Professor Arun Kumar Biswas
The Asiatic Society
1, Park Street
achieved the distinction of being the only country in the ancient and
the medieval world to produce pure zinc metal and high zinc-brass
alloys. The saga of zinc in ancient India has been established only
recently by a team of scholars from India (Hegde, Biswas) and England
(Craddock, Willies). The present author has recorded the current status
of our knowledge on the subject in a paper and in a book. This provides
a brief summary and also includes a hitherto unpublished material on
the Bidri alloy.
earlier occurrence of zinc in man - made artifacts is in the form of
the copper alloy known as brass. Ever since the discovery of copper and
the alloying elements of tin, arsenic, lead, etc., different materials,
including zinc, were used to alloy and harden copper.
earliest method of making brass was possibly the cementation process in
which finely divided copper fragments were intimately mixed with
roasted zinc ore (oxide) and reducing agent, such as charcoal, and
heated to 1000oC in a sealed crucible. Zinc vapour formed,
dissolved into the copper fragments yielding a poor quality brass, zinc
percentage of which could not be easily controlled.
of zinc with copper increases the strength, hardness and toughness of
the latter. When the alloy is composed of 10-18% zinc, it has a
pleasing golden yellow colour. It can also take very high polish and
glitter like gold. For this property, brass has been widely used for
casting statuary, covering temple roofs, fabricating vessels, etc.
Reduction of zinc oxide around 1000oC is crucially important : below 950oC no zinc is produced. Zinc is obtained in the vapour form at this temperature, since its b.p. is 913oC.
With trace of oxygen, the zinc vapour would be reoxidised and hence the
successful operations in the past must have been done in closed
crucibles. If the temperature were higher than 1083o C
during brass-making, then copper would melt and flow down to the bottom
of the crucible forming a puddle there, exposing a very small surface
area of the metal for alloy formation.
Brasses containing upto 36% zinc are known as a-
brasses, which undergo easy cold work. Brasses containing more than 46
% zinc are brittle. With zinc content between 36 and 46%, we have a+b brasses which are lighter, harder and more suitable for casting statuary.
and Haedecke demonstrated experimentally that brass produced by the
cementation process could not contain more than 28% zinc. Brass
founders trying the cementation process have verified this observation.
materials of antiquity containing more than 28% zinc in copper matrix
must have been prepared by mixing the two metals, which could have been
possible only after the discovery of zinc as a separate metal and its
preparation by a process such as distillation. The antiquity of brass
artifacts can, therefore, be divided into two eras, one preceding, and
the other following the discovery of zinc as a separate metal.
BRASS BEFORE THE DISCOVERY OF ZINC
claim that the earliest artifact noted so far containing an appreciable
amount of zinc anywhere in the world is from India. Lothal (2200 1500
BC) showed one highly oxidised antiquity (No. 4189) which assayed :
70.7 % copper, 6.04 % zinc , 0.9% Fe and 6.04 % acid-soluble component
(probably carbonate, a product of atmospheric corrosion). The material
could have been prepared through smelting of zinc-bearing copper ore or
the cementation route described earlier. The raw materials might have
come from the Ahar-Zawar area. The Harappan site of Rosdi, also in
Gujarat, has yielded a few samples of chisel, celt, rod and bangle,
made of brass and assaying upto 1.54% zinc.
materials might have been used for making the brass-bronze items of
Atranjikhera during the PGW era (1200-600) BC. One copper-based item
contained 11.68% Sn, 9.0% Pb and 6.28% Zinc, while another item assayed
20.72% Sn and 16.20% Zn. Both the samples contained traces of iron and
sulphur, indicating the possibility of chalcopyrite and
sphalerite-galena having been the source materials, which could easily
come from the Ahar-Zawar area. Most of the brass samples in ancient
India contained variable proportions of Zn, Sn and Pb (Table 1).
Table 1 Analysis of Some Brass Object in Ancient India
|S.No||Date & Site||Object||Analysis %||Remarks|
|1.||- 1500 BC Lothal||No.4189 Copper Object||70.70||6.04||-||-||Ref.5|
|Chisel, Celt |
|4.||4th century BC|
|5.||2nd century BC||Bangle||73.72||19.70||0.10||5.84||Ref.8|
|6.||2nd Century AD|
|Female figure carrying flower container Indo Parthian||88.60||7.60||0.13||2.49||Ref.6 pp.56-57|
|7.||5th century AD||Gandhara Buddha||68.50||20.25||3.86||3.62||Ref.13|
|8.||6th century AD Akota||Ambika||76.70||16.32||1.61||4.04||Ref.6, pp.104-105|
|9.||7th Century AD Mahudi||Rishabhanatha||66.00||12.80||5.90||1.50||Ref.6, p.66|
|10.||8th century AD Kashmir||Shiva||82.00||17.00||1.00||-||Ref.14|
|11.||9th Century AD Nalanda||Buddha||78.95||15.15||0.74||3.03||Ref.15|
|12.||11th century AD, W.Tibet||Manjusri||65.50||30.40||0.30||1.70||Ref.16|
We have drawn attention to the brass items of Lothal and Atranjikhera and their possible link with the 1260 + 160, 1136 + 160 BC and 1050+ 150 C-14 dates of the timber samples in the Rajpura Dariba silver-lead-zinc mine near Udaipur.
