In 1889, the Ducktown Sulphur, Copper, Gold and Iron Company bought the properties, and began producing copper and iron from the deeper high-sulfide ores, which previous companies were unable to work successfully. The ores were treated by open roasting in which the ore was piled in large stacks with alternating layers of wood, and burned. The method released large quantities of sulfur dioxide, which killed much of the vegetation in the immediate area. Open roasting was replaced by pyrite smelting in 1904, and the smelters began recovering the most of the sulfur in the form of sulfuric acid rather than releasing it to the atmosphere. Froth flotation was added in the 1920s.