Metallurgy Ancient Indian Metallurgy Vedic texts give us unique insights into the development of ancient Indian metallurgy Man and metals have an ageold relationship  Different periods of early human Civilization have been named after metals  The attributes of gold influenced the mind and heart of Indians so much so that they conferred upon the supreme spirit the designation of hirnyagarbha  It was so called because he remains in a golden egg as an embryo  The two important sources for the History of Indian metallurgy are archaeological excavations and literary evidence  Although a considerable amount of information on this subject from the study of archaeological finds is available literary evidence has not been studied to the extent it deserves Unique information related to metals and metallurgy is available in different Sanskrit texts beginning with Vedic texts to medieval and premodern texts  There are both direct and indirect types of references  An attempt has been made here to give a glimpse of some such references The Rigveda has widely referred to hiranya which is the oldest Sanskrit word for gold  It has also mentioned products made from gold such as water vessel necklace and visor  Chariots decorated with gold have also been mentioned  The Rigveda 10758 mentioned that the river Sindhu Indus contains gold  The word hiranyayi was used for the river  Another Rigveda hymn 82618 states that the path of the river Sindhu contains gold and the word used for it is hiranyavartanih  It is interesting to note that Sayana translated this word as hiranmayobhayakula ie both banks containing gold  The above hymns are some of the earliest indirect references to the alluvial placer gold deposits in India  The river Sindhu was an important source of gold in ancient times  It is interesting to note the references for the availability of alluvial placer gold in the river Sindhu are also reported in modern times  Tucci reported in 1977 that there was near the Indus Sindhu source as there are even now great mines of gold in the region of the Manasarovar and in Thokjalyug  Further in the itinerary in Khotanese Saka from Gilgit to Chilas written between 958 972  AD the Indus is called Ysarnijittaji 8212  the golden river which is not a mere poetic attribute but a reality Gold obtained from the river Jambu was called jambunanda and that from the river Ganga was called gangeya  These were also alluvial placer gold  The Pali text Anguttara Nikaya narrated the process of the recovery of gold dust or particles from alluvial placer gold deposits in allegorical form The Mahabharata referred to pipilika gold ants gold  Heaps of this type of gold was presented to the king Yudhishthira  at the time of rajasuya yagna ceremony  Pipilika gold was powdery in nature and of high purity  It was obtained by panning the auriferous soil of ant hills formed by ants or termites as a part of their nature on the land containing placer gold deposits and hence the name ants gold  Kautilya described a variety of gold called rasaviddha which was naturally occurring dissolved gold in liquid form  He stated that one pala a measure of this solution converts one hundred palas of silver or copper into gold which refers to the  cementation of gold on the surface of metals like silver and copper  A similar type of dissolved gold know as hatakaprabhasa was mentioned  in Gandavyuhasutra  Kalidas also mentioned such gold solutions and termed it Kanaka rasa  It is astonishing to note how people recognized such gold solutions in the past Native gold is invariably by no means a pure metal  It contains upto 20 percent silver copper iron lead bismuth platinum group metals and other metals as impurities  Thus native gold would have different colours depending upon the nature and amount of impurities present  It is logical to assume that the different colours of native gold were a major driving force for the development of gold refining process  Although evidence of gold refining is available in Vedic texts in an allegory form it was the Arthashastra of Kautilya which presented it in detail Gold refining was a twostage process  The first stage was the melting of impure gold alongwith lead which removed base metal impurities but not noble metals like silver  The second stage was to heat impure gold sheets with the soil of Sindhu State which contained salt  The sodium chloride present in the soil reacted with silver and the resulting silver chloride absorbed in the surrounding soil  This was a solid state process which involved diffusion of silver in impure gold and the subsequent formation of silver chloride at the goldsoil interface It is important to note that Kautilya stated that the starting sheet of impure gold must be thin as this would improve the kinetics of the solid state refining  Usage of gold in granular form as was the case at least in part in the Sardis refinery of the Lydian kingdom of Anatolia would result in lower yield Another important metal referred to in Rigveda is ayas  It has a shining