THE MAKING OF

There are two basic components to every firework, each as fundamentally essential as the other to the whole. First of all you need a suitable container with which to construct the firework. This vessel is not just there to carry the label and stop the contents from spilling out, it is the casing that controls, shapes and contains the energy released from the burning within. Different cases make similar mixes perform in many different ways by virtue of their dimension, openings, wall strength and volume. It is the container that enables the banger to go bang as opposed to phutt and it is the strong tube and narrowly choked outlet of a rocket that converts the energetic gases produced by the burning fuel into useful thrust and resultant flight. Left to its own devices, if uncontained, the propellant charge of a rocket would flare noisily and briefly but would go nowhere.

Although plastics and some metals have made a few inroads into use as firework containers, plastic in particular has found use in some modern rockets and shells, it is nevertheless remarkable that even today, centuries after their development, it is still the combination of paper and glue that makes up the bulk of all firework cases. From a few light turns of paper forming the tube of a pinwheel to the hugely strong cardboard mortar tubes used for blasting display shells to their performance height, it is the strength, resilience, adaptability and cheapness of paper that continues to be used to great effect.

It is remarkable how much manual effort and time goes into making fireworks. The banger, that most simple of fireworks was a good example being completely hand-made and involving up to twenty separate production steps from tube rolling, end sealing, filling, fusing and so on and these many-fold steps were repeated over and over again as the bangers were produced in their millions each year, by the hands of actual people and all for a few scant seconds of fizzing fuse and a momentary bang. The echo would often last longer. Unlike mass-produced confectionery, were the product is predominantly machine made, being dipped, moulded, flattened, cut and filled, with wrappers heat sealed on conveyor-belts, fireworks bring the end user and the maker into a virtual one-to-one contact. The handiwork of the maker is clear to see in the slight inaccuracies encountered - the label a little crooked, or wrinkled, a blob of glue peeking out from beneath a rocket stick. Such imperfections add to the charm and also reveal the long repetitive hours spent manufacturing in some far away firework shed. In these days of a premium being set on the handcrafted nature of some products, a higher price being levied for revealing the touch of the maker, this endearing feature of fireworks is to be applauded.

The second key component of a firework is of course the actual filling, the pyrotechnic recipe of fuels, oxidisers, colour and spark producers. There are two good reasons why this is not the place to provide full technical details with regards the making of fireworks; firstly, firework making is illegal to the unlicensed and lethal to the foolhardy and secondly the subject is complex, rather lengthy and is therefore more effectively covered elsewhere.

Heat is the obvious key to the function of any firework mixture; heat to energise the compounds, react chemicals and turn elements incandescent amidst a flow of superheated gases. In fireworks the heat is supplied by the energetic oxidation of a fuel. However unlike the fuel burning within the engine of a car, oxygen from the air is not required for the reaction in pyrotechnic mixtures because all the required oxygen is handily supplied from within the mixture itself by the thermal breakdown of oxygen rich compounds. The heat causes the compound to decompose thereby liberating oxygen which oxidises the fuel producing yet more heat and yet more oxygen. This highly efficient exothermic reaction is what enables fireworks to burn both under water and in outer space.

The most basic core component of fireworks is gunpowder. It is there in rocket motors, bursting charges, lifting charges and reports (bangs.) Potassium nitrate, charcoal and sulphur, in a 75:15:10 ratio, when thoroughly mixed and processed, form this most important of firework ingredients. By adding other compounds to this backbone material, additional effects can be created.

Some of the commonest effects and colours are produced using the following materials. This is by no means a definitive or complete list but it does give a bit of idea as to what makes up the contents of that innocuous looking tube standing in the back garden with a tendril of smoke drifting up from the fuse.

Using the salts of strontium, in a suitable mixture will produce pleasing and vivid red colours, whilst orange colours are created using the salts of calcium.

To make a bright yellow, sodium compounds - sodium oxalate for instance, are added to the mixture.

Green is tricky and its actual production is rather interesting. Gaseous barium monochloride, or monohydroxide, in a flame emits bright green light, but gaseous barium oxide turns the flame white. The trick is to get lots of barium monochloride into the flame, while keeping the amount of gaseous barium oxide as low as possible. For a really good green, barium chlorate is the best material to use. It provides oxygen for the combustion as well as the barium and chlorine needed to make barium monochloride in the flame but unfortunately it is also rather dangerous. Luckily, chemistry comes to the rescue here. The barium monochloride can be created in the flame as the firework burns by the chemical reaction of more stable barium compounds and chlorine rich fuels such as P.V.C. The net result being a strong green colour.

