An Encyclopedia of the History of Technology part 11 ppsx

PART ONE: MATERIALS 82 Haug & Co, who found the business so profitable that they began to consider the prospect of further co-operation with the English Crown. A preliminary survey of Britain’s mineral resources by Daniel Hochstetter in 1563 revealed favourable prospects, and in 1564 substantial deposits of silver-bearing copper ore were found at Keswick in Cumbria. In September 1564 the initial Patent for working copper ores in Britain was granted jointly to Daniel Hochstetter and Thomas Thurland, Master of the Savoy. The organization thus established, formally incorporated in 1568 as the Company of Mines Royal, was the first joint stock company to be set up in England for the manufacture of a commodity (copper) rather than for trading purposes only. From the legal controversies stimulated by the grant of a Royal monopoly for a ‘new method of manufacture’, patent law as we now know it emerged, evolved and refined itself. A sister metallurgical enterprise, established in 1565, was the Society of Mineral and Battery Works. It was a specialist organization, concerned with the manufacture of brass and wire, and owed its existence largely to the enterprise of Sir William Humfrey, Assay Master of the Mint. Humfrey’s partner in this venture, Christopher Schutz, an expert in brass manufacture, was the manager of the calamine mining company of St Annenberg, Saxony. ‘Battery’ was the name originally applied to all sheet metal utensils which had been formed into the shape required by beating with a hammer. By the eighteenth century the term applied specifically to beaten hollow ware of brass or copper. Before Humfrey, who was one of the original shareholders in the Mines Royal Company, applied to Lord Cecil for the privilege of introducing ‘battery works’ into England all the brass required was imported from Europe. A further object of the Mineral and Battery works was to introduce improved methods of wire drawing into England, where the wool trade was then rapidly expanding and large quantities of fine brass and iron wire, needed for the manufacture of wool carding equipment, were imported from the Continent. The Society’s Patents, granted in September 1565, gave Schutz and Humfrey the sole rights to mine calamine and to make brass in England. They were also authorized to work mines and minerals in any of the English counties not already under the jurisdiction of the Mines Royal Company. By June 1566 calamine deposits were discovered at Worle Hill in Somerset, at the western end of the Mendips on land belonging to Sir Henry Wallop. Zinc ore from this deposit contained less lead and was superior in quality and yield to that which was currently imported from Aachen. A brass manufacturing site was sought within easy reach of the Mendip hills. The partners eventually erected their manufacturing plant along the Angiddy Brook at Tintern, where lead and copper working had been carried out on a small scale since mediaeval times. Schultz estimated initially that his works would produce 4ocwt (2032kg) of iron wire and 20cwt (1016kg) of brass wire per week. This output was never NON-FERROUS METALS 83 achieved, and not until the end of 1567 was any brass at all produced at Tintern. Although of the right colour, indicating that it contained the appropriate amount of zinc, it lacked ductility and could not be drawn into wire. An innovation introduced by Schultz had been the use of pit coal rather than charcoal as fuel for the cementation furnaces, and it has been suggested that the sulphurous fumes thus introduced embrittled the brass as they did iron. In 1569, Humfrey and Schultz gave up their manufacturing endeavours and leased the Tintern works to a man experienced in drawing iron wire. Brass manufacture was in fact completely ignored until 1582 when a group of merchants headed by Sir Richard Martyn bought the rights to mine calamine and make brass for the sum of £50 per annum. The factory they set up at Isleworth, west of London, made brass of excellent quality for a number of years under the managership of a London goldsmith, John Brode. The manufacturing operation became very profitable, and when Brode refused to provide the Society with details of his manufacturing processes, they revoked his licence and drove him into bankruptcy. In 1605, Brode appealed against the decisions of the Society to the House of Lords, claiming that he was ‘the first here in England that co-mixed copper and calamine and brought it to perfection to abide the hammer and be beaten into plates, kettles and pans by hammers driven by water’. This was probably perfectly true. After this failure brass sheet and battery ware was imported from Europe so cheaply that few British brass-making enterprises managed to survive. Since the death of Daniel Hochstetter in 1581 the mining activities of the Mines Royal Company at Keswick had steadily declined. After the Civil War the industry declined very rapidly indeed, since Parliament refused either to reduce the duty on imported copper or to protect English manufacturers against the importation of cheap imported brassware. After 1650 hundreds of tonnes of high grade zinc ore were shipped to the Meuse valley and other European