A bloomery is a type of 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...

 once widely used for 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...


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...

Shingling (metallurgy)
Shingling was a stage in the production of bar iron or steel, in the finery and puddling processes. As with many ironmaking terms, this is derived from the French - cinglage....

) and further 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 into wrought iron
Wrought iron

. The bloomery has now largely been superseded by the blast furnace
Blast furnace

, which produces pig iron
Pig iron


Structure and process

A bloomery consists of a pit or chimney
A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the...

 with heat-resistant walls made of earth

, clay

, or stone
Rock (geology)

A tuyere, also can be spelled as tuyère, is a tube, nozzle or pipe through which air is blown into a furnace or hearth.Air or oxygen is injected into a hearth under pressure from bellows or a blast engine or other devices...

s, allow air to enter the furnace, either by natural draft, or forced with bellows
A bellows is a device for delivering pressurized air in a controlled quantity to a controlled location.Basically, a bellows is a deformable container which has an outlet nozzle. When the volume of the bellows is decreased, the air escapes through the outlet...

 or a trompe
A trompe is a water-powered gas compressor, commonly used before the advent of the electric-powered compressor. A trompe is somewhat like an airlift pump working in reverse....




 and the iron ore. The charcoal is produced by heating wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 to produce the nearly pure carbon

 fuel needed for the smelting process. The ore


Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 from the incomplete combustion

 of the charcoal reduces
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 the iron oxides in the ore to metallic iron

, without melting the ore; this allows the bloomery to operate at lower temperatures than the melting temperature of the ore. As the desired product of a bloomery is iron which is easily forgeable, nearly pure, and with a low carbon content, the temperature and ratio of charcoal to iron ore must be carefully controlled to keep the iron from absorbing too much carbon and thus becoming unforgeable. Because the bloomery is self-fluxing the addition of limestone

 is not required to form a slag.

The small particles of iron produced in this way fall to the bottom of the furnace and become welded together to form the spongy mass of the bloom. The bottom of the furnace also fills with molten slag, often consisting of fayalite
Fayalite is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system with cell parameters a 4.82 Å, b 10.48 Å and c Å 6.09.Iron rich olivine is a relatively common constituent of acidic and...

, a compound of silicon

, oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and iron mixed with other impurities from the ore. Because the bloom is highly porous, and its open spaces are full of slag, the bloom must later be reheated and beaten with a hammer to drive the molten slag out of it. Iron treated this way is said to be wrought, and the resulting nearly pure iron wrought iron or bar iron. It is also possible to produce 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...

 by manipulating the charge of and air flow to the bloomery .


Iron appears to have been smelted in the west as early as 3000 BC, but bronze smiths, not being familiar with iron, did not put it to use until much later. In the west, iron began to be used around 1200 BC, presumably as a replacement for bronze, which was becoming harder to come by due to shortages of copper

 and tin


The onset of the Iron Age
Iron Age

Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 content indicates that this is meteor


 smelting operations.

Imperial China


 has long been considered the exception: by 5th century BC, metalworkers in the southern state of Wu had invented the blast furnace, and the means to both cast iron and to decarburize the carbon-rich pig iron produced in a blast furnace to a low-carbon, wrought iron-like material. It was thought that the Chinese skipped the bloomery process completely, starting with the blast furnace and the finery forge
Finery forge
Iron tapped from the blast furnace is pig iron, and contains significant amounts of carbon and silicon. To produce malleable wrought iron, it needs to undergo a further process. In the early modern period, this was carried out in a finery forge....

 to get wrought iron. Recent evidence, however, shows that bloomeries were used earlier in China, migrating in from the west as early as 800 BC, before being supplanted by the locally developed blast furnace. Supporting this theory was the discovery of 'more than ten' iron digging elements found in the tomb of the Qin Duke Jing (d. 537 BCE), whose tomb is located in Fengxiang County, Shaanxi (a museum exists on the site today).

Medieval Europe

Early bloomeries were relatively small, smelting less than 1 kg of iron with each firing. Medieval Europe saw the construction of progressively larger bloomeries, leveling off at around 15 kg on average, though exceptions did exist. The use of waterwheels to power the bellows allowed the bloomery to become larger and hotter; European average bloom sizes quickly rose to 300 kg, where they levelled off through the demise of the bloomery. Water powered bellows and larger bloomeries also increased the heat to the point where the iron could melt; this was not considered desirable because it allowed carbon to diffuse into the molten iron, producing unworkable pig iron. Molten iron was not desirable until the advent of the blast furnace.

