Technology as seen through the case of ferrous metallurgy in Han China

Donald B. Wagner

Translated into Italian by Fabrizio Pregadio and published in Enciclopedia Italiana: Storia della scienza: Scienza in Cina,ed. by Karine Chemla, in cooperation with Francesca Bray, Fu Daiwie, Huang Yi-Long, and Georges Métailié. Roma: Istituto della Enciclopedia Italiana.

Box 1 || Box 2 || Bibliography || Figures || Chinese characters

In 117 BCE the Emperor Wu-di 武帝 approved a proposal for the establishment of a state monopoly of iron production and trade throughout the Han Empire. This measure was long a subject of bitter contention, and remained so for centuries. It was a useful historical example to be discussed by many later writers in connection with political questions of their own time: for example Wang Anshi on the New Policies of 1069 and Thomas T. Read in 1935 on Roosevelt's New Deal (see Qi Xia, 1988, p. 580; Read, 1935). A brief chronological history of the Han state's administration of the iron industry is given in Box 1.

At the other end of the Eurasian continent, by contrast, the idea of a Roman state monopoly of the iron industry would have been absurd. While there did exist large state ironworks run by the Roman army, most iron production occurred in thousands of tiny units scattered in villages throughout the Empire. There would have been no way at all of enforcing a monopoly, and it is also difficult to imagine what advantage the Roman state might have derived from such a monopoly.

The difference lay in the technology of iron production. Bloomery smelting, the only iron-smelting process known in Europe until Medieval times, lends itself well to small-scale production. It was used in early China to some (unknown) extent, but by the 3rd century BCE it appears that most iron was being produced in blast furnaces, which provide very large economies of scale. These techniques are described in Box 2.

As to the actual fabrication of artefacts from the iron produced in one of these ways, the work of the blacksmith, East or West, is an inherently small-scale operation, while iron-casting, used in China very early but not in Europe until Medieval times, is most efficient at a somewhat larger scale of production.

The book Discourses on salt and iron (Yan tie lun) 鹽鐵論, a compilation of contributions to both sides of the controversy over the monopoly, contains several passages which shed light on the question of the scale of production. It appears that the iron industry in China before the monopoly included both large- and small-scale producers. The government side of the controversy describes the large-scale sector:

In the past, great and powerful families obtained control of the benefits of mountains and seas. They extracted iron ore to smelt and cast it, and they boiled the seas to make salt. One family might gather a multitude of over a thousand persons, nearly all of them common bandits. Travelling far from their homes and abandoning the graves of their ancestors, they became dependent on the great families. Being assembled in deep mountains and remote marshes, engaging in illicit enterprises and following the power of factions, their tendency to commit wrongs was a danger. [Wang Liqi, 1992, p.p. 78–79; cf. Gale, 1967, p. 35; Baudry–Weulersse et al., 1978, p. 74]

A major argument for the state monopoly was thus the necessity of controlling these powerful industrialists with their large armies of workers.

Under the monopoly, archaeological evidence indicates that iron production took place in large-scale blast-furnace works. The proponents of the monopoly describe the operation of these works and contrast it with their view of earlier private iron production:

Forced labourers and master craftsmen work daily for the state in the public interest. Their raw materials are supplied in abundance and their equipment is complete. When ordinary people gather together [to make iron], their time is too short and they are fatigued by the work; the strength of the iron is not 'melted and refined' and 'the hard and the soft are not harmonised'. For this reason the administration proposed that possession be taken of the salt and iron industries, so that usage would be unified and prices equalised, to the benefit of the common people and public and private [interests].  . . . The local officers instruct [the workers], the craftsmen do their work effectively, hard and soft are harmonised, and the implements are practicable. What suffering does this cause the people, and why should the farmers be distressed? [Wang Liqi, 1992, p. 429; cf. Baudry–Weulersse et al., 1978, p. 194]

(The technical terms used in this passage are unfortunately incomprehensible today.) The opponents of the monopoly have a very different view of both the past and the present:

Earlier, when foundrywork and salt-boiling were permitted to the people on the payment of a self-assessed tax, salt and grain were sold together. Implements were practical and suitable for use. Today the iron implements produced by the State are mostly crude and coarse. Expense is not spared, the convict labourers are driven, but their hard work is not used effectively. When the members of a household united, and father and son pooled their labour, all sought to make excellent implements. Inferior implements were not sold. At busy times for agricultural activity the implements were transported to the fields for distribution. People traded with each other, exchanging money and products, grain, and new and old [implements]. Sometimes they sold on credit, so that they did not abandon their vocation. The agricultural implements were supplied, and each one got what he needed. . . . Now that [the state has] taken possession of the sources and monopolised the trade, implements are hard and brittle and there is no choosing between good and bad. The responsible officers are often not at their posts, so that the implements are difficult to obtain.  . . .  Salt and iron are sold at high prices, so that the common people are troubled. Some of the poorest must till with wooden implements . . . and eat tasteless food. [Wang Liqi, 1992, pp. 429–430; cf. Baudry–Weulersse et al., 1978, p. 195]

