Claude on Question 21, Sep 15

The Three Ingredients

Black powder—known then simply as "gunpowder"—consisted of saltpetre (potassium nitrate), charcoal, and sulphur. The proportions varied by nation and era, but by the 18th century most European powder works settled near 75% saltpetre, 15% charcoal, and 10% sulphur, with military powders generally richer in saltpetre than mining or sporting grades.

Saltpetre was the bottleneck and the strategic prize. Until the late 18th century, Europe imported enormous quantities from India, where it was extracted from nitrate-rich soils in Bihar and Bengal—a trade that gave the British East India Company considerable leverage. Domestic production relied on "nitre beds": heaps of manure, straw, urine, and ash left to decompose for months or years under sheds, then leached with water and the liquor boiled down and recrystallized. In France, salpêtriers held royal warrants entitling them to dig up the floors of stables, cellars, and dovecotes—a deeply resented privilege. Antoine Lavoisier's reform of the French Régie des Poudres in the 1770s systematized this collection and roughly doubled French output, which mattered considerably for the American Revolution.

Sulphur came largely from Sicilian volcanic deposits, refined by distillation. Charcoal was made from specific soft woods—willow, alder, buckthorn, or hazel—charred in closed retorts or covered pits, since wood species and charring temperature noticeably affected the powder's character.

The Mills

Manufacturing was a water-powered industrial process, not a workshop craft. Refined ingredients were ground separately, then combined and subjected to "incorporation"—prolonged mechanical working, kept damp to reduce the risk of ignition, which drove the saltpetre into the porous charcoal. Older works used stamp mills, with heavy wooden pestles lifted by cams on a waterwheel shaft, but these were notoriously prone to setting off the charge. Over the 18th century, edge-runner mills—massive stone or iron wheels rolling in a circular trough—became standard, first in the Netherlands and then elsewhere. Incorporation could run for hours.

The resulting damp "mill cake" was pressed under screws or hydraulic presses into hard slabs, then broken and "corned"—granulated by passing through sieves and separating the grain sizes. Corning was an important refinement: uniform grains burned at predictable rates, and different sizes suited cannon, muskets, or priming. Grains were then tumbled in barrels, sometimes with graphite, to round and glaze them so they resisted moisture and flowed smoothly, then dried in stove houses and packed in barrels with copper hoops.

Quality Control and Hazards

Proof was tested with the éprouvette—a small mortar that threw a standard ball, or a spring-loaded device measuring the force of a fixed charge. Chemists including Lavoisier, Charles Hutton, and Benjamin Robins worked on ballistics and powder strength, gradually putting the trade on a more quantitative footing.

The work was lethal. Mills were built with light roofs and blast walls, sited along rivers and separated by earth banks and tree screens so that an explosion in one building wouldn't propagate. Workers wore leather or felt shoes, tools were of bronze or wood, and iron was banned from working areas. Even so, major powder works recorded deaths regularly; the Faversham works in Kent and the Du Pont mills founded on the Brandywine in 1802 both had long casualty lists.

The Broader Picture

Gunpowder was effectively a state industry. Britain purchased the Faversham works in 1759 and developed Waltham Abbey into the Royal Gunpowder Mills; France ran the Régie; most states licensed or monopolized production because military capacity depended on it. The American colonies had almost no capacity in 1775, which forced heavy reliance on French supply and on hasty domestic nitre-bed schemes.

If you're interested in going deeper, Brenda Buchanan's Gunpowder, Explosives and the State is the standard scholarly collection, and the Royal Gunpowder Mills at Waltham Abbey and the Hagley Museum in Delaware both preserve machinery and buildings you can visit.