The Science Behind Fireworks: From Black Powder to Rainbow Colors

Jul 27, 2026

Introduction

Every firework in the night sky is a precisely controlled chemical and physical performance. From igniting the fuse to the final burst, in just a few seconds, it involves multiple processes such as combustion, gas expansion, ejection, explosion, and light radiation. Understanding these principles not only allows us to appreciate fireworks more safely but also helps professionals design more stunning effects.

I. Black Powder: The Power Heart of Fireworks

The basic propellant for traditional fireworks is black powder, a mixture of potassium nitrate (75%), charcoal (15%), and sulfur (10%) in approximate proportions. When ignited, potassium nitrate provides oxygen, charcoal acts as fuel, and sulfur lowers the ignition point and increases stability.

When black powder burns, it produces a large amount of high-temperature gas (mainly carbon dioxide, nitrogen, and water vapor). The gas rapidly expands inside the sealed firework tube, pushing the upper effect load (stars, bursting charge) out of the tube. This process follows Newton's third law: the downward-expelled gas creates an equal and opposite reaction force that propels the firework upward.

II. Stars: Colored Sparkles During Burst

Stars are small particles responsible for the light effects in fireworks, usually made by compressing fuel, oxidizer, and coloring agents into spherical or cylindrical shapes. When an aerial shell explodes in the air, these stars are scattered around, burning at high temperatures and emitting light.

The burning temperature, particle size, and composition of stars determine brightness and duration. Larger particles burn longer but are dimmer; smaller particles are brighter but short-lived. Professional fireworks designers adjust star formulas and sizes to control the layering of aerial patterns.

III. Metal Salts: The Magicians on the Palette

The reason fireworks are colorful lies in the ability of different metal ions to emit specific wavelengths of light at high temperatures. Common coloring agents include:

Strontium (Sr): Red, e.g., strontium nitrate.
Barium (Ba): Green, e.g., barium chlorate.
Copper (Cu): Blue, e.g., copper chloride.
Sodium (Na): Golden yellow, e.g., sodium nitrate.
Calcium (Ca): Orange-red.
Aluminum/Magnesium powder: Silver-white flash, increases brightness.

By mixing multiple metal salts, transition colors such as purple, cyan, and pink can be achieved. This is also a core area of continuous experimentation for Sunsong Fireworks' R&D team.

IV. Sound Effects and Shapes: Beyond Visual

In addition to color and brightness, fireworks can produce sound effects by adding special chemicals:

Whistle: A hollow tube structure causes gas to pass through at high speed, producing a sharp whistling sound.
Burst sound: Adding flash powder creates a loud bang.
Crackling sound: Adding dragon egg chemicals to stars produces continuous crackling when burning.

Shape effects rely on the geometric arrangement of stars inside the shell. For example, uniform distribution of stars inside a spherical shell can form a peony pattern; arranging them in a ring can produce a donut or smiley face pattern.

V. Eco-Friendly and Future Trends

Traditional fireworks discharge produces metal particles, smoke, and residue. In recent years, the industry has been moving towards low-smoke, sulfur-free, biodegradable casings. Sunsong Fireworks is also actively developing:

Sulfur-free black powder alternative formulas to reduce sulfur dioxide emissions.
Biodegradable paper and plant fiber casings to reduce environmental burden.
Electrically controlled ignition systems to improve accuracy and reduce duds.
Digital fireworks and drone formations as low-carbon supplements to physical fireworks.

Future fireworks shows will focus more on harmony between humans and nature, allowing the beauty of the night sky to bloom sustainably.