appearance  Ayashas different meanings in different periods  In early Vedic period it means either copper or copper alloys  One of the important products made from ayas as stated in the Rigveda was the weapon of Indra called vajra  It was made by the process of sinchan casting  In the later Vedic period ayas or karshnayas means iron  In the Atharvaveda rajata silver trapu tin and sisalead have been mentioned Kautilya also described the method for refining silver which was similar to the first stage process used in gold refining  Further Kautilya stated a very  interesting qualitative test for ensuring the purity of cast silver ingots According to it the surface of the cast pure silver ingots should exhibit an appearance of chulika ie projections similar  to cocks comb  In other words  the top surface of the pure silver ingot has a rising appearance at certain places  In fact this is a reference to the spitting and sprouting behaviour of silver  Oxygen dissolves readily in molten silver  Molten silver dissolves approximately 20 times its own volume of oxygen near the melting point at one atmosphere pressure of oxygen  Just below the melting point the solid silver can dissolve oxygen only upto half its own volume under similar conditions The large difference in solubility of oxygen in the liquid and solid state causes the evolution of oxygen during solidification of molten silver  Bubbles of oxygen are then given off resulting in spitting at the free surface  As a result liquid silver from the interior is ejected on the surface of the ingot and a shape similar to a cocks comb is formed on the top surface after solidificationThis author carried out the experimental replication of the formation of  chulika on a small size cast pure silver  If silver contains base metals such as lead and copper then the dissolved oxygen would combine with it to form respective oxides  In such a situation the phenomenon of spitting would not be observed and the surface would be smooth In this context it is interesting to note that the law governing the solubility of gases in metals known as Sieverts law came into existence only in the early 20th Century  However ancient Indians recognized the practical aspect of Sieverts law in judging the purity of silver There is a rich Sanskrit terminology for metals from which interesting information on history of metallurgy can be derived  Only a few uncommon terms would be cited  Silver has a tendency to tarnish  It tarnishes readily when exposed to atmosphere containing sulphur and looks blackish  Due to this characteristic an uncommon Sanskrit name of silver is durvarna  The copper produced in Nepal was called naipalika or nepalaka and  was of  high purity  Tin recovered from leadtin  alloy was called nagaja ie that obtained from naga lead  Similarly tin recovered from the impure gold containing tin was called svarnaja  India was not rich in tin metal  Our ancestors were conscious of this problem and also exploited secondary sources for tin recovery  The presence of lead adversely affects the characteristics of gold and hence it was also called as hemaghna The Rasaratnasamuchchaya described three types of ferrous materials viz munda tiksnaand kanta  When iron ore pieces are reduced by charcoal  in solid state iron blocks containing  porosity results  For this reason the reduced iron blocks are also called sponge iron blocks  Any useful products can only be obtained from this material after removing the residual porosity by hot forging  The  hot forged sponge iron blocks are also termed as wrought iron  Munda was wrought iron  As the name suggests tiksna has superior hardness as compared to munda  Tiksna represented crucible steel made by liquid metallurgy and also probably further carburised wrought iron  Special  varieties of iron were called kanta  An exciting example of wrought iron produced in ancient India is the World famous Delhi Iron Pillar  It was erected in the present position in Delhi in the 5th Century AD by king Chandra Varman  However the engraved Sanskrit inscription suggests that it was probably brought here from elsewhere in the Gupta period  The average composition wt of the  wrought iron of the pillar is Fe 015 C 005 Si 005 Mn 025 P 0005 Ni 003 Cu 002 N  The most significant aspect of the pillar is that there is no sign of any corrosion in spite of the fact that it has been exposed to the atmosphere for about 1600 years Another striking feature of the pillar is its manufacturing technology  It was made by successive hot forging of directly reduced sponge iron blocks produced from the solid state reduction of iron ore by charcoal in a die  The joint lines that have not been completely removed by forging are clearly visible on the pillar  This author discussed this aspect in detail and opined that this procedure is basically very similar to current metal powder forging techniques with a difference that the latter is not usually used to make a long product by joining pieces together Powder Metallurgy 1990 33 2 119  In