Non-Flammable Fireworks from the Land of the Rising Sun
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The following article was originally published in the journal for educators Chemia w Szkole (eng. Chemistry in School) (1/2022):
As I write this article at the beginning of January, the echoes of New Year's Eve celebrations still resonate in my memory. Fireworks displays, a long-standing tradition, were once again an integral part of the festivities.
Pyrotechnics, derived from the Greek word pyro (πῦρ, meaning fire), is a practical branch of chemistry—closely linked to engineering and technology—focused on designing devices that utilize combustible materials to produce visual, thermal, acoustic, or smoke effects.
Pyrotechnics is not limited to fireworks; it also finds applications in safety equipment such as flash and bang charges, emergency signaling flares, and automotive safety mechanisms like seatbelt pretensioners and airbags. In other words, pyrotechnics serves both civilian and military purposes.
One of the more entertaining applications of pyrotechnics is the production of fireworks. The term originates from the German word Feuerwerk and refers to low explosive pyrotechnic devices designed for visual and signaling purposes that, when ignited, produce stunning light and sound effects.
The first fireworks—just like the gunpowder used in them—most likely originated in what is now China. As early as the period of the Southern and Northern Dynasties (420–589 AD), fireworks were used in religious ceremonies. It is unsurprising that they later found applications on the battlefield and eventually evolved into various forms of firearms.
Handling most professional-grade fireworks requires specialized knowledge, and producing flammable and explosive pyrotechnic mixtures is not only dangerous but also highly discouraged for amateurs. Every now and then, news reports surface about self-taught pyrotechnicians who, along with bystanders, suffer severe injuries or even fatalities due to accidents. For this reason, I will not describe such experiments or encourage their performance.
However, there are much safer types of fireworks. One of them is the so-called sparkler. These can be described as a type of firework designed for use in indoor environments.
Sparklers typically consist of a thin metal—usually steel—wire, partially coated with a pyrotechnic compound that, when ignited, produces a shower of sparks. The pyrotechnic mixture is composed of approximately 45–50% barium nitrate Ba(NO3)2 and iron Fe or aluminum Al shavings, which create bright, silvery-white sparks during combustion (Photo 1).
The presence of toxic barium compounds in sparklers means they should be handled with care, especially when burning, and kept away from food products.
Interestingly, Japanese tradition features a similar small and relatively safe firework known as senkō hanabi (jap. 線香花火) [1]. Like our sparklers, senkō hanabi produces a spectacular shower of sparks when ignited. However, its chemical composition and construction are entirely different. What makes it particularly fascinating is that some versions of this firework rely on an almost non-flammable, and thus very safe, mixture of non-toxic chemical compounds. However, it is important to note that in Japan, some traditional versions of senkō hanabi are still made using flammable and even explosive substances.
My dear reader, you might agree that the idea of safe yet beautiful and uniquely exotic fireworks is quite appealing. The concept becomes even more worthwhile considering that, beyond providing a mesmerizing visual effect, experiments like these can inspire students and enthusiasts to explore chemistry further.
Production
As I mentioned earlier, producing this version of senkō hanabi requires only readily available, non-toxic, and inexpensive materials. These are:
- Sulfur S,
- Sodium bicarbonate NaHCO3,
- Charcoal C.
Sulfur is a nonmetal that exists in several allotropic forms, the three most important being rhombic, monoclinic, and amorphous sulfur. Under normal conditions, it is a crystalline, brittle, yellow substance.
Sodium bicarbonate, also known as baking soda, is widely used in baking as a leavening agent—when heated, it decomposes, releasing carbon dioxide CO2, which makes dough rise. It is also used as a food additive, a pH regulator, a component of effervescent drink powders and tablets, and a remedy for acid indigestion. Instead of sodium bicarbonate, potassium bicarbonate KHCO3 can be used as an alternative.
The final ingredient is charcoal, a lightweight, black substance produced by the pyrolysis of wood. It consists primarily of elemental carbon, along with some ash and organic impurities. The best charcoal for making Japanese sparklers comes from softwood trees, particularly pine (Pinus).
It is relatively easy to produce small amounts of highly pure charcoal from dry pine wood (Photo 2, left).
To create charcoal, place a few pieces of dry pinewood in a metal can. The can should be sealed relatively well, either by crimping its opening or using a fitted lid. Since some flammable gases are produced during the pyrolysis of wood, a few small holes should be made in the can to allow them to escape and burn off. However, these holes should be small enough to limit oxygen intake. The can is then placed in a fire and heated until gas emission ceases. Once cooled, the can will contain very lightweight, porous, and pure charcoal (Photo 2, right). This charcoal is extremely brittle and must be finely ground to a powder, as the effectiveness of the final product depends largely on the particle size of this material.
All required substances are shown in Photo 3.
According to an online recipe, the components must be mixed in a weight ratio of 7:4:2 [2]. I measured:
- 1.75 g (0.06 oz) of sodium bicarbonate,
- 1 g (0.035 oz) of sulfur,
- 0.5 g (0.018 oz) of charcoal.
Unlike typical pyrotechnic mixtures, this composition is an exception because it does not contain strong oxidizers and reducing agents. Therefore, the components can be safely ground together in a mortar and pestle (Photo 4).
A fascinating paradox of this mixture is that, when directly exposed to an open flame, it behaves more like a fire suppressant rather than a fuel—thanks to the sodium bicarbonate content, which releases carbon dioxide (CO2) when heated, cutting off the oxygen supply and preventing further combustion. This unique property makes the composition particularly well-suited for educational demonstrations.
