Analysis
Pig iron had been exported from Virginia and Maryland since the 1720s, but little came from other colonies, nor did bar iron. The continuance of this was encouraged, as was the production and export of bar iron (which required a finery forge using a helve hammer not a trip hammer).
Conversely, the Act was designed to restrict the colonial manufacture of finished iron products and steel. Existing works could continue in operation, but no expansion would be possible in the output of:
- knives, scythes, sickles and other edged tools as a tilt hammer would be needed to produce thin iron, and a steel furnace to make steel.
- nails which were made from rod iron, from a slitting mill.
- Tinplate, which required a rolling mill. This was the raw material from which tinsmiths made a wide variety of goods from tinned sheet iron.
This was a continuation of a long term British policy, beginning with the Navigation Acts, which were designed to direct most American trade to England, and later Great Britain, and to encourage the manufacture of goods for export to the colonies in Britain.
The Iron Act, if enforced, would have severely limited the emerging iron manufacturing industry (as opposed to the production of cast or bar iron) in the colonies. However, as with other trade legislation, enforcement was poor because no one had any significant incentive to ensure compliance. Nevertheless, this was one of a number of measures restrictive on the trade of British Colonies in North America that were one of the causes of the American Revolution.
Part of the reason for lax enforcement may be due to the involvement of Colonial Officials in iron works. Virginia Governors Gooch and Spotswood were both deeply involved in iron manufacture. Gooch was a part owner of the Fredericksville Ironworks. Spotswood owned Tubal Ironworks (a blast furnace and probably finery forge) and the double air furnace at Massaponnax. Other prominent members of the Virginia aristocracy and House of Burgesses involved in the iron industry included John Tayloe II (Bristol Iron Works, near Fredericksburg; Neabsco Iron Works; and Occoquan Ironworks), Augustine Washington, George's father (Accoceek/Potomac Ironworks), and Benjamin Grimes (Grimes Recovery and a bloomery near Fredericksburg).
Pig iron, also known as crude iron, is an intermediate good used by the iron industry in the production of steel. It is developed by smelting iron ore in a blast furnace. Pig iron has a high carbon content, typically 3.8–4.7 %, along with silica and other dross, which makes it brittle and not useful directly as a material except for limited applications.
Wrought iron is an iron alloy with a very low carbon content in contrast to that of cast iron. It is a semi-fused mass of iron with fibrous slag inclusions, which give it a wood-like "grain" that is visible when it is etched, rusted, or bent to failure. Wrought iron is tough, malleable, ductile, corrosion resistant, and easily forge welded, but is more difficult to weld electrically.
The Wealden iron industry was located in the Weald of south-eastern England. It was formerly an important industry, producing a large proportion of the bar iron made in England in the 16th century and most British cannon until about 1770. Ironmaking in the Weald used ironstone from various clay beds, and was fuelled by charcoal made from trees in the heavily wooded landscape. The industry in the Weald declined when ironmaking began to be fuelled by coke made from coal, which does not occur accessibly in the area.
A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also be a plant where steel semi-finished casting products are made from molten pig iron or from scrap.
Henry Cort was an English ironware producer who was formerly a Navy pay agent. During the Industrial Revolution in England, Cort began refining iron from pig iron to wrought iron using innovative production systems. In 1784, he obtained a patent for an improved version of Peter Onions's puddling process, for refining cast iron, although its commercial viability was only realised in the 1790s, through further innovations introduced by Richard Crawshay and Homfray of the Cyfarthfa Ironworks in Merthyr Tydfil.
A bloomery is a type of metallurgical furnace once used widely for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. Bloomeries produce a porous mass of iron and slag called a bloom. The mix of slag and iron in the bloom, termed sponge iron, is usually consolidated and further forged into wrought iron. Blast furnaces, which produce pig iron, have largely superseded bloomeries.
An ironworks or iron works is an industrial plant where iron is smelted and where heavy iron and steel products are made. The term is both singular and plural, i.e. the singular of ironworks is ironworks.
Saugus Iron Works National Historic Site is a National Historic Site about 10 miles northeast of Downtown Boston in Saugus, Massachusetts. It is the site of the first integrated ironworks in North America, founded by John Winthrop the Younger and in operation between 1646 and approximately 1670. It includes the reconstructed blast furnace, forge, rolling mill, shear, slitter and a quarter-ton trip hammer.