brass-making centres to be turned into brassware, subsequently to be sold in English markets at prices well below that of the domestic product. When the Society of Mineral and Battery Works became aware of the extent and profitability of this illicit commerce they did not attempt to restrict it, finding it more expedient to impose royalties, of the order of five shillings on each ton of the ore exported. By the 1680s it had become very evident that the privileges granted to the Mines Royal Company and to the Society of Mineral and Battery Works had been exercised in a repressive manner to the detriment of the non-ferrous industry. The Crown monopoly on metallurgical mining rights was finally abolished in 1689 when the Mines Royal Act was passed. Further legislation passed in 1693 enabled manufacturers to participate freely in metallurgical activities. The British non-ferrous metal industry began to revive in the 1670s, when development work by Sir Clement Clarke at his lead works at Stockley Vale in Bristol led to the use of coal-fired reverberatory furnaces firstly for refining PART ONE: MATERIALS 84 lead, and then in 1687 to the refining of copper. John Carter, a protégé of Clarke, subsequently went into partnership with a group of London merchants headed by William Dockwra to establish in 1692 the Copper Works of Upper Redbrook, north of Tintern on the River Wye, where deposits of copper ore had recently been discovered. Dockwra had in 1691 become the proprietor of a brass works at Esher in Surrey which had initially been set up in 1649 by Jacob Mummer, a German immigrant. At Esher, brass made by the cementation process was cast into stone moulds to produce flat ingots weighing seventy punds. These were then rolled to sheet, slit, drawn to wire and finally made into pins. The copper for the Easher brass works came from Upper Redbrook, then being profitably managed by John Carter. A rival copper refinery, the English Copper Company, was established soon afterwards at Lower Redbrook, only a short distance downstream. In its early days, copper refining operations at Lower Redbrook were controlled by Gabriel Wayne, who, like John Carter, had formerly been employed by Sir Clement Clarke. Wayne, however, soon perceived the limited opportunities for expansion along the River Wye, and in 1696 he set up a new copper refinery at Conham, on the banks of the River Avon two miles to the east of Bristol, where the water was still navigable. His business associate in this enterprise was the merchant Abraham Elton. The improved reverberatory furnaces built at Conham owed much to the earlier Clarke developments and to the practical lessons learned at Lower Redbrook. The sulphide copper ores used at Conham were shipped directly ip the Avon from Cornwall and also from North Molton in Devon. After the ores had been roasted at Conham they were melted with lime in a reverberatory furnance to remove silicious impurities. The iron and sulphur remaining in the purified matte thus attained was then gradually removed by reverberatory melting under oxidizing conditions until crude copper in metallic form began to separate from the melt. At that time Bristol was a very logical centre for metallurgical activity, since it also offered a port from which metal products could be exported to all parts of the world, and locally mined coal was available at prices very much lower than eleswhere in the country. The decision to produce brass at Bristol was made in 1700 by Abraham Darby, Edward Lloyd and several other businessmen who were all Quakers of Bristol. Copper was being locally produced on a large scale by three competing refineries, and William Dockwras’s works at Esher was the only brass-making establishment in England worthy of note. Darby was a manufacturer of malt mills, while Edward Lloyd was a cidermaker, and both these activities involved the extensive use of brass fittings and components. Around 1703, it appears, Darby went to Holland, hired some Dutch or Low Country workers and set up the Brass Works at Baptist Mills. This was situated on the River Frome about 2.5km north-east of the point where this NON-FERROUS METALS 85 tributary emerges into the Avon. Darby’s immigrant workers seem to have been skilled in casting large thin slabs of brass into flat granite moulds and in the manufacture of hollow ware and other brass utensils by standard battery procedures. In the early days at Bristol the ingots were beaten into sheet by hammering and in this respect the activities at Baptist Mills were technically behind those at Esher where brass had been rolled into sheet for a considerable time. The Bristol enterprise flourished, however, and by 1708 an additional mill had been set up on the River Avon at Keynsham. In 1707, Darby had begun to appreciate the potentialities of cast iron. He withdrew from the brass company in 1708 and acquired an established blast furnace at Coalbrookdale, where in 1709 he demonstrated for the first time, the feasibility of making iron of high quality by using coke rather than charcoal as fuel for the blast furnace (see p. 153ff). The indications are, therefore, that Darby was the man responsible for the use of coke rather than charcoal in the brass works at Baptist Mills, to