PUDDLING AFTER HENRY CORT
All the iron for ships, bridges, railway rails, tyres and axles from the Workshop of the World and which made possible the industrial revolution, was manhandled at the end of long bars and poles of various kinds in great glowing balls of metal weighing about a hundredweight a piece.
From W.W. Jenkins, Death of the Puddler.
The most reliable evidence about the spread of the puddling process is that collected by Charles Hyde.
He reckons that only four works are puddling when Cort's business collapses in 1789.
There is Cort's plant at Fontley, which is puddling successfully using old cast iron recovered from the Navy.
At Rotherhithe, Cyfarthfa and Penydarren they are trying to puddle coke-smelted pig.
Rotherhithe gives up shortly after the Cort collapse. While the other two establishments work to improve the process, two more take it up.
First is James Cockshutt's family base at Wortley near Sheffield. Hyde says they install their puddling furnace in 1790.
Doubtless they are following James's advice. He returns to Wortley when Crawshay breaks with him in 1792.
The other early puddlers are at Pentyrch, north of Cardiff, where a furnace is installed at the end of 1792.
Hyde's story that Wilsontown starts puddling in 1789 is refuted by other evidence.
All these ironmasters face a problem not encountered by Cort, who has been working with iron originally smelted using charcoal. But their starting material (“grey iron”) is coke-smelted, and contains impurities (later found to be rich in silicon) that accumulate in the puddling furnace, causing the quality of its output to deteriorate.
Richard Crawshay’s Letterbook gives an indication of some of the attempts to improve the process at Cyfarthfa. It seems that Samuel Homfray is bent on similar work at Penydarren. Although Crawshay and Homfray are frequently at loggerheads, it looks likely that any improvement made by one will be quickly picked up by the other, so it is difficult to assign credit for the adaptations that emerge.
Those adopted at Penydarren are given in a document published in 1806, and submitted as part of Homfray’s evidence to the 1811-2 inquiry. The procedure described differs in two important respects from that patented by Cort.
The first difference is a preliminary refining stage (similar to the first stage of the Wright & Jesson process), when siliceous impurities are removed. The product is known as white iron or finer’s metal.
The other difference is further purification of the shingled product by rolling it flat, then cutting it into slices which are piled, re-heated and re-rolled. This stage can be repeated once to maximise purity, but further repetition has negligible effect. Final rolling is done with the shaping rollers introduced by Cort.
Though the origin of these adaptations cannot be certain, researcher Paul Luter has uncovered fresh evidence suggesting that at least one is the work of Homfray’s employee Joseph Firmstone, who later sets up his own works using the process in the West Midlands.
By 1798 the new process is well established. with both John Wlkinson and William Reynolds introducing it at their works (documents recently unearthed show Reynolds sending iron bars to Samuel Jellicoe in 1796). Dowlais takes it up in 1801.
It is disputable how much of the increase in wrought iron production over this period is due to puddling. But it is deemed significant enough for ironmasters to raise a subscription for Cort’s widow in 1800.
The coming of the railway brings a big boost to wrought iron production. Cyfarthfa, Penydarren and Dowlais all benefit.
Attached to the mill were eighteen balling furnaces, and twenty puddling furnaces, and in March, 1847, these turned out no less than 6,144 tons of rails.
From Wilkins, The History of Merthyr Tydfil p273, describing additions to the Cyfarthfa works in 1846.
Meanwhile Joseph Hall comes up with a significant improvement at his Tipton works.
Called wet puddling or pig boiling, it adds a new ingredient to the mixture in the furnace: iron coated with iron oxide, which is more effective than air in removing the carbon impurity and does not require the iron to be refined first.
By the middle of the century the Hall process has been taken up by most works. It is well covered in descriptions of puddling after this period.
The largest ironworks had batteries of blast-furnaces – up to 18 at Dowlais, where 6000 workpeople were employed, in 1842 – and dozens of puddling furnaces.
From Crouzet, The First Industrialists: The problem of origins (Cambridge 1985).
In 1865 there were 2,116 puddling furnaces in existence in the Black Country, with a potential output of 20,000 tons of finished iron a week.
From Gale, The Black Country Iron Industry, p104 (London 1966).
In the second half of the eighteenth century the forward march of puddling is thrown into reverse by new processes for steelmaking.
These not only produce a more useful and versatile output. They rely far less on the skills of workmen.
Nevertheless puddling continues on a small scale until the 1970s, and a relic of the last puddling works can be seen at the Blists Hill site near Ironbridge.
A puddler would normally be expected to work six 12-hour shifts a week, during each of which he would be expected to puddle six heats of 3¾ cwt of iron. Puddlers were always in demand, and more than most skilled workers they tended to migrate in search of higher wages. It was a particularly strenuous occupation and the puddler's working life was normally reckoned to be over by the time he reached 40.
From Barrie Trinder, The Industrial Revolution in Shropshire, p167 (3rd Edition, Phillimore 2000.)