Brooke Martin
Roman candles are a traditional type of firework constructed with bentonite, lifting charge, pyrotechnic stars, black powder, and delay charge. They come in a variety of sizes, from 6mm to 8cm in diameter, and can be found in many colours. The number of shots or balls in a Roman candle can vary, with some shooting up to 192 colourful starballs into the sky. Due to their tendency to malfunction, they are banned in some countries and states. Making Roman candles can be challenging, as the delay composition must be tightly packed to prevent premature ignition, and the number of shots can vary from 5 to 10 in a single candle.
| Characteristics | Values |
|---|---|
| Construction | Bentonite, lifting charge, pyrotechnic star, black powder, and delay charge |
| Length | Variable |
| Diameter | 6 mm (0.24 in) for consumers, up to 8 cm (3.1 in) for professional displays |
| Ignition | From the top, pointed upwards and away from people |
| Shots/Balls | 5-192 |
| Colors | Red, white, blue, green, gold, silver, and assorted |
| Effects | Comet tails, crackling, strobing, glittering, reports (loud noises) |
| Safety | Banned in Finland, the Netherlands, California, Delaware, Florida, and several other US states |
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What You'll Learn
Construction and ingredients
Roman candles are traditional fireworks constructed with bentonite, a lifting charge, pyrotechnic stars, black powder, and a delay charge. The fireworks are loaded into a heavy-gauge cardboard tube and can vary in length and diameter. The diameter ranges from 6 mm (0.24 in) for consumer-grade Roman candles to 8 cm (3.1 in) for professional displays. The delay charge is packed tightly into the tube to prevent the flame from reaching around the sides. This slow-burning delay charge ignites the lift charge, which propels the stars out of the tube.
The construction of Roman candles involves several steps to ensure the fireworks function properly and safely. Firstly, the tube sections are glued together using Elmer's glue, and a jig is used to ensure perfect alignment. Each section is loaded with lift powder, tissue paper, and a pyrotechnic star. After assembling all the sections, the candle is reinforced with tape to provide additional strength and stability.
The ingredients used in Roman candles are carefully chosen to achieve the desired colours and effects. The colours of the stars are manipulated by adding specific compounds that release visible light and other radiation when ignited. For example, potassium perchlorate (KClO4) can be used as an oxidiser to create barium compounds, emitting green light. Alternatively, SrCO3 can be added to produce red or pink stars, but more oxidisers and fuels are needed to sustain combustion.
The lifting charge, also known as lift powder or black powder, plays a crucial role in propelling the stars out of the tube. It is packed loosely beneath the pyrotechnic star, allowing the fire to spread and ignite the lifting charge rapidly. This charge burns quickly, providing the force necessary to eject the stars into the sky. The delay charge, on the other hand, burns slowly, controlling the timing between each star's ignition.
Safety is a critical consideration when constructing Roman candles. The delay charge must be tightly packed to prevent premature ignition of the stars. Additionally, the proper tape is used to reinforce the tube and prevent rupture due to the pressure created by the pyrotechnic material. These safety measures aim to prevent common failures associated with Roman candles, such as rapid-fire ejections and tube ruptures.
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Safety precautions
Roman candles are a popular type of firework that can be held in the hand or mounted on a stable surface. They are constructed with bentonite, lifting charge, pyrotechnic stars, black powder, and delay charge. While they can be a source of entertainment, they also come with risks if not handled properly. Here are some safety precautions to follow when using Roman candles:
Buy from a reputable retailer:
Always purchase Roman candles from licensed and regulated dealers. Avoid buying them from unlicensed or dubious sources, as these products may be unsafe or poorly made.
Use in an open, outdoor area:
Roman candles should only be used outdoors in wide-open spaces, away from people and any flammable structures or materials. Ensure there is plenty of distance between the fireworks and any potential hazards. The recommended safety distance for spectators is typically 8 to 25 meters.
Wear safety gear:
Protective gear, such as safety glasses and gloves, should always be worn when handling Roman candles to minimize the risk of injury. The protective eyewear can shield your eyes from any flying debris or sparks, while the gloves can provide a barrier between your skin and the fireworks.
Secure the Roman candle:
Always place the Roman candle in a stable, upright position. Using a stable holder or mounting the candle on a non-flammable surface, such as a brick or cement block, is essential to prevent it from tipping over when ignited. Alternatively, you can set the Roman candle directly into the ground at an angle, following the instructions on the packaging.
Do not hold the Roman candle during functioning:
Despite some instructions suggesting holding Roman candles in your hand, it is highly dangerous. Do not hold them during functioning, and never put your hand or any part of your body over the candle. The explosive nature of Roman candles means that your aim may not be accurate, and the expulsion of the fireball can be uncontrollable, potentially causing harm to yourself or others.
Clear the area and maintain a safe distance:
Before lighting the Roman candle, clear a wide area that is free from people and any combustible materials. Once the fuse is ignited, quickly move to a safe distance away from the trajectory of the firework. Protect yourself from the flaming balls as they descend, and ensure that they do not ignite any surrounding areas or property.
