Thomas and George Cranege (also spelled ''Cranage''), who worked in the ironworking industry in England in the 1760s, are notable for introducing a new method of producing

wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag Inclusion (mineral), inclusions (up to 2% by weight), which give it a ...

from

pig iron Pig iron, also known as crude iron, is an intermediate product of the iron industry in the production of steel which is obtained by smelting iron ore in a blast furnace. Pig iron has a high carbon content, typically 3.8–4.7%, along with silic ...

Experiment of 1766

The process of converting pig iron into wrought iron (also known as bar iron) was at that time carried out in a

finery forge 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 ...

, which was fuelled by

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...

. Charcoal was a limited resource, but coal, more widely available, could not be used because the

sulphur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

in coal would adversely affect the quality of the wrought iron.W. K. V. Gale, ''Ironworking'',

Shire Publications Shire Books are published by Bloomsbury Publishing, a book publishing company based in London, England, and formerly by Shire Publications Ltd. and Osprey Publishing. Shire offers low priced, concise non-fiction paperbacks on a wide range of su ...

George Cranege worked in

Coalbrookdale Coalbrookdale is a village in the Ironbridge Gorge in Shropshire, England, containing a settlement of great significance in the history of iron ore smelting. It lies within the civil parish called the Gorge. This is where iron ore was first s ...

in Shropshire, at the ironworks established by

Abraham Darby I Abraham Darby, in his later life called Abraham Darby the Elder, now sometimes known for convenience as Abraham Darby I (14 April 1677 – 5 May 1717, the first and best known of several men of that name), was an English ironmaster and foundr ...

, and his brother Thomas worked at a forge in

Bridgnorth Bridgnorth is a town in Shropshire, England. The River Severn splits it into High Town and Low Town, the upper town on the right bank and the lower on the left bank of the River Severn. The population at the 2011 Census was 12,079. History B ...

in Shropshire. They suggested to Richard Reynolds, manager of the works at Coalbrookdale, that the conversion process could be done in a

reverbatory furnace A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term ''reverberation'' is used here in a generic sense of ''re ...

, where the iron did not mix with the coal. Reynolds was sceptical, but authorized the brothers to try out the idea.

Samuel Smiles Samuel Smiles (23 December 1812 – 16 April 1904) was a British author and government reformer. Although he campaigned on a Chartist platform, he promoted the idea that more progress would come from new attitudes than from new laws. His prim ...

''Industrial Biography: Iron Workers and Tool Makers''
chapters 5 and 7, at

Project Gutenberg Project Gutenberg (PG) is a Virtual volunteering, volunteer effort to digitize and archive cultural works, as well as to "encourage the creation and distribution of eBooks." It was founded in 1971 by American writer Michael S. Hart and is the ...

Richard Reynolds, in a letter dated 25 April 1766 to his colleague

Thomas Goldney III The Goldney family were a wealthy English merchant trading family, most associated with Wiltshire and latterly Bristol. Later branches of the family became the Goldney baronets. Wiltshire The Goldney family made their monies as weavers and clot ...

, described his conversation with the Craneges and the experiment:

I told them, consistent with the notion I had adopted in common with all others I had conversed with, that I thought it impossible, because the vegetable salts in the charcoal being an
alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
acted as an absorbent to the sulphur of the iron, which occasions the
red-short Red-short, hot-short refers to brittleness of steels at red-hot temperatures. It is often caused by high sulfur levels, in which case it is also known as sulfur embrittlement. Description Iron or steel, when heated to above 900 °F (460 ...
quality of the iron, and pit coal abounding with sulphur would increase it.... They replied that from the observations they had made, and repeated conversations together, they were both firmly of opinion that the alteration from the quality of pig iron into that of bar iron was effected merely by heat, and if I would give them leave, they would make a trial some day.... A trial of it has been made this week, and the success has surpassed the most sanguine expectations.... I look upon it as one of the most important discoveries ever made....

A patent for the process, dated 17 June 1766, in the name of the brothers Cranege, was secured. It apparently made little difference to the lives of the brothers. The process was improved soon afterwards, by

Peter Onions Peter Onions (1724 – 1798) was an English ironmaster and the inventor of an early puddling process used for the refining of pig iron into wrought iron. Biography Onions was born in Broseley, Shropshire, later moving to Merthyr Tydfil in Wal ...

who received a patent in 1783, and by

Henry Cort Henry Cort (c. 1740 – 23 May 1800) was an English ironware producer although formerly a Navy pay agent. During the Industrial Revolution in England, Cort began refining iron from pig iron to wrought iron (or bar iron) using innovative producti ...

who received patents in 1783 and 1784 for his improvements.

References

{{reflist History of metallurgy People of the Industrial Revolution