GPT on Question 21, Sep 26

In the 18th century, black powder was manufactured in specialized powder mills, often located away from towns because explosions were common. It consisted of three familiar materials: saltpeter (potassium nitrate), charcoal, and sulfur. Broadly, production involved:

• 1.Refining the ingredients
  Saltpeter was purified by dissolving and recrystallizing it. Sulfur was refined, and charcoal was produced from selected light woods in low-oxygen ovens.

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

• 3.Incorporating the mixture
  The ingredients were blended and compressed under heavy, water-powered wooden or stone wheels. Workers kept the material damp during much of this stage to reduce dust and sparks. This produced an integrated “mill cake” rather than a simple loose mixture.

• 4.Corning or granulating
  The cake was broken into grains and passed through sieves. Different grain sizes were selected for muskets, cannon, pistols, blasting, and priming powder. Granulated powder burned more consistently than the older loose “serpentine” type.

• 5.Drying, glazing, and packing
  The grains were dried in controlled buildings, sometimes tumbled to smooth them and reduce dust, then packed in wooden barrels or other non-sparking containers.

Powder mills were deliberately divided into small, widely separated structures, frequently with lightweight roofs or walls designed to vent explosions. Machinery was commonly powered by water, and workers used wooden, leather, copper, or bronze tools rather than iron wherever possible. Despite these precautions, mill explosions remained a serious occupational hazard.

The quality of 18th-century powder depended heavily on saltpeter purity, charcoal type, grain size, and the thoroughness of incorporation. Governments therefore regulated production closely, and major military powers operated or contracted large centralized mills.