Blue is produced by gaseous copper monochloride in the flame. Good blues can be produced with a number of copper compounds in combination with appropriate oxidisers, fuels and chlorine donors. Blue was once a difficult colour to produce in fireworks, but again chemistry has come to the rescue. Beautiful blues are easily produced with mixtures based on ammonium perchlorate, the oxidiser used in the solid rocket boosters on the space shuttle. This chemical is both an excellent oxidiser and an excellent chlorine donor, exactly what is needed to make a good copper chloride blue.

Purple is another colour that is rather easily produced by modern compositions based on ammonium perchlorate. Copper and strontium compounds in suitable proportions produce a mixture of red and blue light, giving various shades of purple.

White was traditionally produced with antimony sulfide but for really brilliant whites, mixtures producing very hot flames, rich in barium oxide are better. For example a good silver colour is made with a mixture that includes barium nitrate and powdered aluminium. Adding fine particles of metallic aluminium, or titanium to a suitable mixture, will create lovely silver glitter and shimmering silver sparks.

For gold, simply add fine iron particles. This is what produces the sparkle of sparklers. Gold streamers on the other hand, found in some very graceful golden rocket tails and willow shells, can be produced by adding carbon black (essentially soot) to the mixture. Although horribly filthy to work with, this material produces some of the most beautiful of all firework effects. One commonly used effect, often encountered at the end of the finale in large displays, sees a mass of brilliant bursts and loud noise suddenly stop, whilst high above a beautiful and huge golden willow quietly opens, its gentle branches slowly curving down and cascading in waves after wave of tiny golden points. That's thanks to the cleaver use of soot.

If you like noisy and bright, crackling sparks then small particles of magnalium, a magnesium-aluminium alloy, are added to the mixture.

If a whistle is required then the intriguing burning characteristics of sodium salicylate can be used. When it is burned with a suitable oxidiser, the cyclic decomposition of this material, a series of small but rapidly occurring explosions, which resonate within the firework casing to create the sound. The musical note produced drops in pitch as the mixture burns away so increasing the length of the resonating air column - the firework case acts like an organ pipe.

Many, if not all of these ingredients will be present within even the cheapest family selection box as well as being found in all large firework displays. The mixtures are identical and only the size of the object marks them out as different.

Fireworks fall into several distinct and universally recognisable types. Most of these fireworks, found commonly in selection boxes, have been with us for centuries, gradually being perfected and tweaked with new colours, sounds and effects being added to spice up their otherwise predictable action.

Fountains are the simplest and purest of fireworks and were likely the very first to be perfected in the early days of pyrotechnics. They are usually cylindrical, with either short squat tubes or long thin tubes, or cone shaped creating the ever popular volcano. Restricted at the mouth or left fully open, they can produce showers, plumes or jets of coloured fire and sparks, can last a few gentle seconds or a whole noisy minute, can produce a few inches of lazy, floating sparks or a roaring jet some 10 metres in height.

Roman Candles. Taking the form of long narrow tubes they fire single or multiple stars into the air, one after the other with a small pop each time. The stars theyshoot into the sky vary enormously as does the size of the candle itself some being tiny and some being 70mm in diameter, a metre in length and capable of projecting a series of fully functioning shells into the air. They can let loose simple coloured stars, long shimmering tailed comets, brilliant search-light stars, mini-shells, bangs, hummers and whistles.

Mines. Sometimes also called Jack-in-the-Boxes, the garden variety of these simple devices consist of wide, squat tubes, filled loosely with a gunpowder bursting charge and an assortment of stars and effects. Sometimes using a fountain or a small roman candle as an initial time delay they appear at first fairly unspectacular until, with a loud bang, they blow their main contents into the sky in a wide bouquet.

Rockets. These are possibly the most exciting and spectacular of all retail fireworks. They are also a very old type of firework, being one of the first to be fully developed, unfortunately with the intention being that of war instead of entertainment. Stabilised with a long wooden stick, at their simplest they consist of a narrow, strong tube with one end sealed and the other restricted, or choked, to force the heavily rammed gunpowder charge within to burn with sufficient force to lift the rocket free from the ground. Rockets can be tiny, some so small they are carried up in the heads of larger rockets were upon release they dash away like demented tadpoles but on the other hand they can be enormous, the solid rocket motors of the NASA Space Shuttle are effectively the largest fireworks ever produced and work in exactly the same way as the smallest garden rocket, except they produce over three million pounds of thrust instead of a handful of coloured stars.