the Harappan era, copper used to be alloyed with tin and arsenic; since
these were scarce commodities, alternative alloying elements had to be
looked for. Artisans in the Rajasthan-Gujarat region might have
stumbled on to zinc ore deposit as a new source of alloying element.
et al surveyed the evidences of early brass artifacts in the West. The
earliest brass artifacts known in the West come from excavations at the
Gordion Tomb in Phrygia, dating from the 8th and 7th centuries BC
onwards. These came after the Lothal and Atranjikhera traditions. From
the 7th Century BC, the Greeks commented upon brass or oreichalkos, but
always as an expensive, exotic metal not produced in Greece. There was
no zinc in the early Greek bronzes, Etruscan bronze of the 5th century
BC contained 11% zinc.
ZINC METAL AND HIGH ZINC BRASS
earliest brass containing more than 28% zinc, which could be made only
after the isolation of pure zinc metal came from Taxila. Craddock
pointed out the overriding importance of the vase (BM 215-284)
excavated from the Bhir Mound at Taxila and dated to the 4th century
BC. This brass sample contains 34.34% zinc, 4.25 % Sn, 3.0 % Pb, 1.77%
Fe and 0.4% Nickel. This is very strong evidence for the availability
of metallic zinc in the 4th century BC. Possibly India was the first to
make this metal zinc (rasaka) by the distillation process, as practised
for the other metal mercury (rasa).
are references to zinc and brass in the lost (4th century BC) text
Philippica or Theopompus, quoted by Strabo in his Geography :
is a stone near Andreida (north west Anatolia) which yields iron when
burnt. After being treated in a furnace with a certain earth it yields
droplets of false silver. This added to copper, forms the so-called
mixture, which some call oreichalkos" (Strabco, Geogrraphy, Book XIII,
reference pertains probably to the process of downward distillation of
zinc ( droplets of false silver ) and its subsequent mixing with copper
to make brass oreichalkos (arakuta in Kautilya s Arthasastra) described
in detail in the post-Christian era Sanskrit texts.
is quite possible that the zinc making technology travelled west from
India during 6th-5th centuries BC, as it did later again in the 18th
century AD. The pseudo-Aristotelian work On Marvellous Things Heard
say that amongst the Indians the bronze is so bright, clean and free
from corrosion that it is indistinguishable from gold, but that amongst
the cups of Darius there is considerable number that could not be
distinguished from gold or bronze except by colour" (quoted by Craddock)
Indian emphasis was on the gold-like brass and not on the zinc metal.
The Greeks, however, used zinc metal as such in a few cases. In the
course of the excavation of the Agora in Athens, a roll of sheet zinc
was found in a sealed deposit dating from the 3rd or 2nd century BC.
Analysis showed it to be nearly pure zinc with 1.3% lead, 0.06 % Fe and
0.005% Cu with traces of Mn, Mg, Sn, Ag and Sb (quotated by Craddock).
Although Needham and Forbes doubted the above evidence on the ground
that the pieces were beyond the contemporary technology . Craddock
certifies this to be genuine sample. It is quite possible that the
Greeks had carried the material or the technology which had existed in
Taxila as early as 4th century BC and possibly much earlier in
MINING ARCHAEOLOGY AND SMELTING RELATED TO INDIAN ZINC ORE
recent pioneering work on the zinc-lead-silver mining archaelogy in the
southern part of Rajasthan by Willies et al and the relevant C-14 dates
have firmly established India s primacy in non-ferrous ore mining in
the ancient world.
ancient workings in the South Lode (100 m depth) of Rajpura-Dariba mine
(80 km north-east of Udaipur) have been C-14 dated as 1260 BC, 1050 BC
and the East Lode workings as 375 BC, 360 BC, 250 BC, 120 BC, 150 AD
etc. Thus, it is clear that the tradition of underground mining in
India goes back to the thirteenth century BC, if not earlier. The
earliest emphasis was possibly on copper ore; at Rajpura-Dariba, the
other targets were lead, silver and possibly zinc ore, which is
strongly suggested by the brass artifacts of Lothal and Atranjikhera.
art of smelting zinc ore and recovery of zinc metal by distillation
must have been discovered before 4th century BC when Taxila produced
the brass vase containing 34.34 % zinc. This possibility is reinforced
by the facts of mining archaelogy. Starting from the 5th century BC, we
have many C-14 datings in Rajpura-Dariba, Rampura-Agucha (40 km south
of Ajmer) and most crucially, in the Zawar mine systems.
