Furnace from the La Tène period

Some 1.5 metres high, this dome-shaped iron smelting furnace weighs a full 3.75 tons. Over 2,000 years old, it was uncovered at an excavation in Engsbachtal near Siegen. A wind tunnel made of stone slabs is attached to the stove. This offers insight into the history of iron production: inside the furnace a fire of leaves and brushwood was ignited, upon which charcoal and ore were kept glowing in alternating layers and continually topped up. In this process the lighter slag separated from the heavy iron. Then the oven’s wind tunnel was opened and the semi-fluid slag flowed off. What was left was a dough-like residue, called bottom ash, which contained iron in the form of grains. These were further smelted to form larger lumps of iron. Salvaging and transporting the oven was not easy in October 1934. It had to be underpinned with planks and encased in slats and iron straps so that it could be pulled up a 50 meter-long, steep forest track with a pulley. To bring it into the museum, a hole had to be broken through the castle wall.