Potting and stamping
Encyclopedia
Potting and stamping is a modern name for one of the 18th century processes for refining pig iron
Pig iron
Pig iron is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel...

 without the use of charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

.

Inventors

The process was devised by Charles Wood
Charles Wood (ironmaster)
Charles Wood was an ironmaster and one of the inventors of the potting and stamping method of making wrought iron from pig iron.-Parents:...

 of Lowmill, Egremont
Egremont, Cumbria
Egremont is a market town and civil parish in the Borough of Copeland in Cumbria, England, south of Whitehaven and on the River Ehen. The town, which lies at the foot of Uldale Valley and Dent Fell, was historically within Cumberland and has a long industrial heritage including dyeing, weaving and...

 in Cumberland
Cumberland
Cumberland is a historic county of North West England, on the border with Scotland, from the 12th century until 1974. It formed an administrative county from 1889 to 1974 and now forms part of Cumbria....

 and his brother John Wood of Wednesbury
Wednesbury
Wednesbury is a market town in England's Black Country, part of the Sandwell metropolitan borough in West Midlands, near the source of the River Tame. Similarly to the word Wednesday, it is pronounced .-Pre-Medieval and Medieval times:...

 and patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

ed by them. The process was improved by John Wright and Joseph Jesson of West Bromwich
West Bromwich
West Bromwich is a town within the Metropolitan Borough of Sandwell, in the West Midlands, England. It is north west of Birmingham lying on the A41 London-to-Birkenhead road. West Bromwich is part of the Black Country...

, who also obtained a patent.

Process

The process involved the melting of pig iron in an oxidising atmosphere. The metal was then allowed to cool, broken up by stamping, and washed. The granulated iron was then heated in pots in a reverberatory furnace
Reverberatory 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 resultant bloom was then drawn out under a forge hammer
Trip hammer
A trip hammer, also known as a helve hammer, is a massive powered hammer used in:* agriculture to facilitate the labor of pounding, decorticating and polishing of grain;...

 in the usual way.

Adoption

During the 14-year term of the patents, the process was little used except by the inventors. However from c.1785, shortly before Wright & Jesson's process came out of patent, it seems to have been adopted by many ironmaster
Ironmaster
An ironmaster is the manager – and usually owner – of a forge or blast furnace for the processing of iron. It is a term mainly associated with the period of the Industrial Revolution, especially in Great Britain....

s in the West Midlands
West Midlands (region)
The West Midlands is an official region of England, covering the western half of the area traditionally known as the Midlands. It contains the second most populous British city, Birmingham, and the larger West Midlands conurbation, which includes the city of Wolverhampton and large towns of Dudley,...

.

Ultimately, the process was replaced by puddling
Puddling (metallurgy)
Puddling was an Industrial Revolution means of making iron and steel. In the original puddling technique, molten iron in a reverberatory furnace was stirred with rods, which were consumed in the process...

, though it remains unclear how quickly.
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