Zawar (24o21' N, 73 o41'E)
is about 30 km south-west from Udaipur, where the ancient mines
(earliest C-14 date obtained so far is 430 BC) are found, both opencast
and underground. Zawar Mala, Mochia and Balaria are some of the
specific mines in this area.
host rock of the Zawar mines is sheared dolomite, the result of
metamorphism of sedimentary dolomites. The ore was geologically
deposited syngenetically as disseminated lenses within the dolomite
beds. Zinc occurs as sphalerite or as marmatite in which zinc sulphide
is in solid solution with iron sulphide. Also associated with the rock
are galena, hydrozincite, pyrite, silver, etc.
workings are found at outcrops on the ridge of Zawar Mala, and as deep
as the 470 m (above sea) levels of the modern Zawar Mala mine, some 120
m below surface. The upper parts accessible from there were a few tens
of metres below surface, isolated by a roof fall. At the surface, mine
openings occur at intervals of 50 m or so. Willies investigated one
mine of more commodious proportion Pratapkhan or Pratap s mine in
which Rana Pratap Singh, rival of Akbar, took refuge during 1595 1600
A.D. A flat room floored with phyllite slabs is inferred as Pratap s
refuge. The quarried materials used to feed a zinc smelter just below
the narrow valley.
The earliest C-14 datings in the Zawar mines are 430 + 100 BC of the PRL 932 sample from the Zawar Mala mine and 380 + 50
BC of the BM 2381 sample from the Mochia mine. Similar datings from
Rajpura Dariba (e.g. 375 BC), Rampura Agucha (370 BC), etc. confirm
widespread underground mining of lead-zinc ores in the southern
Rajasthan during the fifth-fourth centuries BC onwards.
Subsequent C-14 datings in the said mining area are : 250 BC, 200, 170, 140, 120 BC, 60 AD, 110AD, 150 AD.
regards the recovery of zinc from the ore, the crucible
reduction/distillation method was put to large scale commercial
practice in the 13thcentury AD; this will be described
later. Indirect and circumstantial evidences suggest that distillation
method was in vogue much earlier, probably from the 4th century BC onwards, although not on a large scale, as we find in the 13th century AD context.
this connection, we recall the evidence from Rampura Agucha. The
zinc-lead-silver ore at the site was selectively mined at least as
early as 370 and 250 BC. An appreciable amount of zinc must have been
separated from the zinc-rich ore (present-day ore in the site contains
13.5% zinc), as revealed from the low-zinc content slag. One sample of
slag assayed as low as 0.01% zinc. Near the slag dump area several
retort-like pieces were reported. When assembled, their appearance
suggested a cylinder approximately 20 cm long with walls 4-5 cm thick
and an innermost pipe-like feature with a coating dirty white material,
mainly zinc sulphate. They could be mistaken for tuyeres but for their
closed pointed ends. This is highly suggestive of a used retort. Along
with this, some thin walled tube-like object containing a thin coating
of blister type material was also found.
is conceivable that the retorts were being used in the said context for
roasting zinc ore to obtain the light, white, smoky zinc oxide, which
the ancient Greeks called pompholyx or philosopher s wool. In the
modern zinc plant at Udaipur, roasting of zinc sulphide concentrate
produces not only zinc oxide (and sulphur dioxide gas) but also some
zinc sulphate, which was detected in the 4th-3rd century BC retort in Rampura Agucha.
said retorts, already found sealed at one end, must have been closed or
sealed at the other and also to prevent the escape of smoky zinc oxide
into the atmosphere. The retorts were possibly modified to serve as
reduction distillation chambers (to produce metallic zinc), the final
version of which, notified in the 13th century AD context,
would be described later. Very significantly, Tiwari et al. noted that
the slag sample from Agucha containing only 0.01% zinc but as high as
9.30% lead, was attached to baked earthen materials which could be
part of the earthen appliance used for smelting . We suggest the
possibility that the earthen appliance was a zinc distillation retort.
Remains of zinc furnaces have been found at Sojat in Jodhpur also.
BRASS AND ZINC IN ANCIENT INDIA
may now turn our attention to the antiquity of brass in ancient India.
