Cold-Blast Charcoal Furnace

Furnace Stack made of fieldstone
Furnace stack in 1958 before reconstruction of Cast House

NPS Photo

Hopewell Furnace is a cold-blast, charcoal fueled iron furnace, typical of other furnaces from the late 18th and early 19th century. When operating, one would immediately notice the intense heat radiating off the stones. A dull roar would be heard inside the furnace. A yellow glow would have been visible at the bottom of the casting arch with the furnace founder watching intently.

The furnace was filled from the top with layers of charcoal, iron ore and limestone. The water wheel provided a room temperature blast of air, thus the term cold blast, which helped the fire reach 3,000 degrees Fahrenheit. The furnace's contents would shift downward and melt into iron and slag. Every 12 hours the furnace was drained. The iron was cast into products and the slag was discarded. This process ran continuously for months on end, only stopping when the furnace's fire brick lining needed to be replaced.

Last updated: December 19, 2020

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