Chapter 1: Historical Introduction

Working with fire probably began about half a million years ago when patriarchal cavemen realised that they felt the cold and began rubbing pieces of wood together until the friction caused an ignition. In fact, it is none too easy to generate fire in this way but we have all seen contrivances driven by coils of leather that spin a pointed stick against a wooden notch until it smokes and eventually bursts into flame.

Now it was originally thought that fire was a kind of substance and that this substance generated flames when it met the air. It is only within the last 200 years or so that fire was correctly interpreted as being a form of energy where the flames are defined as regions of luminous hot gas.

To find evidence of the first application of fire in the creation of ‘special effects’ it is necessary to go back some 1400 years when the naturally-occurring substances petroleum and naphtha were employed by the Greeks as an early form of napalm. In the characteristically unfriendly practices of those times, one Kallinikos from Heliopolis of Syria set forth in armed conflict against the Arabs. He had equipped fast-sailing galleys with cauldrons of what amounted to burning crude oil and proceeded to set the boats of the enemy ablaze, with the men still aboard. The incendiary was called ‘Greek Fire’.

The ploy must have worked because the subsequent narrative tells us that the Byzantines then capitalised on their secret weapon by the wholesale destruction of the Moslem fleet at Cyzicus and continued to win naval battles in this way for several centuries afterwards.

By about the eighth century ad, Chinese alchemists, amongst others, were preoccupied with discovering the elixir of life. Concoctions were made containing all manner of substances including oils, honey and beeswax, but among the most significant, so far as future firework makers were concerned, were the ingredients sulfur and saltpetre. Unbeknown to the ancients, their brew of honey, sulfur and saltpetre (potassium nitrate) was special in that, on evaporation over heat, the contents would suddenly erupt into a wall of flame. By chance, the experimenters had produced the exact proportions by which the molten sulfur and what was left of the honey were acting as fuels that were subsequently oxidised by the oxygen from the potassium nitrate in what is now known as an ‘exothermic chemical reaction’, and a fairly vigorous one at that! In purified form, the chemicals sulfur and saltpetre are used to this day in what is without doubt the most important tool of the firework makers, i.e. gunpowder.

These dangerous early experiments led to many secret or banned recipes, but enough information was disseminated to enable the details of the discovery to be brought to Europe. However, the place and date of the invention of true gunpowder are still unknown and have been the subject of extensive but inconclusive investigation.

Once the reactive tendencies of potassium nitrate were unleashed it was simply a matter of time before the third vital ingredient, charcoal, was added to complete the famous gunpowder recipe of charcoal, sulfur and potassium nitrate. Needless to say, much time and effort were expended before the alchemists produced a successful product.

As with many notable inventions, the credit for the discovery is usually coloured by patriotism, each country putting forward its own ‘inventor’. What is significant, however, is that by about 1000ad the Chinese were using a propellant similar to gunpowder in crude forms of rockets (Flying Fire), together with grenades and even toxic smokes. For example, a recipe in the Wu Ching Tsung Yao dated 1044 describes a mixture containing sulfur, saltpetre, arsenic salts, lead salts, oils and waxes to give a toxic incendiary that could be launched from a catapult.

More peaceful uses of these crude articles appeared in the form of ‘fire crackers’ – the first fireworks? One mixture corresponded quite closely to modern gunpowder in that it contained saltpetre, sulfur and willow charcoal. The ‘fire cracker’ was said to consist of a loosely-filled parchment tube tied tightly at both ends and with the introduction of a small hole to accept a match or fuse. All of these incendiary mixtures, presumably containing saltpetre, are mentioned in Chinese work dating from the eleventh century ad. Thus, in theory at least, the Battle of Hastings could have been one of ‘Greek Fire’, incendiary rockets and grenades.

Skipping about two centuries, the activities of one experimenter typify the development of early black powder. His work took place between about 1235 and 1290ad and he is reputed to have been the first scholar in Northern Europe who was skilled in the use of black powder. In essence, his work provided the backbone of all early chemical purification and formulation, without which the development of true gunpowders would not have been possible. His name was Roger Bacon (Figure 1.1).

