130 7·The Iron Age already reduced in the melt to the extent that it yielded steel.This process,which is called puddling today,was rediscovered in Eng- land in 1784.During the latter part of the Han dynasty (202 B.C.-A.D.220),immense industrial complexes were operating near Zheng-Zhou and other places containing several huge furnaces (4 X 3 m in area and about 3 m high)which might have pro- duced several tons of iron per day.Moreover,the Chinese already used the technique of stack casting,that is,they arranged several molds on top of and next to each other,which enabled them to cast up to 120 articles at the same time.The large-scale produc- tion of plowshares,hoes,cart bearings,and harness buckles made the output quite cost-effective.It thus allowed a wide distribu- tion of tools for working the fields and digging irrigation chan- nels,which in turn might have led to a larger production of agri- cultural crops and probably even to an increase in population. In other words,the change that was brought about by the intro- duction of iron and steel slowly revolutionized the way the Chi- nese and probably other peoples lived and worked.Nomads have no need for agricultural tools,but the availability of these tools probably contributed to the settlement of some nomads.And fi- nally,iron paved the way from agriculture to industry.The po- tential for China to become a world-wide industrial power al- ready 2000 years ago was laid by these inventions and by their large-scale exploitation.But Chinese bureaucracy upheld by Con- fucian-trained civil servants apparently stifled new ideas and the expansion of major trade beyond the boundaries of China. The same revolutionizing developments that were caused by the use of iron were eventually also seen in other parts of the world.Goods made of iron were traded virtually everywhere.Iron axes reduced the amount of forests to provide fuel and to clear land for feeding more people.Weapons made of iron or steel (see for example Plate 7.2)unfortunately provided the means to con- quer and often destroy other civilizations.Knights wore armors of iron.Indeed,iron was and still is,in many cultures,the sym- bol for strength,power,and will. One particular amazing demonstration of iron workmanship is the famous iron pillar next to the Qutub Minar tower on the outskirts of Delhi in India.The pillar made of forged iron is seven meters tall and has a purity of about 99.2%,containing only small amounts of sulphur (0.08%),phosphorus (0.11%),silicon (0.46%),and carbon (0.08%).It dates back to the fourth century A.D.and probably was manufactured by heating and hammering together a large number of small iron pieces.Most amazingly, however,the iron pillar has not experienced any corrosion dur- ing the 1500 years in which it has been exposed to air.It is spec- ulated that the lack of rusting is due to a combination of climatic
already reduced in the melt to the extent that it yielded steel. This process, which is called puddling today, was rediscovered in England in 1784. During the latter part of the Han dynasty (202 B.C.–A.D. 220), immense industrial complexes were operating near Zheng-Zhou and other places containing several huge furnaces (4 3 m in area and about 3 m high) which might have produced several tons of iron per day. Moreover, the Chinese already used the technique of stack casting, that is, they arranged several molds on top of and next to each other, which enabled them to cast up to 120 articles at the same time. The large-scale production of plowshares, hoes, cart bearings, and harness buckles made the output quite cost-effective. It thus allowed a wide distribution of tools for working the fields and digging irrigation channels, which in turn might have led to a larger production of agricultural crops and probably even to an increase in population. In other words, the change that was brought about by the introduction of iron and steel slowly revolutionized the way the Chinese and probably other peoples lived and worked. Nomads have no need for agricultural tools, but the availability of these tools probably contributed to the settlement of some nomads. And finally, iron paved the way from agriculture to industry. The potential for China to become a world-wide industrial power already 2000 years ago was laid by these inventions and by their large-scale exploitation. But Chinese bureaucracy upheld by Confucian-trained civil servants apparently stifled new ideas and the expansion of major trade beyond the boundaries of China. The same revolutionizing developments that were caused by the use of iron were eventually also seen in other parts of the world. Goods made of iron were traded virtually everywhere. Iron axes reduced the amount of forests to provide fuel and to clear land for feeding more people. Weapons made of iron or steel (see for example Plate 7.2) unfortunately provided the means to conquer and often destroy other civilizations. Knights wore armors of iron. Indeed, iron was and still is, in many cultures, the symbol for strength, power, and will. One particular amazing demonstration of iron workmanship is the famous iron pillar next to the Qutub Minar tower on the outskirts of Delhi in India. The pillar made of forged iron is seven meters tall and has a purity of about 99.2%, containing only small amounts of sulphur (0.08%), phosphorus (0.11%), silicon (0.46%), and carbon (0.08%). It dates back to the fourth century A.D. and probably was manufactured by heating and hammering together a large number of small iron pieces. Most amazingly, however, the iron pillar has not experienced any corrosion during the 1500 years in which it has been exposed to air. It is speculated that the lack of rusting is due to a combination of climatic 130 7 • The Iron Age
