Gunpowder, Explosives and the State

A Technological History

Brenda J. Buchanan

• Publisher: Routledge
• Year: 2016
• Print ISBN: 9780754652595
• eBook ISBN: 9781351931908
• Edition: 1
• Topic: History
• Subtopic: World History
• Index: History

Gunpowder studies are still in their infancy despite the long-standing civil and military importance of this explosive since its discovery in China in the mid-ninth century AD. In this second volume by contributors who meet regularly at symposia of the International Committee for the History of Technology (ICOHTEC), the research is again rooted in the investigation of the technology of explosives manufacture, but the fact that the chapters range in scope from the Old World to the New, from sources of raw materials in south-east Asia to the complications of manufacture in the West, shows that the story is more than the simple one of how an intriguing product was made. This volume is the first to develop the implications of the subject, not just in the sense of relating it to changing military technologies, but in that of seeing the securing of gunpowder supplies as fundamental to the power of the state and imperial pretensions.The search for saltpetre, for example, an essential ingredient of gunpowder, became a powerful engine of sea-going European trade from the early seventeenth century. Smaller states like Venice were unable to form these distant connections, and so to sustain a gunpowder army. Stronger states like France and Britain were able to do so, and became even more powerful as the demand for improved explosives fostered national strengths - leading to a development of the sciences, especially chemistry, in the former case, and of manufacturing techniques in the latter.

PART ONE

MODERN PERCEPTIONS AND ANCIENT KNOWLEDGE

Chapter 1

Realities and Perceptions in the Evolution of Black Powder Making

Robert A. Howard

First presented at the 25th Symposium of ICOHTEC, Lisbon, 1998.

Making black powder has often been termed a ‘black art’. Even today, with the large quantity of literature available, the description is still valid. Aside from the problem of over reliance on traditions on the part of some of the makers, the reason is that those involved in the actual manufacturing do not usually have ready access to the literature or the experiences of the past. Also, black powder is not the primary concern in the field of explosives, since it is now essentially obsolete for most of its previous uses. Ideally, the burning characteristics of powder should match its intended use. Here begins the reasonably complex series of variables on both the use/need and the production side of the equation. It was not until the middle of the nineteenth century that a really good grasp of both sides had evolved.¹

A Practical Approach to Black Powder Making

On the production side of the equation, there are essentially four ingredients (nitrate, sulphur, charcoal and water). Each of these, depending upon the quantity present and its quality (with a purity deemed suitable), can make a difference in the resultant powder. There are also six or seven mechanical processes (depending on when, and the type of powder being made), each of which can affect the final product. To make this more complicated, the variables are not confined to only one influence. This chapter will attempt to sort out the variables, determine their influences, and describe their past perceptions. A warning to would-be makers using this paper: mistakes are generally fatal in nature and, fortunately for the author, the evidence is likely to be vaporized, making tedious recriminations difficult.

The critical need in making powder is to manufacture a product with absolutely predictable burning characteristics. Functionally this means the speed of the burn (or the rapidity of the generation of gases) and the force (or the amount of gas generated) both need to be regulated. Practically, the stability of the grains needs to be assured, meaning they should not disintegrate in transport. The grains should also be stable during combustion. If not, the larger grains will break down into smaller grains during combustion, and the combustion rate will accelerate during the burn. Powder needs to be hygroscopically stable. It should not absorb water and become worthless. The last problem is that of chemical stability. This seems to be a direct factor of the presence or absence of microorganisms in the water used to make the powder, which can attack the nitrate and degrade the quality of the powder.²

With the current but perhaps declining knowledge of powder, it is hard to realize that the early makers did not know enough to postulate (or articulate?) their needs. They lived in a world of four elements (earth, fire, water and wind) and four related humours, without the vocabulary to express accurately either the chemistry or the physical nature of the burning. Not only is the creation of vocabulary one of the key factors in the advancement of technology, the lack of it historically creates many problems for this twenty-first-century author in organizing this account. Since no approach is faultless, the procedure chosen is to look at the powder composition by ingredient and the manufacturing by step or method, and see what effect they have on the resultant powder. We can then look at the vocabulary and powder testing devices with some knowledge of what the perception and realities really were. It should be noted that this chapter has the bias of an American author who has access to the Guttmann Collection but not to all the European sources.³