The final mixture appears as a dark gray powder with a slightly hygroscopic nature, meaning it should be kept away from moisture.
The last necessary material is suitable paper. It should not be too thin and fragile, yet thick sheets like standard notebook or printer paper are also unsuitable. Single layers of separated multi-ply paper towels can work, but a better choice is moderately thick tissue paper (Photo 5).
The paper should be cut into strips approximately 1.5 cm (0.6 in) wide and at least 10–15 cm (4–6 in) long. The dimensions may require slight adjustments based on experimentation. Each strip is then folded to create a shallow trough (Photo 6).
Next, a small amount of the prepared mixture is placed in the fold of the paper, about 1–2 cm (0.4–0.8 in) from one end. Only a pinch is needed—approximately 10–30 mg—as using a larger amount does not prolong the burning time but makes ignition more difficult (Photo 7).
The paper strip is then folded along the crease, and rolling begins from the side containing the mixture (Photo 8).
Care must be taken to ensure that the chemical mixture remains concentrated in a single spot—close to the end of the rolled paper. The finished firework should resemble the one in Photo 9.
As seen in the image, the finished senkō hanabi features a small bulge containing the pyrotechnic mixture, supported by a tightly rolled paper handle. Traditional Japanese craftsmen often leave a decorative, unrolled section of paper at the end.
Properly stored in a dry place, these fireworks can be kept for long periods. Since only a few grams of the mixture are needed to produce a large number of senkō hanabi, this method is both efficient and cost-effective.
The Effect – A Reward for the Effort
Although this homemade firework is relatively safe, it is important to remember that it still generates high temperatures when burning. Therefore, it should only be used over heat-resistant surfaces and away from flammable materials. The combustion process also releases small amounts of sulfur oxides, so it should be conducted outdoors, under a fume hood, or in a well-ventilated area.
Normally, senkō hanabi is held in the hand, with the chemical end pointing downward. However, for the sake of this demonstration, I placed it in a holder (Photo 10).
One challenge with this firework is its ignition. A regular match or lighter will not suffice—an appropriate mini-torch or high-temperature flame source is required. To ignite senkō hanabi, the section containing the mixture must be heated for a short time without burning through the supporting paper roll (Photo 11).
The burning process consists of several distinct phases.
Heating can be stopped once a visible molten droplet of reactants forms at the tip of the paper roll, glowing with an orange hue (Photo 12). From this point onward, the reaction proceeds independently.
Shortly after, faint hissing sounds can be heard as small tongues of flame emerge from the molten droplet (Photo 13).
While the sight of a glowing droplet emitting flickering flames is mesmerizing, an even more stunning effect follows moments later—a cascade of orange sparks begins to radiate from the molten droplet (Photo 14).
After a few more seconds, the large sparks give way to a delicate, shimmering shower of tiny glowing specks (Photo 15).
This marks the final stage of the firework’s combustion. Shortly afterward, the fire extinguishes itself, leaving only smoldering paper.
Using potassium bicarbonate instead of sodium bicarbonate results in slightly different spark patterns and a longer burn time. However, in this case, the molten droplet stage with flames does not occur.
During the burning process, the glowing droplet slowly moves up the rolled paper, gradually shrinking. This requires careful handling—any sudden movement or vibration could dislodge the droplet, prematurely ending the display.
Explanation
Most conventional fireworks rely on a mixture of fuel (such as sulfur or carbon) and an oxidizer (such as chlorate or nitrate salts), often with additional chemical compounds to produce specific effects. These mixtures are highly flammable and sensitive to mechanical stimuli, meaning they can ignite or explode due to impact, friction, or compression. Various additives are used to reduce mechanical sensitivity. However, they remain extremely dangerous due to their inherent combustibility and explosiveness.
By contrast, the firework described in this article contains no strong oxidizers. The precise mechanisms of the chemical reactions occurring during combustion have not yet been fully studied. However, analysis of the molten droplet has revealed the presence of sodium (or potassium) sulfides reacting with carbon in the presence of atmospheric oxygen [3] [4]. In an oxygen-free environment, the firework extinguishes immediately.
Interestingly, senkō hanabi is associated with a profound concept in Japanese culture known as mono no aware (jap. 物の哀れ)—a deep, empathetic appreciation of the fleeting beauty of the world and human life [5]. This emotion, while positive, often carries a touch of sadness and nostalgia, beautifully mirroring the transient nature of senkō hanabi, which burns brightly but fades quickly, susceptible to the slightest gust of wind or an unsteady hand.
Further readings:
- [1] Shimizu T., Fireworks: The Art, Science, and Technique, Pyrotechnica Publications, Teksas, 1996 back
- [2] The World's First non-Flammable Fireworks (a novel way to make Senko Hanabi Sparklers, online: https://www.youtube.com/watch?v=O3-ucafI1MY [14.01.2022] back
- [3] Van Der Sypt F., The Senko Hanabi Sparkler: A Study Of Factors Affecting Construction And Performance, Journal of Pyrotechnics, 32, 2013, pp. 27-42 back
- [4] Van Der Sypt F., The Senko Hanabi Sparkler: A Study Of Its Reaction Mechanism, Journal of Pyrotechnics, 32, 2013, pp. 43-56 back
- [5] Japan: Profile of a Nation, Kodansha International Ltd., Tokio, 1995, pp. 307 back
All photographs and illustrations were created by the author.
Addendum
As a supplement to the article, I am presenting my video on this topic below:
Subtitles are available in both Polish and English.
Marek Ples