Hot shot furnaces were state of the art for defense systems of their day. Soldiers heated cannonballs in specially designed furnaces until they glowed red hot. They carefully loaded the hot shot into cannons and fired at wooden ships. Even after skipping on water, hot shot could start disastrous fires. Although Fort Pulaski had three furnaces, hot shot was never used here. Hot shot became obsolete with the widespread use of ironclad ships and exploding shells during the Civil War. The foundations remain from two of Fort Pulaski's hot shot furnaces.