Iron Bridge Llangollen Canal


Telford used cast iron that had been made near the canal for the aqueducts at Chirk and Pontcysyllte, in bridges over the canal, like Rhos-y-Coed bridge at Trevor, and in structures throughout Britain.


If coal powered the Industrial Revolution, then iron built it. With coal, iron ore and limestone around Trevor, Cefn Mawr, Acrefair and the wider area, the canal was not only able to serve the new industries but was built by them as well.

At Ironbridge in Shropshire, industrialists developed blast furnaces capable of melting iron that could then be cast into parts for new constructions. Thomas Telford had been County Surveyor for Shropshire and learned from the work of these ‘ironmasters’ when he and William Jessop designed Chirk and Pontcysyllte Aqueducts.

One Shropshire man, William Hazledine, took advantage of the situation. He opened the Plas Kynaston ironworks in Cefn Mawr specially to bid for work on Pontcysyllte aqueduct. Later these works supplied Telford with cast iron parts for bridges he built throughout Britain, transported via the canal.

Ironworking was a dangerous and risky business. It made some people very rich and bankrupted others. It employed thousands of people in north east Wales and in Shropshire, but it maimed and scarred many of them. It helped to shape the villages at the centre of the World Heritage Site, and, via the canal, it carried the name of Ruabon across Britain.


This reconstruction of the works at Ynysfach shows cast iron being produced for the works at Cyfarthfa, Merthyr Tydfil. Ynysfach was much larger than Plas Kynaston but the processes carried out there were the same as those for producing iron used for Pontcysyllte Aqueduct. Click here to see the video.

Blist’s Hill Victorian Town

This video of ironworkers using Victorian machinery and methods to make wrought iron, at Blist’s Hill Victorian Town, near Ironbridge, Shropshire. Although it is not the same process as used at Plas Kynaston, it shows the heat and conditions which ironworkers had to endure.

More Information About Iron

Ironstone is a common rock across the north Wales coalfield. Iron is extracted by burning it at high temperatures. The grey stone changes colour to rusty red when exposed to the air. You can see this in many local buildings, such as the wall around the canal basin at Trevor.

ironstone in Trevor wall
ironstone in Trevor wall ©Andrew Deathe

Ironstone is heated to a very high temperature with a fuel, usually coke. Limestone is added as a ‘flux’. This binds to the impurities in the ironstone to form ‘slag’ which can be removed. The molten iron is poured into moulds shaped from sand, making bars that are called ‘pigs’. These examples are from other Welsh foundries.

Bars of pig iron from Wales
Bars of pig iron from Wales ©National Museum Wales

Charcoal made from wood was traditionally used for smelting iron but it was difficult to produce in large quantities. Coal was first used for smelting in north Wales at Pont y Blew, near Chirk, in 1710. The surviving bridge linked the furnace and a water-powered forge on opposite sides of the River Ceiriog.

Pont y Blew bridge
Pont y Blew bridge ©

Coke is coal that has been cooked, or ‘coked’ in an oven, heating it up to remove impurities like sulphur. It burns better than coal to create the heat needed to melt iron from ironstone in blast furnaces. A bank of nineteenth century coking ovens survive near the canal in Acrefair.

Acrefair coke furnaces
Acrefair coke furnaces ©Crown copyright: RCAHMW

Iron was produced, or ‘smelted’ in blast furnaces. Coke, ironstone and limestone were put into the top of the furnace. Steam-powered bellows blasted air in to make the fire hotter. Molten iron was poured or ‘tapped’ at the base. The heat was tremendous and the fires lit up the sky at night.

Illustration of generic 18th century blast furnace
Illustration of generic 18th century blast furnace

Being able to cast iron in large quantities allowed new technologies to develop. The world’s first major iron bridge was opened in 1781, at the town now called Ironbridge, England. Telford was impressed by the bridge but thought it could be better designed. The first of his many iron bridges was opened at nearby Buildwas, in 1797.


The area around Coalbrookdale, Shropshire, was a major centre for the development of the iron industries. Telford was County Surveyor from 1787 and learned a lot from the ironmasters there. He went on to form lifelong friendships and business partnerships with many of them. He used their iron in projects across Britain and Ireland.

Coalbrookdale painting
Coalbrookdale painting

William Hazledine (1763-1840) was a Shropshire ironmaster. He was so keen to get the contract for the Pontcysyllte aqueduct that he built the Plas Kynaston works near Cefn Mawr in 1800, to be as close as possible to the site. From 1802 his works produced all of the ironwork for the aqueduct.

Hazledine portrait
Hazledine portrait ©Shropshire Museum

Plas Kynaston iron was used for many of Telford’s later projects. It can be found at the Waterloo Bridge in Betws y Coed, Wales, Eaton Hall Bridge in Cheshire, England and the Craigellachie Bridge in Moray, Scotland. The castings for Craigellachie Bridge were transported on the canal to Chester and then by sea.

Craigellachie Bridge
Craigellachie Bridge ©

Cast iron letters along the arch of the Waterloo Bridge in Betws y Coed, Wales, say ‘This arch was constructed in the same year the Battle of Waterloo was fought’. In fact, the structure was cast in 1815 at Plas Kynaston but was not erected at Betws y Coed until the following year.

Waterloo bridge, Betws y Coed
Waterloo bridge, Betws y Coed ©Ray Jones

Plas Kynaston Ironworks was not large compared to some of the later ironworks in the area. There are no contemporary images of it, but it would have looked similar to William Hazledine’s Calcutts Works in Jackfield, Shropshire. Ironstone, coal and limestone were brought here, and the iron transported away, on the River Severn.

Calcutts Ironworks model
Calcutts Ironworks model ©Andy Dingley

From 1829, a branch canal linked Plas Kynaston Ironworks to the main canal basin at Trevor. The branch continued past a brickworks and a colliery. Almost nothing remains of this canal today. The remaining end is just north of the Trevor basin, with some of it buried under waste ground near the visitors’ car park.

Ironworks at Trevor
©Andrew Deathe

North of Plas Kynaston Ironworks was the later Acrefair Ironworks. Created in 1817, it became part of New British Iron Company and employed up to 1500 people until 1887. Only the surrounding wall and a bank of coke ovens survive today but the last blast furnace stood until 1963.

Acrefair blast furnace
Acrefair blast furnace: From the collections of the National Monuments Record of Wales: © Copyright: NMR Site Files Collection

Exuperius Pickering owned a small ironworks at Newbridge. It forged the links for his Chain Bridge, near the canal at Berwyn. His son, Exuperius Junior, built a later works at Trevor. In the woods by the canal you can see huge lumps of ‘clinker’ – waste from iron smelting – that may have come from these works.

Clinker lump
Clinker lump ©Andrew Deathe

A use of iron on the canal that can’t usually be seen is an iron cap on the weir at Horseshoe Falls. Added in 1822, the cap creates an even level across the length of the weir. An innovation in its time, its success meant that iron weirs soon became the norm.

Horsehoe Falls
Horsehoe Falls ©Ian Capper