Bloomery type furnaces typically produce a range of iron products from very low carbon iron to cast iron. Cast iron occurs when the iron melts and absorbs 2% to 4% carbon. It cannot be forged. Natural steel is also produced, ranging for approximately 0.2% to 1.5% carbon. The master smith had to select bits of low carbon (wrought) iron and low carbon (mild) steel, forge weld them together to make sheets, pile bits of high carbon steel on the sheet, put another low carbon sheet on top,and forge weld it all together. Then he had to forge it out thin, fold it , and forge weld it. This pound-out, fold and weld process eventually got the material more or less homogenous and got rid of much of the slag. The process had to be repeated up to 15 times when high quality steel was needed, as for a sword. This is part of the reason decent swords were so expensive. Each welding heat burns out about 0.03% carbon, so the mastersmith had to make sure there was enough high carbon steel in the raw mixture.

British Isles

In England

 and Wales

, despite the arrival of the blast furnace in the Weald
The Weald is the name given to an area in South East England situated between the parallel chalk escarpments of the North and the South Downs. It should be regarded as three separate parts: the sandstone "High Weald" in the centre; the clay "Low Weald" periphery; and the Greensand Ridge which...

 in about 1491, bloomery forges (probably using water-power for a hammer as well as the bellows) were operating 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,...

 region beyond 1580. In Furness
Furness is a peninsula in south Cumbria, England. At its widest extent, it is considered to cover the whole of North Lonsdale, that part of the Lonsdale hundred that is an exclave of the historic county of Lancashire, lying to the north of Morecambe Bay....

 and 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....

Garstang is a town and civil parish within the Wyre borough of Lancashire, England. It is ten miles north-northwest of the city of Preston and eleven miles south of Lancaster, and had a total resident population of 4,074 in 2001....

) did not close until about 1770.


They survived in Spain

 and southern France

 as Catalan
Catalonia is an autonomous community in northeastern Spain, with the official status of a "nationality" of Spain. Catalonia comprises four provinces: Barcelona, Girona, Lleida, and Tarragona. Its capital and largest city is Barcelona. Catalonia covers an area of 32,114 km² and has an...

 forges to the mid-19th century, and in Austria

 as the stuckofen to 1775. In Adirondacks, New York
New York

, new bloomeries using the hot blast
Hot blast
Hot blast refers to the preheating of air blown into a blast furnace or other metallurgical process. This has the result of considerably reducing the fuel consumed in the process...

 technique were built in the 19th century.

New World

In the Spanish colonization of the Americas
Spanish colonization of the Americas
Colonial expansion under the Spanish Empire was initiated by the Spanish conquistadores and developed by the Monarchy of Spain through its administrators and missionaries. The motivations for colonial expansion were trade and the spread of the Christian faith through indigenous conversions...

The encomienda was a system that was employed mainly by the Spanish crown during the colonization of the Americas to regulate Native American labor....

s, and pueblos. As part of the Franciscan Spanish missions
Spanish missions in California
The Spanish missions in California comprise a series of religious and military outposts established by Spanish Catholics of the Franciscan Order between 1769 and 1823 to spread the Christian faith among the local Native Americans. The missions represented the first major effort by Europeans to...

 in Alta California
Alta California
Alta California was a province and territory in the Viceroyalty of New Spain and later a territory and department in independent Mexico. The territory was created in 1769 out of the northern part of the former province of Las Californias, and consisted of the modern American states of California,...

, the "Catalan forges" at Mission San Juan Capistrano
Mission San Juan Capistrano
Mission San Juan Capistrano was a Spanish mission in Southern California, located in present-day San Juan Capistrano. It was founded on All Saints Day November 1, 1776, by Spanish Catholics of the Franciscan Order...


Orange County, California
Orange County is a county in the U.S. state of California. Its county seat is Santa Ana. As of the 2010 census, its population was 3,010,232, up from 2,846,293 at the 2000 census, making it the third most populous county in California, behind Los Angeles County and San Diego County...

's first industrial complex."

External links
