Gemini on Question 21, Sep 29

The manufacture of black powder (gunpowder) in the 18th century was a highly refined, labor-intensive, and incredibly dangerous process. During this era—defined by global empires, the American and French Revolutions, and constant warfare—gunpowder production transitioned from a medieval craft to an early industrial science.

The ideal recipe for black powder was roughly 75% saltpeter, 15% charcoal, and 10% sulfur.

Here is the step-by-step process of how it was manufactured in the 1700s.

1. Sourcing and Purifying the Ingredients

The quality of black powder depended entirely on the purity of its ingredients.

• •Saltpeter (Potassium Nitrate): This was the oxidizer and the hardest ingredient to obtain. In the 18th century, it was extracted from "niter beds." These were essentially compost heaps made of manure, soil, decaying plant matter, and human or animal urine. Left for months or years, bacteria converted the nitrogen in the waste into nitrates. The soil was then washed (leached) with water. Wood ashes were added to the water to provide potassium, creating potassium nitrate. The liquid was boiled down in massive copper vats until pure saltpeter crystals formed.
• •Charcoal: Charcoal served as the primary fuel. Gunpowder makers preferred soft, fast-growing woods like willow, alder, or buckthorn/dogwood, as they burned rapidly and left little ash. The wood was stripped of bark and baked in iron cylinders (retorts) or covered earthen pits with restricted oxygen. This burned off moisture and impurities, leaving pure carbon.
• •Sulfur: Sulfur lowered the ignition temperature of the powder. It was mostly mined from volcanic regions, with Sicily being the primary supplier for Europe. It was purified through sublimation—heated until it vaporized, then condensed back into a pure yellow solid to remove rock and dirt.

2. Milling and Incorporation

Once purified, the ingredients had to be ground into a fine dust and intimately mixed together. This was the most dangerous part of the process.

Mixing dry powder could easily cause a catastrophic explosion from static electricity or a stray spark. Therefore, the ingredients were mixed wet—usually moistened with water, though urine or distilled spirits were sometimes used.

In the early 18th century, this was done using Stamp Mills. These were water-wheel-driven machines that repeatedly dropped heavy wooden pestles into wooden bowls containing the wet ingredients.
By the late 18th century (spearheaded by French chemist Antoine Lavoisier), powder mills shifted to Edge Runner Mills. These featured massive, heavy stone wheels (often made of limestone or marble to prevent sparks) rolling in a circular trough. This effectively crushed and kneaded the wet ingredients together into a highly blended paste called "mill cake."

3. Pressing and Corning (Granulation)

In earlier centuries, powder was left as a fine dust called "serpentine," but this was problematic. During transport on bumpy wagon rides, the heavy saltpeter would sink to the bottom of the barrel while the light charcoal floated to the top, ruining the mixture. Furthermore, fine dust absorbed moisture from the air and burned unpredictably.

The 18th-century solution was "corning."

• 1.Pressing: The wet mill cake was placed between copper or wooden plates and subjected to massive pressure using screw presses. This squeezed out excess water and formed dense, solid slabs resembling slate.
• 2.Corning: These hard slabs were broken up with wooden mallets and forced through heavy parchment or wire sieves. This broke the powder down into small, uniform granules (corns).
• 3.Sorting: The granules were sifted into different sizes. Large grains burned slower and were used for cannons; medium grains were for muskets; and very fine grains were used for pistols or priming pans.

4. Glazing

To make the powder moisture-resistant and easier to pour, the grains were "glazed." The granules were placed into large wooden barrels and tumbled for several hours. The friction of the grains rubbing against each other smoothed their rough edges. Often, a small amount of graphite was added to the barrel, giving the powder a slick, shiny, dark grey/black finish that prevented it from clumping in high humidity.

5. Drying and Packaging

The finished granules still contained moisture and had to be dried. The powder was spread thinly onto wooden trays and placed in a drying house. These houses were heated by a stove, but to prevent fires, the stove was usually fed from the outside of the building, with a thick brick wall separating the fire from the drying racks.

Finally, the powder was packed into wooden barrels bound with wooden hoops (iron hoops could spark).

Safety Measures in the 18th Century

Because explosions were a constant threat, powder mills were built with specific safety protocols:

• •No Iron: Iron and steel tools were strictly forbidden. Shovels, bowls, and gears were made of copper, bronze, wood, or leather.
• •Clothing: Workers were not allowed to wear clothing with metal buttons, and they wore leather shoes with wooden pegs instead of iron nails to prevent sparking on stone floors.
• •Architecture: Mill buildings were intentionally built with thick stone walls on three sides, but with a flimsy wooden roof and a weak fourth wall facing a river or forest. If an explosion happened, the blast would be directed outward and upward, saving the rest of the factory and the expensive water-wheel machinery.