Entrance to the Bridge House at Hopewell Furnace National Historic Site
Historical Furnace Village Main Page
An iron furnace is essentially a large chimney that is loaded with raw materials from the top, and finished materials—molten iron in this case—come out at the bottom. At the top, workers called fillers constantly fill the furnace with repeated layers of charcoal, ore, and flux via the charging hole. (Flux is a mineral such as limestone that causes the waste materials in the ore to collect together like metal to a magnet.) When ready, the furnace is lit and large amounts of air are blown into it to create a temperature of over 2,800º F. This heat melts the ore and flux, and the molten iron and waste materials called slag collect at the bottom of the furnace. A couple times each day, workers release the molten iron and slag by tapping the furnace, which is commonly done by punching a hole in or removing the refractory clay that plugs the exit. Because the slag is lighter than iron, it floats on top and can easily be removed.
Furnace Cross Section graphic
Charging hole (now covered with a grate) of the furnace at Hopewell Furnace National Historic Site
The Hopewell furnace used 15 bushels of charcoal, 400 to 500 pounds of ore, and 30 to 40 pounds of limestone every half hour, so fillers had to work 24 hours a day when the furnace was in blast (producing molten iron). To keep the fillers, raw materials, and equipment out of the rain and snow, a Bridge House was constructed at the upper level of the furnace (the Cast House was the protective building at the bottom level). A protective roof spanned the gap between the Bridge House and the adjacent Charcoal House (where the charcoal was stored) to further keep the workers and raw materials dry.
In the photo below, the white building is the Cast House and the gray, wooden building above it and to the right that looks like a barn is the Bridge House (the Charcoal House is out of the frame to the right). A stone platform was built to elevate the Bridge House to the same level as the top of the furnace.
Bridge House and Cast House of the Hopewell Furnace
On display inside the Bridge House are examples of the types of wheelbarrows and carts the fillers used to transport the raw materials.
Collection of wheelbarrows and carts used to transport raw materials to the furnace charging hole of the Hopewell Furnace
Inside the Charcoal House at Hopewell Furnace National Historic Site
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Last updated on June 12, 2024
