Claude on Question 21, Sep 30

Black powder manufacturing in the 18th century was one of the era's most important — and most hazardous — industries, and it underwent significant technical and administrative change over the century.

The three ingredients

Saltpeter (potassium nitrate) was the hardest to obtain and the most valuable component, making up roughly three-quarters of the mixture. Europe had two main sources:

• •Imported Indian saltpeter, dug from nitrogen-rich soils in Bengal and Bihar, became dominant for Britain through the East India Company. Control of Bengal after 1757 gave Britain an enormous strategic advantage, and British powder was widely considered the best in Europe partly for this reason.
• •Domestic niter beds, where manure, urine, straw, and ash were layered and left to decompose for a year or more under the action of nitrifying bacteria (a process not understood chemically until the 19th century). The resulting liquor was leached, boiled, and recrystallized. In France, "saltpeter men" held the legal right to enter cellars, stables, and dovecotes to scrape nitrous earth — an intensely unpopular privilege.

Sulfur came mainly from Sicilian volcanic deposits, refined by distillation or sublimation.

Charcoal was made from soft woods — willow, alder, black alder, and buckthorn were favored — charred in closed retorts or covered pits at relatively low temperature, which produced a friable, reactive charcoal rather than a hard fuel charcoal.

The milling process

Manufacturing proceeded in fairly standardized stages:

• 1.Refining and grinding each ingredient separately to fine powder.
• 2.Incorporating — the critical stage, where the mixture was worked together with a small amount of water into a dense cake. Early 18th-century mills used vertical stamps (wooden pestles in mortars), but these were prone to friction ignition. Over the century, edge-runner mills with heavy stone or iron wheels rotating in a pan largely replaced them; they were faster, produced more uniform powder, and were somewhat safer.
• 3.Pressing the incorporated mass into hard slabs.
• 4.Corning or graining — breaking the pressed cake and sieving it into grains of specified size. This was essential: grain size controls burning rate, so cannon powder, musket powder, and fine sporting powder were separate products.
• 5.Glazing — tumbling the grains in barrels, sometimes with graphite, to round them and reduce dust and moisture absorption. This became common in the later 18th century.
• 6.Drying in stoves or open-air sheds, then barreling.

Industry and administration

Mills were sited on fast streams for water power and deliberately built as scattered, lightly constructed buildings with blow-out walls, separated by earth berms and trees, so an explosion in one would not propagate. Workers wore leather or felt shoes without nails, used wooden and bronze tools, and mills were frequently flooded and swept. Explosions were nonetheless routine and often fatal.

Notable centers included Faversham and Waltham Abbey in England (the latter bought by the Crown in 1787 to secure quality), Essonne and Essonnes in France, and Frankford and later Brandywine in North America.

Two developments are worth highlighting:

• •Antoine Lavoisier was appointed to France's Régie des Poudres in 1775 and substantially reformed it — improving saltpeter refining, standardizing procedures, ending the hated requisition system in favor of purchase, and roughly doubling French powder output and quality within a decade. His powder work directly supplied the American Revolution.
• •Éleuthère Irénée du Pont, who had trained under Lavoisier, emigrated after the French Revolution and founded his mills on the Brandywine in Delaware in 1802, bringing French technique to an American industry he found comparatively crude.

If you're interested in a particular thread — the saltpeter trade and its geopolitics, the engineering of mill safety, or Lavoisier's administrative reforms — I'm happy to go deeper on any of those.