The history of the forge can be traced back to 1640, and it was still working until around 1910. The industrial site was abandoned in 1929 although the workers’ cottages were occupied until the late 1960s.
Top Forge is a Scheduled Ancient Monument (Grade I) and celebrates the history of iron-working in Britain and especially in South Yorkshire. The Forge is the only surviving water-powered heavy wrought iron forge with its water wheels and hammers (now restored) in situ. It is a site of national importance.
The Industrial Revolution is usually associated with steam power. Wortley Top Forge certainly made its contribution both in the technology of iron making and in supporting the early Railway Age, but only ever used the power of its three water wheels.
The Don valley was an ideal area for iron-making as it had access to ironstone from the Tankersley seam, coppiced timber for charcoal and, of course, water power. Iron has been worked in the valley since the 1300s. Top Forge was built before1640, deliberately in a loop of the river Don in order to shorten the course of the head goyt and to maximise the head of water available between the weir and the tail goyt.
Built by Sir Francis Wortley, the Forge was leased after the Civil War by the Spencer syndicate of Cannon Hall who dominated the iron industry in South Yorkshire for the next 100 years. In 1713 the Forge was extended by Matthew Wilson who was managing five works, including Low Forge, on this stretch of river for his Spencer in-laws. In the1740s, Matthew’s nephew John Cockshutt I added the Tin Mill down river. From the 1760s, his son John Cockshutt II was making innovative changes, taking out patents and building the Forge’s original air pump in 1770. A second son, James Cockshutt was early mentored by John Smeaton the celebrated civil engineer (who later sponsored his Fellowship of the Royal Society). James spent time in Wales and in partnership with Richard Crawshay at Cyfarthfa works near Merthyr Tydfil; they were responsible for introducing Henry Cort’s puddling process for converting pig iron into wrought iron. In the 1790s James returned to manage Wortley Forges and was to introduce Cort’s process at Low Forge – the first site in England.
The last phase of the Forge fits into the Railway Age as Thomas Andrews and then his son Thomas Andrews junior produced wrought iron axles for railway trucks and engines. Thomas Andrews junior became a Fellow of both the Royal Societies of London and Edinburgh for his work as a ‘metalographer’ following Henry Clifton Sorby in using microscopes for quality testing work.
Axle production ceased at Top Forge by 1910 (the price of mild steel from Sheffield had undercut the cost of wrought iron). The Top Forge workshops continued to service the works both upstream and downstream after1912. Low Forge continued to produce wrought iron until 1929 when all activity ceased.
In 1953 after more than 20 years of decay, what is now South Yorkshire Industrial History Society acquired the semi-derelict works where much of the contents had been sold on or scrapped. From the late 1960s volunteers have used old photographs and archive evidence to replace missing items to restore the Forge to its 1900 appearance.
It has been important to repair and then maintain the buildings. These are now listed and we enjoy the oversight and advice of Historic England. Over the years the waterwheels and belly helve hammers have been fully restored; the cranes have had rotten wood replaced; the ‘Sheffield carpet’ of cast iron floor plates has been replaced; the ‘Blower-wheel’ air pump has been recreated; a cast iron furnace case has been acquired and a brick furnace lining for this installed in 2016; an early rolling mill has been motorised for demonstration. In 2017 the volunteers have completed taking down a collapsing C18th stone staircase, replacing non-existent foundations and reconstructing it as good as new/old.
The older breast-shot water wheel and belly-helve hammer was probably installed in 1680s and would have been almost entirely of wood. As each generation updated this structure, we now have a cast iron wheel with a cast iron axle albeit with evidence of a previous wooden tree trunk shaft.
The larger breast-shot wheel and trip hammer was probably installed around 1840 when railway axle making was introduced. Our calculations suggest that the four-lobed cam running at 20 revolutions per minute would have a power output of about 8 HP and each hammer blow about half as effective as a 1 ton drop hammer.
The 1770 Blower wheel which drives the ‘new’ air pump is a pitch-back wheel fed from an 1850 pentrough which suggests Victorian improvements.
