Sir Henry Bessemer is renowned for inventing the Bessemer process, the world's first mass production system for producing high-quality carbon steel. Greater production efficiency led to lower steel prices. Affordable high-quality steel facilitated the construction of countless railways, bridges, buildings and ships that would otherwise have been unviable. It transformed the design, performance and durability of vehicles, munitions and consumer appliances. Understandably then, Bessemer is widely regarded as one of Britain's greatest inventors. We investigate whether his reputation is deserved, then go on a tour of the places he lived and worked.
The Bessemer process
Bessemer's process, in case anyone does not know, was to blow cold air through molten pig iron to separate and remove appropriate amounts of silicon and carbon impurities, thereby leaving carbon steel. It has no external heat source. Somewhat counter-intuitively, the cold air heats rather than cools the pig iron, because it creates exothermic chemical reactions.
The carbon floats away as carbon monoxide. The silicon is converted into silicon dioxide which floats on liquid steel allowing its easy removal. The chemical reaction generates enough heat to be self-sustaining. It can get pretty violent. William Kelly referred to it as 'air-boiling', because the reaction makes the metal roil, as if boiling. Bessemer said it was like a volcano, shooting molten slag up the ceiling in a sheet of white flame.
The process is embodied in a contraption known as a Bessemer Converter, which is an egg-shaped container mounted on a trunnion. It is tipped over to take a charge of molten pig iron, righted for 20 minutes while air is blown in at the bottom, tipped over again to remove the newly separated impurities which float, then tipped over further to empty the steel. The process takes less than 30 minutes to produce 7 tons of steel in a standard 10m device.
The easy part of our investigation is that, notwithstanding some initial difficulty controlling the amount of residual carbon, Bessemer's process worked well. And cheap high-quality steel did have the transformational impact claimed. Bessemer patented his process in October 1855. The first Bessemer Converter went live in 1858. The price of high-quality steel fell from £60/ton in 1855 to less than £10/ton in 1870.
Lower steel prices did indeed make steel viable for a plethora of new purposes. Steel production in Britain grew from 51,000 tons in 1855 to 830,000 tons in 1880 and to 2 million tons by the eve of WWI. Half of the new steel was consumed by railway companies who were thrilled to find that steel rails might last 20 years, whereas their cast-iron and wrought-iron predecessors had to be replaced every 3 to 6 months.
Or should it be the Martien/Kelly process?
An American engineer named William Kelly disputed Bessemer's U.S. patent on the grounds that he had invented the process a year earlier. Kelly reckoned that Bessemer stole his idea, having heard about it from some itinerant foundrymen that he had employed before they went to England. On that basis, Kelly received the patent for the Bessemer process in the United States. It is generally thought, at least in Britain, to be the other way around: that Kelly learned the technique from English foundrymen that had worked for Bessemer. Neither of them were the original inventors: The Chinese had already been blowing cold air through molten pig iron to remove impurities for more than a thousand years.
Another American engineer named Joseph Martien, working at the Ebbw Vale ironworks in Wales, filed a patent application for a forerunner of the Bessemer process just days before Bessemer. The coincidence is more than a little suspicious. It seems likely that one discovered the secret from the other, probably via an itinerant foundryman that worked for both.
No permutation can be discounted. Kelly and Martien were both American and both worked on the East coast. Each could have learned the secret from the other. Kelly and/or Martien and/or Bessemer might have independently devised the idea themselves. Any or all of them might have snitched the technique from itinerant Chinese foundrymen. If one of them was the first in the western world to devise or experiment with the technique, one of their foundrymen could have spilled the beans to either or both of the others.
Bessemer tells his story in his autobiography. He says that he was experimenting with ways to make steel from pig iron ingots using a standard reverberatory furnace (depicted above). The device heats the ingots by the flow of hot air (red line) from a firebox and by the reflection of radiated heat off the parabolic roof. Eventually, the ingots should get hot enough to melt. Bessemer noticed that some ingots beside the cooler walls did not melt but had instead turned to steel on the outside.
