Gemini on Question 21, Sep 22

In the 18th century, the manufacture of black powder (gunpowder) transitioned from a highly skilled artisan craft to an early industrial process. As empires expanded and firearms became the dominant weapon of war, the demand for black powder skyrocketed, leading to the creation of large, water-powered powder mills.

The standard recipe by this time was well-established: 75% saltpeter (potassium nitrate), 15% charcoal, and 10% sulfur.

Here is a step-by-step breakdown of how black powder was manufactured in the 1700s.

1. Sourcing and Preparing the Ingredients

Obtaining the raw materials, particularly saltpeter, was the most labor-intensive part of the process.

• •Saltpeter (Potassium Nitrate): This was the most crucial and difficult ingredient to obtain. In the 18th century, it was largely harvested from "niter beds." Workers created massive compost heaps of manure, rotting vegetation, soil, and animal (or human) urine. Over several months, bacteria converted the ammonia in the waste into nitrates. The soil was then washed (leached) with water. Wood ash (potash) was added to the liquid to convert the calcium nitrate into potassium nitrate. Finally, the liquid was boiled in massive iron kettles until the pure saltpeter crystallized.
• •Charcoal: Not just any wood could be used. Powder makers preferred soft, fast-growing woods like willow, alder, or dogwood, which burned quickly and left very little ash. The wood was stripped of its bark and burned in iron retorts or earthen pits with very little oxygen to carbonize it.
• •Sulfur: Sulfur lowered the ignition temperature of the powder, making it easier to spark. It was generally mined—with Sicily being a major global supplier—and purified by melting or sublimating it to remove rock and soil impurities.

2. Milling and Incorporation

The three ingredients had to be ground into a fine dust and intimately mixed at a microscopic level. Simply stirring them together created a weak powder. They had to be smashed together, a process called incorporation.

• •Water-Powered Mills: In the 18th century, incorporation was done in mills powered by water wheels.
• •Stamp Mills vs. Edge Runners: Early in the century, "stamp mills" were common. Heavy wooden beams (pestles) were repeatedly lifted by a camshaft and dropped into wooden bowls (mortars) containing the ingredients. By the late 18th century, "edge runner mills" became popular. These featured two massive, heavy stone wheels rolling in a circular stone or cast-iron trough, crushing the ingredients beneath them.
• •Wetting the Mixture: Milling dry powder was a recipe for a catastrophic explosion. Millers constantly added liquid—usually water, but sometimes distilled spirits or stale urine—to keep the mixture damp. This damp mixture was known as mill cake.

3. Pressing and Corning (Graining)

Before the 15th century, powder was left as a fine dust called "serpentine." However, serpentine absorbed moisture easily, and the heavy sulfur would sink to the bottom of the barrel during transport in wagons, ruining the mixture. To solve this, 18th-century makers used a process called corning.

• •Pressing: The damp mill cake was layered between copper or wooden plates and subjected to immense pressure using a giant screw press. This squeezed out excess water and created hard, dense slabs of powder, similar in look to slate.
• •Corning: These hard slabs were broken with wooden mallets and forced through wire or parchment sieves. This broke the powder into uniform little granules, or "corns."
• •Sorting: The granules were sifted into different sizes. Large grains burned slower and were used for massive siege cannons. Medium grains were used for muskets. The finest grains burned incredibly fast and were used for pistols or as priming powder in the flashpans of flintlock weapons.

4. Drying and Glazing

• •Drying: The damp corns had to be dried. This was done in specialized drying houses, heated gently by exterior stoves (to keep the fire far away from the powder) or by laying the powder out on large canvas sheets in the sun.
• •Glazing: To make the powder resilient to travel and moisture, the dried grains were placed into wooden barrels that were slowly rotated by the water wheel. The friction of the grains rubbing against each other rounded off their sharp edges. Often, a small amount of graphite was added to the barrel. This coated the grains, giving them a shiny, dark grey/black appearance, sealing them against humidity, and allowing them to pour smoothly down a gun barrel without clumping.

Safety and Working Conditions

Powder mills were incredibly dangerous places. A single spark could obliterate a mill and its workers.

• •No Iron: Workers wore clothes without metal buttons and shoes held together with wooden pegs rather than iron nails. Tools were made of wood, leather, copper, bronze, or brass—metals that do not spark when struck.
• •Architecture of Survival: Powder mill buildings were designed with "blow-out" architecture. They were usually built on the banks of a river. The three walls facing the other mill buildings were built of thick, sturdy stone. The wall facing the river, and the roof, were made of flimsy, lightweight wood. If the mill exploded, the blast was directed out over the river, sparing the rest of the complex and preventing a chain reaction.

By the late 18th century, thanks to the scientific study of chemistry (championed by figures like the French chemist Antoine Lavoisier), black powder manufacturing reached a peak of efficiency and standardization that would remain largely unchanged until the invention of smokeless powder in the late 19th century.