Black powder marked the beginning of centuries of warfare. Invented in Ancient China, it was used in Europe throughout the late Medieval period including at the Battle of Crecy. However, it became more common from the 17th Century being used throughout the Thirty Years War, English Civil War, the Napoleonic War and American Civil War as well as numerous other conflicts. Indeed it wasn’t until the invention of smokeless powder in the late 19th Century that it would be superseded. Mills were crucial for its creation and supply.
Black powder is a mix of saltpetre found in decomposed animal dung, charcoal and sulphur. Mills were used for grinding and mixing these ingredients. Together this powder will burn rapidly producing rapidly expanding gas which can be used to launch projectiles. Originally these ingredients would be ground by hand; however, in the 15th Century a process was developed where it was possible to grind all the ingredients together by adding water into the mix. This also had the added advantage that far greater quantities could be produced using mills.
These mills would drive pestle and mortars originally to grind the mix. Due to safety issues, these were made illegal in the 18th Century, after which only edge runner stones were used. This mix would then be dried to form a cake. A stamping mill would then break up this cake into grains, after which they would be tumbled to remove any sharp edges and glazed to stop them from separating in storage and transport. Finally, the powder would be sieved to the required size.