Crucible steel
Overview
 
Crucible steel describes a number of different techniques for making steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 in a crucible
Crucible
A crucible is a container used for metal, glass, and pigment production as well as a number of modern laboratory processes, which can withstand temperatures high enough to melt or otherwise alter its contents...

. Its manufacture is essentially a refining process which is dependent on preexisting furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...

 products. Crucible steel has aroused considerable interest for well over a thousand years and there is a sizable body of work concerning its nature and production.
Various methods were used to produce crucible steel.
Encyclopedia
Crucible steel describes a number of different techniques for making steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 in a crucible
Crucible
A crucible is a container used for metal, glass, and pigment production as well as a number of modern laboratory processes, which can withstand temperatures high enough to melt or otherwise alter its contents...

. Its manufacture is essentially a refining process which is dependent on preexisting furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...

 products. Crucible steel has aroused considerable interest for well over a thousand years and there is a sizable body of work concerning its nature and production.

Methods of crucible steel production

Various methods were used to produce crucible steel. According to Islamic texts such as al-Tarsusi and Abu Rayhan Biruni
Al-Biruni
Abū al-Rayḥān Muḥammad ibn Aḥmad al-BīrūnīArabic spelling. . The intermediate form Abū Rayḥān al-Bīrūnī is often used in academic literature...

, three methods are described for indirect production of steel. The medieval Islamic historian Abu Rayhan Biruni (c. 973-1050) provides us with the earliest reference of the production of Damascus steel
Damascus steel
Damascus steel was a term used by several Western cultures from the Medieval period onward to describe a type of steel used in swordmaking from about 300 BCE to 1700 CE. These swords are characterized by distinctive patterns of banding and mottling reminiscent of flowing water...

. He describes only three methods for producing steel. The first two methods have a long history in Central Asia
Central Asia
Central Asia is a core region of the Asian continent from the Caspian Sea in the west, China in the east, Afghanistan in the south, and Russia in the north...

 and in the Indian subcontinent
Indian subcontinent
The Indian subcontinent, also Indian Subcontinent, Indo-Pak Subcontinent or South Asian Subcontinent is a region of the Asian continent on the Indian tectonic plate from the Hindu Kush or Hindu Koh, Himalayas and including the Kuen Lun and Karakoram ranges, forming a land mass which extends...

. The first method and the most common traditional method is solid state carburization
Carburization
Carburizing, spelled carburising in the UK, is a heat treatment process in which iron or steel is heated in the presence of another material which liberates carbon as it decomposes. Depending on the amount of time and temperature, the affected area can vary in carbon content...

 of wrought iron
Wrought iron
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

. This is a diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...

 process in which wrought iron is packed in crucibles or a hearth
Hearth
In common historic and modern usage, a hearth is a brick- or stone-lined fireplace or oven often used for cooking and/or heating. For centuries, the hearth was considered an integral part of a home, often its central or most important feature...

 with charcoal, then heated to promote diffusion of carbon into the iron to produce steel. Carburization is the basis for the wootz process of steel. The second method is the decarburization
Decarburization
Decarburization is the process opposite to carburization, namely aimed at decreasing the content of carbon in metals . Decarburization occurs when Carbon in the metal reacts with gasses present in the atmosphere...

 of cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 by removing carbon from the cast iron.
Another indirect method uses wrought iron and cast iron. In this process, wrought iron and cast iron may be heated together in a crucible to produce steel by fusion. In regard to this method Abu Rayhan Biruni states: "this was the method used in Hearth". It is proposed that the Indian method refers to Wootz carburization method i.e. the Mysore or Tamil
Tamil people
Tamil people , also called Tamils or Tamilians, are an ethnic group native to Tamil Nadu, India and the north-eastern region of Sri Lanka. Historic and post 15th century emigrant communities are also found across the world, notably Malaysia, Singapore, Mauritius, South Africa, Australia, Canada,...

 processes.
Variations of co-fusion process have been found preliminary in Persia and Central Asia but have also been found in Hyderabad, India called Deccani or Hyderabad process. For the carbon, a variety of organic materials are specified by the contemporary Islamic authorities , including pomegranate rinds, acorns, fruit skins like orange peel, leaves as well as the white of egg and shells. Slivers of wood are mentioned in some of the Indian sources, but significantly none of the sources mention charcoal.