It is likely that the small-scale household ironworks described here, where 'father and son pooled their labour', used the bloomery process, while the blast furnace was used for iron smelting in the large works run by powerful families with hundreds of workers. In pre-modern economies it is not unusual to find production industries divided into distinct large- and small-scale sectors which co-exist in stable equilibrium. One example is the use of the bloomery in many parts of Europe and America long after the introduction of the blast furnace (see e.g. Percy, 1864, pp. 278 ff; Gordon & Killick, 1992). Another is that in the Chinese province of Guangdong, where two types of blast furnace – very small and quite large – were used for many centuries up to the 18th or early 19th century (see Wagner, 1997, pp. 58–75). In both of these cases (and others as well), although the large-scale technology was more efficient in narrow engineering terms, the small-scale technology offered important advantages under specific local conditions such as the availability of certain resources, the structure of the labour force, and the cost of labour, transportation, and capital.

Under the monopoly, new very large blast-furnace ironworks were built throughout the Empire (see the map, Figure 2). Here both management and skilled labourers (charcoal-makers, miners, furnace-masters, etc.) were taken over from the pre-monopoly ironworks, while the unskilled work was done by convict labourers and possibly by local peasants under corvée requirements. Archaeology shows that the monopoly ironworks were generally built in urban locations, often only a few hundred metres outside the walls of Han cities. This is a shocking location for a charcoal-fuelled blast furnace, which consumed enormous amounts of fuel in competition with the population of the city and also created a nuisance with fire and smoke and produced large amounts of slag to be disposed of. The ore, too, is likely to have been transported over long distances. The efficient location for such an ironworks is in the mountains, near sources of wood for charcoal and away from population centres – the 'deep mountains and remote marshes' of the first passage quoted above. The placement of the monopoly ironworks near cities was undoubtedly for convenience of administration, and perhaps also to simplify the control of large numbers of convict labourers.

Production of iron outside of the state ironworks was forbidden. We may suppose that the prohibition was relatively easy to enforce against the large-scale private works, for in spite of their remote location they produced for large markets and were necessarily highly visible. Furthermore many (perhaps most, or even all) of the private ironmasters were brought into the state bureaucracy as managers of the new ironworks.

Quite another question is whether it was possible to enforce the prohibition against the small-scale works, which cannot have had nearly the same visibility. While this seems unlikely on its face, there is one piece of evidence which suggests that the prohibition was in fact effective. As far as we can tell from presently-available archaeological material, bloomery technology seems to have disappeared totally in China by the early Han period. This is odd: we should expect that the small-scale bloomery technology would have continued in use virtually indefinitely in numerous parts of the Empire, especially those which were remote and isolated. Future archaeological findings may disprove this view, but if it is true that bloomery technology disappeared in China in the early Han then this is more likely to have been caused by the state prohibition than by straight competition with blast furnace technology. If the prohibition was effective for a generation or two the technology would have been forgotten. Significantly, when at some later time (perhaps in the Song period?) a new very-small-scale iron-production technology was developed in China, it used a small blast furnace rather than anything resembling a bloomery (see Wagner, 1997).

A possible additional factor is what we might call 'dumping' by the state. If the products of the monopoly ironworks were sold – at least in the early years – at prices distinctly lower than those of the illegal producers, clearly the prohibition would have been easier to enforce. The prices of the monopoly products would have been almost arbitrary, for it would have been impossible to estimate the true cost of convict and corvée labour, which are likely to have appeared in the accounts as costing nothing.

One of the prime reasons for the establishment of the monopolies was that they provided income for the state. The activist policies of the time, especially the newly-aggressive policies toward the Xiongnu and other nomadic challengers, required new sources of income, and the fortunes being made in industrial production were an obvious target for exploitation. Taxation seems to have been tried, including the 'self-assessed tax' mentioned by the critics in a passage quoted above, but the Chinese state had little experience in the taxation of other activities than agriculture. Clearly both the large-scale and the small-scale producers would have found it easy to misrepresent their production quantities and evade a large part of the tax. The solution chosen was to bring the producers into the government.

