WEALDEN HISTORY OF EARLY IRON MAKING INDUSTRY THE WEALD

It is hard to picture the former iron industry in today's countryside of small fields, woodlands and steep, narrow, gill valleys. But in this landscape exist all the necessary raw materials that allowed iron to be smelted for over 2,000 years. There were no planning laws in those days and no planning officers to put a spanner in the works.

The Wealden geology of sands and clays yielded the iron ore, as well as the stone and brick to build the furnaces; the woodland provided the charcoal fuel; and the numerous small streams and valleys ensured water power for the bellows and hammers of the forges and furnaces.

For two periods - in the first two centuries of the Roman occupation, and during Tudor and early-Stuart times - the Weald was the main iron-producing region in Britain. Julius Caesar first drew attention to iron being produced in the coastal parts of Britain. Archaeologists have found evidence of iron working from the late Iron Age at sites near Crowhurst and Sedlescombe in the south-eastern High Weald.

When the Romans invaded in AD 43, they found a well-established local tradition of iron making, using small, clay bloomery furnaces. With growing markets generated by the building of towns, villas and farms, the Romans encouraged this native industry. Sites from the period have been found all over the eastern part of the High Weald.

The 'Classis Britannica', or British Fleet, an imperial supply organization as well as a navy, took a strategic role in iron production. It managed several large smelting sites in the area around Hastings, such as one at Beauport Park, near Battle. This may have produced as much as 30,000 tonnes of iron over 130 years, and a substantial bathhouse was built there for some of the workforce.

We know little about iron making in the Weald in Saxon times, and the industry receives only one mention in the Domesday Book for Sussex, at a location near East Grinstead.

However, during the Middle Ages iron production grew steadily, concentrated more in the northern part of the Weald. Accounts have survived from 14th-century works at Tudeley in Kent, and excavations have confirmed medieval references to iron makers in Crawley and near Horsham. Towards the end of the period, water-power began to be used for forging iron, heralding the introduction, in 1496, of the blast furnace.

Introduced from northern France, and operated by skilled, immigrant workers, the blast furnace was a much larger, and more permanent structure than the bloomery; and instead of a few kilos of iron being made, daily output was nearer a tonne.

More ore and charcoal were required, and the need to operate the bellows by waterpower, instead of by hand, meant that ponds had to be created to store the water. In addition, the higher temperatures in the furnace meant that a different type of iron was being produced. A second process ˜ the forge, with its own pond and supply of charcoal - was needed to refine the iron.

By the mid-16th century there were 50 furnaces and forges, and that number had doubled 25 years later. All over the Weald, the iron industry was having an effect, with large numbers of people employed in digging ore, cutting wood and transporting both raw materials and products.

Most furnaces made "sows", or lengths, of iron for refining, but from the 1540s a small number began to make cast-iron cannon, a product that grew to be a profitable, and sometimes illegal, export. Improvements in house design led to the building of chimneys, and the need for iron fire-backs to protect the brickwork. Many Wealden farmhouses contain examples of these decorative and functional plates. In several Wealden churches there are examples of iron memorials. The oldest is in Burwash, dating from the 1530s, while Wadhurst church has over 30, dating from the early-17th to the late-18th centuries.

As competition from imported iron increased, the Wealden ironmasters began to concentrate increasingly on gun founding, and examples can be found all over the world, wherever Britain fought or traded. Eventually, the onset of the Industrial Revolution took heavy industry north to the coalfields, and the last furnace in the Weald, at Ashburnham, closed in 1813.

So, where are the remains of iron production? Building stone was too valuable in the Weald to be left unused, so the works were dismantled, and the woods grew back over the former sites. Only the tell-tale waste, called slag, from the smelting process, and some of the hammer and furnace ponds are left to remind us of a once-great Wealden industry.

The Wealden Iron Research Group was founded in 1968, by Henry Cleere and David Crossley, to update the pioneering work of Ernest Straker whose monograph, Wealden Iron, had been published in 1931. Starting off as a federation of local groups, it coalesced in the early 1970s under the leadership of the late Fred Tebbutt, a distinguished amateur archæologist, who became its first Chairman. Much of the early work of the group centred around the update of Straker's work, but it was soon realised that much lay undiscovered.

A survey of an area of the central Weald revealed a dense concentration of early iron smelting sites, or bloomeries, and this has acted as an incentive for future work. Experiments in making iron were started, and the group won the BBC's 'Chronicle' Award for Archæology in 1981. The publication, in 1985, of The Iron Industry of the Weald, by Cleere and Crossley, was the fulfilment of the group's initial aim, but many questions remained unanswered, and the group continues an active programme of research.

