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Coalbrookdale Foundry
Coalbrookdale, Shropshire, UK
associated engineer
Abraham Darby I
Abraham Darby II
Abraham Darby III
date  1708 - 1709
UK era  Stuart  |  category  Building  |  reference  SJ665050
Site of the first successful coke-fired iron smelting furnace in Europe — built by Abraham Darby (the first) in 1708 from parts of an existing charcoal furnace. Part of the furnace survives, marking the change in technology that led the way to Britain's Industrial Revolution. The Coalbrookdale site was run by five generations of the Darby family of Quakers, and remained a foundry company until closure. The site is now preserved for its heritage significance.
Coalbrookdale, in a valley of the River Severn in Shropshire, has a long history of metal working — Caldebroke Smithy existed here in the 12th century, operated by monks from Much Wenlock Priory. In 1536, a bloomer furnace was producing iron by smelting small batches of iron ore with charcoal. By 1544, the site's Lower Forge (SJ667038) and Upper Forge (SJ669042) were in use. Middle Forge (SJ668040) probably opened later.
In the early 17th century, the estate was owned by Sir Basil Brooke (1576-1646), who is believed to have had furnaces and ironworks built on the Coalbrookdale site. The cast iron lintel over the oldest surviving blast furnace bears a painted date of 1638, now thought more likely to be 1658 (noted as 1658 in a Newcomen Society visit on 19th June 1923).
From 1651, the works were leased to a succession of iron founders. From 1688, the lessee was Shadrach Fox, who supplied iron shot and shells to the Board of Ordnance. By April 1703, the furnace he was using had been damaged in an explosion but the forges remained operational.
Foundryman and commercial entrepreneur Abraham Darby (1678-1717) had studied Dutch methods of brass founding and run businesses in Bristol, manufacturing brass pans (est.1702) and founding iron (1703). In April 1707, he patented (Patent No.380) a new and simpler method of casting "bellied" iron cooking pots using dry sand to form the shape rather than loam or clay moulds, which had to be heated.
He relocated to Coalbrookdale, some 30km north west of his birthplace at Wrens Nest in Worcestershire (now part of Dudley, West Midlands), where he established a brass works and a copper smelter (which probably continued in use to 1717). In September 1708, he leased a brick semi-derelict Coalbrookdale blast furnace, rebuilt it larger and started smelting iron.
To release molten iron from iron ore, the ore needs to be heated to a high temperature. Up until then, charcoal was burned to achieve this, with the fire air-fanned. To prevent the heavy ore from crushing the charcoal in the process, iron was made in small pans and removed from the furnace in a semi-liquid state.
Charcoal is made from timber, so its availability is limited to the amount of trees being grown and harvested. By contrast, coal reserves were plentiful at this time and coal mining increasing. In general, smelting with coking coal had been ineffectual to date, because of the sulphur content of the coal. However, the coal at Coalbrookdale contained little sulphur and when burned to cinders produced coke with few impurities.
Darby’s coke-burning trials worked, and on 10th January 1709, the new furnace had its first blast day. With a taller chamber inside the furnace and strong bellows to provide the air blast, the smelting temperature was higher, resulting in larger quantities of fully liquid iron, which flowed easily into the moulds. His cast iron pots proved far cheaper to produce than brass pans and he realised that this would reduce the country's need for imports, and increase the export potential.
Darby established the Coalbrookdale Company in 1709, and in 1714 withdrew from the brass works. He renewed his furnace lease and formed a partnership with John Chamberlain and Thomas Baylies (1687-1756). In 1715, the output of the foundry was 81 tonnes.
A second blast furnace (SJ669049, site of) was built in around 1715, and operational by 1718. The two furnaces, fired by coke, produced pig iron for foundry work. The iron had a high carbon content, making it brittle, so wrought iron was forged from charcoal-fired pig iron.