Most studies of Han economic history stress this financial aspect, but the monopolies solved other problems for the state as well. We have already seen the argument that the monopoly made it possible to bring under control the rich and powerful ironmasters, who 'gathered a multitude of over a thousand persons' who 'abandoned the graves of their ancestors' and 'assembled in deep mountains and remote marshes'. The government side takes up this argument again in another passage:

The Censor-in-chief: When an ordinary man has a valuable object, he will put it in a box to keep it safe. How then should the Ruler treat the mountains and seas? The places of abundance are always in the midst of deep mountains and extensive marshes, and only a wealthy and powerful person can fully exploit their benefits.  . . .
Now [the government's critics wish to] release the common people [to seek] power and profit and abolish the salt and iron [offices], thereby enriching the brutal and tyrannical [industrialists]. They [would then] follow their greedy hearts, the masses would form gangs, and individual households would form factions. The recalcitrant would become increasingly ungovernable, and among the followers of [heterodox] leaders, perverse tendencies would emerge. [Wang Liqi, 1992, p. 67; cf. Baudry–Weulersse, Levi, & Baudry, 1978, pp. 71; Gale, 1967, pp. 30–31]

Blast-furnace iron production is highly capital-intensive, and wealth is required for its exploitation. Further, a certain charisma and knowledge of men is required to keep order among the hundreds of workers at an ironworks. Organising and leading men was, for the government side, one of the prerogatives of the state. The establishment of salt and iron offices brought these potentially dangerous wealthy leaders under the control of the state while simultaneously giving them a secure place within the Imperial order. The use of convict labour removed the command of large gangs of workers to other administrative instances, and the establishment of ironworks near cities brought the industry from its 'deep mountains and extensive marshes' to become a part of civilised society.

Here the government side presents this transformation of the rôle of the industrialist as a victory of the state over the forces of disorder, but on its face it would also seem in many ways to have been an excellent bargain for the industrialists as well. Many Han writers felt that the wrong persons were obtaining official position. The government's critics in the Discourses constantly repeat that official position is for those who have studied the Classics and thereby acquired the proper moral habitus for a servant of the Emperor and administrator of the people. They point out the enormous wealth acquired by those in charge of the monopoly ironworks, and describe graphically the opulence in which they live. The government side does not deny this, but argues that wealth is a natural concomitant of responsible office. Throughout the Discourses the government side takes wealth to be a prime indicator of achievement, while the critics defend cultural values as superior to economic values (see e.g. Wang Liqi, 1992, pp. 121, 207–209; Baudry–Weulersse et al., 1978, pp. 78–79, 116–117; Gale, 1967, pp. 54–58, 103–104).

There are some questions which could have been raised in the debate, but do not in fact appear in the Discourses. One, already mentioned, is ecological: the large monopoly ironworks, placed near population centres, must have polluted their surroundings and contributed significantly to deforestation. Deforestation by metallurgical industry is mentioned briefly in the book Huainan zi (ch. 8. p. 10a; Morgan, 1935, pp. 95–96), but either it was not mentioned in the debate on the iron monopoly, or Huan Kuan did not choose to copy it into the Discourses. Either explanation seems odd, and this question needs more study.

In a more speculative vein, macroeconomic phenomena may also have played a part in the decision to establish the monopolies. A large-scale industry divided into many independent units, operating in free competition with very limited knowledge of current market conditions, will very likely experience the 'boom-and-bust cycle' which is familiar from early capitalist industry. In the demand-led 'boom' period, overinvestment and overproduction lead to falling prices and the ruin of overextended industrialists; a 'bust' period follows, with unemployment, insufficient production, and, in time, rising prices leading to a new boom. Such a cycle would have been a danger to the stability of the Han state, especially if it involved many hundreds of unemployed workers in the mountains who had 'abandoned the graves of their ancestors' and had little choice but to become bandits. There seems to be nothing anywhere in the sources of Han history which can easily be interpreted as a reference to a boom-and-bust cycle, but the historiographic question is how such a cycle would have appeared from the vantage point of the government's ministers. This would depend very much on what sort of information the central government received from its representatives in the provinces, and the question seems impossible to answer. On the other hand we may note that under the state monopoly the same underlying economic causes might well have led to chronic overproduction, and this is in fact one of the complaints of the government's critics in the Discourses (see Wang Liqi, 1992, p. 430; Baudry–Weulersse et al., 1978, p. 196).

In the Roman Empire, though iron production was rarely concentrated, there were other industries whose technology did encourage large-scale production. Rostovtzeff (1957, pp. 349–352) notices a trend in the Imperial period away from 'house-economy' toward large-scale 'capitalist' industry and then back toward a smaller scale of industrial production. This course of development is loosely analogous to that seen in Han China, with the rise of blast furnace iron production, the establishment of large ironworks under the monopoly, and the later rise of illegal iron production, very likely on a smaller scale than the monopoly ironworks. Any detailed comparison is of course rendered pointless by two important differences in Han China: a technology which provides extremely large economies of scale and a powerful interventionist government.

