Stories from PA History
Story Glossary
The Pennsylvania Iron Industry: Furnace and Forge of America Glossary

Anthracite coal:
A hard coal containing water, called moisture; mineral impurities, called ash, which are left when coal is completely burned; volatile matter, or gases expelled when coal is burned and fixed carbon, the matter that burns at a higher temperature after the volatile matter has been expelled. Anthracite coal, which is almost completely carbon, is found in eastern Pennsylvania.

Bessemer converter:
A method for making steel by blasting compressed air through molten iron to burn out excess carbon and impurities. The capacity of a converter was from 8 to 30 tons of molten iron with a usual charge being around 15 tons. "Henry Bessemer patented this tilting converter for carrying out his pneumatic steel-making process. He lined the vessel with refractory brick and. fitted ports at the bottom connected to an air compressor. Artisans tilted the converter back, poured in liquid pig iron, turned on the air blast, and tilted the vessel upright. Air blowing through the metal burned the silicon and carbon out of the pig and released enough heat to keep the metal molten. When conversion was complete, the operator tilted the vessel forward, shut off the air, and poured the liquid steel into ingot molds. (From Ferdinand Kohn, Iron and Steel Manufacture [London: William Mackenzie, 1869], pi. 25, facing p. 78)"

Bituminous coal:
A soft coal containing water, called moisture; mineral impurities, called ash, which are left when coal is completely burned; volatile matter, or gases expelled when coal is burned; and fixed carbon, the matter that burns at a higher temperature after the volatile matter has been expelled. Bituminous coal, which has a lower proportion of carbon and higher proportion of volatile matter than anthracite coal, is found in western Pennsylvania.

Iron slabs produced at bloomery forges or refinery forges. Blooms are further hammered or rolled to shape them into other products.

Bloomery forge:
A water-powered mill where workers heated iron ore and hammered it into small iron blooms, separating the iron in the ore from other elements mixed with the iron. This process wasted iron and charcoal fuel, and produced iron that was inferior to iron made more efficiently in blast furnaces and refinery forges.

Fuel used in iron blast furnaces. It is created by smoldering wood, driving off water and other impurities in the wood, and leaving behind nearly pure carbon. Charcoal has more heating power than wood does

Bituminous coal that is burned under controlled conditions to drive off volatile matter (gases expelled when coal is burned), leaving carbon and ash from the coal fused together in the form of coke. With its higher proportion of combustible carbon, coke generates more heating power than bituminous coal does.

Skilled worker who slowly smoldered cut wood, converting it into charcoal that had more heating power than wood

Skilled workers who heated and hammered pig iron, driving off carbon impurities, and converting the pig iron into wrought iron

The most skilled worker at a blast furnace, responsible for keeping the furnace in blast efficiently and successfully.

Hot blast:
An apparatus that recycles hot gases blown out the top of a blast furnace, preheating the air blast and raising the temperature inside the furnace. Hot blast improved the efficiency of charcoal furnaces over cold-blast furnaces. It also made possible the use of anthracite coal and bituminous coke as fuels, which ignited and burned at higher temperatures than charcoal did.

Iron ore:
Naturally occurring deposit of iron mixed with other elements. In Pennsylvania four types of ore predominate: magnetite, red hematite, brown hematite, and carbonate. These types vary in the proportions of iron and other elements they contain.

Skilled worker who made casts, and then poured molten iron into the casts where it cooled and hardened, making various products.

Pig iron:
Iron produced directly from a blast furnace. Molten iron flowed from the furnace into a channel consisting of large molds in a sand floor. The flow of molten iron continued into smaller molds attached to the sides of the large ones at right angles. The arrangement of smaller and larger molds reminded ironworkers of pigs (the smaller molds) spread at the sides of sows (the larger molds). Thus ironworkers called the ingots made in smaller molds "pigs," the ones in larger molds "sows," and the overall product "pig iron."

Skilled workers who manipulated the semi-molten iron in a puddling furnace, stirring and working it until most carbon and impurities were driven out and it was converted into wrought iron.

Refinery forge:
Charcoal-fueled furnaces produced iron that was brittle and unmalleable because of carbon and impurities that remained in the iron after smelting. Refinery forges reheated and hammered the iron, driving off more of the carbon and impurities, creating wrought iron that was stronger and more malleable.

Rolling mill:
Mills that included puddling furnaces, and sets of rolls through which iron was passed to shape it into various products, such as railroad rails. Rolling mills superceded forges in making wrought iron products.

Slitting mill:
Slitting mills had heavy, water-powered shears that cut bars of iron into strips. The strips were then heated and passed through rollers that reduced the strips to a desired thickness. Next the strips were reheated and passed through grooved rollers that cut the strips into slits. The slit iron often went to naileries, which put points on one end of the iron slits and heads on the other end, producing nails.

Wrought iron:
An easily welded or forged iron containing approximately 0.2 percent carbon. Wrought iron contains less carbon and other impurities than pig iron, is less brittle than pig iron, and is more easily hammered or rolled into other shapes.

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