Tinplate consists of sheets of steel coated with a thin layer of tin to impede rusting. Before the advent of cheap mild steel, the backing metal was wrought iron. While once more widely used, the primary use of tinplate now is the manufacture of tin cans.
Puddling is the process of converting pig iron to bar (wrought) iron in a coal fired reverberatory furnace. It was developed in England during the 1780s. The molten pig iron was stirred in a reverberatory furnace, in an oxidizing environment to burn the carbon, resulting in wrought iron. It was one of the most important processes for making the first appreciable volumes of valuable and useful bar iron without the use of charcoal. Eventually, the furnace would be used to make small quantities of specialty steels.
A hammer mill, hammer forge or hammer works was a workshop in the pre-industrial era that was typically used to manufacture semi-finished, wrought iron products or, sometimes, finished agricultural or mining tools, or military weapons. The feature that gave its name to these workshops was the water-driven trip hammer, or set of hammers, used in the process. The shaft, or 'helve', of the hammer was pivoted in the middle and the hammer head was lifted by the action of cams set on a rotating camshaft that periodically depressed the end of the shaft. As it rose and fell, the head of the hammer described an arc. The face of the hammer was made of iron for durability.
A finery forge is a forge used to produce wrought iron from pig iron by decarburization in a process called "fining" which involved liquifying cast iron in a fining hearth and removing carbon from the molten cast iron through oxidation. Finery forges were used as early as the 3rd century BC in China. The finery forge process was replaced by the puddling process and the roller mill, both developed by Henry Cort in 1783–4, but not becoming widespread until after 1800.
Osmond iron was wrought iron made by a particular process. This is associated with the first European production of cast iron in furnaces such as Lapphyttan in Sweden.
Cornwall Iron Furnace is a designated National Historic Landmark that is administered by the Pennsylvania Historical and Museum Commission in Cornwall, Lebanon County, Pennsylvania in the United States. The furnace was a leading Pennsylvania iron producer from 1742 until it was shut down in 1883. The furnaces, support buildings and surrounding community have been preserved as a historical site and museum, providing a glimpse into Lebanon County's industrial past. The site is the only intact charcoal-burning iron blast furnace in its original plantation in the western hemisphere. Established by Peter Grubb in 1742, Cornwall Furnace was operated during the Revolution by his sons Curtis and Peter Jr. who were major arms providers to George Washington. Robert Coleman acquired Cornwall Furnace after the Revolution and became Pennsylvania's first millionaire. Ownership of the furnace and its surroundings was transferred to the Commonwealth of Pennsylvania in 1932.
Oregrounds iron was a grade of iron that was regarded as the best grade available in 18th century England. The term was derived from the small Swedish city of Öregrund, the port from which the bar iron was shipped. It was produced using the Walloon process.
The Calico Acts banned the import of most cotton textiles into England, followed by the restriction of sale of most cotton textiles. It was a form of economic protectionism, largely in response to India, which dominated world cotton textile markets at the time. The acts were a precursor to the Industrial Revolution, when Britain eventually surpassed India as the world's leading textile manufacturer in the 19th century.
The Lancashire hearth was used to fine pig iron, removing carbon to produce wrought iron.
The Fitzroy Iron Works at Mittagong, New South Wales, was the first commercial iron smelting works in Australia. It first operated in 1848.
The Low Moor Ironworks was a wrought iron foundry established in 1791 in the village of Low Moor about 3 miles (4.8 km) south of Bradford in Yorkshire, England. The works were built to exploit the high-quality iron ore and low-sulphur coal found in the area. Low Moor made wrought iron products from 1801 until 1957 for export around the world. At one time it was the largest ironworks in Yorkshire, a major complex of mines, piles of coal and ore, kilns, blast furnaces, forges and slag heaps connected by railway lines. The surrounding countryside was littered with waste, and smoke from the furnaces and machinery blackened the sky. Today Low Moor is still industrial, but the pollution has been mostly eliminated.
The US iron and steel industry has paralleled the industry in other countries in technological developments. In the 1800s, the US switched from charcoal to coal in ore smelting, adopted the Bessemer process, and saw the rise of very large integrated steel mills. In the 20th century, the US industry successively adopted the open hearth furnace, then the basic oxygen steelmaking process. Since the American industry peaked in the 1940s and 1950s, the US industry has shifted to small mini-mills and specialty mills, using iron and steel scrap as feedstock, rather than iron ore.
