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GLOSSARY
Anchor plates: Cast iron plates on the exterior of the furnace through which the ends of the tension rods extend. Also called faceplates. See Tie rods.
Ashlar masonry: A squared block of building stone. Masonry of such stones with joints no wider than a quarter of an inch. The Oswego Furnace in George Rogers Park is an example of Ashlar masonry.
Binders: See Tie rods.
Blast: A pressurized stream of air injected into the base of a furnace to aid combustion. The blast at the Oswego Furnace was produced by a blowing machine powered by a water turbine. (See 'blowing tubs.')
Blast furnace: A tower-like furnace for smelting, or separating, metal from impurities in the ore. A blast of air is injected into the base of the furnace to produce the intense heat required.
Blast house: The building that housed the blast machinery.
Blast pipe: See Tuyere.
Blowing in: Starting up the furnace by lighting the fuel and then turning on the blast.
Blowing out: Shutting down the furnace by burning off the fuel and turning off the blast.
Blowing tubs: Blast-producing machinery consisting of a pair of wooden cylinders and water-driven pistons. This system replaced the giant bellows of early blast furnaces.
Bosh (boshes): The widest part of the furnace shaft, shaped like an inverted cone. This was the zone where the ore began to melt.
Bridge house: A covered bridge linking the top of the furnace and the hill immediately behind it. (See Charging bridge.)
Bustle pipe: A large air duct that wrapped around the lower part of the bosh. It typically fed three blast nozzles that forced air into the bottom of the shaft.
Cast iron: Iron containing about 1.7 percent of carbon, which makes it structurally strong but also brittle. Unlike wrought iron, cast iron is not malleable.
Casting: The process of tapping iron from a blast furnace and filling molds in the sand floor of the casting house. Casting can also refer to the work of a foundry where metal is melted and poured into molds to make various products.
Casting arch (work arch): The tall arch in the front of the furnace where iron and slag are tapped.
Casting house: A sand-floored building where pig iron was cast. One end of the building was open to the casting arch of the furnace.
Charcoal furnace: A blast furnace that used charcoal as its fuel as opposed to coke or anthracite.
Charcoal kiln: A conical or domed brick oven for making charcoal.
Charcoal pit (meiler): A circular stack of wood covered with earth and leaves, which causes the wood to smolder slowly and turn to charcoal. The term "pit" is misleading because the mound or meiler was built on level ground, not in a depression.
Charge: A carefully measured amount of charcoal, ore and lime that is fed into the furnace every 15 or 20 minutes.
Charging bridge: A bridge connecting the top of the furnace to the terrace behind it. Raw materials stored on this charging terrace could be easily moved across the bridge and fed into the top of the furnace. (See Bridge house.)
Charging terrace: See Furnace bank.
Coke: Coal that has been heated to a high temperature to burn off impurities. Used as an industrial fuel because it burns with intense heat and little smoke.
Crucible (hearth): The bottom of the furnace shaft where molten iron and slag collect. This area is sometimes called the "hearth."
Cupola furnace: A tall cylindrical furnace used to melt iron in a foundry.
Downcomer: A large cast iron duct that carried heated air from a stove on top of the furnace to the bustle pipe and tuyeres below.
Firebrick (refractory brick): Bricks made of a mixture of clay and ground stone (ganister) that can withstand the high temperatures in a blast furnace.
Flux: A basic material, such as lime, added to the furnace charge. It unites with impurities in the ore to form slag.
Foundry: An establishment where metal is melted and poured into molds to make "castings."
Furnace bank (charging terrace): The hill behind the furnace where iron ore, charcoal and limestone were stored in sheds.
Hard driving: Techniques introduced by Andrew Carnegie to increase blast furnace production. They included larger furnaces, more powerful blowing engines, regenerative hot blast stoves, and automated handling of raw materials.
Hearth: The firebrick foundation supporting the crucible. This term is sometimes used to refer to the crucible.
Heat exchanger: See Hot-blast stove.
Hot blast: A furnace blast preheated to 400o or more.
Hot-blast stove (heat exchanger): A brick stove where air for the blast was heated before it was blown into the furnace. It contained a double row of large U-shaped cast iron pipes, which were heated by waste gases from the furnace. This stove was usually located on top of the furnace.
Inwall: Another name for the shaft above the bosh. A lining of sand, clay or rubble between the inwall and the stack allowed for expansion and contraction of the smelting chamber.
Iron ore: Iron-rich rock. The ore (limonite) mined in Oswego came from two sites: the Patton Mine in the hills south of the lake and the Prosser Mine on Iron Mountain.
Limestone: Sedimentary rock primarily composed of the mineral calcite. Limestone was used as a flux in iron smelting because it combined with impurities in the ore to form slag.
Limonite: A hydrated form of hematite or iron oxide. Also known as "bog ore."
Pig (pig iron): Rough bars of iron from a blast furnace, which were cast in sand molds in the floor of a casting house. (See Sow.)
Random rubble masonry: Building with irregular stones bedded in mortar. (The top ten feet of the Oswego Furnace are random rubble masonry.)
Salamander (bear): A mass of solidified iron that accumulated in the bottom of a furnace. It typically penetrated the brick hearth and had to be removed when its size threatened to interfere with furnace operations. The name 'salamander' refers to a mythological creature that can live in fire.
Shaft: The vertical chamber inside a furnace. It is lined with firebrick and consists of three zones: the inwall, the bosh, and the crucible.
Slag: The glassy byproduct of iron smelting. Slag, which is mostly silica, contains impurities from the ore.
Slag notch (slag hole): The hole or notch through which molten slag was withdrawn from the furnace. Since slag floats on top of iron, the slag notch was higher than the iron tap hole.
Smelting: The process of extracting metal from ore by heating it in a reducing atmosphere to remove oxygen and impurities.
Sows: Long trenches in the sand floor of a casting house. Each sow fed molten iron into a row of short molds called "pigs" from their fancied resemblance to nursing piglets. (See Pig.)
Stack: A stone tower shaped like a truncated pyramid. The stack supported the immense weight of the charge and the volcanic temperatures inside the smelting chamber.
Steel: Iron that contains from 0.3 to 0.5% carbon which makes it more rigid than wrought iron, but more ductile than cast iron.
Tap hole: A hole near the base of the furnace through which molten iron was tapped. This hole was plugged with fire clay between tappings.
Tension rods: See Tie rods and Anchor plates.
Tie rods (Binders): Iron rods that prevented the stack from expanding from the heat of the furnace. The rods ran through the masonry and were secured at each end with iron faceplates and wedges driven through slots in the ends of the rods. (Also known as tension rods.)
Tunnel head: The open top of the shaft where raw materials were charged into the furnace.
Tuyere ("twee-yer"): An iron nozzle for injecting air into the furnace. Water-cooled sleeves surrounded the tuyeres to prevent them from melting in the 2800º temperatures.
Tuyere arches: The arches where the tuyeres or blast pipes were inserted into the furnace.
Wrought iron: Malleable iron that contains only a trace of carbon.
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