Wheels and spinning fireworks. Represented by a few distinct types these ever popular fireworks include all rotating devices including Pinwheels, of which more will be said later. There are wheels driven by small rocket motors, called drivers, fixed to card or wooden slats that rotate rapidly around a central fixing. They can consist of a single driver, a pair or most commonly a trio of drivers. Some of the larger wheels might contain multiple drivers, two or more firing at once for extra push, with small colour pots or fountains added to create concentric rings of colour within the vortex of sparks. Some of these wheels can even slow down, stop and reverse their direction with the ignition of rearwards facing drivers adding an element of surprise to the erformance. Driver propelled wheels can be truly monstrous in size with some Maltese festival wheels measuring as much as 10 metres in diameter, with wheels within wheels and all capable of turning entirely under their own pyrotechnic thrust. Another type of turning device consists of a rapidly burning gunpowder mix which is forced to exit its container not by the end, as in the case of a rocket, but through a hole bored into the side of the casing. With a nail fixed firmly through the device at right-angles to the emitted jet these devices, called Saxons, will spin up to phenomenal speeds and in doing so produce spectacular roaring disks of colour and sparks.

Sparklers. The only hand-held firework now permitted for sale since the banning of hand-held fountains and rains. These simple little fireworks, consisting of nothing more than a metal wire dipped into a slurry of pyrotechnic mixture, produce small showers of crackling sparks upon ignition.

Another type of firework, now regrettably restricted solely to professional use are called shells and are by far the most spectacular and most ubiquitous of all display fireworks. Fired from strong tubes called mortars, they rise into the air before erupting with a loud bang and projecting all manner of shapes, colours, sounds and effects. They can be cylindrical or spherical in shape, can have one burst or can make a series of bursts called a multi-break and they make all the chrysanthemums, peonies, willows, palms, spiders, circles and other shapes seen in sky above most large displays. Shells can be as small as 25mm in diameter but have been as large as a metre and although the largest likely to be encountered in a British display would be 300mm in diameter, the largest available off-the-shelf measures in at a whopping 600mm in diameter, weighs over 100 kilos and explodes 600 metres in the air with a final spread of nearly half a kilometre.

Beyond the basic fireworks types currently available and those restricted to professional use there are the remaining items, many of which are included within these pages but all of which are now either banned or otherwise restricted from use. These missing types include many of the most popular and most fondly remembered of all fireworks...

Bangers - playful mischief-makers, beloved of boys and an utter nuisance to many, their short fizzing fuse delay was followed by an instant of noise. Despite undergoing a series of down-gradings in volume across the years in light of safety and nuisance they were finally silenced forever by the end of the nineties.

Air Bombs, single shot flash candles, recent casualties to noise and nuisance restriction. Pushed into the ground on their brightly coloured plastic spike, they appeared initially to be a simple little fountain, gentle and unremarkable, which would suddenly weaken and with a pop fire a projectile into the air which would burst overhead with a loud, brilliant flash. They were withdrawn from sale as recently as 2004

Jumping Jacks, known as Rip-Raps or more correctly as English Crackers. Removed from the shelves by 1972, these very old fireworks were the most unusual of all in outward appearance, being a snake-like zigzag of narrow, gunpowder filled pipe, bound with string or tape which upon ignition would bounce, leap and spin in all directions accompanied by a rapid series of bangs. Great fun but not one for the faint hearted.

Flying Squibs, Serpents, Demons or fliers, small rapidly burning stickless rockets that would shoot erratically across the ground, some ending their brief flight with a small bang. They flew for their last erratic time in 1972.

UFO's, Flying Saucers, Helicopters and Airplanes, more correctly titled Tourbillions (from the French for whirlwind) these once popular little fireworks, complete with their cardboard wings would spin up from the ground in whirling fiery vortexes, wobbling and rising unsteadily into the air with a loud swishing sound. They too had gone by 1972, a year which proved to be a bad one for firework lovers.

And lastly there are the small Pinwheels, also known as Catherine Wheels, one of the most popular and recognisable of all the fireworks. Although larger versions are still available, these smaller ones, little more than a couple of turns of gunpowder filled paper tubing wrapped around a small central disk, span vigorously for a few seconds before slowing to stop in a ring of fluffy fire leaving a circle of scorching on the surface of whatever they were fixed to. They were always there, tucked away in the bottom of a selection box, requiring a little more effort than other fireworks in that they needed a hammer to be nailed to a suitable support. Upon lighting they might refuse to spin, sometimes needed a prod from a stick, were always short lived but when they worked managed to pack into their tiny performance more than enough energy and spirit to make up for their shortcomings. These small pinwheels were never actually banned but they failed to survive the minimum distance requirements imposed in recent times for the safe viewing of garden fireworks. They left their little card centres nailed to the garden fence for the last time during the nineties and are never likely to return.

My thanks to Barry Sturman for his invaluable technical advise on the chemistry of this section.