The Ingredients

The ingredients of powder are nitrate, sulphur, charcoal and water. Today this occurs in the classic ratio of 75:10:15, or else in the ratio of 12.5% for both the sulphur and charcoal and 75% for the nitrate, with the water being one half of one percent of the product by weight. The water has a dual physical role in the manufacture. It somewhat reduces the explosion hazard during production and also acts as a binder by helping to produce a stable grain of powder. After the beginning of the nineteenth century, a very small amount of pure carbon was added in the glazing process in the form of graphite. This formed a coating which made the powder pour better, impressing the North African markets, but not measurably contributing to the burning reaction’s chemistry. The issues of purity for the three major ingredients have long been known to be very important. Water purity is discussed in note 2, and graphite purity does not seem to have been an issue.

Sulphur (or Brimstone)

This ingredient is the easiest to discuss since it is an element, and once purified has no other properties of any great consequence. It is easily recognized since it gives off an unpleasant odour when it burns and causes great chaos in the digestive tract when ingested. In the powder burning reaction, about 2.65% of the gases (by volume) are hydrogen sulphide. Of the solids by weight, about 15.10% is potassium sulphate, 14.45% is potassium sulphide and 8.74% is pure sulphur.⁴ While it does help in the burn, on the downside there is some sulphur dioxide generated which combines with the moisture in the air to produce sulphurous acid, a corrosive agent. It seems to attack iron guns more than it does bronze ones.

To purify sulphur, two major methods were used historically. The first was in a specially cast iron cauldron with a tube on its side to allow pouring.⁵ The other was by sublimation where the sulphur was changed to a gaseous state in which the unsuitable ‘flowers of sulphur’ were deposited and further heating produced the liquid sulphur, which was run into a receiving pot and resolidified. Later, around the turn of the nineteenth–twentieth century, the Frasch process was devised to mine sulphur in an essentially pure form by using pressurized superheated water to wash the material out of buried volcanic deposits and force it to the surface, depositing it above ground. Currently, pure sulphur is a byproduct of gasoline refining and is very inexpensive and plentiful. Historically the most common impurity in sulphur was dirt, which would retard the burning reaction. The most important source of the early years, the volcanic regions of Sicily, occasionally had rocks added to increase the weight and add to the profit of the miner / refiner / seller. By the early nineteenth century the sulphur reaching the USA was crudely refined in Sicily, refined further in Marseilles, the entrepôt in France, and yet again at its destination. The DuPont Company built a refining operation in Delaware but abandoned the process when refiners in New York were able to supply pure sulphur after the war of 1812.

Charcoal

Charcoal is one of the more complex topics. The physical nature of the charcoal plays a role in the combustion process. Small amounts of creosote in the charcoal (a byproduct of the manufacturing process) were quite accurately thought in the nineteenth century to give a better burn. The powders made with charcoal and creosote were called moist burning powders. Small amounts of ash kept the powder slightly alkaline, making stable grains. Chemically the carbon contributes the gaseous products of combustion, carbon dioxide

(49.29%) and carbon monoxide (12.47%); and the solid byproducts of combustion, potassium carbonate (61.03%), potassium thiocyanate (0.22%),ammonium carbonate (0.08%), and carbon (0.08%). Since wood is a hydrocarbon, the hydrogen in the burning reaction also comes from the charcoal. In gases this is found in methane (0.43%), hydrogen sulphide (2.65%), and hydrogen (2.19%); and in solids, ammonium carbonate.

The physical nature of the charcoal as opposed to that of pure carbon is critical to the quality of the powder. A fixed carbon content of about 70% is optimum. As perhaps a vast over simplification, charcoal is a porous maze. In fact, it is commonly used as a filter. The softer, less dense woods give a more complex and larger maze than the denser hardwoods. The softer woods such as alder, hazel and most particularly willow are the woods of choice for making black powder. This is essentially because they provide charcoal that is easier to ignite. Also, the softer woods break down more easily into particles like cellulose bundles and are not as difficult to pulverize as those of the hard woods. Classically wood was burned under controlled conditions in mounds to make charcoal. Beginning late in the eighteenth century, another process came into being by which the wood was distilled in large iron retorts with fires built underneath them. By carefully controlling the fire and hence the temperature, the distillation process proceeded with very little production of wasteful ash and less danger to the charcoal burners, who had previously risked being consumed in their own smouldering mounds. Toward the end of the century, superheated steam was used instead of direct fire. Some of the later powders, such as the so-called ‘brown prismatic’ powders (German patented), were based on the production of special unburned or brown charcoal.

