Between its founding in 1765 and 1824, 7 blast furnaces were established on the site of the Cyfarthfa Ironworks.
The blast furnaces were built into the hillside surrounding the Cyfarthfa site to provide natural insulation and allow the raw materials of coke, iron ore and limestone to be added at the top of furnaces. The temperature inside the furnaces would then be raised to around 1300 °c. When the resulting molten iron was just right, the furnace keeper would open it at the bottom, the molten iron would then be tapped into sand beds or ‘pig beds’ in the casting houses in front of the furnaces. This molten iron would then solidify into ‘iron pigs’, and later be refined into a useable metal.
The housing to six of the blast furnaces of the Cyfarthfa Ironworks can still be seen at the site today.