Text by Jeremy Hodgkinson of the Wealden Iron Research Group. Illustrations by Mike Codd, West Sussex County Council

The Wealden Iron Research Group (WIRG) website provides information on a wide range of the groups activities together with a general introduction to iron production in the Weald. The Weald has been identified as a key iron-producing region for the British Isles and it contains nearly 800 identified iron-making sites dating from the pre-Roman period up to the 19th century. The WIRG, established in 1968, has carried out a wide range of activities on the Weald. The website contains information on the group's research aims, meetings, excavations and other fieldwork together with details on how to become a member.

One of the key group activities is conducting a programme of experiments intended to replicate the bloomery smelting process used in the Weald during the Roman occupation. The website contains a highly detailed and well-illustrated section on these experiments together with details of the groups publications and annual bulletin of research. Aside from providing details on the WIRG itself, the website also contains a brief history of the iron industry in the weald from prehistory to nineteenth century.

The WIRG website is simply and consistently set out using frames and is via navigation a standardised side menu. The illustrations are clear, are captioned and linked to larger versions. The site also contains a number of links to related websites.

Membership of WIRG is open to individuals, families and institutions, students and those of pensionable age, and includes a bi-annual Newsletter and the Wealden Iron Bulletin. Activities include a Field Group, which organises a programme of fieldwork in the autumn and winter, bi-annual meetings with visiting speakers, small-scale excavations, and a variety of other projects undertaken by its members. WIRG administers the Tebbutt Research Fund which awards small grants towards research into the Wealden iron industry.

Individual	£7.00	(Optional) OAP	£6.00
Family	£10.00	Student	£3.00
Institution	£10.00

Download an application form in PDF format by clicking HERE. Complete and post it to The Hon. Secretary WIRG, 2 West Street Farm Cottages, Maynards Green, HEATHFIELD, Sussex, TN21 0DG, with your cheque made payable (in sterling) to Wealden Iron Research Group. If you pay tax, you may wish to complete a Gift Aid form to help the Group reclaim your tax.

According to history, cast iron was first produced succesfully by the Chinese 800-700 B.C.(1) Even though iron was produced many centuries before, it apparently could not be cast because the furnaces were incapable of producing the required temperatures. However, the Chinese, as pointed out by Simpson(1), "had developed melting equipment capable of producing greater draft than hitherto had been possible".

Another reason for the succes of the Chinese in being able to produce cast iron, as mentioned by Simpson 1), was that they reduced iron oxide by heating in the presence of an exess amount of carbon, apparently in the form of charcoal. This procedure resulted in a soft, pure iron with a melting point of 1530⁰C (2786⁰F). The iron was then carburized, reducing its melting point to about 1170⁰C (2138⁰F) thereby making it easier to melt in their high draft furnaces.

Additional references indicate that the Chinese used some high phosphorus coal along with high phosphorus iron ore as charge materials (1,2). These materials, by lowering melting temperatures, reduced the amount of blast needed to melt the iron.

From these early beginnings, the interest in cast iron continued to grow. Many applications for this "new cast metal" were made possible by improvements in melting equipment and techniques as well as great progress in the art of molding. Several engineering applications employed cast iron from time to time, including iron chain suspension bridges, the first of which were constructed by the Chines in 56 A.D. (2) However, iron was not generally cast in what might be called "substantial quantities" in Europe untill the fourteenth century A.D. (1).

The Development of the Blast Furnace

Although the early furnaces for melting iron were probably a very crude form of blast furnace, the development of the Catalan forge in Spain in the eight century A.D. was most likely the forerunner of the blast furnace (1). In the Catalan forge, iron ore and charcoal were charged vertically in the top, resulting in a "loupe" or ball of iron which was "hooked out and hammered into a bloom".(1) By modifying this simple furnace, the Swiss made an improved melting unit which was vertical, above the ground, and charged with alternate layers of ore and charcoal. The next improvements leading to the development of the true blast furnace were made by German and Swedish craftsmen in about 1000 A.D.(1).

During the next 300 years these early blast furnaces were improved and made larger. In 1325 A.D., water driven bellows, which delivered sufficient draft to make hot molten metal directly from the blast furnace, were introduced. Development of these bellows led to the production of substantial amounts of pig iron in Europe by 1400 A.D.(1) and marked the beginning of modern iron foundry practice.

Early Improvements in the Quality of Cast Iron through the Use of Fluxes.

When the famous Spanish Armada attempted to invade England in the sixteenth century, an important step in improving the quality of cast iron was discovered(3). In his historical book "Full Fathom Five" about an expedition organized to recover the buried wrecks of the "invincible" Armada off the coast of England, Colin Martin (3) indicates that the cast iron cannons, shot and anchors of the Spanish fleet were inferior to those used by the British. Martin cites this as an important reason why the British were able to defeat the Spanish and thus prevent the conquest of England.

Even though the Spaniards possessed a good quality hematite ore, they produced poor quality iron guns, anchors and shot due to their lack of knowledge of the behavior of cast iron.