Do not use alcohol or attempt to take apart the candle:
Using alcohol while handling Roman candles can impair your judgment and increase the risk of accidents. Additionally, never attempt to take apart the Roman candle, as it contains explosive components that can be dangerous if tampered with.
Douse used candles with water:
After the display, it is essential to douse used Roman candles with water to ensure they are no longer explosive. This step helps to prevent accidental reignitions or unintended explosions.
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Colour variations
Roman candles are a traditional type of firework that ejects one or more stars or exploding shells. They come in a variety of colours, sizes, and effects. The colours of the stars are manipulated by adding compounds that release visible light and other radiation when ignited.
For example, potassium perchlorate (KClO4) is used as an oxidizer, and the chemical reactions involving the dissociated elements of perchlorate—potassium and chlorine ions—create barium compounds that emit green light. Alternatively, SrCO3 can be added to the candle to produce a red or pink star.
Some Roman candles feature an assortment of colours in one candle, such as red, white, and blue, or gold, silver, red, and green. Other candles feature a single colour, such as blue or gold. Some popular colour variations and their effects include:
- Red, white, and blue comets with strobing comet tails
- Assorted colours with pearl effects
- Gold, silver, red, and green palm tails with crackling effects
- Blue pearls with a report finale
- Gold crackling tail
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Homemade Roman candles
Making homemade Roman candles can be dangerous and may be illegal without the proper licensing where you live. It is not a beginner-level project, and it is recommended that only adults with prior pyrotechnic experience attempt to make Roman candles. If you are new to making fireworks, try starting with simpler projects such as smoke bombs or sparklers. If you choose to make Roman candles, ensure you follow safe practices and use good judgment.
Roman candles are simple traditional fireworks that shoot coloured fireballs into the air. They consist of a cardboard tube sealed at the bottom and lit by a fuse from the top, with one or more charges stacked along the length of the tube. The simplest Roman candles come with a single bore, but you can experiment with multiple tubes for a more complex display. Just remember that each additional tube increases the pressure during launch, so ensure your packaging can withstand it.
Typically, the charges are separated from each other by a layer of clay or sawdust. Black powder is used in Roman candles due to its ability to rapidly burn when ignited, producing a large amount of gas that creates a loud bang and bright light. This powder serves two main purposes: it acts as the propellant charge that shoots out the stars or other effects, and it is used as part of the delay composition between the stars. Once a star has been shot out, the firework needs time to reset before launching the next one.
To make Roman candles, you will need to cut out little discs of tissue paper the same diameter as the tube to go between the stars and the lift powder. You can use Elmer's glue to assemble the candle and a 1/4-teaspoon kitchen scoop to measure the black powder lift charges. After assembling the sections of the Roman candle, with lift charges and stars installed, allow the delay increments to dry overnight in a drying box or a few days in a warm location. Finally, bundle the Roman candles together and tape them to a stake to ensure they launch upwards when ignited.
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Professional vs consumer sizes
Roman candles are a traditional type of firework that ejects one or more stars or exploding shells. They come in a variety of sizes, with consumer-grade Roman candles having a tube diameter of 0.24 inches (6 mm) and professional-grade fireworks reaching up to 3.1 inches (8 cm).
Consumer-grade Roman candles are designed for personal use and can be easily purchased online or from fireworks stores. They are smaller in size, typically ranging from 0.25 inches to 1 inch in diameter. These candles offer a range of effects, including colourful stars, crackles, comet tails, and glitter trails. Some common consumer-grade Roman candles include the Patriotic candle, which shoots 70 shots of red, white, and blue comets, and the Classic Roman Candle, which features red and green stars.
Professional-grade Roman candles, on the other hand, are larger and used in professional fireworks displays. These candles have a diameter of 3 inches or more and can reach up to 8 cm. To ensure safety and compliance with local regulations, professional-grade Roman candles are typically handled by licensed pyrotechnicians. They offer more significant effects and can include variations such as loading comet shells instead of stars.
It is important to note that Roman candles can be dangerous, and they are banned in some countries due to their tendency to malfunction. In the United States, for example, they are illegal to possess or set off in several states, including California, New York, and Massachusetts. Therefore, it is crucial to follow safety instructions and local regulations when using Roman candles, regardless of their size or grade.
When choosing between professional and consumer sizes, it is essential to consider the intended use, local regulations, and safety precautions. Consumer-grade Roman candles are ideal for personal use, backyard displays, or small gatherings, while professional-grade candles are more suitable for large-scale, professional fireworks displays.
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Frequently asked questions
A Roman candle is a traditional type of firework that ejects one or more stars or exploding shells.
Roman candles are made with bentonite, lifting charge, pyrotechnic stars, black powder, and delay charge.
The device is ignited from the top, which should be pointed into the sky, away from people. The delay powder is packed tightly in the tube, so the flame moves down slowly as it is consumed. When the flame reaches the topmost pyrotechnic star, the star is ignited and propelled out of the tube.
The stars of Roman candles can be found in a variety of colours, including green, red, pink, blue, gold, and silver.
Roman candles can be purchased from fireworks retailers, such as Phantom Fireworks and Keystone Fireworks. However, they are banned in some countries and states due to safety concerns, so be sure to check your local laws before purchasing or using them.