Nitrate

The nitrate is essentially the oxidizer in the burning reaction. There has been some considerable discussion about which nitrates were present in the early powders. Potassium nitrate is the nitrate of choice for black powder, although it has been suggested that calcium nitrate was present in some of the earlier powders.⁶ In the 1850s sodium nitrate was substituted in some forms of blasting powders, and ammonium nitrate has been used for this purpose, especially in ‘fiery’coal mines.

There are three factors to consider: which nitrate was present; the proportion of nitrate to the other ingredients; and the chemical purity of the nitrate. Of the three chief nitrates for powder, potassium, sodium and calcium, potassium is the most active and the best. Sodium is considerably more hygroscopic and weaker. Calcium, if it were present as has been suggested, is by far the weakest. The problem facing historians is that chemical elements as such were not recognized during the early period of gunpowder production, and virtually anything that was a white crystalline powder was called ‘salt’.

As has been pointed out by Dr Bert Hall in Weapons and Warfare in Renaisssance Europe,⁷ the amount of nitrate available and, most importantly, its price, were essential influences on the use of powder-based armaments. Most modern powders use 75% nitrate, which has been a tradition for musket-type powders for over 400 years. Some earlier texts recommend that the larger the gun, the less the amount of nitrate needed to a point of having about 50–66%.⁸ A smaller amount of nitrate, of course, retards the burning rate which in turn modifies the excessive breech pressures in guns.

The purity of the nitrate is important for two reasons. Impurities, especially those that do not participate in the combustion, get in the way of combustion or retard it. Also some impurities, especially the chlorides, become part of the solid residue and mix with the moisture in the air, producing acidic residue which degrades the weapons.

The early means of making nitrates consisted of collecting and purifying wastes. By the mid-nineteenth century the process for making artificial potassium nitrate was known, but not widely used. By the turn of the twentieth century it was in use. Today most of the potassium nitrate is made for fertilizer and is reasonably pure, although some chloride contamination may occasionally be found. Very pure potassium nitrate is also available in bulk quantities, at a somewhat higher price.

The Manufacturing Process

Unlike the later chemical explosives or smokeless powders, black powder is a mechanical combination of the ingredients. How this is done is highly critical to the way it burns.

Pulverizing

Pulverizing is the initial mixing of the charcoal and sulphur in a ball mill. Variants of this procedure included also the nitrate, a practice followed at the DuPont mills from their establishment in the early nineteenth century to about 1880. But mixing the three ingredients in the ball mill was an unsafe operation and is rarely done anymore, except in the making of fuse powders. In the pulverizing process the charcoal is broken down into particles and mixed with the sulphur. The quality of the powder is greatly dependent on how well this is done, which usually equates to how long the ball mill rotates with its load. The longer it is milled (the large barrels used by DuPont ran for several hours), the better the mix, until a point is reached beyond which there are severely diminishing returns. Without pulverization, all the particle reduction mixing is done in the incorporating process.

Incorporating

Incorporating is the simple process of either stamping or rolling the ingredients together. Other ideas have been tried, some with disastrous results. The following are some examples. The nitrate has been heated and the sulphur and charcoal stirred in, which proved hazardous in the extreme. Water was used to dissolve the nitrate, the other ingred...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• List of Illustrations
• List of Tables
• Notes on Contributors
• Acknowledgements
• Foreword
• Editor’s Introduction: Setting the Context
• Part One: Modern Perceptions and Ancient Knowledge
• Part Two: The Production of Saltpetre and Gunpowder in Europe
• Part Three: The Overseas Transfer of Technology from Europe
• Part Four: Military Technicalities
• Part Five: Modern Developments
• Index