Have you ever gazed at a firework display and wondered what’s behind the mesmerizing burst of colors? It’s not magic, but rather a brilliant and precise blend of chemistry and physics. The dazzling spectacle is created by a combustion reaction, where specific chemical compounds are superheated to produce the vibrant lights, sounds, and effects we all love. 

The anatomy of a firework

At its core, a firework is a miniature chemical factory, engineered to produce a dramatic effect. For an aerial firework, it consists of a shell containing a few key components: 

A lifting charge: This initial burst of black powder, located at the bottom of the shell, propels the firework high into the sky.

Stars: These are small, compressed pellets that contain all the chemical ingredients needed to produce the color and light. They are arranged in specific patterns to create different shapes.

An oxidizer: A chemical compound that provides the oxygen needed for the fuel to burn. This allows the firework to burn rapidly and brilliantly in the air, where there isn’t enough atmospheric oxygen.

A fuel: A chemical like charcoal or aluminum that burns to produce the high temperatures needed to ignite the color-producing compounds.

A bursting charge: A second explosive charge that ignites the stars at the firework’s peak altitude, sending them scattering across the sky.

A time-delay fuse: A carefully timed fuse ensures the bursting charge goes off at just the right moment. 

How do fireworks get their colors?

The secret to the vivid colors lies in the metal salts packed into the “stars.” When these salts are intensely heated by the bursting charge, their electrons jump to a higher, more energetic state. As they fall back to their normal energy level, they release that energy in the form of light. Each metallic element emits light at a specific wavelength, which our eyes perceive as a particular color. 

Here’s a breakdown of what creates some common firework colors: 

Red: Strontium salts are used to create a deep red color.

Green: Barium salts produce a brilliant green light.

Blue: Copper compounds are responsible for blue hues. Blue is notoriously difficult to produce because the copper compounds are sensitive to temperature.

Yellow/Gold: Sodium compounds are used to create a vibrant yellow or gold light.

Orange: Calcium chloride is the chemical compound behind a brilliant orange color.

White/Silver: Bright white light and silver sparks are produced by burning metals such as magnesium, aluminum, or titanium.

Purple: This is often created by combining strontium (for red) and copper (for blue) compounds. 

Sounds and shapes

To create a whistling sound, manufacturers use chemical compounds like potassium benzoate in narrow tubes. As the fuel burns, it creates gas that escapes, causing the tube to vibrate at a high frequency.

Crackles and snaps: These effects are made by including bismuth oxide, which burns in a quick, intermittent manner.

Custom shapes: Pyrotechnicians meticulously arrange the “stars” in specific shapes inside the shell. When the firework bursts, the stars are flung outward, and the careful arrangement creates patterns like rings, hearts, or willows. 

This Diwali, as you witness the spectacular lights in the sky, you can appreciate the intricate science and artistry that go into every single display.