History

Crucible steel is generally attributed to production centres in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 and Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

 where it was produced using the so-called “wootz” process and it is assumed that its appearance in other locations was due to long distance trade. Only recently it has become apparent that places in Central Asia like Merv
Merv
Merv , formerly Achaemenid Satrapy of Margiana, and later Alexandria and Antiochia in Margiana , was a major oasis-city in Central Asia, on the historical Silk Road, located near today's Mary in Turkmenistan. Several cities have existed on this site, which is significant for the interchange of...

 in Turkmenistan
Turkmenistan
Turkmenistan , formerly also known as Turkmenia is one of the Turkic states in Central Asia. Until 1991, it was a constituent republic of the Soviet Union, the Turkmen Soviet Socialist Republic . Turkmenistan is one of the six independent Turkic states...

 and Akhsiket in Uzbekistan
Uzbekistan
Uzbekistan , officially the Republic of Uzbekistan is a doubly landlocked country in Central Asia and one of the six independent Turkic states. It shares borders with Kazakhstan to the west and to the north, Kyrgyzstan and Tajikistan to the east, and Afghanistan and Turkmenistan to the south....

 were important centres of production of crucible steel. The Central Asian finds are all from excavations and date from the 8th to 12th centuries AD, while the Indian/Sri Lankan material is as early as 300 BC.In addition India's superior iron ore has trace vanadium and other rare earths which unintentionally leads to the formation of carbon nano tubes in Indian crucible steel which was famous throughout the middle east for its ability to retain its edge even after prolonged usage.

Central Asia

Central Asia has a rich history of crucible steel production, beginning during the late 1st millennium AD. From the sites in modern Uzbekistan and Merv in Turkmenistan, there exists good archaeological evidence for the large scale production of crucible steel. They all belong in broad terms to the same early medieval period between the late 8th or early 9th and the late 12th century AD Contemporary with the early crusades
Crusades
The Crusades were a series of religious wars, blessed by the Pope and the Catholic Church with the main goal of restoring Christian access to the holy places in and near Jerusalem...

 and predating the Indian evidence by several centuries.

Uzbekistan

The two most prominent crucible steel sites in eastern Uzbekistan carrying the Ferghana Process are Akhsiket and Pap in the Ferghana Valley, whose position within the Great Silk Road
Silk Road
The Silk Road or Silk Route refers to a historical network of interlinking trade routes across the Afro-Eurasian landmass that connected East, South, and Western Asia with the Mediterranean and European world, as well as parts of North and East Africa...

 has been historically and archaeologically proved. The material evidence of the sites consists of large number of archaeological finds relating to steel making from 9th-12th centuries AD in the form of hundreds of thousands of fragments of crucibles often with massive slag
Slag
Slag is a partially vitreous by-product of smelting ore to separate the metal fraction from the unwanted fraction. It can usually be considered to be a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and metal atoms in the elemental form...

 cakes. Archaeological work at Akhsiket, has identified that the crucible steel process was of the carburization of iron ore. This process appears to be typical of and restricted to the Ferghana Valley in eastern Uzbekistan, and it is therefore called the Ferghana Process. This process lasts in that region for roughly four centuries.

Turkmenistan

Evidences of the production of crucible steel have been found in Merv, Turkmenistan, a major city on the 'Silk Road'. The Islamic scholar, al-Kindi
Al-Kindi
' , known as "the Philosopher of the Arabs", was a Muslim Arab philosopher, mathematician, physician, and musician. Al-Kindi was the first of the Muslim peripatetic philosophers, and is unanimously hailed as the "father of Islamic or Arabic philosophy" for his synthesis, adaptation and promotion...

 (AD 801-866) mentions that during the ninth century the region of Khorasan, the area to which the cities Nishapur
Nishapur
Nishapur or Nishabur , is a city in the Razavi Khorasan province in northeastern Iran, situated in a fertile plain at the foot of the Binalud Mountains, near the regional capital of Mashhad...

, Merv, Herat
Herat
Herāt is the capital of Herat province in Afghanistan. It is the third largest city of Afghanistan, with a population of about 397,456 as of 2006. It is situated in the valley of the Hari River, which flows from the mountains of central Afghanistan to the Karakum Desert in Turkmenistan...

 and Balkh
Balkh
Balkh , was an ancient city and centre of Zoroastrianism in what is now northern Afghanistan. Today it is a small town in the province of Balkh, about 20 kilometers northwest of the provincial capital, Mazar-e Sharif, and some south of the Amu Darya. It was one of the major cities of Khorasan...

 belong, is a steel manufacturing centre. Evidence from a metallurgical workshop at Merv, dated to the ninth- early tenth century A.D., provides an illustration of the co- fusion method of steel production in crucibles, about 1000 years earlier than the distinctly different wootz process. The crucible steel process at Merv might be seen as technologically related to what Bronson (1986, 43) calls Heyderabad process, a variation of the wootz process, after the location of the process documented by Voysey in the 1820s.

