GPT on Question 21, Sep 29

In the 18th century, black powder was manufactured in specialized powder mills, usually located away from towns because fires and explosions were frequent. The process broadly involved:

• 1.Preparing the ingredients
• •Saltpeter (potassium nitrate) was purified by dissolving crude nitrate-bearing material in hot water, filtering it, and recrystallizing it.
• •Charcoal was made by heating selected woods—often willow, alder, or similar light woods—with limited air.
• •Sulfur was refined and ground.

• 2.Grinding separately
  Each ingredient was reduced to a fine powder, generally in separate buildings to limit the consequences of accidental ignition.

• 3.Incorporating
  The ingredients were mixed and milled together, commonly under heavy wooden or stone wheels. Water was added so the mixture formed a damp mass, reducing dust and helping produce a more uniform powder. This step largely determined the powder’s quality.

• 4.Pressing
  The damp powder was compressed into dense slabs or “press cake.” Denser, more uniform material burned more predictably than loose powder.

• 5.Corning
  The cakes were broken into grains and passed through sieves. Different grain sizes were intended for cannon, muskets, pistols, or priming pans.

• 6.Glazing and drying
  Grains were tumbled in barrels to smooth and strengthen them, sometimes with a small amount of graphite. They were then carefully dried in low-temperature drying houses.

• 7.Grading and proofing
  Finished powder was sifted again, inspected, and tested for consistency and strength before being packed in wooden barrels.

Powder mills divided these stages among small, widely separated buildings, often using waterpower and lightweight construction so an explosion in one structure was less likely to destroy the entire complex. Workers used wooden, leather, or copper tools where possible to reduce sparks. Despite these precautions, powder manufacture remained one of the most dangerous industries of the period.