Born in about 1214, Bacon became a monk but was educated at Oxford before gaining a doctorate in Paris. His subjects included philosophy, divinity, mathematics, physics, chemistry and even cosmology. He carefully purified potassium nitrate (by recrystallisation from water) and went on to experiment with different proportions of the other two ingredients (sulfur and willow charcoal) until he was satisfied that,

Of course, ‘The Church’ was not wildly enthusiastic with the prospect of one of its disciples practising such fiendish alchemy, and Bacon served ten years’ imprisonment. But he preserved his most famous recipe of ca. 1252ad in the form of an anagram, which on deciphering reads ‘of saltpetre take six parts, five of young hazel (charcoal) and five of sulfur and so you will make thunder and lightning’. In percentage terms, the 6:5:5 formula translates as saltpetre 37.50 parts by weight, charcoal 31.25 and sulfur 31.25 parts.

In fact, Roger Bacon's formula was not too dissimilar from early Chinese recipes. But being natural products, all three ingredients were of variable purity. For example, the crude Indian or Chinese saltpetre was richer in true saltpetre than the European material, but all required recrystallisation. The preferred process seems to have involved wood ashes, containing potassium carbonate, which precipitated deliquescent calcium salts from the saltpetre solution. The solution was then passed through a filter, boiled to reduce the volume of water and then left until the transparent plates of purified saltpetre were formed.

Sulfur occurs widely in nature as the element and was thus easily obtainable by the ancients. The Chinese had rich natural deposits, and the substance is readily purified by sublimation, a process in which the native sulfur is heated and the evolved vapour collected directly as a pure solid.

Charcoal was made from common deciduous woods such as birch, willow or alder, the last two being preferred.

The wood is simply carbonised at relatively low temperatures in a restricted air supply to form an amorphous, quasi-graphitic carbon of very fine particle size. Although of reasonably high purity, it is the enormous surface area per unit mass of the charcoal which makes it very adsorbent to water vapour, and this property is conferred to the black powder mix, as Roger Bacon would have soon realised.

Guns were invented shortly after Bacon's death in about 1292 and so he never used the term ‘gunpowder’. However, he had certainly had experience of fireworks for which his early black powder recipe would have been perfectly suitable. In the Opus Majus he wrote:

In experimenting with fireworks, Roger Bacon and other medieval chemists discovered that a loose, open tray of powder was all that was needed to produce a flash, but in order to produce the bang the powder needed to be confined, and this has great significance. And even with his unbalanced 6:5:5 formula, Bacon was able to deduce these fundamental ballistic effects.

This short introduction to gunpowder would not be complete without reference to its final development and one or two subsequent events that were to change the course of history.

In lighting a firework we are going back at least 1000 years. The potassium nitrate in the blue touch-paper or the match burns in much the same way as it did when the Arabs or the Chinese played with their fire crackers. The smell of the sulfur when it forms hydrogen sulfide on combustion would have been much the same, as would the dense white smoke that is so characteristic of gunpowder. But modern fireworks are reliable products. The gunpowder has a consistent burning rate and is less affected by moisture than it would have been in the eleventh century. Obviously it was in the interests of the future markets that the experimenters persevered, and their pioneering work was by no means trivial.

First, true gunpowder is not just a ‘loose’ mixture of unground potassium nitrate, sulfur and charcoal. Indeed, if the three ingredients are mixed in this way then a greyish powder results that is almost impossible to light. If ignition does occur the burning is fitful and prone to extinguishment. In order to overcome these deficiencies the ingredients must be brought into intimate contact. The charcoal and sulfur are milled together with 2–3% of water in a tumbling barrel, then the potassium nitrate is added and the damp mixture is further milled under rollers before being pressed into a cake using a hydraulic press at a pressure of about 2 tonnes.

As with the modern fireworks industry, pressing is preferred over more forceful techniques, but even so, fires regularly break out in presses. Milling is not without hazard either, especially when the large wheel mills weigh several tonnes and the powder batch is around 150 kg.

After pressing, the gunpowder cake is broken and this corning or granulating is the most dangerous of all manufacturing operations.