avoid sulphurous contamination of the metal from raw coal, and that he introduced the practice of turning the coal into coke by roasting it in the brass furnace itself during the preliminary stages of brass making. Between 1710 and 1712 over 400 cartloads of coal per week were used by the Bristol Brass Works. In September 1709, as the Company for Brass and Battery Work at Bristol, they combined with their former competitors, the proprietors of the Brass Wire Works at Esher, to form the Societies of Bristol and Esher for making Brass, Battery and Brass Wire. Compared to the Bristol establishment, the works at Esher were small, and here the production of wire was concentrated. Brass sheet and battery ware were produced at Bristol. By 1712, Baptist Mills were producing 255 tonnes of brass a year, well in excess of the 210 tonnes then being imported from Europe. Between 410 tonnes and 540 tonnes per year of copper were then being produced in Bristol by two large copper refineries, both situated on the River Avon. The site at Crew’s Hole, half a mile downstream from the Conham works, had been established by the Bristol Brass Company to ensure their own requirements of copper which increased greatly after their amalgamation with Esher. In the early 1720s, Henric Kahlmeter of the Swedish Board of Mines visited England and reported that the two copper refineries at Bristol and those at Upper and Lower Redbrook were the ‘most considerable’ of those he had seen. By that time the four companies were working as a loose form of trade association to run a group of copper mines in Cornwall and Devon. By working together and refusing to buy copper ore until prices fell the group was able to obtain its supplies from primary producers at very low terms. The brass works at Bristol were then being managed by Nehemiah Champion, a man of considerable technical ability. In 1723 he applied for and obtained Patent No. 454 which was concerned with the preparation of copper used for the manufacture of brass by the calamine process. PART ONE: MATERIALS 86 Champion’s leap forward was to use granulated copper rather than broken fragments. By this approach, which greatly improved the surface-to-volume ratio of the copper, the uptake of zinc during cementation increased from 28 to 33 per cent, approaching the level which is now known to be the theoretical maximum possible by cementation. Since copper was the most expensive component of the alloy, Champion’s approach gave him an important commercial advantage over his competitors, and helped to ensure the prosperity and growth of his works. The calamine brass process The brass cementation process used at Baptist Mills did not differ significantly in principle from that used by the Romans. Fairly comprehensive details of the brass-making processes used during the sixteenth century were given in 1574 by Lazarus Ercker, a native of Annaberg in the Saxon Erzgebirge, and Chief Superintendent of Mines in the Holy Roman Empire. The cementation process he describes differs from that of Theophilus and Pliny in that alum and salt were added to the copper/ charcoal/calamine mixture charged into the crucible. After smelting in eight small pots, the brass was transferred to a large crucible and cast into ingot moulds of large flat ‘Britannish Stone’. It is interesting to recall that small quantities of salt were found in the zinc retorts of Zarwar (see p. 77). The Swedish brass-making techniques described by Swedenborg in 1734 were virtually identical to those outlined 160 years previously by Ercker, with the exception that neither salt nor alum were added to the charge. The copper and calamine were still melted in eight small crucibles, the combined contents of which were then cast into sandstone ingot moulds. In 1720, Kahlmeter reported that the thirty-six brass-making furnaces in operation at Baptist Mills were grouped into six separate brass houses, which were worked as required to produce 305 tonnes of brass per year. As in Ercker’s and Swedenborg’s descriptions, cementation was effected in eight small crucibles of Stourbridge clay, which were inserted into each circular furnace and emptied twice every twenty-four hours. The calamine used by Champion was carefully calcined to convert it from the carbonate to the oxide and was then ground into a fine powder before being incorporated into the cementation charge. Apart from the use of water granulated copper, the main technical innovation introduced by Champion appears to have been in the way the cementation furnaces were arranged in groups of six under large brick covers similar to those used in the glass industry. This formation, which provided improved draught and ventilation, was commonly adapted when brass making moved from Bristol to Birmingham towards the end of the eighteenth century. NON-FERROUS METALS 87 William Champion and his zinc metal process Nehemiah Champion’s youngest son, William, visited most of the industrial centres of Europe before returning to Bristol in 1730 at the age of twenty. Metallic zinc was then being imported from the Far East at prices around £260 a ton, too costly for the manufacture of battery brass, although it was in great demand for manufacturing those brasses of low zinc content and