Rostovtzeff, writing in the 1920's, discusses several possible explanations for the 'failure' of large-scale industry to develop further in Roman Europe. He concludes that a major factor was a failure of demand. The belief is still widespread today that technological progress will naturally tend toward large-scale production; only when this development does not take place is a historical explanation thought to be necessary. However many historians and economists now recognise both the complexities of industrial scale (see e.g. Galbraith, 1967; Schumacher, 1973) and the assumptions hidden in the idea that certain familiar developments constitute necessary 'progress' (Wagner 1997).

The quotations above from the debate in Han China include arguments which are common today. Small-scale production can have important political, social, and ecological advantages; large-scale production can be technically superior, producing a better product, and can be more efficient in its consumption of scarce resources. In a pre-modern context, however, its overall economic efficiency is limited by the cost of transportation. An explanation appears to be needed for the rise of large-scale production as well as for the later tendency toward a smaller scale.

A factor which tends to be ignored is one particular scarce resource, skilled labour. In the context of rising demand in a large market, localised small-scale production may not be capable of spreading out to all regions of demand because of a scarcity of skilled workers; demand can be satisfied only by concentrated large-scale production, which usually requires fewer skilled workers for a given production rate. This advantage can very well outweigh the disadvantage of higher transportation costs, at least for a time. As more workers learn the necessary skills and establish themselves in the industry, however, local small-scale production may well again become dominant. This argument fails only with the radically lowered transport costs of modern times.

A common and not very interesting truism in modern debates is that 'technology has consequences'. This statement can be stiffened considerably: particular technologies have particular consequences. In the case considered here, the iron-production technology of Roman Europe encouraged small-scale localised production, and a direct consequence of this was that iron was never politically or financially interesting to the state. In China, one consequence of a technology which gives significant economies of scale was that a powerful state took a direct interest in iron production and thereby further increased its economic and political power.

Box 1: The Han state monopoly of the iron industry

In the Warring States period several of the individual state governments were directly involved in the administration of iron production. This was especially true of the state of Qin, whose administrative system became that of the Qin Empire from 220 BCE

The Han dynasty from 206 BCE continued the Qin system until 158 BCE, when controls were relaxed in some way. Very little is known of how these earlier administrative systems functioned, but it is clear that they afforded considerable freedom to private enterprise. A number of industrialists are said to have amassed huge fortunes in iron production, both before and after the relaxation.

During the activist reign of the Emperor Wu-di (140–87 BCE) a number of measures were adopted which may be called, risking anachronism, 'interventions in the economy'. These included state monopolies on the salt and iron industries (117 BCE), a system of 'equable transportation' (junshu, ca. 110 BCE) to equalise commodity prices through space and time, a monopoly on the production of fermented liquors (98 BCE), and various measures concerning coinage.

What we know of the actual administration of the iron monopoly is largely from a later time. In A.D. 2 there were 48 'Iron Offices' (tieguan) distributed throughout the Empire (see the map, Figure 2). Each administered at least one ironworks, often several. About thirty of these ironworks have been excavated by archaeologists, and inscriptions on their products give additional information. The Iron Offices produced pig iron from ore in blast furnaces and sold cast-iron implements as well as iron raw material. Wrought-iron artefacts, including virtually all iron and steel weapons, were made from this raw material by other state establishments, not directly connected with the monopoly administration.

From the beginning the monopolies were subject to a great deal of criticism. Curiously, most of the criticism seems to have come from provincial agricultural interests rather than the industrialists. This led to an inquiry in 81 BCE which is the putative subject of the famous book Discourses on salt and iron (Yan tie lun, compiled by Huan Kuan in the period 74–49 BCE). The inquiry had very little effect on government policy, and the criticism continued.

The monopolies were abolished in 44 BCE and reinstated three years later. Very little is known of the details of this incident, but it is likely that the abolition was ideologically motivated while the reinstatement was a matter of practical necessity. A major industry cannot be privatised at a stroke without consequences for the entire economy: probably quite serious problems became apparent within a short time, and the government found it necessary to return to former arrangements.

During the reign of Wang Mang (9–23 CE) draconian measures were taken to enforce the monopolies. It appears from archaeological and other evidence that while the state Iron Offices continued production, and perhaps still accounted for the greater part of Han iron production, private producers were now openly flouting the law.

The 1st century BCE had seen the gradual erosion of the powers of the central government in favour of powerful provincial families, and Wang Mang's reforms represent a last-ditch effort to reassert central authority. After Wang Mang's fall and the restoration of the Han in 25 CE an administrative reorganisation took place which in effect endorsed the central government's loss of power. In the case of the iron industry, it would seem that the Iron Offices continued production, but that private production was also permitted. (See Bielenstein, 1979, pp. 16, 25, 153–154 for a different interpretation.)

In 85 CE the monopolies were briefly reinstated; they were abolished again in 88.