"Thus a new direction was given to my thoughts, and after due deliberation I became convinced that if air could be brought into contact with a sufficiently extensive surface of molten crude iron, it would rapidly convert into malleable iron [i.e. low carbon steel]."
Bessemer's account relies on a mini-Bessemer chemical process in the reverberatory furnace. It is credible. If the oxidisation starts at less than the melting temperature of iron, the chemical reaction will create enough extra heat to melt the surface of the ingot. When most of the surface carbon and silicon has oxidised away, the chemical reaction will stop and the ingot will cool back to the ambient temperature of that part of the furnace. The surface will solidify thereby preventing oxygen getting to the impurities inside. If a little carbon was still in the surface when the reaction stopped, it could be mild steel, exactly as Bessemer describes. Hmm.
Bessemer had previously been conducting experiments on glass in a reverbatory furnace. It is plausible that he was looking for new experiments for which he could use this furnace. A technique for making steel in a reverberatory furnace had been introduced about the same time at Low Moor Ironworks. It used a puddling process. We suspect - although he understandably never said so - that his initial plan was to recreate, and then try to improve, the Low Moor process.
The next part of Bessemer's story looks plausible to us. We checked it against other serendipitous discoveries by Goodyear, Roentgen, Becquerel, Fleming, Spencer, de Mestral and others. They all take the form "I was investigating X when I noticed Y" or "I was expecting X but found Y". Bessemer's seems to fit. Moreover, if he knew the likely result in advance - because he had stolen the fully formed technique from Martiens, Kelly or the Chinese, for instance - we think he would have come up with a more heroic story, that he would have prepared more thoroughly and that he would not have bothered with preliminary experiments on reverberatory furnaces.
Bessemer's jump from experiments in a reverbatory furnace to a tilting blast furnace is more suspicious. Static blast furnaces had been around for 300 years in western Europe, so that is not suspicious in itself. But Bessemer, Kelly and Mertiens all seem to have experimented with steel production in tilting blast furnaces at much the same time. Industrial espionage was rife in Victorian times. The Chinese did not participate in international law, so their inventions were freely available in the developed world. On balance, we think that Bessemer, Martien and Kelly were all trying to recreate the Chinese air boiling process, each having separately heard about it, directly or indirectly, from itinerant Chinese foundrymen.
Regardless how Bessemer came to experiment with tilting blast furnaces for the mass production of steel, he stole a march on Kelly and Martien because he had more money. We think he was indeed the first person to successfully scale up the air boiling process into something commercially viable.
Bessemer's greatness and momentousness
Making a great discovery is not necessarily a sign of greatness and it is particularly not a sign of momentousness. As we always say about discoveries, someone else would have devised the exact same discovery eventually. The benefits of any discovery are just the advances that are brought forward by the time it would have taken for someone else to make the same discovery. In the case of the Bessemer process, this is unlikely to have more than a year or two, and might have been no more than a few months if Martien and/or Kelly independently made the same discovery. The brought forward benefits would have been modest.
Bessemer's greatness and momentousness therefore derive from the business he built around his Bessemer process patents. His rivals were ruthless. Intellectual Property theft was rife. Hardly any inventors benefited from the fruits of their inventions. Bessemer was one of three notable exceptions in Britain, the others being Richard Arkwright and James Watt.
Bessemer played his hand well but it has to be said that he was incredibly lucky. Very few inventors are good businessmen and hardly any build successful businesses on their own. He did have partners at Henry Bessemer & Co, all of which were trustworthy relations through marriage, but they were not businessmen either. Bessemer was effectively forced to take the steps that made him successful. It happened like this.
Bessemer wanted to monetise his invention by licensing the Bessemer process to established foundries. They were reluctant to cannibalise their profits by paying for the license. They hoped to wait out the patent expiry. But Bessemer was making enough money from his bronze dust business to construct his own foundry. The threat of getting undercut forced the incumbants' hand. Most were forced to take a Bessemer license, or risk going out of business.