South India/Sri Lanka

Despite the extensive number of reports that claim the importance of India in producing vast quantities of wootz, few archaeological sites have been investigated. There are many ethnographic accounts of Indian crucible steel production, however, scientific investigations of crucible steel remains have only been published from four regions: three in India and one in Sri Lanka. Indian/Sri Lankan crucible steel is commonly referred to as wootz. It is generally agreed that wootz is an English corruption of the word ukko or hookoo. European accounts from the 17th century onwards have referred to the repute and manufacture of ‘wootz’, a traditional crucible steel made specially in parts of southern India in the former provinces of Golconda
Golconda
Golconda may be:Places:* Golkonda, ruined city and fortress in India* Golconda, Illinois, town in the United States* Golconda, Nevada, former town in the United StatesOther:* Golconda...

, Mysore and Salem. As yet the scale of excavations and surface surveys is too limited to link the literary accounts to archaeometallurgical evidence.

South India

The known sites of crucible steel production in south India, i.e. at Konasamudram and Gatihosahalli, date from at least the late medieval period, 16th century.
One of the earliest known sites, which shows some promising preliminary evidence that may be linked to ferrous
Ferrous
Ferrous , in chemistry, indicates a divalent iron compound , as opposed to ferric, which indicates a trivalent iron compound ....

 crucible processes in Kodumanal
Kodumanal
Kodumanal is a village located in the Erode district in the southern Indian state of Tamil Nadu. It was once a flourishing ancient trade city known as Kodumanam, as inscribed in Patittrupathu of Sangam Literature. The place is a important Archaeological Site, under the control of State...

, near Coimbatore in Tamil Nadu
Tamil Nadu
Tamil Nadu is one of the 28 states of India. Its capital and largest city is Chennai. Tamil Nadu lies in the southernmost part of the Indian Peninsula and is bordered by the union territory of Pondicherry, and the states of Kerala, Karnataka, and Andhra Pradesh...

. The site is dated between the third century BC and the third century AD. By the seventeenth century the main centre of crucible steel production seems to have been in Hyderabad. The process was apparently quite different from that recorded elsewhere. Wootz from Hyderabad or the Decanni process for making watered blades involved a co-fusion of two different kinds of iron- one was low in carbon and the other was a high-carbon steel or cast iron. Wootz steel
Wootz steel
Wootz steel is a steel characterized by a pattern of bands or sheets of micro carbides within a tempered martensite or pearlite matrix. It was developed in India around 300 BCE...

 was widely exported and traded throughout ancient Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, the Arab world
Arab world
The Arab world refers to Arabic-speaking states, territories and populations in North Africa, Western Asia and elsewhere.The standard definition of the Arab world comprises the 22 states and territories of the Arab League stretching from the Atlantic Ocean in the west to the Arabian Sea in the...

, and became particularly famous in the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

, where it became known as Damascus steel.

Sri Lanka

Recent archaeological investigations have suggested that Sri Lanka also supported innovative technologies for iron and steel production in antiquity. The Sri Lankan system of crucible steel making was partially independent of the various Indian and Middle Eastern systems. Their method was something similar to the method of carburization of wrought iron. The earliest confirmed crucible steel site is located in the knuckles range in the northern area of the Central Highlands of Sri Lanka dated to 6th -10th centuries AD. In twelfth century the land of Serendib (Sri Lanka) seems to have been the main supplier of crucible steel, but over the centuries slipped back, and by the nineteenth century just a small industry survived in the Balangoda
Balangoda
Balangoda is a town in Sabaragamuwa Province of Sri Lanka. Its 143 km away from Colombo and 43 km away from Ratnapura. It is the one of biggest towns of the Ratnapura District which is one of the two districts belonging to Sabaragamuwa Province . According to the 2001 census Balangoda has a...

 district of the central southern highlands.

West-facing process

A series of excavations at Samanalawewa indicated the unexpected and previously unknown technology of west- facing smelting
Smelting
Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores...

 sites, which are different types of steel production. These furnaces were used for direct smelting to steel. Because of their location on the western sides of hilltops for use of wind in the smelting process they are named west-facing. Sri Lankan furnace steels were known and traded between the 9th and 11th centuries and earlier, but apparently not later. These sites were dated to the 7th-11th centuries. The coincidence of this dating with the 9th century Islamic reference to Sarandib is of great importance. The crucible process existed in India at the same time that the west- facing technology was operating in Sri Lanka.