[Sources: chiefly Shi ji 史記 (ch. 30) and Han shu 漢書 (chs. 24, 91). See Watson 1993, vol. 3, pp. 61–85; Swann, 1950; Twitchett & Loewe, 1986, pp. 160–163, 187–190, 508, et passim]

Box 2: The technology of iron production in Han China

The evidence available on the technology of iron production before the introduction of the monopoly in 117 BCE consists largely of the microstructures of iron artefacts (some of the artefacts are shown in Figure 1). These show that both foundry and smithy techniques were used. Steel was regularly used in edged weapons and tools, and was often quench-hardened. Tools of cast iron were normally heat-treated to improve their mechanical properties, making them tougher and less likely to break in use (this is what is called in English malleable cast iron).

For the pre-monopoly period we have virtually no material to clarify the primary iron production technology: how iron was produced from ore, how (or whether) cast iron was converted to wrought iron, and how steel was made. There have simply not been proper excavations of any iron smelting sites of the period.

The archaeology of ironworks dating after the introduction of the monopoly is, on the other hand, very rich. Probably we owe our wealth of knowledge of the state ironworks to the needs of the bureaucracy, which dictated that the ironworks should be near administrative centres, rather than in mountain forests, which would have been a more economically rational location. The continuity of Chinese economic geography means that sites in such locations are more likely to be discovered and excavated by modern archaeologists.

The diagram of Figure 3 shows the structure of iron production at the Han state ironworks. Cast iron was produced in blast furnaces, and this was either cast into useful products in a cupola furnace or converted to wrought iron in a fining hearth. Three well-published major excavations of Han state ironworks sites, all in the province of Henan, give us good information on all three processes (see Anon. 1962, 1978a; Zhao Qingyun et al., 1985; Li Jinghua, 1991; Li Jinghua & Chen Changshan, 1995). Minor excavations in other provinces indicate that the technology of the state ironworks did not vary greatly throughout the Empire.

Blast furnaces

A blast furnace is a shaft furnace in which cast iron is produced from ore. Ore, fuel, and a flux (normally limestone) are charged periodically into the top of the shaft, an air blast is blown continuously into tuyères near the bottom, and iron and slag are periodically tapped out at the bottom. Operation continues day and night for periods of days, weeks, or even years.

One typical blast furnace (at Guxingzhen in Gong County, Henan) was built on a very thick foundation, at least two metres thick. The furnace base, about 50 cm thick, is of tamped earth with a high proportion of fine sand, powdered charcoal, and powdered iron ore. This is not a very strong material, and it was reinforced with a retaining wall of tamped red clay. About 50 cm of the walls of the furnace, of the same material, remain. In general those parts which were exposed to the greatest temperatures were made of materials heavily tempered with powdered charcoal, which is stable at all temperatures so long as it is not exposed to air.

What makes a reconstruction of this furnace possible is a large piece of sintered iron, estimated to weigh 20 tonnes, found buried in a pit near it. It fits very well what remains of the base of the furnace, and gives us the shape of the lower part as well as the location of one of the tuyères. Figure 4 shows a reconstruction of the internal structure of the blast furnace, based on this and other evidence, by Liu Yuncai, Li Jinghua, and others.

The shaft of the furnace was elliptical, ca. 3 x 4 metres, with the hearth somewhat smaller. The elliptical shape made it possible to run a blast furnace with smaller blast pressure; it was used in Europe to some extent in the 19th century, and clearly it was very useful in the Han, when most blast furnaces were operated by human labour rather than water or steam power.

Estimates of the original height range from 4.5 to 6 metres. There is evidence that the furnace was shored up with tamped earth extending quite far (9 metres or more) from the walls. Presumably this shoring also acted as a ramp for the charging of the furnace, as shown in the sketch by Li Jinghua reproduced in Figure 5.

Examination of raw materials and slag from the site allows some conclusions on the operation of the blast furnace. The charge consisted of ore, charcoal, and limestone (mineral coal was not used in iron smelting in China before the 10th century, in Europe the 18th century). The ore is a rich hematite with very low sulphur. Hammers and anvils were used in breaking up the ore into pieces typically ranging in size from 2 to 5 cm. These were sieved to eliminate smaller pieces, leaving enormous hills of ore-gravel here and at other ironworks sites; this was done because small pieces in the charge would have made the furnace burden less porous, necessitating greater blast pressure. The ore was not calcined (roasted) before being charged into the furnace; this is a surprise, for calcining is a normal part of most smelting processes, ancient or modern. The purpose of calcining is to make the ore more porous and friable, but it would have made the furnace burden as a whole more compact and therefore less porous.

