Jargon Buster
Firework Effects Explained
Do you know your Chrysanthemums from your Dahlias, your Flower Crown from your Fish?
When you read a firework’s effect description you may be forgiven for being a little overwhelmed. Most effects are either a literal description such as ‘whistle’ or based on the natural world such as ‘willow’ and reflect how the designer tries to replicate what is seen in nature. Don’t forget the result you see in those few seconds can take years of research to perfect. The effect combines the skills of a designer, a chemist and a technician to make the components and build the firework.
Please do get in touch if you’d like to know more about any aspect of fireworks.
At www.hexfireworks.co.uk we live, eat, and breathe fireworks so would love to hear from you. Call on 01462 817640 or email whoosh@hexfireworks.co.uk
Let’s dig a bit deeper and look at each of the effects in turn.
Bengal – These are a slow burning firework which produce a short flame of coloured light and come in a wide variety of colours. They are often used to illuminate buildings or provide a ground level of colour with contrasts above.
Brocade - When you see the beautiful gold strands arching over the sky as aerial shell bursts, you are probably looking at brocade. It is produced by the combustion of fine metal powder. Fired in large quantities, most commonly as part of a finale sequence, it is hard to beat because of the duration of the stars and the way they fill the sky.
Butterfly - Butterfly units are made from spark generating compositions that are fast burning. The tubes are often short, approximately 3cm and plugged at both ends. The tubes have two small holes through the side wall of the tube on opposite sides which are primed. When the composition burns through the two holes the tube spins in the air.
Chrysanthemum - These are stars that have an additional spark producing layer added to the exterior. When the aerial shell or Single Ignition Barrage (SIB) unit bursts a trail of sparks are seen before a colour appears just before the star burns out.
Comet - These are effectively stars but are cylindrical and made in a press. Tail comets often use charcoal or fine metal powders which burn away as the comet moves through the air leaving behind it trails of gold or silver sparks. A colour producing comet will not produce a tail but instead makes a large bright colour dot that is much bigger and brighter than a star. Most often used when fired out of a tube, such as in a SIB.
Crackle – These stars are often used as a finale for consumer fireworks. Some metal alloys, especially magnesium and aluminium will make a crackling noise when they are the size of a grain of sugar and were used in fireworks in the past in this simple form. Modern formulations have been developed so that the crackle effect can be incorporated into stars and comets. Made with nitrocellulose the composition is mixed to a stiff putty before being pushed through a strong wire mesh to achieve the desired size. The granules are then left to dry before use. The technician must work quickly because the mixture will soon harden and become unusable. They involve two stages of reaction. The initial spark burns momentarily before reacting violently, producing the distinctive crackle noise and branching sparks.
Crossette – A crossette is a specially engineered comet. They are a cylinder of compressed composition with a chamber in the top in the form of a cross. This chamber is filled with flash burst (more powerful than gunpowder) and sealed. The comet is then wrapped in paper so that only the non-chambered end is exposed. When the crossette fires from a tube or is ejected when a shell bursts the exposed end then lights. As it does so the comet burns away and finally reaches the bursting charge. The comet then splits into four pieces, and these are projected across the sky.
Dahlia – These are large, bright, long duration stars, sparsely used in a bursting firework such as an aerial shell or SIB aerial unit. The limited number draws your eye to the colour and duration of the star. They are often combined with a second colour or effect. An example might be brocade with red dahlia.
Diadem - A diadem differs from a pistil, but in a subtle way. A diadem, or ‘small crown’ is a short lived, tight cluster of stars in the centre of an aerial burst. With a pistil the stars are seen for longer and as a more obvious central feature, hopefully perfectly spherical.
Falling Leaves – When these were first introduced, they were a real novelty and are still able to fascinate audiences. The ‘leaf’ is a type of fuse, the size of a match, filled with colour star composition and is very light. This lightness allows the leaf to slowly drift down creating clouds of colour.