7·The Iron Age 131 factors,high P and S contents,and a large heat capacity.Another, larger iron pillar was found at Sarnath,which was produced be- tween 300 and 200 B.C.and before it broke was almost 14 m tall. The time at which iron was first smelted in India is not exactly known.However,iron production is mentioned in the Rigveda, which is the oldest known Hindu religious book.Conservative es- timates place its origin around 1200 B.C.Other sources claim that iron smelting in India did not commence before 600 B.C. Another specialty of India that was produced and sold virtu- ally across the entire continent from the first millennium B.C.un- til the middle ages was the so-called wootz steel which was later named Damascus steel.It is said that it was the raw material for the best swords and daggers of that time (see Plates 7.3 and 7.4).Wootz steel was made by placing small pieces of wrought iron or sponge iron (see above)together with some wood chips and leaves in small clay crucibles which were sealed with a clay lid and then heated in air-blast-enhanced fires.This enabled the carbon from the plant material to evenly penetrate the iron,thus providing an essentially homogeneous iron-carbon steel.(In con- trast to this,the Mediterranean or Chinese technologies allowed only a portion of the work piece to be steel,as described above. The other parts were either wrought iron or cast iron.)The In- dians succeeded in keeping their technique a secret until the sev- enth century A.D.,after which the Syrians near Damascus and the Spaniards near Toledo came up with their own versions.The Damascus swords of later times were produced by joining and folding through hammer-welding alternate bars of iron and steel. Application of a dilute acid colored the steel sections leaving the iron relatively bright.Wootz steel was also reinvented in Eng- land during the eighteenth century. When reporting about the advances which major civilizations contributed to the art of iron and steel making,it is often over- looked that less known peoples were also able to prepare iron goods.Their contributions might not have been as spectacular as those described above,but they still had some local impact on the lives in certain societies.Among them were the Haya people, who lived near the shores of Lake Victoria,which is part of to- day's Tanzania in East Africa.Their folktales are full of stories about iron making,and the vocabulary with which they are told is enriched with reproductive symbolism.(A PBS documentary entitled,"The Tree of Iron,"witnesses to this effect.) During the Middle Ages the knowledge of metallurgy in gen- eral and iron and steel making in particular precipitated into written documents.Among them were books like De re metallica by the German extractive metallurgist and miner Georgius Agri- cola,who summarized in 1556 the then-available knowledge on
factors, high P and S contents, and a large heat capacity. Another, larger iron pillar was found at Sarnath, which was produced between 300 and 200 B.C. and before it broke was almost 14 m tall. The time at which iron was first smelted in India is not exactly known. However, iron production is mentioned in the Rigveda, which is the oldest known Hindu religious book. Conservative estimates place its origin around 1200 B.C. Other sources claim that iron smelting in India did not commence before 600 B.C. Another specialty of India that was produced and sold virtually across the entire continent from the first millennium B.C. until the middle ages was the so-called wootz steel which was later named Damascus steel. It is said that it was the raw material for the best swords and daggers of that time (see Plates 7.3 and 7.4). Wootz steel was made by placing small pieces of wrought iron or sponge iron (see above) together with some wood chips and leaves in small clay crucibles which were sealed with a clay lid and then heated in air-blast–enhanced fires. This enabled the carbon from the plant material to evenly penetrate the iron, thus providing an essentially homogeneous iron–carbon steel. (In contrast to this, the Mediterranean or Chinese technologies allowed only a portion of the work piece to be steel, as described above. The other parts were either wrought iron or cast iron.) The Indians succeeded in keeping their technique a secret until the seventh century A.D., after which the Syrians near Damascus and the Spaniards near Toledo came up with their own versions. The Damascus swords of later times were produced by joining and folding through hammer-welding alternate bars of iron and steel. Application of a dilute acid colored the steel sections leaving the iron relatively bright. Wootz steel was also reinvented in England during the eighteenth century. When reporting about the advances which major civilizations contributed to the art of iron and steel making, it is often overlooked that less known peoples were also able to prepare iron goods. Their contributions might not have been as spectacular as those described above, but they still had some local impact on the lives in certain societies. Among them were the Haya people, who lived near the shores of Lake Victoria, which is part of today’s Tanzania in East Africa. Their folktales are full of stories about iron making, and the vocabulary with which they are told is enriched with reproductive symbolism. (A PBS documentary entitled, “The Tree of Iron,” witnesses to this effect.) During the Middle Ages the knowledge of metallurgy in general and iron and steel making in particular precipitated into written documents. Among them were books like De re metallica by the German extractive metallurgist and miner Georgius Agricola, who summarized in 1556 the then-available knowledge on 7 • The Iron Age 131