After Darby’s premature death in 1717, the Coalbrookdale Company was owned by a partnership led by Thomas Goldney II (1664-1731) and managed by Richard Ford. The company produced mainly cast iron goods, using iron from the two blast furnaces and from melting pig iron in air furnaces. In 1718, the works cast its first steam engine pipework and in 1722, its first iron engine cylinder — like the pots, both stronger and cheaper than brass.
During the 1720s, the works expanded and more furnaces, moulding shops and associated buildings were constructed. From 1724 onwards, cylinders and other parts for Newcomen engines were being produced and it seems the company held a virtual monopoly on cylinder casting right up until around 1760.
In 1728, Darby’s son Abraham Darby II (1711-63) joined the business, becoming eligible for a share of the profits in 1732 and a full partner in 1738. He proved as innovative as his father. In the 1730s, he devised a way to produce coke pig iron suitable for making wrought or bar iron in charcoal finery forges — a process sometimes known as potting and stamping. (It would not be until the 1780s that puddling or reverbatory furnaces, which lowered the carbon content of the iron by oxidation, would be used for this process.)
In 1734, Middle Forge was converted into a boring mill for steam engine cylinders. In 1736, the foundry’s iron output was said to be 51 tonnes per year. In 1740-8, putting aside Quaker reservations about warfare, Coalbrookdale also cast cannons.
In 1742, Darby II installed a steam engine to recirculate the water powering the ironworks’ waterwheels, so the blast furnaces would not have to stop operating during water shortages. In 1748, a network of timber wagon ways was constructed around the works. The following year, 1749, annual iron output was 152 tonnes.
Further expansion occurred in 1754, with the acquisition of the Bedlam Furnaces in Madeley Wood, east of Coalbrookdale, and various mines and mineral rights. At Horsehay and Ketley, north of Coalbrookdale, a total of four coke-fired furnaces were constructed and put in blast on 5th May 1755, 1756 and 1757. During the 1750s, engines for recycling water to the blast furnaces were constructed at Lightmoor, Horsehay, Ketley and Madeley Wood.
Finance was provided by Thomas Goldney III (1696-1768), with Richard Reynolds (1735-1816) as manager at Horsehay. In 1757, the company’s mines in Wrockwardine Wood, to the north east, began supplying iron ore to the works. In the same year, Reynolds married Hannah Darby (1735-62), daughter of Darby II, gaining shares in the Coalbrookdale Company as a junior partner.
In 1763, Darby II died and Reynolds managed the company. Under his leadership the Coalbrookdale Foundry became the most important in England, carrying out work now recognised as milestones of the Industrial Revolution. Engine parts were cast for James Brindley (1716-72), James Watt (1736-1819) and Boulton & Watt, among others.
On 17th June 1766, brothers Thomas and George Cranage, both company employees, patented a method for producing wrought iron in a reverbatory (air) furnace. Their method was apparently trialled at the Coalbrookdale Foundry in 1767, after which the company paid them £30 for the patent. Two reverbatory furnaces were erected in the Upper Forge, with a slitting mill added in 1776.
In 1767, the foundry produced rails for the first cast iron tramways in the country, and later for railways. The company replaced their own timber rail network with cast iron, laying 813 tonnes of rails between Ketley, Horsehay and Coalbrookdale, between 1768 and 1771.
In 1768, 18-year-old Abraham Darby III (1750-89) became a partner in the Coalbrookdale Company. Reynolds remained associated with the company and continued to improve the works. In 1775, he bought the Goldney shares.
Darby III is probably best known for Iron Bridge, the first iron bridge in the world, across the River Severn. In 1777, he rebuilt his grandfather’s 1709 blast furnace in order to manufacture the necessary ironwork. The bridge opened on 1st January 1781. A rail link was constructed between the river wharfs at Iron Bridge and Horsehay in 1779.
In 1780, Reynolds transferred his Coalbrookdale Company shares to his sons William Reynolds (1758-1803) and Joseph Reynolds (1768-1859), who also managed the ironworks at Ketley. By 1794, Francis Darby (1783–1850) and Richard Darby (1788–1860), the sons of Darby III, were involved with the Coalbrookdale Company.