History of research on crucible steel

In the first centuries of the Islamic period, there appear some scientific studies on swords and steel. The best known of these are by Jabir ibn Hayyan 8th century , al-Kindi 9th century, Abu Rayhan Biruni in the early 11th century, Murda al Tarsusi in the late 12th century, and Fakhr-i- Mudabbir 13th century. Any of these contains far more information about Indian and damascene steels than appears in the entire literature of classical Greece
Classical Greece
Classical Greece was a 200 year period in Greek culture lasting from the 5th through 4th centuries BC. This classical period had a powerful influence on the Roman Empire and greatly influenced the foundation of Western civilizations. Much of modern Western politics, artistic thought, such as...

 and Rome
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

. The first European references to crucible steel seem to be no earlier than the Post Medieval
Post Medieval
Post Medieval is an archaeological term, meaning anything of a period after the end of the medieval period. In England, this effectively means anything from the Tudor period or after. Some archaeologists consider the Post Medieval period to end around 1750 with a Modern period after this, but...

 period. European experiments with “Damascus
Damascus
Damascus , commonly known in Syria as Al Sham , and as the City of Jasmine , is the capital and the second largest city of Syria after Aleppo, both are part of the country's 14 governorates. In addition to being one of the oldest continuously inhabited cities in the world, Damascus is a major...

” steels go back to at least the sixteenth century, but it was not until the 1790s that laboratory researchers began to work with steels that were specifically known to be Indian/wootz. At this time, Europeans knew of India's ability to make crucible steel from reports brought back by travellers who had observed the process at several places in southern India.
From the mid- 17th century onwards, there are numerous vivid eyewitness accounts of the production of steel by European travellers to the Indian subcontinent. These include accounts by Jean Baptist Tavernier in 1679, Francis Buchanan in 1807, and H.W. Voysey in 1832.
The 18th, 19th and early 20th century saw a heady period of European interest in trying to understand the nature and properties of wootz steel. Indian wootz engaged the attention of some of the best-known scientists. One was Michael Faraday
Michael Faraday
Michael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....

 who was fascinated by wootz steel. ‘It was probably the investigations of George Pearson in 1795 reported at the Royal Society, which had the most far- reaching impact in terms of kindling interest amongst European scientist in wootz. He was the first of these scientists to publish his results and, incidentally, the first to use the word “wootz” in print.
Another investigator, David Mushet
David Mushet
David Mushet was a Scottish metallurgist and the youngest son of Margaret Cochran and William Mushet.-Early life:Mushet was born on October 2, 1772, in Dalkeith, near Edinburgh. He was educated at Dalkeith Grammar School....

, was able to infer that wootz was made by fusion. David Mushet patented his process in 1800. He made his report in 1805. But the first successful European process had been developed by Benjamin Huntsman
Benjamin Huntsman
Benjamin Huntsman was an English inventor and manufacturer of cast or crucible steel.-Biography:Huntsman was born the third son of a Quaker farmer in Epworth, Lincolnshire. His parents were Germans who had emigrated only a few years before his birth.Huntsman started business as a clock, lock and...

 some 50 years previously in the 1740s.

Blister steel

It was possible to produce quality steel in Europe, by importing the highly valued Swedish
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 iron. Although it was not understood at the time, the Swedish ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

 contained very low levels of common impurities, leading to higher quality irons and steels from otherwise identical techniques applied to other ores. Swedish bar iron was packed into stone boxes in layers with charcoal in between them and heated in a furnace for an entire week. The result was a bar of metal known as blister steel - the surface of the bars became uneven from a multitude of blisters (or blebs) - which varied in quality from one bar to the next and within each bar. A number of blister rods were then wrapped into a larger bundle
Faggoting (metalworking)
Faggoting or faggoting and folding is a metalworking technique used in the smelting and forging of wrought iron, damascus steel, and other steel. Faggoting is a process in which rods or bars of iron and/or steel are gathered and forge welded together. The faggot would then be drawn out lengthwise...

 and re-heated and hammer-forge
Forge
A forge is a hearth used for forging. The term "forge" can also refer to the workplace of a smith or a blacksmith, although the term smithy is then more commonly used.The basic smithy contains a forge, also known as a hearth, for heating metals...

d to mix together and even out the carbon content, resulting in the final product, shear steel. Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 was particularly well invested in this process, largely due to being physically close to Sweden, and became a major steel exporter in the 18th century. The technique was the cementation process
Cementation process
The cementation process is an obsolete technique for making steel by carburization of iron. Unlike modern steelmaking, it increased the amount of carbon in the iron. It was apparently developed before the 17th century. Derwentcote Steel Furnace, built in 1720, is the earliest surviving example...

.

