In this blog post, we’ll explore the principles behind the creation of fireworks’ colors and shapes, how their diverse sounds are produced, and the scientific principles hidden behind them.
Before delving into fireworks displays, it is essential to first understand the structure of fireworks. Fireworks are a unique invention that combines scientific principles and artistic elements, having evolved over a long history. Their origins date back to ancient China, where they were used in the form of simple bamboo bombs to ward off evil spirits. Over time, gunpowder was invented, leading to significant advancements in both the structure and purpose of fireworks.
Today’s fireworks essentially consist of a shell casing containing a time fuse, a break charge, and a star. This complex internal structure is the key element that allows beautiful and dazzling fireworks to illuminate the sky. When the lift charge is ignited and the firework ascends, the time fuse acts as a timer to detonate the firework at the desired height, igniting the break charge at the appropriate moment. This causes the break charge to ignite and scatter the stars, causing the firework to explode.
The reason fireworks can take on various shapes is directly related to the arrangement of the stars. By arranging the stars in the desired shape, the shape of the firework is determined. For example, if you want the firework to explode in the shape of a star, you simply arrange the stars in a star shape inside the shell casing. Additionally, the size of the firework can be adjusted by controlling the amount of break charge placed inside the shell casing. If the amount of break charge is large, the force pushing the sparks out will be much greater. Consequently, the firework will be larger. Conversely, if the amount is small, the pushing force weakens, resulting in a smaller firework.
The reason fireworks display such a variety of colors is due to the different types of metals used inside the shells. The reason a substance emits light is related to the electrons it possesses. When an electron transitions from an outer electron shell with a higher principal quantum number to an inner shell, it emits light corresponding to the energy difference between the two shells. If the emitted light falls within the visible light wavelength range, we can observe it. However, since the energy level differences between electron shells vary by substance, the wavelengths of the emitted visible light differ. Therefore, the color of the light emitted during a flame reaction varies depending on the type of substance. In fireworks, strontium (Sr) compounds are used to produce red, sodium (Na) compounds to produce yellow, and copper (Cu) to produce turquoise. In addition, calcium (Ca) produces orange, barium (Ba) produces green, and potassium (K) produces purple. By combining various metals, fireworks of diverse colors can be created.
So why are metallic elements used specifically? This is also related to the wavelength of the emitted light. Since the wavelengths of light emitted when non-metallic elements undergo electronic transitions do not fall within the visible light spectrum, the desired color can be achieved simply by using metallic elements, regardless of the presence of non-metallic elements.
In fireworks displays, the auditory aspect plays just as significant a role as the visual aspect in the viewing experience. Fireworks produce a variety of sounds, ranging from delicate pops to thunderous booms. This is determined by the “salute.” A salute refers to a loud explosion produced without a visual display; it is a very simple device consisting of black powder packed into a paper tube with a time fuse inserted. Mixing finely ground titanium with a rapidly burning oxidizer creates a powder called flash powder. This powder serves to rapidly amplify heat and pressure.
At 0 degrees Celsius, the speed of sound is 331 m/s. In air, the speed of sound increases by 0.6 m/s for every 1-degree rise in temperature. Furthermore, sound waves are longitudinal waves that propagate through air particles as a medium. Here, a longitudinal wave refers to a wave in which the direction of vibration of the medium matches the direction of the wave. When a longitudinal sound wave propagates, areas of high and low density exist within the medium. Consequently, pressure increases in areas where air particle density is high, and decreases in areas where air particle density is low. The magnitude of this pressure change is called sound pressure; the higher the sound pressure, the louder the sound.
In other words, when the temperature rises due to the flash powder, the sound of the firecracker exploding travels farther and faster. As the pressure increases, the sound pressure level rises, making the sound of the firecracker seem even more majestic to listeners. This is how the volume of the sound is adjusted to control the auditory experience of the fireworks display. In addition to sound volume, adding aluminum (Al) to a firecracker produces a crackling sound as it burns, and drilling holes in it can create a whistling sound. Thanks to these techniques, viewers can enjoy a variety of sounds while watching a fireworks display.
Finally, it is important to consider the safety of fireworks. This is because fireworks can lead to serious accidents if used or stored improperly. In particular, large-scale fireworks displays require sophisticated safety procedures and regulations. Fireworks experts undergo rigorous training, and when planning a fireworks show, factors such as weather conditions, wind direction, and the location of spectators must be thoroughly considered. When these safety measures are properly followed, we can safely enjoy both the beauty of the fireworks and their majestic sounds.