Some estimates of blast furnace operating parameters can be made by calculating materials balances. The ore contains about 50% iron, and very little iron is found in the slag, so about 2 tonnes of ore were needed for each tonne of iron produced. Most of the silica (SiO2) in the slag comes from the ore, and there is about five times as much silica in the slag as in the ore, so about 400 kg of slag were produced. The lime (CaO) in the slag comes largely from the ore and the limestone; the ore was ca. 5 per cent lime and limestone is about 50 per cent lime, less than 100 kg of limestone was used per tonne of iron produced.

There appears to be no reliable way to estimate pig iron production per day or year. Perhaps we can assume that production per year was of the same order of magnitude as that of 19th- and 20th-century Chinese traditional blast furnaces of the same size, a few hundred tonnes per year. If we were to assume an average annual production of 100 tonnes per Iron Office, then total annual legal production in the Han empire as a whole would have been about 5,000 tonnes, or about 0.1 kg per person. Obviously one cannot lend much credence to this figure, but perhaps it gives a feel for the general scale of Han iron production.

Cupola furnaces

It is possible that molten iron was sometimes cast directly into moulds from the blast furnace, as was common in the West until comparatively recent times, but there is no evidence for this, and it seems likely that for most, perhaps all, iron casting the iron was melted in a cupola furnace. A cupola furnace is a shaft furnace charged with fuel (coal or charcoal) and iron (pig or scrap) through the top and supplied with a blast blown in at the bottom. The iron melts in contact with the burning fuel and is tapped out at the bottom. A modern cupola is operated continuously for a day or two at a time, seldom longer.

Cupola furnaces have been found at numerous Han ironworks sites, and from this material Chinese metallurgists and archaeologists have produced the reconstruction shown in Figure 6. It is built of brick with an inner and outer layer of refractory clay. The height is 3–4 metres, inside diameter ca. 1.5 m. The base includes a hollow space, 17 cm high, supported by 12–15 cylindrical bricks. The fuel used was charcoal.

The design of the furnace suggests that great attention was paid to the generation of extremely high temperatures at a relatively high fuel efficiency. The hollow base and the thick (20–30 cm) walls provided thermal insulation. It can be seen that air from the bellows passes through a pipe up one side of the furnace, over the top, and down the other side to the tuyère. This arrangement provides for recycling of heat otherwise lost through the top. There is good evidence for this reconstruction: many of the earthenware pipes found have been subjected to such high heat that their surfaces are partially vitrified, and the directions of glass drips indicate the spatial orientations of the pipes in use.

The bellows

Nothing remains of the apparatus which produced the powerful air blast required by the blast furnaces and cupola furnaces. Whatever the precise form of the bellows, ancient texts indicate that it could be powered by human, animal, or water power. There is not much archaeological material to throw more light on this subject, but a Western Han feature at the one Han foundry site gives an interesting hint. Nearby the remains of several cupola furnaces is a circular pit, 2.6 metres deep and ca. 8 metres in diameter. A narrow stairway cut into the earth leads down into it. It is likely that workers or animals walked around in this pit turning some mechanism which powered the bellows. Whatever the mechanism used here, its purpose was to convert rotary motion to reciprocal motion, and a similar arrangement could have been used for water power.

Fining hearths

In the traditional Chinese iron industry in recent centuries the usual method of converting the high-carbon cast iron from the blast furnace to low-carbon wrought iron was by the fining process (Wagner 1997), and this method seems also to have been used in the Han period. The remains of a number of small hearths, believed to be fining hearths, have been found at several Han ironworks sites.

It is possible that we have a picture of iron-fining in the Han period in the tomb-relief shown in Figure 7. The bellows is the round object on the left. The blast is directed downward, presumably into a cavity dug into the ground. The worker standing on the left works the bellows. The activities of the next two workers, one lying down and one standing, are unclear. The next may be holding a piece of hot iron with tongs on an anvil while several (perhaps four) workers hammer it.


Classical sources

Han shu 漢書 [The history of the Former Han dynasty, 206 BCE – 23 CE, by Ban Gu, 32–92 CE]. Critical ed., 12 vols. with continuous pagination, Beijing: Zhonghua Shuju, 1962.

Huainan zi 淮南子 [The Master of Huainan, essays compiled at the court of Liu An, King of Huainan, sometime before 139 BCE]. Sibu beiyao ed. Shi ji [Records of the Grand Historian, by Sima Qian, ca. 145–90 BCE]. Critical ed., 10 vols. with continuous pagination, Beijing: Zhonghua Shuju, 1962.

Yan tie lun 鹽鐵論 [Discourses on salt and iron], by Huan Kuan, 1st cent. BCE Edition Wang Liqi, 1992.


Baudry–Weulersse, Delphine, Jean Levi, & Pierre Baudry (trs.), Chine, an –81: Dispute sur le sel et le fer. Yantie lun. Présentation par Georges Walter. Paris 1978.