Only none of the licensees could make the Bessemer process work consistently. One problem was that leaving the right amount of carbon proved horribly hit and miss. The most malleable steel has roughly 0.03% carbon. The hardest steel has roughly 1.7%. Not much room for error. A small miscalculation of the original carbon content, a small timing error, or bad luck with impurities, caused the process to create the wrong type of steel or unwanted malleable iron. Bessemer knew this to be a problem, for which he had never found a solution.
Even when Bessemer's licensees got the residual carbon content right, their steel was not as high quality as he had promised. Bessemer worked out that this problem was caused by sulphur and phosporus impurities in their iron ore. Bessemer instructed them to use purer ore, but this made the process unviably expensive.
Robert Forester Mushet devised a solution to both problems. His idea was to oxidise away all carbon impurities, lower the temperature, then add back exactly the amount of carbon needed for the type of steel being produced. He improved on this by using a mineral named spiegeleisen as the source of the added carbon because its manganese content also removed sulphur impurities. Mushet patented his process. Bessemer claimed that Mushet's patent was invalid because the properties of manganese in steel making were well known, although they could not have been well known to anyone else in Britain, or they would already have been using it.
Bessemer spiked Mushet's patent by refusing to give Mushet a Bessemer process license, with the veiled threat that he might revoke the Bessemer process licence from anyone that took out a Mushet license. It was enough to prevent Mushet finding customers, which left him unable to afford the patent renewal. Bessemer acquired it relatively cheaply. William Kelly, meanwhile, still held the U.S. patent for the Bessemer process. Bessemer acquired that cheaply when Kelly got into financial difficulty. Now holding all the aces, virtually every bulk steel manufacturer in the world had to take a Bessemer license. This was the source of his success.
Away from steel, Bessemer successfully filed 119 other patents. Most were duds. There were a few exceptions. His first successful invention was a way of compressing plumbago into pencil lead. Another was a new way of producing oil paint. Both were sold cheaply and made their purchasers rich. The latter was re-purposed in the production of linoleum, which became a huge global business. Bessemer designed the first modern solar furnace, although it was not much use in the days before electricity generation. He invented the system of contra-rotating rollers now used for producing continuous metal strip. He claimed to have invented the centrifugal pump. None of these inventions were adopted during their patent protection. None of them had anything like the commercial impact of the Bessemer converter.
Bessemer's only other commercially successful innovation was for high-volume production of bronze dust. It gives a clue to his approach. His rather ignominious contribution was to reverse engineer and upscale the secret production process that had been used for generations by the only other manufacturer in the western world, a family firm in Germany. He felt no guilt because they had snitched the technique from the Chinese.
Bessemer's paint oil process was a refinement of his bronze dust process, also snitched from the Chinese. James Gwynne said that Bessemer's centrifugal pump was only a minor variation of an invention he had made and patented the previous year. As we conclude above, we suspect that the Bessemer process derived ultimately from the Chinese. It seems to us that Bessemer had effectively created an invention process, based on deconstruction, reverse engineering, refinement and/or upscaling of existing processes or recent inventions.
In his autobiography, Bessemer says that his most valuable skills were inventiveness and tenacious perseverance. Misdirection we fear. In reality, his most valuable skill was understanding how best to use, abuse, avoid and enforce patent laws. He was a bully, who not only enforced his patents but used the threat of legal action to subdue competitors that were probably not infringing his patents.
Bessemer's main practical skill was to apply proven engineering and marketing techniques from one industry to another. He used that skill to refine and improve existing production processes and techniques. He used his patent knowledge and deep pockets to avoid patent litigation, or to buy out rivals cheaply. This might be morally dubious, but it is a valid business model. Others followed. By and large, it is how Edison worked. More recently, it is how Apple have grown into one of the world's most successful businesses. It just isn't inventive or innovative.
