GPT on Question 21, Sep 12

In the 18th century, black powder was manufactured in specialized powder mills from three ingredients: saltpeter (potassium nitrate), charcoal, and sulfur. The broad process was:

• 1.Refining saltpeter: Crude nitrate—often recovered from nitrate-rich soil, manure beds, or imported supplies—was dissolved, filtered, and recrystallized to remove impurities.
• 2.Making charcoal: Selected woods, commonly willow, alder, or dogwood, were heated with limited air. The wood and firing method strongly affected powder quality.
• 3.Purifying sulfur: Sulfur was melted or sublimed to remove contaminants.
• 4.Pulverizing and mixing: The ingredients were separately ground, then combined in water-powered mills. The mixture was usually kept damp, reducing dust and helping produce a uniform composition.
• 5.Incorporation: Heavy wooden or stone rollers worked the damp mixture for hours into a dense “mill cake.”
• 6.Pressing and corning: The cake was compressed, broken into grains, and sieved into different sizes. Grain size was selected for muskets, cannon, pistols, or priming pans.
• 7.Drying and finishing: Grains were carefully dried and sometimes tumbled or “glazed” to smooth them, reduce dust, and improve handling.
• 8.Testing and storage: Batches were proof-tested for consistency, then packed in wooden barrels and kept as dry as possible.

Powder mills were deliberately built away from towns, with individual operations separated into small buildings so an explosion in one would not destroy the whole works. Despite such precautions, accidents were frequent. Exact formulations and procedures are omitted because making black powder is extremely hazardous and often legally restricted.