Gale, Esson M. (tr.), Discourses on salt and iron: A debate on state control of commerce and industry in ancient China, Taipei, 1967.

Golas, Peter, Science and civilisation in China, originated by Joseph Needham. Vol. 5: Chemistry and chemical technology. Part 13: Mining. Cambridge, 1999.

Hartwell, Robert. 'A cycle of economic change in imperial China: Coal and iron in northeast China, 750–1350.' Journal of the economic and social history of the Orient, 1967a, 10, 102–59.

Loewe, Michael, Attempts at economic co-ordination during the Western Han dynasty, in S. R. Schram (ed.), The scope of state power in China, Hong Kong 1985, pp. 237–67.

Swann, Nancy Lee (tr.), Food and money in ancient China: The earliest economic history of China to A.D. 25, Princeton, N.J. 1950.

Twitchett, Denis & Michael Loewe (eds.), The Cambridge history of China. Vol. 1: The Ch'in and Han empires, 221 B.C. – A.D. 220, Cambridge 1986.

Wagner, Donald B., Iron and steel in ancient China, Leiden 1993. (Handbuch der Orientalistik, vierte Abteilung: China, no. 9).

Wagner, Donald B., The traditional Chinese iron industry and its modern fate, Richmond, Surrey 1997.

Wagner, Donald B., The state and the iron industry in Han China, Copenhagen, forthcoming in 2000.

Wang Liqi (ed)., Yan tie lun jiaozhu (dingben) [Critical edition of 'Discourses on salt and iron' (definitive version)], 2 vols., Beijing 1992. Orig. 1958.

Watson, Burton (tr.), Records of the Grand Historian. [1]: Qin Dynasty; [2]: Han Dynasty I, rev. ed.; [3]: Han Dynasty II, rev. ed., 3 vols., Hong Kong & New York 1993. [Vols. 2–3 orig. 1961].

References for specific points

Anon. (1962), Gongxian Tieshenggou [Excavation of a Han-period ironworks site at Tieshenggou in Gong County, Henan], Beijing 1962. Important corrections, Zhao Qingyun et al., 1985.

Anon. (1978a), Zhengzhou Guxingzhen Han dai yetie yizhi fajue jianbao [Excavation of a Han-period iron-smelting site at Guxingzhen in Zhengzhou, Henan], Wenwu ['Cultural relics'], 1978 (no. 2), pp. 28–43. Translation, Dien et al., 1985, pp. 1040–65.

Anon. (1978b), Henan Han dai yetie jishu chutan ['The iron and steel making techniques of the Han dynasty in Henan'], Kaogu xuebao ['Acta archaeologia Sinica'], 1978 (no. 1), 1–24 + plates 1–2. English summary p. 24.

Anon. (1981), Lintong Zhengzhuang Qin shiliao jiagongchang yizhi diaocha jianbao [Investigation of a Qin stone-dressing site at Zhengzhuang in Lintong County, Shaanxi], Kaogu yu wenwu ['Archaeology and cultural relics'], 1981 (no. 1), pp. 39–43 + plates 12–13.

Anon. (1985), Lintong xian Chenjiagou yizhi diaocha jianji [Investigation of a site at Chenjiagou in Lintong County, Shaanxi], Kaogu yu wenwu ['Archaeology and cultural relics'], 1985 (no. 1), pp. 19–22.

Bielenstein, Hans, The restoration of the Han dynasty. Vol. IV: The government, Bulletin of the Museum of Far Eastern Antiquities, 1979, 51, pp. 1–300.

Dien, Albert E., Jeffrey K. Riegel, & Nancy T. Price (eds.), Chinese archaeological abstracts, vols. 2–4. Institute of Archaeology, University of California, Los Angeles, 1985.

Galbraith, John Kenneth, The new industrial state, London, 1967.

Gordon, Robert B. & David J. Killick (1992), The metallurgy of the American bloomery process, Archeomaterials, 1992, 6 (no. 2), pp. 141–67.

Li Jinghua, Nanyang Beiguan Wafangzhuang Han dai yetie yizhi fajue baogao [Excavation of a Han-period iron-smelting site at Wafangzhuang, Beiguan, in Nanyang, Henan], Huaxia Kaogu ['Huaxia Archaeology'], 1991 (no. 1), pp. 1–110.

Li Jinghua & Chen Changshan, Nanyang Han dai yetie [Iron production in Nanyang, Henan, in the Han period], Zhengzhou 1995.

Liu Yuncai, Guxing gaolu fuyuan de zai yanjiu [Revision of the reconstruction of the blast furnace at Guxingzhen in Zhengzhou, Henan], Zhongyuan Wenwu ['Cultural relics from the Central Plains'], 1992 (no. 3), pp. 117–19.