Fish – These are a self-propelled unit that are seen to ‘swim’ across the sky. Here you can see the strands packed in with stars for a double effect. Fish and Falling leaves are very similar in appearance. The movement of the fish is produced by the burning speed of the fuse (1) .
Flower Crown – This is a long duration, twinkling, silvery gold star often contrasted with a coloured star.
Ghost - Now you see me, now you don’t. Ghost shells are the ultimate demonstration of the star maker’s skill. Stars not only change colour as they burn but the colour is seen to move across the sphere as it expands and can often reverse back or split into quarters or rings or even spirals! Combined with a perfect spherical burst they are a thing of beauty and awe when seen in the flesh.
Glitter – ‘Spritzels’ has to be one of the best words in fireworks. Coined by Lloyd Scott Oglesby (2) it is used to describe the liquid droplet state of glitter before it flashes. Glitter compositions have a two stage process. This spritzel is often dark to start with but carries all the chemical elements required to heat up as is burns and results in the secondary flash that produces the glitter effect.
Horsetail - This is an aerial effect. A single ignition unit bursts gently from one weaker end or from a weakly burst shell. Often brocade or some other long duration, tailed star is used. The desired effect is to be able to see the trails whilst maintaining the close pattern required to replicate the horsetail image. Often fired in succession to create a ‘scene’ during a display.
Hummer – This is like a butterfly in construction. A short tube, plugged at both ends, but this time with a single hole which pierces the tube at an angle. This creates a jet of gas which causes the tube to spin around its length. This produces the distinctive humming noise.
Kamuro - Or ’boys’ haircut’ in Japanese. A loose, untied style. Like willow in that it is a long duration star but is often silvery gold with a slight twinkle in it. Beautiful fired across the calibres during a finale where the designer can create a layered effect. It can often be displayed with a contrasting pistil such as purple or the stars may terminate with white strobes. Large calibre, high quality, Kamuro shells are often fired on their own as a feature shell at the end of display.
Palm Tree – These are stars projected out of an aerial unit that produce thick ‘fronds’ in the form of a palm tree. There are fewer stars in the unit and are quite often silver with a thick, comet based, trunk as it rises.
Pistil – A sign of a good aerial professional shell is a well-defined pistil (centre). An aerial shell technician’s reputation is often established by their ability to produce a perfectly round burst, with even stars distribution and key, a perfectly round contrasting pistil. A classic combination would be red stars as the main body of the shell and a silver pistil. But this is where it gets exciting. It is only the designer’s and technician’s ability that limits the possibilities, and this can be seen in exhibition shells. These will have stars that change colour several times and will have colour changing pistils. The colours may even swap sides as the shell expands. Pistils can also be a feature of SIBs.
©Robert Axiaq from Lija, Malta
Peony – This is used to describe a bursting effect where there is often a simple colour star producing a dot of light. With great skill the stars can be made to change colour. The skill is knowing which order to present the colours. Different luminosities require different transitions and the temperature at which each colour ignites varies, so layers of prime may be needed between colour composition. Complex colour changes can take 40 days to make as layers are built up and dried then built up again. This is how ghost shell stars are made. There may be three or four colour changes but many variations to get the smoothest sweep across the finished shell burst. In the picture below you can see a seed covered with many layers of composition in a colour changing star.
Rain – This is often a metal based composition and can be used to make stars or comets. They are commonly silver or gold in colour and produce a twinkling effect reminiscent of rainfall.
Salute/Maroon - loud! Made with a simple, two part composition of oxidiser and fine metal powder, when confined the fast burning speed breaks the casing with tremendous force. Salutes are used to great effect in Spanish Mascleta displays where the power and rhythm, combined with whistles and coloured smoked, are used for unrestrained daytime noise. Salutes aren’t often used in the U.K. We don’t have the venues or the culture for noisy displays.
