Waste Management

Waste Management. Catoctin Furnace Iron Trail. , The mounds you see around you are heaps of the furnace's waste product, called slag. When iron ore is superheated in the furnace, molten iron sinks to the bottom and the impurities and limestone residue rise to the surface. As part of the smelting process, these impurities are skimmed and discarded. When they harden, they turn into slag, which can look like volcanic glass or lava rock.

Slag was removed from the furnace about every six hours, and the amount of slag created by the furnaces became such a problem that slag was used to fill holes and to surface roads all over the village. Eventually, the output of slag exceeded the amount that could be used, so it was simply piled in heaps near the furnace. How much of the forest floor that you see today might lie on top of old slag mounds?, [Captions:] , « (Top left) Black slag., » (Top right) Gray slag. Depending on the minerals present in the iron ore and the speed at which the slag cooled, slag can look dramatically different. It can be glassy and smooth, dull and bubbly, or delicate and crystalline-looking>, « (Left center) Crystalline slag. Slag can have unique features, such as this piece, which exhibits a crystalline structure., » (Right) Slag pours out from the furnace into a pot in this 1938 photograph. A similar process was used earlier at Catoctin Furnace., (Above) An 1873 woodcut by Jules Tavernier and Paul Frenzeny, The Manufacture of Iron Carting Away the Scoriae, shows workers carting away slag from a furnace., « (Bottom left) Workers rolling slag for a replacement roadway foundation in Lewis County, West Virginia.