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Lancashire hearth

Lancashire hearth

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The Lancashire hearth was used to fine pig iron
Pig iron
Pig iron is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel...

, removing carbon to produce wrought iron
Wrought iron
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

.

Origins


Until the early 19th century, the usual method of producing wrought iron involved a charcoal-fired finery in a finery forge
Finery forge
Iron tapped from the blast furnace is pig iron, and contains significant amounts of carbon and silicon. To produce malleable wrought iron, it needs to undergo a further process. In the early modern period, this was carried out in a finery forge....

. By the beginning of the century, this was an obsolescent process, which was being replaced by the coal-fueled puddling process. However, charcoal continued to be used in some forges after most of the iron industry had abandoned it.

In 1813 when John Bradley & Co. (whose leading partner was James Foster
James Foster (ironmaster)
James Foster was a prominent Worcestershire ironmaster and senior partner in the important iron company of John Bradley & Co., Stourbridge, taking its name from his elder half-brother. As well as the Stourbridge ironworks, the business owned a number of coal and ironstone mines, furnaces, forges...

) took over forges at Eardington
Eardington
Eardington is a small village and civil parish in Shropshire, England. It is near the A442 road and is two kilometres south of the town of Bridgnorth, along the B4555 road...

 in Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...

, a potting and stamping
Potting and stamping
Potting and stamping is a modern name for one of the 18th century processes for refining pig iron without the use of charcoal.-Inventors:The process was devised by Charles Wood of Lowmill, Egremont in Cumberland and his brother John Wood of Wednesbury and patented by them...

 forge, they reverted to using charcoal. In 1820, he bought Hampton Loade
Hampton Loade
Hampton Loade is a village in Shropshire, England along the Severn Valley. It is situated on the east bank of the River Severn at , and is notable for the unusual current-operated Hampton Loade Ferry, a cable ferry to the hamlet of Hampton on the west bank...

 Forge, which then became a tinplate works and in 1826 another charcoal forge. This was followed by others establishing charcoal forges at Horsehay
Horsehay
Horsehay is a village on the western outskirts of Dawley, which, along with several other towns and villages, now forms part of the new town of Telford in Shropshire, England. Horsehay lies in the Dawley Hamlets parish, and on the northern edge of the Ironbridge Gorge area.Its name is Anglo Saxon...

 in 1832 and at the Old Park ironworks of the Botfield family about 1826. Cookley
Cookley
Cookley is a village in the Wyre Forest District of Worcestershire, England, a few miles to the north of Kidderminster, and close to the villages of Kinver and Wolverley. It lies on the River Stour, and the Staffordshire and Worcestershire Canal in the civil parish of Wolverley and Cookley...

 Forge in the Stour valley also reverted to charcoal working in 1814, supplying wire
Wire
A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various...

 and tinplate mills.

By the 1830s, these forges were sometimes producing over 2000 tons of iron per year, compared with a few hundred from earlier finery forges. It is likely that these forges were using a more efficient variety of hearth, which from Swedish usage has come to be known as a Lancashire hearth.

Spread


Faced with competition from cheaper British iron production, the Swedish iron industry needed to find a new cheaper method of making iron. In the 1810s, experiments were made with puddling
Puddling (metallurgy)
Puddling was an Industrial Revolution means of making iron and steel. In the original puddling technique, molten iron in a reverberatory furnace was stirred with rods, which were consumed in the process...

, but this proved unsatisfactory, as it needed coal of which Sweden had none. After Gustav Ekman visited Britain, he published a report of his observations. He had seen closed finery hearths in south Wales and near Ulverston
Ulverston
Ulverston is a market town and civil parish in the South Lakeland district of Cumbria in north-west England. Historically part of Lancashire, the town is located in the Furness area, close to the Lake District, and just north of Morecambe Bay....

, then in Lancashire
Lancashire
Lancashire is a non-metropolitan county of historic origin in the North West of England. It takes its name from the city of Lancaster, and is sometimes known as the County of Lancaster. Although Lancaster is still considered to be the county town, Lancashire County Council is based in Preston...

 (now Cumbria
Cumbria
Cumbria , is a non-metropolitan county in North West England. The county and Cumbria County Council, its local authority, came into existence in 1974 after the passage of the Local Government Act 1972. Cumbria's largest settlement and county town is Carlisle. It consists of six districts, and in...

). Those in south Wales were similar to puddling furnaces, but in Lancashire, he saw closed furnaces, where the metal was in contact with the fuel. On his return to Sweden, Ekman experimented and built furnaces similar to what he had seen near Ulverston, most probably at Newland ironworks
Harrison Ainslie
The firm of Harrison Ainslie & Co. was a British firm of ironmasters and iron ore merchants, selling high quality haematite from their mines on Lindal Moor to smelters in Glasgow, Scotland, South Wales and the Midlands. From a 21st century perspective, they are more interesting as the last...

.

In 1829-30, Waern installed a furnace of the south Wales type at Backefors
Bäckefors
Bäckefors is a locality situated in Bengtsfors Municipality, Västra Götaland County, Sweden. It had 689 inhabitants in 2005.The Movie Kopps was filmed in was filmed here in 2003.The hospital Dalslands Sjukhus is located here....

 ironworks, while independently Ekman built Lancashire hearths at Dormsjö and Söderfors
Söderfors
Söderfors is a locality situated in Tierp Municipality, Uppsala County, Sweden with 1,597 inhabitants in 2005....

. From there the process spread to other forges. In 1887, 406 hearths made 210,500 tons of iron. The last Lancashire forge in Sweden was at Ramnäs, closed in 1964.

In Shropshire, charcoal iron production continued on a significant scale, but declined after 1870, rods for wire-drawing being a significant product. However most charcoal forges were probably closed by 1890.

Process


The Swedish Lancashire hearth consisted of a rectangular closed furnace with a chimney (8 metres high) at one end and a working arch in front of the hearth proper at the other. Pig iron was charged through a door at the foot of the chimney and stacked on an iron-clad bridge so that it could be heated by the waste gases from the hearth. The hearth was blown through a single water-cooled tuyere
Tuyere
A tuyere, also can be spelled as tuyère, is a tube, nozzle or pipe through which air is blown into a furnace or hearth.Air or oxygen is injected into a hearth under pressure from bellows or a blast engine or other devices...

 with pre-heated air. The hearth consisted of a rectangular box of iron plates, the bottom plate being water-cooled. Surplus slag was removed with a shovel between finings, but some was left to help the process. Pig stacked on the bridge at the back of the hearth was then pulled forward with a hook and charcoal added. The blast was then turned on and fining began.

When the pigs began to melt, rabelling began (as in the Walloon process) using two bars of iron one to stir the iron and the other to lift it back into the blast. Periodically the tuyere had to be cleaned of matter adhering to it with a third (lighter) bar. Finally, the iron was gathered into a 'loop' which was lifted out of the hearth with a heavier bar and tongs, and taken to the shingling hammer
Trip hammer
A trip hammer, also known as a helve hammer, is a massive powered hammer used in:* agriculture to facilitate the labor of pounding, decorticating and polishing of grain;...

.

The process was more fuel-efficient and more productive than its predecessors.