This photograph, taken approximately 1910 by Pierre A. Gentieu (1842-1930), depicts a black powder press in the New Machine Shop where it was manufactured before being deployed into the Hagley Yards.

Black powder presses used heavy mechanical or hydraulic force to compact a moist, fine paste of black powder ingredients (saltpeter, charcoal, and sulfur) into dense, solid slabs known as press-cake. This process removed moisture and increased density, creating a hard cake that was then broken into grains, sieved, and sometimes glazed (graphited) for different firearm uses, ensuring consistent, powerful, but controllable ignition. The pressing was a critical step to achieve a uniform, desired density, which significantly affected the powder's burning rate.