English crucible steel

A new technique was developed in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 by Benjamin Huntsman
Benjamin Huntsman
Benjamin Huntsman was an English inventor and manufacturer of cast or crucible steel.-Biography:Huntsman was born the third son of a Quaker farmer in Epworth, Lincolnshire. His parents were Germans who had emigrated only a few years before his birth.Huntsman started business as a clock, lock and...

, a clockmaker in search of a better steel for clock springs. It was only in 1740 after he moved to Handsworth
Handsworth, South Yorkshire
Handsworth is a suburb of south eastern Sheffield, in South Yorkshire, England. Handsworth has a population of approximately 15,000. It covers an overall area of approximately...

 near Sheffield
Sheffield
Sheffield is a city and metropolitan borough of South Yorkshire, England. Its name derives from the River Sheaf, which runs through the city. Historically a part of the West Riding of Yorkshire, and with some of its southern suburbs annexed from Derbyshire, the city has grown from its largely...

, and after years of experimenting in secret he perfected his process. Huntsman's system used a coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

-fired furnace capable of reaching 1,600 °C, into which ten or twelve clay crucibles, each holding about 15 kg of iron, were placed. When the pots are at a white heat they are charged with blister steel broken into lumps of about ½ kg, and a flux
Flux (metallurgy)
In metallurgy, a flux , is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time...

 to help remove impurities. The pots are removed after about 3 hours in the furnace, impurities skimmed off, and the molten steel poured into ingot
Ingot
An ingot is a material, usually metal, that is cast into a shape suitable for further processing. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods.-Uses:...

s. Sheffield's Abbeydale Industrial Hamlet
Abbeydale Industrial Hamlet
Abbeydale Industrial Hamlet is an industrial museum in the south of the City of Sheffield, England. The museum forms part of a former steel-working site on the River Sheaf, with a history going back to at least the 13th century...

 has preserved a water-wheel powered, scythe-making works dating from Huntsman's times, which is still operated for the public, several times per year using crucible steel made on the Abbeydale site.

Before the introduction of Huntsman's technique, Sheffield produced about 200 tonnes of steel per year based on Swedish wrought iron (see Oregrounds iron
Oregrounds iron
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 process to create it is known as the Walloon method....

). The introduction of Huntsman's technique changed this radically; one hundred years later the amount had risen to over 80,000 tonnes per year - almost half of Europe's total production. This discovery enabled Sheffield to develop from a small township into one of Europe's leading industrial cities.

The steel was cast in a specialised workshop called a 'crucible furnace', which consisted of a workshop at ground level and a subterranean cellar. The furnace buildings varied in size and architectural style, gradually becoming larger towards the latter part of the 19th century as technological developments enabled multiple pots to be fired in one melt and gas was gradually introduced as a means of fuel to heat the crucibles. Each workshop had a series of standard features, such as rows of melting holes, teaming pits, roof vents, rows of shelving for the crucible pots and annealing furnaces to prepare each pot prior to firing. Additional ancillary rooms for the weighing each charge and for the manufacture of the clay crucibles were either attached to the workshop, or located within the cellar complex.

Crucible steel elsewhere

Another form of crucible steel was developed in 1837 by the Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

n engineer, Pavel Anosov. His technique relied less on the heating and cooling, and more on the quenching process of rapidly cooling the molten steel when the right crystal structure had formed within. He called his steel bulat
Bulat steel
Bulat is a type of steel alloy known in Russia from medieval times and regularly mentioned in Russian legends as material of choice for cold steel. The name булат is a Russian transliteration of the Persian word پولاد , meaning steel...

; its secret died with him. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 crucible steel was pioneered by William Metcalf
William Metcalf (steel)
William Metcalf was an American steel manufacturer.Metcalf was born at Pittsburgh, Pennsylvania, and graduated from Rensselaer Polytechnic Institute. Troy, New York, in 1858...

.

Conclusion

Crucible steels remained the world's best, although very expensive, for some time. The introduction of the Bessemer process
Bessemer process
The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly...

 and other steelmaking processes gradually replaced it, being able to produce steel of similar (or better) quality on a much larger scale more quickly and cheaply. The Bessemer process and more modern methods differ from crucible steel production in that they remove carbon from the pig iron, but stop before all the carbon is removed, whereas the ultimate raw material for tradition crucible steel was wrought iron, to which carbon had been added by cementation.

Crucible steel did not disappear when the Bessemer process was introduced. Cast steel is still the preferred method for specialty steel production, especially tool steel
Tool steel
Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures...

. While more expensive than the Bessemer and other later methods of steel production, it is still among the most precise. So rather than disappearing it became a niche market.

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