The water supply for the Forge comes through sluice gates (recently rebuilt) alongside a weir built half a mile upstream. The dam (recently de-silted) is comparatively small but was enhanced by other dams in the working years. Three culverts supply water to the three wheels.
It is interesting to note that the Wortley Ironmasters were sound practical engineers. Number 1 hammer has a wooden spring mechanism and an enormous drome beam protects the structure from shock. Both hammers can be adjusted so that the sweet spot of the hammer falls within the anvil face.
There are four rotating cranes and three of them overlap in their areas of operation allowing work to be lifted from forge to horse drawn transport. Of course the very heavy and very hot wrought iron was handled by crane during the forging process.
The complex of associated works on this stretch of the river Don made servicing workshops essential for repair of ironwork and of woodwork. These separate buildings date from perhaps 1750s. The eastern hull was the blacksmiths’ shop below and the joiners’ shop above which was accessible only by an external staircase. The western hull (accessible by a separate entrance) has always been known as the foundry but with only a little evidence of this activity. It is claimed that a small extension at the extreme west end might have contained a cementation furnace.
The blacksmiths’ shop now houses the restoration workshop with a range of working machine tools mostly of first half 1900s vintage. The Foundry contains a group of medium sized stationary steam engines which operate on compressed air: an 1840s horizontal engine from Wilson’s snuff-mill ; an vertical engine ex Neepsend gasworks mortar-mill; an 1890s Buxton & Thornley horizontal engine; a paired set of 1920s engines by Marshalls of Gainsborough from Rotherham Technical College. The joiners’ shop contains a collection of smaller stationary engines and machine tools; the 1817 cast iron roof frame is of special interest.
The ironmaster’s house, built in 1680s, was reduced to extend the forge after1713 and later extended in 1780s, and eventually became a pair of workers’ cottages when the ironmaster moved across the road to a finer house called The Grange. These cottages now help to illustrate the physical side of domestic life in the 1900s. The Yorkshire range needs black-leading, the washhouse has a copper and a mangle, and the tin bath hangs on a nail on the wall. The privy across the yard has torn newspaper hung on a nail!
The South Yorkshire Industrial History Society, who own the site, has over the years been given stationary steam engines and much industrial machinery and the Forge became an Industrial Museum almost by accident.
A presentation of pre 1950s belt-driven metalworking machinery is in the ‘South Yorkshire Ironworks’ building. A collection of mechanical hammers and a blacksmith’s hearth are in the ‘smithy’. The Elizabeth mill engine, a nodding donkey, a mine sinking engine and another selection of medium sized stationary steam engines is on display in the ‘Barns’ area near the car park.
The story of iron and steel
Long ago (3000BC), metal working developed through the bronze age.
Some metals are sufficiently inert that the pure native metal can be picked up and, being comparatively soft, can be easily worked.
The reduction of ores with charcoal will produce copper and tin from sulphides, oxides or carbonates. Bronze is an alloy of copper and tin.
It is possible that iron meteorites might have fallen into the hands of metal workers in ancient times. Picked up most easily in deserts or snowfields, this material might be beaten (forged) into high status, magical, objects. Such a knife was found in Tutankhamun’s tomb.
From 1200BC it was possible for ironworkers to smelt iron from its oxide ore.
An ore will always contain impurities such as sandstone silicates.
When smelting iron in a small bloomery, carbon in charcoal form can combine with the oxygen in the iron oxide to free particles of iron. (Actually, carbon monoxide from the carbon is a very effective reducing agent—finally converting to carbon dioxide.)
The bloom will contain unreacted iron oxide and carbon and slag as well as the reduced iron.
Reheating and subsequent hammering on an anvil will help the iron particles to cohere and express out much of the slag and other unwanted material.
The early ironworkers managed to achieve a temperature high enough to render the slag molten but not high enough to melt the iron and so it was by lucky chance that the iron billet which was eventually formed was a comparatively soft malleable iron of very low carbon content which could be easily fire welded.
The small amount of slag which still remained in the iron has some helpful properties in both resistance to weathering corrosion and as a flux during hot hammer welding.
The working of the bloom gives us the name of the material ‘wrought’ iron.
