Gemini on Question 21, Sep 12

In the 18th century, the manufacture of black powder (gunpowder) transitioned from a highly localized craft to a large-scale, proto-industrial process. Driven by near-constant global conflicts—such as the Seven Years' War and the American Revolution—nations built massive, usually water-powered, powder mills.

The standard recipe by this time was generally established as 75% saltpeter (potassium nitrate), 15% charcoal, and 10% sulfur, though slight variations existed depending on the nation and the powder’s intended use (e.g., cannons vs. muskets).

Here is the step-by-step historical process of how black powder was manufactured in the 18th century:

1. Sourcing and Refining the Ingredients

The hardest part of manufacturing black powder was acquiring pure ingredients.

• •Saltpeter (Potassium Nitrate): This was the most critical and expensive ingredient. Because it was not readily available in nature in Europe, it was farmed in niter beds. Humans mixed manure, urine, straw, and rotting vegetable matter in long trenches, periodically turning and watering them with urine. After about a year, the soil was leached with water to extract calcium nitrate. Wood ashes (potash) were added to the liquid to convert it into potassium nitrate. The liquid was then boiled down and crystallized.
• •Charcoal: Not just any wood would do. Powder makers preferred fast-growing, light woods like willow, alder, or dogwood. The wood was stripped of bark and carefully burned in earthen mounds or brick kilns to remove moisture and impurities without turning it to ash.
• •Sulfur: Sulfur was mined primarily in volcanic regions, with Sicily being the primary exporter to Europe. It was purified by melting and skimming off the impurities, or by sublimation (boiling it and capturing the vapor).

2. Milling and Incorporation

The raw ingredients had to be ground into a fine dust and intimately mixed. Doing this while the ingredients were dry was an absolute guarantee of a massive, fatal explosion, so the process was done wet.

• •The ingredients were moistened with water (or sometimes stale urine or cheap spirits) to form a paste.
• •In the early 18th century, stamp mills were common. These were large water-powered wooden pestles that dropped repeatedly into wooden mortars containing the damp powder.
• •By the late 18th century, edge-runner mills became the standard. These consisted of two massive, vertically mounted stone wheels (weighing several tons) that rolled in circles inside a circular stone or iron trough. The heavy stones crushed and smeared the wet ingredients together into a highly uniform dough called "mill cake."

3. Pressing

The damp mill cake was scooped out of the mills and stacked between plates of copper or hardwood. It was then placed into a massive screw press (operated by hand or animal power). The pressure squeezed out excess water and compressed the paste into dense, hard slabs called "press cake," which looked like slate.

• •Note: Pressing was a relatively new innovation in the 18th century; it made the powder much denser, which increased its explosive power.

4. Corning (Granulation)

This was arguably the most important technological step in historical powder making. Earlier centuries used "serpentine" powder—a fine dust that absorbed moisture easily and separated into its base ingredients during bumpy wagon transport. 18th-century powder was "corned."

• •The hard press cakes were broken into smaller pieces with wooden mallets.
• •These pieces were forced through sieves made of parchment punched with holes, or brass wire mesh.
• •This broke the powder into uniform little granules (corns). Granulated powder burned instantly and evenly because air could pass through the spaces between the grains, igniting the whole charge at once.

5. Glazing

The freshly corned powder had rough edges that would easily grind back into dangerous, useless dust during transport. To prevent this, the grains were "glazed."

• •The granules were placed into large wooden barrels spun by waterwheels.
• •The tumbling action caused the grains to rub against one another, rounding off their rough edges.
• •Often, a small amount of graphite was added to the barrel. This gave 18th-century powder its signature shiny, black look, made it highly resistant to moisture, and allowed it to pour smoothly down the barrel of a musket.

6. Drying and Dusting

The glazed powder was still slightly damp. It was taken to a drying house. Because lighting a fire in a room full of gunpowder was suicidal, drying houses used "gloom stoves." These were heavy iron plates set into the wall of the building; a fire was built on the outside of the building to heat the iron plate, radiating heat into the room without exposing the powder to sparks or open flame.

Finally, the dry powder was passed through a final set of screens to sift out any remaining dust. The dust was sent back to the mills to be recycled, and the finished grains were sorted by size. Coarse grains were used for cannons, medium grains for muskets, and fine grains for pistols and priming pans. It was then packed into wooden kegs (usually holding 100 pounds) for military or commercial distribution.

Working Conditions and Danger

Manufacturing black powder in the 1700s was incredibly dangerous. Powder mills blew up with alarming regularity. To mitigate the risk, 18th-century mills were built with thick stone walls and flimsy wooden roofs—so if an explosion happened, the blast would be directed upward rather than outward. Workers were forbidden from wearing clothes with metal buttons or carrying iron tools. They wore wooden clogs, leather shoes, or walked barefoot, and the floors were frequently wetted down to prevent any accidental sparks.