Tag: hot-shot furnace

Wikipedia says: Heated shot or hot shot is round shot that is heated before firing from muzzle-loading cannons, for the purpose of setting fire to enemy warships, buildings, or equipment.

The United States incorporated hot-shot furnaces into the design of coastal fortifications during the construction of the Second System of seacoast defenses, just prior to the War of 1812. Colonel Jonathan Williams left his post as Commandant at the US Military Academy to build hot-shot furnace fortifications such as Castle Clinton and Castle Williams in New York Harbor during this period. When French engineer General Simon Bernard came to the US in 1816 to head the Board of Fortifications, for the construction of permanent forts to defend the US coastline, he introduced the idea of hot-shot furnaces of the French pattern. The chain of US coastal forts built between 1817 and the American Civil War, such as Fort Macon, subsequently had one or more hot-shot furnaces included as part of their standard defences.

A hot-shot furnace was typically a free-standing brick or stone structure with special iron racks and grates, varying in size according to the number of round shot they were to heat and the number of cannon they served – a large furnace might hold 60 or more round shot. They were commonly 6 to 8 feet (1.8 to 2.4 m) wide, and anything from 8 to 30 feet (2.4 to 9.1 m) in length. A chimney was situated at one end with a firebox located in the front or side of the opposite end. The interior of the furnace was lined with fire brick and had sloping iron rails sized to hold round shot. Cold round shots were placed in the furnace and allowed to roll down the inclined rails in rows. The first shots halted over the firebox at the low end and were heated “cherry red”, approximately between 800 and 900 °C (1,470 and 1,650 °F). When they were removed, the next shots rolled down to take their place and be similarly heated. Care had to be taken not to overheat the shot, as any that were hotter than “cherry red” were likely to become misshapen, and jam in the bore of the gun. A furnace could heat a 24 pounder shot in around 25 minutes, with larger rounds taking a few minutes longer.

Three men were required to manage a furnace. One maintained the fire and added cold shot, a second man removed heated shot from the furnace, and the third man cleaned them. Special tools were required to handle heated shot. An iron fork was used to remove heated shot from the furnace, then the shot was placed on a stand and cleaned by rubbing off loose surface scale with a rasp. A pair of tongs with circular jaws was used to handle the shot at the furnace. To carry the shot to the cannons, hot-shot ladles were used. The ladles had an iron cup for the shot with one or three handles. Round shot less than 24 lb (11 kg) weight size could be carried by one man with a single-handle ladle, while larger shot needed a three-handle ladle, carried between two men like a stretcher.