In our opinion, Bessemer is no where near the top rank of Britain's inventors. He lived at a time when virtually every device and every manufacturing process could be improved out of all recognition by someone with a bit of spark. Given his wealth, skills and contacts, five commercially successful products is a disappointing return.
Our main interest here is in momentousness, by which we mean lasting benefit. Bessemer, like Richard Arkwright and James Watt, was more momentousness than typical inventors because he developed the Bessemer process into a successful business and made a lot of money out of it. He used that money to benefit society and to help promote Britain's reputation for engineering excellence. He helped to build the British Empire. True, he was lucky, but he avoided many potential pitfalls. At one point he was among the wealthiest and most successful businessmen in a Victorian Britain that was packed with successful businessmen. Despite his shortcomings, we think he was one of Britain's most momentous inventors and mechanical engineers, fully justifying our five medal rating.
Some of our tours take months. Bessemer's took two days. He was born in the tiny village of Charlton on the outskirts of Hitchin, then moved to London as a teenager and seldom left.
In a rather embarrassing inditement of his product, the 1/4 inch sheet steel sign that marks the northern end of Charlton village has cracked in two. There are no obvious signs of vandalism. Perhaps the manufacturer is making the point that steel is no longer made in Bessemer converters. As the sign says, Henry Bessemer was born here in 1813.
Charlton House, where he was born, is still there. We used to say that it was opposite 'The Windmill' pub, but the pub has closed. Don't rely on satnavs or phone maps either. They all lead to another Charlton House. The best way to find Bessemer's home now is to park in what used to be the pub car park beside the footpath to the Hicca Way. Here is the MB2 doing just that, with the former pub back left and Charlton House back right. If the car park is developed, look for the footpath sign pointing to Hitchin Hill.
The Bessemers must have been pretty wealthy. Henry explains that the house was on a small country estate. Assuming it was within the 1870 field boundaries, it stretched back some 200m east and 300m south. The house is large and sprawling, looking as if it has been extended many times. It is privately owned now. We peeked in through the window, only to find the owners sitting in their parlour peeking out. Oops. Still, they didn't seem to mind us taking a picture of the blue plaque beside their window.
Bessemer talks in his autobiography about his childhood delights and inspirations. Daguerreotype photographs feature prominently. We forget how magical it must have been to see a photograph for the first time. He says how he was spellbound by the scenes in 'Arabian Nights'. He mentions his school, and picking up yellow clay beside the road with which he made models, and two sources of inspiration. One was his father's type foundry. The other a nearby watermill. He says that the type foundry was on his father's estate. No outbuildings are visible now. It must have gone. As far as we know, no one has ever found his school or the watermill. We went in search.
Bessemer talks at length about the watermill: "I was very fond of machinery, and of watching it in motion ; and if ever I was absent from meals, I could probably have been found at the flour mill at the other end of the village, where I passed many hours, gazing with pleasure upon the broad sheet of water falling into the ever-receding buckets of the great overshot water-wheel." The River Hiz passes through the village. We walked up and down looking for the remains of a water mill. Nothing obvious. He says that the watermill was at the other end of the village. Charlton House is just about in the middle today. The 1880 Ordnance Survey map below only shows a handful of houses. We gather that the mill was probably at least 200m from Charlton House.
Charlton House is labelled B on the map above. Bessemer says that the wheel has an overshoot of water. It must be at a waterfall. There could not have been a waterfall at the southern end of the village because The Hiz only rises a few hundred metres south of the village. The only waterfall labelled on the map is at W. We went to look. There is an old looking brick dam - picture below - exactly where we would expect to find the mill. There are bricks in the ground, as if there had once been a building. We think it must have been the mill's location. Admittedly, there is no waterfall now, or indeed any significant water drop. It was obviously there in 1880. We guess that it must have silted up, which probably put paid to the mill.
Bessemer gives no clues about his school. Some have assumed that he must have attended William Wilshere's school in Hitchin, now the site of the British Schools Museum. It opened in 1810, so it is possible. But Wilshere opened the school specifically for children of the poor and specifically to help them to read and write. Henry Bessemer came from a wealthy family. We know he was literate from a young age because he read Arabian Nights. There is only one other school on the 1880 Ordnance Survey map (S) that is within walking distance. It is on the A602, 1500m from Bessemer's house (B). We went to check it out.