Morgan, Evan (tr.), Tao the great luminant: Essays from Huai Nan Tzu, with introductory articles notes analyses, Shanghai 1935; repr. Taipei 1966.

Percy, John, Metallurgy: The art of extracting metals from their ores, and adapting them to various purposes of manufacture. [Vol. 2:] Iron; steel, London 1864.

Qi Xia, Song dai jingji shi [The economic history of the Sung period], 2 vols., Shanghai 1987–8.

Read, Thomas T., Iron, men and governments, Columbia University quarterly, 1935, 27, pp. 141–6.

Rostovtzeff, M., The social and economic history of the Roman Empire. 1st ed. 1926; German ed. 1931; Italian ed. 1933; 2nd English ed., rev. by P. M. Fraser, 2 vols., Oxford 1957.

Schumacher, E. F., Small is beautiful: A study of economics as if people mattered, London 1973.

Tylecote, R. F., Ancient metallurgy in China, The metallurgist and materials technologist Sept. 1983, pp. 435–439.

Zhao Qingyun (et al.), Gongxian Tieshenggou Han dai yezhu yizhi zai tantao [A reinvestigation of the Han ironworks site at Tieshenggou in Gong County, Henan], Kaogu xuebao ['Acta archaeologia Sinica'], 1985 (no. 2), pp. 157–83 + plates 1–4. English abstract pp. 182–3.


Figure 1. Iron artefacts from two Qin-period workshops associated with the Mausoleum of the First Emperor, reproduced from Anon., 1981, p. 41, fig. 3; Anon., 1985, p. 21, fig. 6.
1. Manacles. Total length 38 cm.
2. Punch. Length 8.5 cm, diameter 1.2 cm.
3. Spatula. Total length 11.8 cm, breadth of edge 2.7 cm. The end of the handle is bent around to form a hook.
4. Split spike with eye head. Length 10 cm, thickness 0.4 cm.
5. Spike. Length ca. 26 cm.
6. Chisel. Length ca. 13.5 cm.
7. Ladle. Incomplete length 25 cm.
8. Rectangular implement cap. Breadth of edge ca. 15 cm.
9. Hook. Distance between ends ca. 7.5 cm.
10. Ring-handled knife. Length ca. 16.5 cm.
11. Fragment of spade-head. Incomplete length 8.7 cm.
12. Ploughshare. 17 x 8–14.5 cm.
13. Unidentified implement. Length 28.2 cm, breadth 1 cm.
14. Knife. Length ca. 11–13 cm.
15. Sickle blade. Length 20 cm, breadth 2.1–2.8 cm.
16: U-shaped spade-cap.
17: Rectangular implement-cap.
18: Sickle-blade.
19: Rectangular implement-cap.
20, 23: Ring-handled knives.
21: Iron collar.
22: Ploughshare.
24: Spatula.

Figure 2. Relief map of central China showing the locations of Iron Offices according to a list prepared in A.D. 2. The map shows modern provincial boundaries and Han place names. Parts of this map are by Digital Wisdom Inc., Tappahannock, Va., U.S.A.

Figure 3. Flow diagram of iron production in a Han state ironworks. The fuel was charcoal. Cast iron was produced in blast furnaces, and this was either cast into useful products in a cupola furnace or converted to wrought iron in a fining hearth. Steel was made from wrought iron by any of a number of processes and used in the making of implements which a hard sharp edge.

Figure 4. Speculative reconstruction of the internal structure of a Han blast furnace. Dimensions are given in millimetres. See also Figure 5. Originally due to Liu Yuncai, Li Jinghua, and others (Anon., 1978a, p. 8, fig. 3; Liu Yuncai, 1992, pp. 118–119); modified by DBW.

Figure 5. Sketch by Li Jinghua of the operation of a Han blast furnace (redrawn by R. F. Tylecote, 1983, p. 437, fig. 4). The inner structure of the furnace is shown in Figure 4. The piled up earth shores up the furnace walls and also provides a ramp for the transport of charcoal, iron ore, and limestone to the furnace mouth.

Figure 6. Speculative reconstruction of a Han cupola furnace. Reproduced from Anon., 1978b, p. 12, fig. 4. Charcoal and iron are charged into the top and molten iron is periodically tapped out at the bottom. Air blast is carried by ceramic pipes over the top of the furnace to heat it before it enters at the bottom.

Figure 7. Detail of a rubbing of an Eastern Han period tomb-relief discovered at Hongdaoyuan in Teng County, Shandong. Archives of the Needham Research Institute, Cambridge. The relief is believed to show the fining of cast iron to wrought iron.

Chinese characters

Ban Gu
Han shu
Huainan zi
Huan Kuan
Liu An
Shi ji
Sima Qian
Wang Anshi
Wang Mang
Yan tie lun