Meanwhile, production was stepped up at Horsehay. A forge was built in 1781 or 1784 that included a steam-driven hammer. By 1790, a water-powered rolling mill — possibly the first in the world — was making wrought iron boiler plates, bars and hoops. Seven Boulton & Watt rotative steam engines, with sun-and-planet gearing rather than crankshafts, were erected — two at Horsehay, four at Ketley and one at Coalbrookdale.
In Coalbrookdale, Middle Forge boring mill was rebuilt in 1780, a pumping engine was constructed in 1781, and the Upper Forge slitting mill was converted to forging around 1783. In 1785, a blowing engine and two new finery forges were built at Upper Forge, and a hammer engine was constructed but operated only for six years (1787-93). The forges produced mainly frying pans and nails.
Wrought iron making using the puddling process was patented by Peter Onions (1724-98) on 7th May 1783 (Patent No.1370), and Henry Cort (1740-1800) in 1783 (Patent No.1351) and on 13th February 1784 (Patent No.1420).
In 1795, the company manufactured the structural ironwork for Thomas Telford's Buildwas Bridge (dem.1905), some 3km west of the original iron bridge. Advances in technology meant it required only 181 tonnes of cast iron for a span of 39.6m. In 1796, a new slitting mill was constructed at Ketley. The furnaces at Coalbrookdale produced 2,703 tonnes of pig iron, those at Horsehay 1,481 tonnes and at Ketley 5,150 tonnes.
Recession began to gnaw at the iron industry in 1796 and the Coalbrookdale Company found itself in financial difficulty. The company sold the Bedlam Ironworks at Madeley Wood to William Reynolds & Company. In August, the Darby and Reynolds interests were separated completely — the Coalbrookdale Company bought back William Reynolds' 10 percent equity for £8,000 and he purchased the company’s half share of the Ketley Ironworks, to own it outright.
In 1802, the Coalbrookdale Foundry made the boiler and parts for Richard Trevithick's high pressure steam engine. At the same time, Trevithick was probably developing and trialling a locomotive that ran on the iron rails at the works, as detailed in a drawing of 1803 — a full size replica of the locomotive is on display at Blist Hill Museum in Ironbridge.
In 1806, Coalbrookdale’s furnaces produced 3,009 tonnes of pig iron and Horsehay’s furnaces 3,895 tonnes. Coalbrookdale Foundry cast parts for the atmospheric steam engine installed at Killingworth High Pit in 1810, subsequently improved by George Stephenson (1781-1848).
Between 1818 and 1822, closure of the works was considered, and the Coalbrookdale blast furnaces were shut down. The forges remained in use. The blast furnaces at Horsehay continued to operate, and in 1823 produced 4,932 tonnes, increasing to 6,942 tonnes in 1830. Horsehay became famous for its decorative cast ironwork, winning the Society of Arts gold medal (1849).
Abraham Darby IV (1804–1878), a great nephew of Darby III, was made a partner of the Coalbrookdale Company in 1830. In 1832, Richard Darby resigned from the company, leaving Francis Darby, Darby IV and Alfred Darby (1807–1852), another great nephew of Darby III, in charge. Under their stewardship, the works at Horsehay were much expanded.
About 1839, the company acquired the works at Lightmoor, between Coalbrookdale and Horsehay. In 1845, the company bought the land on which all their ironworks stood from the Lord of the Manor. Two years later, in 1847, Lower Forge closed. In 1849, Darby IV relinquished his management after a series of family disagreements, but retained a financial interest in the company. He sold his 88 shares (he held 88 out of a total 720) in 1852, to Mary Darby.
By the time of the Great Exhibition in 1851, the ironworks were the largest in the world with an output of 2,032 tonnes a week. The ornamental gates the foundry made for London’s Crystal Palace were later re-positioned in Hyde Park, where they remain. At that time, the foundry employed 3,000-4,000 men and boys at Coalbrookdale and Horsehay.