Spider – As the name suggests this bursting pattern and star design are meant to emulate a spider. The star is very hard because it must travel flat across the sky at high speed before falling to create the spider image. The spider ‘legs’ are often contrasted with a colour pistil or ring.
Star – This may seem a simple one to define but should be limited to an effect which produces a dot of colour with no tail. Stars are most commonly round at approximately 5-8mm, but this can vary depending on the burning speed of the composition and the size of the shell being used. 20mm stars are often used for 24” plus size shells. The technique for making stars is highly skilled and is passed from generations of technicians and hands on experience is priceless. We will cover this in a future article. Dahlia stars tend to be large and fewer in number for an effect.
Strobe – These are an effect that flashes on and off and is most found as a type of star or as a Bengal (a type of flare). The strobe is produced by having a catalyst in the composition which tries to inhibit burning, thus creating the flash. The ideal is 1 to 2 hertz or flashes per second. Some strobes have been found to improve with age, such as in bengals; the frequency slows over time to produce distinct bright flashes which light up the surrounding area. Professional display shells on the other hand are not kept for more than a few seasons. After a period, it has been found that the stars ‘go off’ and no longer strobe and indeed can fail to ignite, so fall to the ground. Once this occurs the shells must be safely destroyed.
Tourbillion/Serpent/Spinner - These are tubes that have a restriction in one end and closed at other. They are filled with a composition with produces sparks so that as the tube is ejected from the launch tube or burst in a shell the composition lights and produces a tumbling, often twirling spray of sparks through the sky.
Waterfall - As the name implies this effect is designed to mimic a waterfall. These can either be a series of composition filled tubes suspended on a taut wire which are lit together, allowing the sparks to float downwards creating a curtain of sparks, or as a type of aerial bursting unit.
A waterfall effect produced by an aerial bursting unit differs to a horsetail effect. Waterfalls burst softly as does a horsetail, but the trailing stars spread out wider to create the waterfall effect. A horsetail will turn over immediately after the unit bursts and the tails will stay closer together. Waterfalls are at their most effective when fired in succession; the effects overlap and can create an impressive waterfall scene.
Whirl - These come in many variations but can be simply made using an unrestricted tube so that the composition burns more freely allowing the tube to fall without twisting.
Whistle - Whistle units are tubes sealed at one end and open at the other. They have a small amount of composition pressed into the sealed end. This is normally 3 to 4 grams. In very simplistic terms when this burns the pressure waves generated oscillate in the tube because of cycles of burning and detonation making the distinctive whistle sound (3). Whistle mixture a very explosive and must be manufactured with great care. The descending whistle sound is a result of the burning surface receding thus making the tube longer, in turn altering the wavelength of the sound. A longer the tube the deeper the whistle. The various hypotheses as to the exact physics of how a whistle works have been hard to study since sensitive measurement equipment has to be positioned in a hostile environment. A recent research paper details the intricacies of generating a pyrotechnic whistle (4). Note that there is not much composition required and the profile is flat.
Screecher - These are made in a similar way, but the inner profile is different which creates a different sound profile. A definite screech.
Willow - Designed to replicate the delicate bows of a willow tree these effects can be with or without a matching tail. Most often seen using charcoal based compositions willows are fired in succession to great effect. The distinctive deep gold of charcoal based compositions allow for long lasting umbrellas of stars.
References and bibliography:
1. Yugen Liao - Guandu Fireworks, China
2. Glitter Chemistry, Clive Jennings-White, (Pyrotechnic Chemistry, Pyrotechnic Reference Series No.4, 2004)
3. Fireworks, Principles and Practice, 4th Edition, ISBN 0-8206-0407-0, Rev. R Lancaster MBE, FRSC
4. Investigation on the Acoustic Properties of Pyrotechnic Whistles, Research Paper, Dayu Ding, 2019
Article reviewed by: Rev. R Lancaster MBE, FRSC and Robert Axiaq, St Michael's Firework Factory, Lija, Malta.
Technical drawings assistance: Pyroshine Fireworks.