Pure iron is so soft that one cannot make tools which will remain sharp and much experimentation took place in making knives, swords, axes etc.
In fact a very small carbon content in the iron (say 0.5%) can produce a solid solution of iron carbide in the iron which we call steel.
Wrapping an iron sword in organic (carbonaceous) material such as leather and cooking it in a charcoal furnace might well harden the surface so that it could be sharpened.
The development of early blast furnaces in the 1500s and 1600s allowed iron to be smelted in larger quantities.
A tall chimney-like structure loaded with layers of charcoal and crushed iron ore (and a little limestone) and furnished with a bellows-driven air blast, reduced the ore to free iron which then melted and was tapped off onto a sand floor producing pig iron (so named from the shape of the channels which guided the ingots).
Glassy slag could be tapped off separately and perhaps broken up into crozzle – a crude water-impervious building material.
We know that carbon will dissolve in molten iron and pig iron contains about 4% carbon by weight. Pig iron is very brittle and totally useless for blacksmithing work. The brittleness is partly caused by carbon coming out of solution in the iron crystals as a graphite.
Molten pig iron can be poured into sand/clay moulds to form cast iron objects which are strong in compression but weak in tension.
Much effort went into refining pig iron to reduce its carbon content so that blacksmiths could work it.
Eventually a successful, efficient process was invented by Henry Cort at Fontley in Hampshire(1783 patent).
In 1787 Cort agreed that Richard Crawshay should use the puddling and rolling process at the Cyfarthfa works in Merthyr Tydfil. The managing partner was James Cockshutt of Wortley.
The Bessemer process blew oxygen through molten pig iron to burn out most of the carbon to form steel. It was often easier to burn out all the carbon and then replace a controlled amount to give steel of a given carbon content. however, Henry Bessemer was not an experienced metallurgist and some problems had to be solved. The phosphoric iron ores in Britain gave poor results until the converters were lined with alkaline dolomite which converted the phosphates to basic slag. A problem of excess oxygen occluded in the metal was solved by Robert Mushet by adding a proportion of manganese ore to the melt. Manganese oxide passed out into the slag.
It is interesting to note that David Mushet (Robert’s father) had found that a manganese steel alloy was very hard wearing and was used by Sir Robert Hadfield for railway wheel tyres and heavy duty railway points.
Later (1869) Siemens open hearth steel making began using a hot blast alternating between two hearths.
Carbon will dissolve in molten iron and will make it harder (steel 0.5% C) and more brittle (pig iron 4% C).
The early ironmakers smelted iron from iron ore and charcoal in a small bloomery, producing a spongy porous bloom containing particles of iron, unreacted iron oxide and charcoal and some stony slag. The iron did not actually melt and so carbon was not absorbed. When this bloom was reheated and worked with hammers, the iron was consolidated and the impurities mostly squeezed out.
This ‘wrought’ iron, containing less than 0.1% carbon, is comparatively soft, can be forged by blacksmiths and easily hammer-welded.
From the 16th century, iron could be smelted in the newly developed blast furnaces but at a higher temperature which allowed carbon to dissolve in the molten iron. This pig iron can be used to cast iron objects in a foundry but cannot be forged. It was necessary to burn out the dissolved carbon in a finery forge to make ‘wrought ‘ iron for blacksmiths.
In the 1790s Henry Cort’s more efficient puddling process was introduced at Wortley Low Forge and the wrought iron was also rolled into bars. These bars were used in the local wireworks and in many small nail forges.
The wrought iron still contains about 2% of stony slag which gets rolled within the bars. It is thought that this glassy slag helps as a flux during hammer-welding and gives some resistance to rusting at the surface. Old rolled wrought iron bar usually exhibits slag lines on the surface giving a wood-grain fibrous appearance.
The puddling process works because pure iron has a higher melting point than iron with dissolved carbon and wrought iron can be raked out of the puddle as the carbon content is reduced by the furnace.
Puddling efficiency was greatly improved in 1830s when the reverberatory furnace was lined with iron oxide to supply oxygen to oxidise the carbon in the molten pig iron instead of just depending on air at the surface.