The historical evidence indicates that in the smelting and fluxing of the ore, the refining after smelting, and in the molding and casting techniques, the Spanish were years behind the English. Practically all of their iron castings contained slag. The inferior quality and brittle nature of the shot, coupled with the explosive force of the potent "black powder" caused the shot to crack and partially disintegrate prior to hitting its target. Similarly, many of the cast iron guns exploded during the firing, indicating poor strength and poor ability to absorb shock and vibration. For the same reasons Spanish anchors broke under the stresses of heavy seas and were the cause of many shipwrecks.

What were the reasons for the superiority of the English cast iron, which was the envy of their continental competitors? Martin points out that there was no magic formula. All of the practices of the 16th century founders of the Weald of Sussex, the seat of the English iron industry at that time, are known to us. The practice of weathering the ore for several months washed out many impurities. The ore was then crushed and washed again. Fossilized gray shells inherent in the ore resulted in a high degree of fluxing during smelting, allowing the removal of surface dross and other impurities.

The advanced knowledge of the British founders during this period is demonstrated by the fact that the gun and shot molds were dried and warmed prior to the casting of the iron. The metal, in turn, was poured each time at as even a temperature as possible. This practice minimized what we refer to today as "undercooling" and established close to equilibrium conditions of solidification.

After pouring, the castings were allowed to cool gradually in the molds to room temperature. This procedure minimized the stresses in the finished castings. The Spanish, on the other hand, as pointed out by Martin, cooled the castings as quick as possible in order to expedite production. Their practice often involved water quenching the castings, which contributed to stresses and cracking.

For several years after the defeat of the Spanish Armada, iron founders on the continent attempted to determine the reasons for the better quality of the British castings. In 1619, a Dutchman, Jan Andries Moerbeck, proved that he was on to something new and revolutionary in the art of iron founding, by applying for and obtaining a twelve year patent involving the use of iron ore from the Weald of Sussex. By comparing the English ore having build-in flux, with their flux free, but otherwise good quality hematite ore, the Dutch developed the use of limestone for fluxing. This new technique spread rapidly across the continent to Germany, France and, eventually, Spain, and should be credited as a major contribution in the development of engineering cast irons.

Refinements in the Process of Making cast Iron

The next significant development, credited to an English iron-founder named Darby in 1730, was the discovery and production of coke which lowered the cost of producing cast iron. This development encouraged experiment for better quality cast iron with improved mechanical properties. As a result, the French founders tried remelting pig iron in separate, smaller furnaces. This type of refining resulted in more uniform iron with respect to chemistry and was another big step toward the development of engineering grade cast iron. Untill this time, apparently most iron castings were poured from iron directly from the blast furnace.

The improved quality iron produced by remelting pig iron in separate furnaces made it possible for James Watt to build the first steam engine in 1765. Watt's steam engine, in turn, was used to provide the air blast for operating the first cupola build in 1794 by John Wilkinson (1). The controlled air blast plus the higher melting temperatures in the cupola further improved the quality of the cast iron. As a result, designers, engineers, builders and others became more interested in cast iron as an engineering material.

Applications for the steam engine in such fields as land and sea transportation, agricultural equipment and, later, electrical poweer generation, created a demand for large quantities of high quality gray cast iron. As this demand grew, so did the need for higher strength and better quality iron requiring more efficient melting equipment, improved charge materials, and closer control of the melting operations.

The Early Use of Ferrosilicon in Cast iron

About 1810, Bergelius, a Swedish chemist, and, Stromeyer, a German physicist, operating independently, produced ferrosilicon (1). A mixture of silica, carbon and iron fillings was melted in a sealed crucible. Stromeyer produced several grades of ferrosilicon by this method.

Although there appears to be no record as to how the ferrosilicon was used, it was probably added to the melting furnace. Most likely the iron founders became interested in a source of silicon because of the differences in silicon content in the various pig irons produced by the different furnaces due to varying silica content in the iron ores used. The advantages of higher silicon in making softer and less brittle irons were obvious. By adding silicon to the furnaces along with charge materials consisting of scrap and pig iron, the foundrymen were able to make consistently good quality cast iron. They soon learned that it was advantageous to have the silicon low in thick section castings and high in thin section. It is not known that ferrosilicon was added to the ladles in the early to middle 19th century.

In 1885, Turner (4) ran a number of experiments in which ferrosilicon was added to white iron to produce high quality gray iron castings. It is reasonable to assume that the ferrosilicon was added to the iron in the ladle. If so, this would be an indication that some of the early investigators recognized the chill reducing potential of adding ferrosilicon to the ladle.

In 1920, G.Schury (5) discussed the use of ferrosilicon briquettes in the cupola. A discusser of the paper indicated that he had added ferrosilicon to molten iron as early as 1890 for improving cast iron properties.

The knowledge of silicon control would trigger another series of improvements on cast iron structures and mechanical properties, a process that in fact is continuing up till the present day.