Derwentcote Steel Furnace

Built in the 1720s, Derwentcote is the earliest and most complete steel-making furnace in Britain.

It produced high-grade steel for springs and cutting tools.

It is one of the few complete examples of the cementation type of furnace, and is the last surviving piece of evidence of cementation steelmaking in the north-east.

The conical chimney houses two sandstone chests into which iron bars were packed with alternate layers of charcoal powder.

When the fire was lit and the chests sealed, flames and heat travelled up through flues and chimneys around them, and temperatures reached 1,100°C. This heat enabled the carbon from the charcoal to diffuse into the iron.

Each cementation cycle, or 'heat', took three weeks, producing about 10 tons of steel. The firing took 6 - 10 days and the furnace was then allowed to cool for a week, before the bars could be extracted.