It is necessary to crack the cake between crusher rolls to form the grains (see Figure 1.2) which are subsequently graded by sieving. The ‘finishing’ process involves tumbling and drying the granulated powder in wooden barrels in the presence of graphite to give a polished or glazed appearance. The granulated and glazed gunpowders were found to be more moisture-resistant than the early fine powders and the ignition and burning consistency was also much improved. It is the ‘fines’ or corning mill dust that is used in fuse powder and by the makers of fireworks.

Of course, in the Middle Ages the emerging gunpowder industry relied on mortars and pestles to do the mixing, and the recipes were changed in what was, in reality, an enrichment of the saltpetre content to give faster burning and ever more powerful powders for yet another historically important invention – the gun.

Thus, in Arabic work dating between perhaps 1300 and 1350ad, gunpowder is described as a propellant. Cannon were also known in Europe by that time and were used in the defence of castles and villages. In 1338, cannon and powder were provided for the protection of the ports of Harfleur and L’Heure against Edward III. From about 1340 onwards there is frequent mention of the use of guns, and by 1400 the Crown in England possessed a stock of guns and gunpowder.

Rocketry was also developed and early in the nineteenth century an Englishman by the name of William Congreve commenced experiments to produce a large war-rocket for use against the French. The object was to provide the rocket with an incendiary or explosive charge and a range of up to 3500 metres where both the propellant and the explosive charge would have been based on gunpowder.

In 1807 Congreve is said to have personally directed the firing of his rockets at the siege of Copenhagen where they are reported to have been effective and by the middle of the nineteenth century all the leading powers in Europe were manufacturing war-rockets.

Although the generic term ‘Congreve rocket’ remains current, the form of the weapon varied considerably and its evolution was gradual. Thus the documented improvements included an iron case, a balancing weight and chain as a substitute for the stick and various methods of imparting spin to the rocket as a means of attaining stability in flight.

And even as recently as 1979, gunpowder remained the propellant of choice for the production of large (70 mm) line carrying rockets. These devices typically weighed some 5 kg of which about 2 kg was propellant pressed inside a metal case. An 8 mm diameter hemp line could be projected to a distance approaching 300 metres while the line also provided flight stability. A wire bridle connecting the rocket to the line ensured that the latter was not burnt by the hot exhaust gases.

It is interesting to record how the composition of gunpowder changed as history progressed (Table 1.1) and how the 75:15:10 mix of 1781 remains in use to the present day.

In fact, most of the improvements to gunpowders after about 1600ad concerned the methods of manufacture, there being no question that the proportions of the three components were correctly balanced for chemical reaction, that is to say ‘stoichiometric’.

An approximate equation for the burning of black powder has been given as in reaction (1.1).

The above reaction corresponds to a composition containing saltpetre (75.7%), charcoal (11.7%), sulfur (9.7%) and moisture (2.9%).

The fireworks industry also benefited from these improvements, which was reflected in the growing popularity of organised displays and the diversity of the pyrotechnic effects so presented.

Historically, it is generally accepted that the first fireworks were developed in far-eastern countries, notably India or China, for display at religious festivals, and that knowledge of the art subsequently spread to Europe, probably via the Arab kingdom. The Italians are credited with introducing the firework industry in Europe, again promoting their use for public occasions before the manufacture was adopted by neighbouring countries such as France and Germany. By the sixteenth century, fireworks displays were being given in England, and it is documented that Elizabeth I witnessed such an event in August 1572.

Although the early displays in England were enthusiastically received, it must be admitted that most of the pyrotechnic art, and indeed the operators and equipment, originated from Europe – foreign workers were still giving displays in England as late as 1775. It may also be noted, in passing, that in the early seventeenth century the making, purchasing or keeping of fireworks was ruled to be illegal; this was due, in no small measure to the famous (or infamous) attempt to blow up the Houses of Parliament in 1605 by a certain Mr Guy Fawkes using 36 barrels of gunpowder.