attractive golden colour used for making cheap jewellery. It was also used for making brazing alloys containing 40 per cent or more of zinc which could not be obtained by cementation. William Champion’s immediate objective on returning from Europe was to produce metallic zinc from English calamine at a price low enough to allow it to be used for routine brass manufacture. His early work soon showed that zinc oxide could only be reduced by carbon at very high temperatures, so that the zinc obtained left the reaction zone in vapour form and oxidized to a blue powder as soon as it made contact with air. The essence of his reduction process, which required six years of ‘great expense, study and application’ before success was achieved, was to condense the vapour rapidly to metal in the complete absence of air. To do this he used a vertical retort and, as can be seen from Figure 1.7(b), the equipment he evolved is remarkably similar in its geometry and general arrangement to the vertical zinc retorts used at Zawar in the fourteenth and fifteenth centuries. An iron tube led from the base of the reaction crucible to a cold chamber below the floor, its end being sealed by immersion in a bowl of water. This ensured that the zinc vapour did not encounter significantly oxidizing conditions before it condensed and settled as granules below the water surface. The reaction crucibles, approximately 1m high, and Qocm in diameter, were arranged in groups of six in each furnace. The distillation process took about seventy hours, during which time around 400kg (882lbs) of zinc were obtained from the six retorts. William Champion encountered some opposition from his colleagues, and he was dismissed from his old firm in 1746. Between 1738 and 1746 he built a new factory for zinc manufacture at Baber’s Tower in Bristol, where he was able to produce 205 tonnes (200 tons) of metallic zinc. This, he found, was virtually unsaleable, since the merchants who imported zinc from the Far East dropped their prices and seemed quite prepared to lose £25 per ingot ton in their efforts to drive him out of business. Moreover the city fathers of Bristol had complained about the fumes emitted by his Baber’s Tower factory which he was forced to demolish. He then built a new large works at Warmley, five miles to the east of Kingswood. In complete contrast to the fragmented operations of the old Bristol Company, the Warmley plant was intended to be completely integrated, co-ordinated facilities for copper smelting, zinc distillation and brass manufacture being arranged on the new site. In 1748 the factory at Warmley was in full production. Copper ore was brought from PART ONE: MATERIALS 88 Cornwall, refined on the site and granulated in water for the manufacture of brass by cementation according to the original patent of William’s father Nehemiah. For the manufacture of ingot moulds, William seems to have departed from tradition in using granite slabs rather than sandstone. The zinc distillation process was carried out at Warmley under conditions of great secrecy, and it was not until 1766 that the processes involved were described by Dr Watson in his Chemical Essays. The Warmley plant grew rapidly, and further capital was raised in 1761 for the erection of 17 new copper refining furnaces. In 1765 the Warmley Company began to manufacture brass pins on a large scale. By 1767, when the fortunes of the Warmley plant were at their peak, the pin-making operation, which was probably undertaken in the old Clock Tower building was in full operation, and the works at Warmley housed two large rotative steam engines. Figure 1.7 (a): Methods of zinc production. Zinc production by the process of Tyryakpatnayantra, or ‘distillation by descending’ is described in the thirteenth-century Hindu alchemical work, Ras Ratnasammuchchaya. This recommends that the retort should be charged with ingredients such as lac, treacle, white mustard, cherry plum, resins, borax, salt and zinc ore. NON-FERROUS METALS 89 Following petitions by his competitors to the Lords Committee of the Privy Seal, Champion’s application for a Charter of Incorporation was rejected in March 1768. This decision destroyed the Warmley Company, since it made it impossible to raise the capital required for continued operation by the issue of transferable shares. Following an unauthorized attempt to withdraw some part of his share capital from the company, Champion was dismissed by his fellow directors in April 1768. He was declared bankrupt in March 1769, when the works at Warmley were offered for sale. These were eventually acquired by the Bristol Brass Company but never extensively used. Figure 1.7 (b): Methods of zinc production. When William Champion introduced his version of this process in Bristol in 1738 his crucibles were charged merely with a mixture of calcined calamine and charcoal. PART ONE: MATERIALS 90 The decline and fall of Bristol brass The demise of the Warmley Company was soon followed by that of the ‘Old Bristol Company’, which had been largely responsible for its failure and destruction. The four brass companies which had prevented William Champion from obtaining his Charter of Incorporation were led by the Brass Battery, Wire and Copper Company of Bristol as