both the cases hot forging in a die is done not only to give the required shape but also to remove the residual porosity present in the starting material Indian crucible steel was a celebrated material worldwide  It was usually produced by simultaneous carburisation and melting of wrought iron in closed crucibles  Valmiki referred to it by the term refined iron  Kautilya termed it vratta because it was of circular shape  Dr Helenus Scott sent specimens of a variety of crucible steel available in Mumbai area to sir Joseph Banks the then President of the Royal Society London for experimental investigation in 1794  He referred to this steel as wootz in his letter  Recent researches  by this author have revealed that the actual name of this steel was the Sanskrit utsa which was erroneously transliterated in Roman Script as wootz by Scott  James Stodart fellow of the Royal Society did extensive work on this steel and mastered its hot forging Stodart was so overwhelmed with its quality that he mentioned this name utsa in Devanagari Script on his trade card alongwith a note that it is to be preferred over the best steel in Europe  It was named utsa because it had a characteristic of oozing out of low melting point liquid phase when heated to moderate temperatures Historically brass an alloy of copper and zinc was known to man much earlier than they were able to extract zinc from its ore on a large scale  In early period zinc was designated as sattva of zinc ore  In medieval period its was designated as yashada in Sanskrit  Zinc oxide   known as pushpanjan has been referred to in Charak Samhita  Rasaratnakar second Century AD provides the earliest documentary evidence for the cementation process for brass making and reductiondistillation process for zinc extraction  Rasarnava and Rasaratnasamuchchayadescribed a typical crucible known as vrintak having a shape similar to that of a long variety of brinjal to be used for making the reductiondistillation chamber  The basic principle of the process resembles that of the large scale 12 Century industrial process for zinc extraction uncovered at Zawar near Udaipur  It is a unique discovery and the retorts used at Zawar are similar to the vrintak crucible The Mahabharata and some Puranas have referred to ferrous arrowheads which were subjected to tailadhauta treatment  Valmiki used this terminology in the context of battle axe  Some of the commentaries of Ramayana have defined tailadhauta as the process used for hardening of ferrous objects  Clearly this terminology was used in the sense of oil quenchhardening of ferrous materials Manasollas written in 1131 AD gives detailed information on fine quality metal image casting by madhuchchhishta vidhan lost wax process  Both sushira hollow and ghana solid images were cast  Although the documentary evidence is of a later period it had been used since a very long time ago  The famous bronze dancing girl from Mohanjodaro  was made by this process  Shilparatna later part of 16th Century has mentioned the process of making fine gold powder from thin gold leaves for painting applications  The powder produced would have a flaky shape which gives higher covering area per unit mass In the Indian tradition people with expertise in technical disciplines were highly regarded  This is reflected in a hymn of Atharvaveda in which karmar ironsmith or metalsmith in general has been called manishi ie a wise  or learned person  Further it has been stated in the Kavyamimansa 10th Century A D that goldsmith ironsmith and similar other people should also be invited by kings in the kavyapariksa sabha ie literary meetings organised to judge the scholarship of poets य धवन रथकर करमर य मनषण उपसतन परण महय तव सरवन कणवभत जनन६ Atharvaveda 356 Metal technology for that matter all other technologies are human creations shaped historically by context  The examples discussed here illustrate how ancient Indians solved metallurgical challenges which helped in the development of Indian metallurgy and also the scientific and technological temper in the people of those times It is understandable that most of the metal technologies of the past are not relevant in present times  However examples from the past can reenergise us towards encouraging local innovations and  enterprise at all levels  Finally it is clear that Vedic and classical Sanskrit texts are knowledge texts and the study of Sanskrit has value because Sanskrit is not just a classical language but a vehicle of discovering our knowledge inheritance and assessing its contemporary relevance 8212821282128212821282128212821282128212 by Dr R K Dube retired Professor and Head Department of Material Science IIT Kanpur Paper published in Financial Chronicle Tuesday April 21 2015 Links वदक वङगमय म वनसपत वजञन क सवरप Botany in the VedasDilip Kumar Mishra वद म रसयन वजञन Chemistry in the VedasSri Prakash Pandey Modern or Einsteinian Physics Versus Indian Oriental PhysicsNG Dongre Hiranya Gold Metallurgy in Rigveda In Special Reference to JewellaryNairanjana Srivastava