The conspiracy is alleged to have begun in 1604 during the second year of the reign of James I, when a group of Catholic fanatics decided that the Establishment must go. Five conspirators, including Guy Fawkes, commenced digging under the main parliamentary building in an attempt to undermine it, and in doing so came across a cellar which was being used by a coal dealer. This they duly filled with ‘powder, faggots and billets’. Timing the event to coincide with the State Opening of Parliament on the 5th of November 1605 meant that the conspirators could also claim the life of the King. However, a warning letter was sent to some members of parliament beforehand, and this was read not only by the Secretary of State but also by James I who, with amazing insight, correctly interpreted it as meaning an explosion on November 5th.

The vaults under the main chamber were visited by the Lord Chamberlain on the 4th November and there they found ‘a tall and desperate looking fellow’ who identified himself as Guido Fawkes. On the 5th of November, magistrates examined the neighbouring house and cellar where they arrested Fawkes who was ‘just leaving’.

Guy Fawkes was tortured and his accomplices arrested, tried and executed. The Establishment was clearly not ecstatic about the fact that the plot had so nearly succeeded, and Fawkes was tried at Westminster on 27 January and ceremoniously executed on 30 January 1606.

All of this was subsequently of great benefit to the British fireworks industry, of course, which has capitalised on the 5th of November celebrations ever since. However, any other country in the world might have bent the truth a little and claimed in the history books that the plot took place on a nice, warm day in August rather than in cold and damp November – even if only for the sakes of the fireworks operators!

By the nineteenth century, English firework makers including Brock, Pain and Wells had established themselves in the London area to be later followed by Standard Fireworks and others in the North. Thus the availability of locally-produced gunpowder and fireworks was enough to eschew any drift towards European suppliers.

The Brock company originated in the early eighteenth Century in London and was soon firmly established as the producer of inovative fireworks to satisfy the increasing demand for public and private displays.

Run as a family business, John Brock established his premises in North London at a time when ‘Pleasure Gardens’ were growing in popularity and provided ideal venues for the erection of tall frames on which to effect the pyrotechnic displays.

By the nineteenth century London had grown significantly in area, and the Brock company was moved to larger premises reflecting the scale of its products, with set-pieces depicting famous victories or battle scenes typically extending to many hundreds of feet.

Some of the most highly acclaimed displays commenced around 1865 at the Crystal Palace where Mr C. T. Brock set a standard for brilliance and colour which was said to defy competition. This improvement was due, in no small part, to the introduction of metal powders and chlorates into the pyrotechnic mixes, an innovation which is used even today.

The twentieth century saw the continuation of the company's influence on fireworks, now worldwide, with Roy Brock organising displays during Princess Elizabeth's twenty-first birthday celebrations in South Africa in April 1947 while Christopher Brock directed a centenary display for the city of Dunedin, New Zealand in 1948. The Brock name enjoyed an association with pyrotechnics until well into the second half of the twentieth century, eventually specialising in defence related products such as simulators and smokes.

The history of Pains Fireworks began in about 1593 when John Pain established his business as a gunpowder manufacturer and armourer near Bow Bridge in East London. It is also documented that twelve years later, in 1605, he had the dubious distinction of being the supplier of the one tonne of powder required by Mr Guy Fawkes for reasons mentioned previously!

Later in the seventeenth Century Peter Pain, a French descendant of the Pain Family, moved to Bow Bridge to join the London arm of the family. During this period customers for Pains gunpowder included Charles II and James II.

It was during the 1700's that Firework Masters from Europe came to England to meet the demand for ever more spectacular displays for members of the Royal Family. Many labourers were employed locally to erect the huge frames and platforms from which to display the fireworks, and amongst the locals were members of the Pain (and Brock) families. In this way William Pain acquired enough knowledge from ‘the Masters’ to present his own displays in London's Parks and Gardens in the late 1700's.

By the early nineteenth century William Pain had passed his skills on to his son James and to a nephew called Joseph Wells, but in 1837 Joseph left to establish Wells Fireworks, a company that also survived into the twentieth Century.

In 1872 James Pain established a fireworks factory near Mitcham in Surrey before setting off to America in 1878 in the company of his son Henry to form the leading firework company in the USA. On returning to England, James expanded the business to the extent that Pains Fireworks became renowned throughout the world.