it was then known. The others were John Freeman and Copper Company of Bristol, Thomas Patten and Coy of Warrington, and Charles Roe and Copper Company at Macclesfield. Brass manufacture represented only a small part of the total activities of John Freeman and Company. Together with the Bristol Brass Company, however, Thomas Patten and Charles Roe produced most of the brass used in Great Britain. Bristol had, in fact, begun to lose its predominance as the centre of copper and brass production in 1763. In the autumn of that year, Charles Roe of the Macclesfield Copper Company first sensed the possibilities of the copper ore deposits of Parys Mountain in Anglesey, and leased part of it from Sir Nicholas Bayly. Extensive bodies of rich ore were found in 1768 and rapidly exploited. The remainder of the Parys Mountain complex was soon being worked by the Warrington Copper Company under Thomas Patten, and the Parys Mine Company which in 1780 opened its own smelting works at Ravenshead in Lancashire. Thomas Williams, the solicitor who led the Parys Mine Company was a man of energy and vision who recognized soon after he joined the industry that the Anglesey copper ore, being abundant, close to the surface and easily worked, could be sold very cheaply at prices which would make the Cornish Figure 1.7 (c): Methods of zinc production. The horizontal zinc retort process, introduced by the Abbé Dony in 1807, was far simpler and more economical to operate. Most of the zinc produced in Europe and the United States between 1820 and 1940 was made in this way. NON-FERROUS METALS 91 mines unviable. By that time the old Bristol Company had relinquished its earlier control of the copper mines in Devon and Cornwall and bought the copper ore needed by its smelting works on the open market. With Parys Mountain copper, Thomas Williams became the major producer and found himself able to control the copper market. Bristol was forced to increase the price of brass, a move which antagonized many customers and had particularly unfortunate consequences in the Birmingham area. Birmingham began to emerge as a centre of brass fabrication at the beginning of the eighteenth century, and the vast quantity of brassware it exported to the Continent was discussed by Daniel Defoe as early as 1728. Much of the brass worked on there was initially imported from Europe, although by the middle of the century it was all obtained either from Bristol or from Thomas Patten at Cheadle in North Staffordshire. A small brass-making factory was established at Coleshill Street in Birmingham in 1740 by the Turner family. By 1780, Birmingham consumed about 1000 tonnes per annum of brass, most of which came from Bristol. By then, however, the Birmingham fabricators were beginning to resent the high price of the brass they bought from Bristol and the attitude of Brass Battery, Wire and Copper Company (derisively referred to as the ‘OC’, or ‘Old Company’) which protected its monopoly by controlling brass prices in such a way that any new brass manufacturers in the Birmingham area were soon forced out of business. A public attack on the brass manufacturers cartel, which was headed by the Old Company, was mounted in the autumn of 1780, when, according to Aris’s Gazette, the Birmingham fabricators ‘boldly stood forth the Champions of Industry, and in Defiance of Oppression, ventured to erect Works and risque their Fortunes therein’. The result of this campaign was the formation of the Birmingham Metal Company, set up in April 1781, initially under the aegis of Matthew Boulton, although he shortly afterwards resigned from the committee. The first action of this company was to negotiate with Thomas Williams for a regular supply of copper on very advantageous terms. Bristol, therefore, rapidly lost its hold on the Birmingham market and its fortunes dwindled. In 1784 the lease Charles Roe had taken at Parys Mountain expired and Thomas Williams then assumed control of the whole copper mining complex of Anglesey. The Bristol Brass Company had encountered serious difficulties during 1786 and the joint proprietors resolved in December of that year that the business should be dissolved and terminated. The firm at that time was owned and managed largely by the Harford family, and in February 1787 the firm was sold for £16,000 to ten Bristol merchants, six of whom were Harfords. Relationships between the Cornish and Anglesey mining concerns had, meanwhile, stabilized. Thomas Williams had been requested by the Cornish Metal Company to market their vast stocks of unsold copper, a task which he accomplished by 1790 without any reduction in copper prices. He also . Charter of Incorporation were led by the Brass Battery, Wire and Copper Company of Bristol as it was then known. The others were John Freeman and Copper Company of Bristol, Thomas Patten and Coy of. Warrington, and Charles Roe and Copper Company at Macclesfield. Brass manufacture represented only a small part of the total activities of John Freeman and Company. Together with the Bristol Brass Company,. the order of five shillings on each ton of the ore exported. By the 1680s it had become very evident that the privileges granted to the Mines Royal Company and to the Society of Mineral and Battery