The story of explosives begins with black powder, used by the world’s major civilizations for six centuries. Until about 1840, it was the only known explosive substance. Production of this mixture of potassium nitrate (“saltpetre”), sulfur and charcoal is straightforward, if moderately dangerous. Raw materials are pulverized and mixed. The resulting mixture is then rolled or pressed into cakes. The cakes are broken into grains for final polishing, drying and blending for specific applications such as blasting or munitions. For safety, production was in small batches, typically located close to the points of use. Numerous rudimentary black powder “mills”, operated by hardy proprietors, served local markets such as a mining district or a munitions factory. With few economies of scale and no incentives for innovation, explosives manufacture was a pre-industrial activity.
Nitroglycerine, a chemical compound, was the first “high explosive” that explodes by denonation instead of burning. Italian chemist Ascanio Sobrero discovered this unstable, sensitive liquid in the 1840s. Production requires mixing glycerin into a blend of nitric and sulfuric acids. The mixing operation produces heat, which can cause a runaway explosive reaction if not controlled. Special acid-resistant vessels, often fashioned from lead, are required to handle the corrosive acids.
Nitroglycerine can produce explosive velocities many thousands of times greater than black powder. Despite Sobrero’s warnings, harnessing the power of nitroglycerine was an irresistible challenge for men of vision and industry willing to risk death. By the 1860s, nitroglycerine had moved from scientific curiosity to a new technology.
The technology of high explosives advanced rapidly. Powerful, reliable, controlled explosive force made possible the extraction of coal and petroleum for energy, and iron ore for steel, at unprecedented scales of effort. Railroads could span continents; the Panama Canal was soon blasted between two oceans. The Hercules plant was a headquarters of innovation in explosives.