James Pain died in 1923 and the running of the Company became the responsibility of his other son, Philip, who died 3 years later (Figures 1.3 and 1.4).

The intervention of two World Wars together with the economic depression of the 1920s and 1930s saw a rise and fall in the fortunes of Pains Fireworks, to the extent that take-overs became inevitable.

In 1963 Pains was amalgamated with the Wessex Aircraft Engineering Company (WAECo) who were based at High Post near Salisbury and who were, in turn, owned by the British Match Company. Within two years Pains Fireworks had relocated from Mitcham to High Post in a move that extended the Factory's product base from fireworks to distress flares, signalling smokes, line carrying rockets and munitions simulators trading under the name of Pains–Wessex.

The picture became even more complicated in 1968 when Wells Fireworks was acquired by Schermuly who operated out of the SPRA (Schermuly Pistol Rocket Apparatus) works at Newdigate near Dorking (Figures 1.5 and 1.6).

In the 1970's Schermuly was, in turn, taken over by British Match and the latter then merged with Wilkinson Sword Limited to form the Wilkinson Match Group.

Thus it was that Pains–Wessex/Schermuly had access to the extensive Wilkinson Sword Research facilities (which resulted in many new and improved military pyrotechnics) while Pains Fireworks gave up shop goods to concentrate on display fireworks, moving back to the old Wells factory in Dartford in 1976 (Figures 1.7 and 1.8).

By now Pains was owned by John Deeker who had spent most of his life working for Pains Fireworks and then Pains–Wessex both as a director and an accountant.

In 1982 Pains moved again, this time to the site of an old chalkpit in Whiteparish near Salisbury where the Deeker family continue to own and promote the business and where Wilf Wells, a former Wells director, spent his remaining years.

Although the Explosives Act of 1875 expressly forbids the manufacture of gunpowder or of fireworks outside a licensed factory there have been tales of the Yorkshire miners who, amongst others, produced squibs (small exploding fireworks) by packing gunpowder into rolled paper cases. These were used for blasting but were also said to be effective in clearing the soot from the flues of domestic homes. Under these circumstances it is not difficult to imagine a cottage industry springing up whereby the squibs were turned into crackers or any other simple form of fireworks which were then sold locally.

And so on to the twentieth century when the emergence of free trading between nations once again meant that fireworks, and more importantly, gunpowder, were available from around the world. Gunpowder is no longer manufactured in the United Kingdom and supplies are procured from Spain, Germany, South America and the Far East, as are fireworks. Of the original esteemed group of factories, few survive today and even fewer make any fireworks, relying instead on the magazine storage of imported products to effect their displays, just as they did 300 years ago.

Clearly gunpowder has played a prominent role in the construction of early fireworks but, unless it was used in conjunction with other pyrotechnic mixtures, the range of effects was very limited. However, it continued to be the main performer in fireworks until the introduction of potassium chlorate some years after the first preparation of this substance by the French chemist Berthollet in 1786.

Even earlier, in the seventeenth Century, John Bate recorded the use of antimony sulfide “to produce a blue flame” in his Book of Fireworks in 1635. The same author also used iron scale in some of his compositions to give rockets a more luminous tail.

In 1801 the French pyrotechnist Claude-Fortuné Ruggieri described the use of metal salts in the production of coloured flames. By the early nineteenth century the firework maker had at his disposal a diverse arsenal of materials, many of which are still in use today. The following substances were documented by Audot and others at around that time:

• POTASSIUM CHLORATE, KClO₃: Used to enhance the colour of flames produced by other metal salts e.g. strontium nitrate, Sr(NO₃)₂ (red flame).

• ANTIMONY SULFIDE, Sb₂S₃: Gives a blue flame.

• IRON AND STEEL FILINGS: Give white and red sparks.

• RED COPPER FILINGS: Give greenish sparks.

• ZINC FILINGS: Produce blue sparks.

• YELLOW AMBER (Organic resin): Gives a yellow flame.

• LAMP BLACK: (Soot) Gives a reddish flame.

• COPPER NITRATE, Cu(NO₃)₂: Gives a blue flame.

