Flash and Blast

Jack Kelly. Gunpowder: Alchemy, Bombards, and Pyrotechnics; The History of the Explosive That Changed the World. Cambridge, MA: Basic Books, 2004. x + 260 pp. $25.

Reviewed by Mary Virginia Orna

In a fast-paced narrative that reads like an adventure novel from start to finish, Jack Kelly skillfully weaves a tale of magic and wonder, violence and mayhem, power and conquest, scientific challenge and technological advance. As the title of this book promises, we learn how this low explosive, the first ever devised and the only one available for a millennium, redrew the map of the world, changed the nature of warfare, and led to theories that would change our view of the nature of reality.

Gunpowder is a mixture of two elements (carbon and sulfur) and a compound (preferably potassium nitrate, or “saltpeter”). Under favorable conditions—intimate mixing, proper grain size, and little or no moisture adhering to the grains—gunpowder works by the rapid burning of sulfur, which requires the lowest ignition temperature, and then of carbon at higher temperatures, in oxygen released by the thermal disintegration of the potassium nitrate. The resulting hot gases (nitrogen and carbon dioxide) expand so rapidly that they push anything they come across—including cannonballs and castle walls—out of the way.

This mixture was invented in China before a.d. 1000 and used there, in varying proportions, for driving off evil spirits and in pyrotechnic entertainment. (Of course, it was not called “gunpowder” until after the invention of guns, nor “black powder” until other explosives were devised that lacked the lustrous appearance of free carbon.) The first known recipe for gunpowder comes from a 1249 work by Roger Bacon, an English alchemist and Franciscan monk. The explosive Bacon described was composed of six parts of saltpeter to five parts of charcoal and five parts of sulfur. Later versions used more saltpeter, eventually stabilizing at a ratio of 15:3:2, which is close to the stoichiometric ratio of 15:2.7:2.4.

It is thought that Bacon’s recipe came from the Far East by way of Arabic manuscripts, and thus the Chinese entertainment industry and European military arts converged. Perhaps no one invention revolutionized the conduct of warfare as much as gunpowder. Almost overnight, military history became the history of the use of this explosive mixture in new and more violent ways. War changed from hand-to-hand combat to killing at a distance; castle walls, once resistant to the most persistent siege, were the easy prey of cannonballs. And the combatants who prevailed were those who grasped the importance of this powerful new weapon and did not scruple to use it.

Although Kelly spills a great deal of ink on the conduct of warfare, describing the effect of gunpowder in the battle of Crécy and other battles in almost excruciating detail, he does not glorify this technical “advance” in any way. He makes it clear that gunpowder is “a most raging and merciless” weapon that makes no distinctions and offers no appeals. The horror that always accompanies the political use of explosives is callous, arbitrary, random, indiscriminate carnage—a reality that our newspapers and television shows remind us of daily.

So, is gunpowder all bad? Is it used only to destroy? For many years gunpowder represented humankind’s furthest advance in the manipulation of natural materials, but it remained a deep mystery because chemistry, which would give a theoretical and practical basis to the action of gunpowder, was still a nascent body of knowledge. Scientific investigation into this “magical and incendiary substance” gave rise to multidisciplinary technological and theoretical advances. For good or for ill, gunpowder influenced the development of engineering, metallurgy, physics, chemistry, trade, industry, social structure, and economics.

Perhaps the most important but least obvious impact was its influence on theories of nature. Studies in the 17th century on the reaction of gunpowder led to the realization that fire is not an element, thus overthrowing the millennia-old “four element” hypothesis. Thoughts about the driving force of gunpowder eventually led Christian Huygens to the idea of the internal combustion engine, and on the basis of its action Robert Hooke laid the foundation for the first coherent theory of combustion, an idea that in some ways anticipated Antoine-Laurent Lavoisier’s oxygen theory of combustion.

Chemists may find that Kelly’s narrative raises more questions than it answers about the nature of gunpowder’s ingredients, the chemical reactions involved, the energy released, and the preference for certain reactants (e.g., potassium nitrate) as opposed to other, more readily available materials (e.g., calcium nitrate). However, as popular books go, this work is remarkably accurate: Kelly relied on the most important primary sources available as the basis of his work. But don’t look for footnotes because there aren’t any. Kelly deliberately omitted them in favor of an annotated bibliography that is probably sufficient for 99% of his readers.

As with most other things in life, gunpowder shows us two faces. It is the energy behind Shakespeare’s “leaden messengers that ride upon the violent speed of fire,” but also the magic substance that gives delight to millions of spectators at pyrotechnic displays and the catalyst that led to important scientific investigations.With the advent of the high explosives like nitroglycerine and of nuclear explosives that can produce much bigger bangs, perhaps it is poetic justice that the major use of gunpowder today is that for which it developed in China a millennium ago: the source of “oohs!” and “ahs!” on the Fourth of July.