14th October 2011

Excavations at the former Ynysfach Ironworks, Merthyr Tydfil, South Wales

The Glamorgan-Gwent Archaeological Trust Ltd are working closely with Merthyr Tydfil College, Davis Langdon and Interserve Construction to investigate elements of the former Ynysfach Ironworks in Merthyr Tydfil, before the construction of a new College building. So far we have discovered the southern engine and boiler houses, a small section of walling belonging to the southern casting house, the eastern wall of the refinery building and remains of five of the refinery furnaces themselves.

Although a foundry is thought to have existed on the site prior to the 19th century, the ironworks that we see preserved in the furnace banks today were built in 1801 for Richard Crawshay by Thomas Jones of Merthyr Tydfil, to the designs of the celebrated local engineer Watkin George. Initially, the ironworks had two furnaces, which were large for the period (53ft in height) and were only the second furnaces in Merthyr Tydfil to have steam-powered air blast capability. As a consequence output was more regular, producing between 65 and 70 tons a week compared to the water-wheel powered ironworks at Cyfarthfa, which could only produce 45 to 62 tons of iron per week.

Ynysfach was expanded in the 1830s with the construction of two more blast furnaces, a new, southern, engine house and reconstruction of the earlier, northern, engine house; much of the refinery building being excavated probably dates to this period.

Ynysfach Ironworks closed during the strike of 1873 and by 1884, when Cyfarthfa was converted to a steel production plant, the Ynysfach furnaces were reconditioned and held in reserve in case of a renewed demand for iron. Ynysfach, however, does not appear to have resumed production after this date, and by 1905 was in a derelict condition. The southern engine house was demolished sometime after 1905 and one chimney stack (belonging to the northern boiler house) was demolished in December 1949 because it was in danger of collapsing.

Currently, the team of archaeologists are uncovering the refinery building and they are exposing exciting elements of the early industrial iron process. Tim Young (Geoarch), an expert in industrial furnaces and smelting, has indicated that the remains discovered so far are starting to illuminate the “Welsh process of converting grey cast iron into wrought iron, first developed in Merthyr Tydfil in the 1790s”. It would appear that the Ynysfach Ironworks were purpose built by Richard Crawshay for this new process.

Rowena Hart, our site director, gave a talk to Roy Noble about the excavations on BBC RadioWales on Friday 14th October. Special thanks go to Alan George (Old Merthyr Tydfil) for kindly providing some of the images.