shell ignites, producing hot gas that pushes the shell upward.
  2. A time-delay fuse inside the shell burns as the shell rises, controlling when the burst occurs.
  3. When the fuse reaches the burst charge, it ignites, causing a rapid explosion that breaks the shell.
  4. The explosion ignites stars—small packets of fuel and metal salts—and scatters them outward.
  5. Each star burns, and its metal salts emit characteristic colors, forming the visible pattern.

Key things to understand

  1. A firework shell contains a core of black powder, a mixture of charcoal, sulfur, and potassium nitrate.
  2. A lift charge at the bottom ignites and launches the shell into the air.
  3. A time-delay fuse burns while the shell rises, eventually reaching the burst charge.
  4. The burst charge explodes, breaking the shell and igniting stars—small packets of color-producing chemicals.
  5. Each star burns, and its metal salts emit characteristic colors: strontium for red, barium for green, copper for blue.

Labelled diagram

  1. Lift Charge

    Black powder at the bottom that ignites to launch the shell upward.

  2. Time Fuse

    A slow-burning fuse that delays the burst until the shell reaches the right height.

  3. Burst Charge

    Explosive core that detonates to break the shell open.

  4. Stars

    Small packets of metal salts and fuel that burn to create colored lights.

  5. Casing

    Paper or cardboard tube that holds the components together.

Anatomy of a Firework Shell

Real-world examples

  • A red firework uses strontium salts, like strontium carbonate, in its stars.
  • Green fireworks often contain barium nitrate or barium chlorate.
  • Blue fireworks are the hardest to make and use copper compounds like copper chloride.
  • Aerial shells are launched from mortar tubes and burst high in the sky.

Common mistake

✗ Myth: Fireworks explode because of gunpowder alone.

✓ Fact: While gunpowder (black powder) is a key component, the colors come from metal salts added to the stars. The explosion is caused by the rapid burning of the burst charge, which is also black powder, but the visual effect is due to the stars.

People also ask

What makes fireworks explode?
Fireworks explode because of a chemical reaction in the burst charge, which is typically black powder. When ignited, it burns rapidly, producing hot gases that expand and break the shell, scattering burning stars.
How do fireworks get their colors?
Fireworks get their colors from metal salts added to the stars. When heated, the metal atoms emit light at specific wavelengths. Strontium gives red, barium gives green, copper gives blue, and sodium gives yellow.
What is inside a firework?
Inside a firework shell, you'll find a lift charge, a time fuse, a burst charge, and stars. The stars are small packets of fuel and metal salts. The shell is wrapped in paper or cardboard.
What chemicals make the different colors in fireworks?
Different metal salts produce specific colors when heated. Strontium salts give red, barium salts give green, copper salts give blue, sodium salts give yellow, and titanium or magnesium produce white sparks.
How do fireworks get their shape, like a smiley face?
The shape is determined by how the stars are arranged inside the shell. For a smiley face, stars are placed in a pattern on a cardboard disk, so when the shell bursts, they fly outward in that shape.
Why do fireworks make a whistling or booming sound?
Whistling comes from a slow-burning fuse that creates a vibrating gas flow. The boom is from the rapid expansion of hot gases when the burst charge explodes, creating a shock wave.
Are fireworks dangerous?
Yes, fireworks contain explosive materials and can cause serious burns or fires if mishandled. Professionals use them, and safety rules exist to prevent accidents.

Part of the guide: Everyday Science: Light, Heat & Matter →