GPT on Question 21, Sep 21

In the 18th century, black powder was manufactured in specialized powder mills, usually located away from towns because fires and accidental explosions were common.

The process, in broad historical terms, was:

• 1.Obtaining the ingredients
• •Saltpeter (potassium nitrate) was refined from mineral deposits, imported supplies, or nitrate-rich earth collected from stables, cellars, and specially maintained “nitre beds.”
• •Charcoal was made from selected woods—often willow, alder, or dogwood—heated with little oxygen.
• •Sulfur was mined or imported and purified.

• 2.Purification and preparation
  Saltpeter was dissolved, filtered, and recrystallized to remove salts and dirt. The charcoal and sulfur were separately crushed and screened. Keeping operations separated reduced, though did not eliminate, the danger.

• 3.Incorporation
  The ingredients were combined in traditional proportions and thoroughly worked in an incorporating mill, often using heavy stone or metal wheels driven by waterpower. The mixture was kept damp so it would blend more uniformly and be less likely to ignite.

• 4.Pressing and corning
  The damp powder mass was pressed into dense cakes. These were then broken up and passed through sieves to produce grains of different sizes—a process called corning or granulation. Grain size affected how quickly the powder burned and whether it was intended for muskets, cannon, pistols, or blasting.

• 5.Glazing, drying, and sorting
  Grains were sometimes tumbled in wooden barrels to smooth and strengthen them, then carefully dried, screened, and packed into wooden barrels or copper-lined containers.

Powder mills were designed to limit chain explosions: individual buildings were widely separated, workers used non-sparking tools and footwear, and some structures had lightweight walls or roofs intended to vent a blast. Even with these precautions, mill explosions were frequent and often fatal.

Earlier “serpentine” powder was simply a loose mixture whose ingredients could separate during transport. By the 18th century, corned powder was standard because it was more uniform, durable, and effective.