Gemini on Question 21, Oct 3

In the 18th century, black powder (gunpowder) was the most critical military and industrial commodity in the world. As global empires clashed, the demand for black powder skyrocketed, shifting its production from small, artisanal workshops to early industrial, water-powered factories.

The manufacturing process was highly dangerous, labor-intensive, and required a deep understanding of early chemistry. Here is a step-by-step look at how black powder was manufactured in the 1700s.

1. Sourcing and Purifying the Ingredients

The standard formula for black powder was roughly 75% saltpeter, 15% charcoal, and 10% sulfur. Procuring and purifying these ingredients was the most difficult part of the process.

• •Saltpeter (Potassium Nitrate): This was the oxygen-provider of the explosion and the hardest ingredient to get. In the 18th century, it was extracted from "niter beds." These were large trenches or heaps filled with manure, straw, rotting vegetables, and urine. They were turned regularly and shielded from rain for over a year. The decaying organic matter produced nitrates.
• •Purification: The compost was leached with water. Wood ash (potash) was added to the liquid to convert the calcium nitrate into potassium nitrate. The liquid was then boiled in massive copper kettles until the impurities were skimmed off and pure saltpeter crystals formed. (Nations without natural sources, like the American Colonies and France during the Revolution, relied heavily on this method).
• •Charcoal: This provided the fuel. Gunpowder makers did not use standard fireplace charcoal, which burned too inconsistently. They used specific, fast-growing woods like willow, alder, or dogwood.
• •Purification: The wood was stripped of bark and baked in sealed iron retorts (a process called pyrolysis). This removed all moisture and volatile gases without allowing the wood to turn to ash, resulting in extremely pure, highly combustible carbon.
• •Sulfur: Sulfur lowered the ignition temperature of the powder, making it easier to spark.
• •Purification: It was mostly imported from volcanic regions, particularly Sicily. It was purified by boiling or sublimation (vaporizing and condensing it) to remove dirt and rock, then ground into a fine yellow powder.

2. Incorporation (Milling)

Once the ingredients were purified, they had to be mixed. If they were simply stirred together dry, they would easily separate during transport, rendering the powder useless. They had to be physically crushed into one another.

In the 18th century, this was done using Edge Runner Mills. Powered by water wheels or horses, these mills featured massive, heavy stone wheels (often limestone or marble, to prevent sparks) that rolled in a circular wooden or stone trough.

• •The ingredients were placed in the trough, and the heavy wheels crushed them together for hours.
• •Crucial Safety Step: The mixture was kept constantly wet—often with water, but sometimes with stale urine or cheap distilled spirits. The moisture prevented friction from creating a spark that would blow up the mill.

3. Pressing

The wet milling process produced a damp, clay-like substance called "mill cake." In this state, it burned rather than exploded.
The mill cake was transferred to a heavy screw press (similar to a wine or printing press). Layers of mill cake were placed between plates of copper or hardwood and squeezed under immense pressure. This compressed the powder into solid, dense slates or blocks.

4. Corning (Granulation)

Before the 15th century, gunpowder was a fine dust (serpentine powder), which absorbed moisture easily and burned inconsistently. By the 18th century, "corning" was the standard.

The dense pressed slates of powder were broken apart with wooden mallets and forced through sieves made of wire or heavy parchment with holes punched in it. This broke the powder down into uniform granules, or "corns."

• •Large granules were sorted for cannons (which required a slower burn).
• •Medium granules were for muskets.
• •Fine granules were for pistols and priming pans.

5. Glazing

The raw granules had rough edges that could break off during transport, turning back into explosive dust. To fix this, the granules were placed into large wooden barrels and tumbled for several hours.
The friction rounded off the rough edges. Often, a small amount of graphite was added to the tumbling barrel. This coated the granules, making them smooth, shiny, and highly resistant to moisture.

6. Drying and Packaging

The glazed powder was still slightly damp. It was spread out on wooden trays and placed in drying houses. Because open flames were strictly forbidden, drying houses were usually heated by long flues connected to a stove located in an entirely separate, external building.

Once fully dried, the black powder was packed into wooden barrels, usually holding about 100 pounds, and sealed for military or commercial distribution.

The Hazards of the Trade

Gunpowder manufacturing in the 18th century was notoriously deadly. Explosions were a matter of when, not if. To mitigate the death toll, powder mills were uniquely designed:

• •No Iron: Workers were forbidden from wearing clothing with metal buttons or shoes with iron nails, which could strike a stone and cause a spark. Tools were made of wood, copper, or bronze (which do not spark).
• •Blow-out Architecture: Mill buildings were usually built on the banks of rivers. They featured three very thick stone walls, but a flimsy wooden roof and a flimsy front wall facing the water. If the powder exploded, the blast would be directed upward and outward over the river, saving the surrounding buildings and the waterwheel.
• •Isolation: Mills were built in deep woods, far away from towns, and surrounded by dense trees planted specifically to absorb the shockwaves of accidental explosions.