In 1861-2, owing to a depression in the iron trade, the Horsehay blast furnaces were blown out and the company’s furnaces at Lightmoor and Dawley Castle supplied Horsehay’s forges and rolling mills with pig iron. In 1864, the foundry manufactured standard gauge locomotives for the ironworks’ sidings, which were connected to the mainline railway. In 1866, the company also owned mines at Broseley.
By 1880, of the four furnaces at Lightmoor and Dawley Castle, only one was still in blast. These works had closed in 1878 and 1883, though brick, tile and pottery manufacture continued at Lightmoor. In 1881, the Coalbrookdale Company Ltd was formed. It took over the coal, ironmastery, ironfounding and engineering businesses of the former Coalbrookdale Company. It also produced steam fire pumps under a patent from Parker & Weston.
In 1886, the Horsehay works were sold to the Simpson family and used for heavy engineering, leaving Coalbrookdale as the company’s only ironworks. Alfred Edmund William Darby (1850-1925), son of Alfred Darby, became chairman of the Coalbrookdale Company Ltd and the last member of his family to be connected with it.
In 1900, the works employed 1,100 men. New foundries and workshops were built at Dale End (1901) and over the infilled pool at Lower Forge (1903). During the 1920s, the company joined with Cockburns, McDowall Steven & Company and Planet to form the Light Castings Group. In 1929, the group was absorbed into Allied Ironfounders Ltd.
In 1930, the Coalbrookdale works were converted to electric power. To increase output and the variety of castings produced, the first completely mechanised moulding and sand conditioning plant in Britain was installed. New buildings were erected over the infilled Upper Forge pool.
In 1935, Lightmoor Brickworks was sold (or perhaps closed). In 1945-6, the company designed and began manufacturing new types of cast iron fire grate and the Rayburn cooker.
In 1950, Allied Ironfounders decided to clear the area around the former Upper Forge to make way for new facilities. The remains of the 1709 blast furnace were rediscovered and, in view of their historical importance, the site was preserved. Deep drainage was installed to combat the high groundwater level, and extensive stabilisation of the 17th century foundations and the furnace structure undertaken. The Coalbrookdale Museum opened nearby in 1959, to commemorate the 250th anniversary of the Coalbrookdale Company (and Darby’s furnace).
Ironworking continued at Coalbrookdale. In 1961, the works employed 600 people and manufactured Rayburn cookers, and Brook and Marves fires. In 1969, Allied Ironfounders Ltd became part of Glynwed Foundries Ltd.
In the summer of 1970, the Coalbrookdale Museum and the famous furnace were leased to the Ironbridge Gorge Museum Trust (established 1967), which manages and cares for all the heritage sites in the gorge. The Coalbrookdale Foundry site is a Scheduled Ancient Monument and, in April 1983, its original blast furnace was Grade I listed.
In 1986, some 1,550 hectares of the Ironbridge Gorge was designated a UNESCO World Heritage Site. The small museum near the furnace was expanded to cover more of the works site, re-opening as the Coalbrookdale Museum of Iron in 2017.
Research: ECPK
"The Shropshire wrought-iron industry c1600-1900: a study of technological change" by Richard Hayman, unpublished PhD thesis, Centre for Lifelong Learning, University of Birmingham, July 2003
"The Discoveries of the Darbys of Coalbrookdale" by T.S. Ashton, Transactions of the Newcomen Society, Vol.5, Issue 1, pp.9-14, London, 1924
"A Sketch of the Industrial History of the Coalbrookdale District" by Rhys Jenkins, Transactions of the Newcomen Society, Vol.4, Issue 1, pp102-107, London, 1923
"The coal and iron industries of the United Kingdom" by Richard Meade, Crosby Lockwood & Co, London, 1882
reference sources   DNB

Coalbrookdale Foundry