There is an old looking, but heavily modernised, building on the corner and two cottages at the spot labelled 'School' on the map. We think the one on the corner (below) looks more like an erstwhile school.
When Henry Bessemer left school, presumably at 14, his father gave him a workshop and machine tools on the estate, so that he could teach himself to become an engineer. There are no outbuildings now, so we guess it has gone.
Bessemer's father decided to move his family to London for business reasons. They arrived on 4th March, 1830, when Henry Bessemer was 17. We could find no evidence for where they lived.
In 1833 Bessemer moved into 15 Northampton Gardens, Islington, as a bachelor. He was married in 1837. This was their family home. His house has been replaced by the University of London's Talt Building. The foundations of Bessemer's house were found during the construction. A blue plaque to Bessemer was unveiled in 2017.
At some point before September 1841, the Bessemers moved into Baxter House at 171 Old St Pancras Road. In the grounds he established the St Pancras Ironworks. They made a wide range of iron products, some of which are listed in the 1868 advert above. It was here that Bessemer devised the Bessemer process and where he conducted his experiments. It was here that he nearly set fire to the roof when his first Bessemer Converter spewed molten slag like a volcano.
There is no trace of Baxter House now. One advert says that it was opposite St Pancras Old Church. The church is now on Pancras Road, so we guess it dropped the 'Old St' prefix during the intervening 150 years. The building opposite is a block of flats named 'The Chenies'. We guess this was the location of Baxter House, although we could find no sign that Bessemer was ever there.
We went looking for surviving St Pancras Ironworks products. Actually, we went looking specifically for St Pancras Ironworks drain covers, manhole covers and pavement lights, due to a slightly weird obsession we have about Wood & Stannard, a foundry that operated from land adjacent to our back garden. We came across these St Pancras Ironworks pavement lights over a cellar in Broad Street, Hereford. They do not hold a candle to those made by rival Hayward Brothers, but they are far rarer.
In 1858, Bessemer moved to Sheffield where, the following year, he opened the Bessemer Steel Works in Carlisle Street. The factory was opposite Bessemer House (below), now at 59 East Carlisle Street. The current Bessemer House dates to 1901, long after Bessemer sold his shares and moved back to London. Never the less, it carries a blue plaque explaining that Bessemer's factory was opposite. When we were last there, it had become dilapidated, with the blue plaque hidden behind a 'For Sale' sign, as if they were ashamed of it. Pests. The factory over the road continued making steel until the 1970s. It has been replaced by a modern industrial park (that does not seem to manufacture anything).
By 1863, Bessemer was a very wealthy man. He bought a 40 acre estate in Denmark Hill from Dulwich College. Architect Charles Barry, who had previously designed the Palace of Westminster, was commissioned to refurbish and extend the main house, which was renamed Bessemer House. A few years later Bessemer Grange was built in the grounds for his daughter's family. Both buildings were demolished after WWII. The land was used for council housing. Bessemer House stood at the exact location of the Basingdon Way roundabout. We could find no indication of its famous history.
While we were in Sheffield, we went to Kelham Island to look at Britain's last surviving complete tilting Bessemer Converter. Very impressive it is too.
Bessemer left his possessions to the London Science Museum. When we were children, we (think we) can remember seeing a complete display hall of Bessemer's possessions, as well as the prototype Bessemer Converter from the Barrow Haematite Steel Company (above). Only the prototype is left on display. It seems that Bessemer's standing has fallen in the last 50 years. Not in our eyes. We think he was at least Watt's equal.
Bessemer died in 1898 at his home in Denmark Hill. He is buried in West Norwood Cemetery in a relatively modest plot; well, modest compared to his contemporaries and resting place neighbours Sir Henry Tate and Sir Henry Doulton.