• BARIUM NITRATE, Ba(NO₃)₂: Gives a green flame.

And finally it is gratifying to be able to report that, for the 5th of November's Guy Fawkes Night celebrations in London in 2007, free firework displays were held at Clapham Common, Alexandra Palace, Blackheath, Streatham Common and Brockwell Park, with crowds of up to 40,000. Long may it continue!

Of gunpowder itself, although it has a long and colourful history, its use as an explosive dwindled into insignificance after the domination enjoyed by the much more powerful high explosives that succeeded it. But besides fireworks, there are still a few ‘niche’ applications where the unusual burning properties of gunpowder and kindred substances may be exploited. For example, as a ‘low explosive’ it is suitable for controlled blasting in which the treatment of the stone must be mild. It is therefore used in the manufacture of roofing slates and in quarrying for paving stones, the powder grains being freely poured into boreholes.

Whilst the 75:15:10 formula corresponds to one of the quickest and most vigorous of the gunpowder compositions, a slower form is required for blasting (as detailed in Table 1.2).

This criterion is satisfied by a reduction in the potassium nitrate content, which also results in a slight reduction in cost.

A significant amount of blasting powder is also made using sodium nitrate in place of the potassium salt. Although hygroscopic, the sodium salt is said to give good performance over a range of climatic conditions provided that a heavy graphite glaze is used to coat the gunpowder grains.

And as well as being used to demolish buildings, gunpowder has assisted in their construction; the Royal Observatory at Greenwich being paid for by the sale of surplus stocks of military powder during the reign of King Charles II.

Gunpowder is also employed by the military in making priming charges for smokeless powders. In the largest calibres the gunpowder grains are sewn into quilted silk bags that fit over the ends of the cordite charges to promote ignition. It also finds use in the production of fuses, pyrotechnic stores, ‘special effects’, bird-scaring cartridges, cartridge actuators and small-arms ‘blanks’.

Apart from its unique property of burning quickly at relatively low confinement it is not prone to detonation. Under normal conditions the maximum rate of explosion is about 500 m s⁻¹. In the absence of moisture, gunpowder in also extremely stable. It has been documented that until World War I it was the practice of the French Army to preserve any batches of gunpowder that had proved especially good. These were used in time train fuses and it was claimed that some batches so preserved dated from Napoleonic times.

Perhaps the most unusual modern application of potassium nitratebased powders is in the fire protection industry. The white smoke mainly consists of potassium carbonate and this has been found to have fire extinguishing properties due to the way in which the potassium salt in the smoke interferes with the combustion chemistry of a fire.

The generally accepted mechanisms for the suppression of fires and explosions by alkali metal salts such as potassium chloride, KCl; potassium bicarbonate, KHCO₃ and potassium carbonate,K₂CO₃ in the form of dry powders or aerosols (smokes) involve heat absorption, endothermic decomposition and radical recombination.

Heat absorption occurs by virtue of the intrinsic thermal mass of the cool material injected into the flame, and by endothermic phase changes, e.g.

The cooling effect is enhanced by endothermic decomposition reactions, e.g.

Free radicals are atoms or groups of atoms possessing an odd (unpaired) electron. Radical recombination occurs when active flame propagating species (O˙, H˙ and ˙OH) recombine (heterogeneously) on particle surfaces or (homogeneously) as a result of gas phase reactions catalysed by alkali metal atoms in the flame, e.g.

Also, the water vapour and carbon dioxide produced in the reactions act as inertants.

Finally, the extinguishing effectiveness of an aerosol is related to the particle size. Smaller particles maximise the surface area for heat absorption, increasing the probability of subsequent decomposition and radical recombination processes.

Large grenades containing up to 2 kg of powder composition have been used by European firefighters where, for example, in burning buildings the smoking grenades are simply hurled through the plate glass windows. Now that really is ‘fighting fire with fire’!

Table 1.2 lists the current applications of black powder. In general, as the balance of the ingredients in the composition shifts from the near stoichiometric 75:15:10 mix, the rate of burning decreases but is still fast enough to be of major importance in firework rockets, delay fuses, igniters and pyrotechnic smokes.