Before the discovery of zinc metal in India (made by the distillation
route) sometime during the fifth-fourth century BC, brass could be
made, as in Lothal and Atranjikhera, only by the cementation route in
which one of the following was smelted along with copper ore : zinc
ore, sphalerite concentrate or the roasted product, philosopher s wool
or zinc oxide. The traditions of making philosophers wool and
cementation brass could have persisted even after the discovery of the
distillation process of making zinc. We invite attention of the readers
to the analysis of some Indian brass objects made before 4th century BC (Table I)
we have indicated earlier, the distillation route of making zinc and
alloying this with molten copper was the only way of making high-zinc
(more than 28%) brass, such as the 4th century BC Taxila
vase (34.34% zinc). The said vase (BM 215-284), excavated from the Bhir
Mound site, was made before the Greek settlement in Sirkap.
bangle from the second century BC Sirkap settlement assayed 19.70%
zinc. The Dharmarajika settlement of the post-Christian era produced
brass objects like bangle and pot with controlled compositions 77-79%
Cu, 12.88-13.07% Zn, 2.5-3.5% Sn and 3-6% Pb.
of the other early brass samples from ancient India have been reviewed
by Neogi and Ray, an extract of which is presented below :
Brass articles of 1st century
BC or AD have been found on excavation of some ancient stupas. General
ventura executed operations for the examination of the stupas at
Manikyalaya in 1830. Three deposits were obtained, of which the third,
at a depth of 64 ft. consisted of a copper box enclosing a brass
cylindrical box cast and a beautifully turned on the lathe. The lid of
brass casket was found on cleansing to be inscribed. From the
inscriptions on the various articles of this deposit and the
accompanying Indo Scythian coins, the great tope at Manikyalaya has
been identified to be a mausoleum of the Indo-Scythian King Kanishka (1st century BC or AD).
inscribed brass urn of the same date as the former has been discovered
in a tope about 30 miles west of Kabul in Wardak district. This urn,
which in shape and size approaches closely the ordinary water-vessels
in use in India to this day, was originally thickly gilt and its
surface has in consequence remained well preserved.
regards coins, both brass and bronze were used in ancient India for
coinage. Circular punch-marked brass coins of Dhanadeva and Aryavarma
of Ayodhya (c, 1st century BC) have been found. Brass coins
of kings of several other dynasties living at that time have also been
collected. From these archaeological and numismatic evidences it is
clear that brass was in common use in ancient India during the first
century BC. A small number of die-struck coins of the Pre-Gupta and
Gupta periods, including a piece attributed to Chandragupta II, are
considered to be made of brass.
Table I features some of the typical brass objects in ancient India up to 11th century AD, before the advent of Muslims in the country.
DISCOVERY OF THE MEDIEVAL ZINC SMELTING OUTFIT AT ZAWAR, NEAR UDAIPUR, RAJASTHAN
April 1980, the Hindustan Zinc Limited (HZL) sponsored a three-year
research project on recovery of zinc from the ancient slags which was
successfully conducted at the Indian Institute of Technology (IIT)
Kanpur by the present author. In 1982, HZL collaborated with British
Museum Research Laboratory (P.T.Craddock, Lyon Willies, etc.) and the
Department of Archaeology, M.S.University of Baroda (K.T.M.Hegde) on
archaeological investigations, and this led to the spectacular
discovery of the zinc distillation outfit, including furnaces and
retorts showing the production strategy, Craddock described the
the third day of the excavation (December 1983), one of the Baroda team
(Hegde) spotted the corner of a refractory plate sticking out from a
heap of spent retorts beside a goat track in a valley on Zawar Mala
With mounting excitement we cleared a small area above and around it to
reveal first, the edges of furnace walls, and then the tops of retorts
still in situ."
archaeological and archaeo-material investigations followed : we now
present the summary of the results of the historical experiments
performed in two continents.
ANCIENT RETORTS AND FURNACES AT ZAWAR
the 1983 excavations, two groups of furnaces were uncovered. A single
bank of seven furnaces upon Zawar Mala contained small retorts 20 cm
long and 10 cm in diameter. In old Zawar, there was a more extensive
arrangement of furnaces using a larger retorts (30-35 cm long and 10-15
cm diameter). In both groups, 36 retorts in a 6 x 6 arrangement were
contained within the truncated pyramid of each furnace. Thus, no less
than 252 retorts were fired simultaneously in a single bank. The
retorts were supported vertically on perforated bricks through which
the condenser tubes passed into the cooler zinc collectors
furnaces are in two parts consisting of a zinc vapour condensation
chamber at the bottom and a furnace chamber at the top. The two
chambers are separated by a perforated terracotta plate. The
condensation chamber measures 65 x 65 cm and 20 cm in height. The
perforated terracotta plate that separates the two chambers is a
composite unit made up of four equal segments of 35 cm2. It
is 4 cm thick, well-baked, and sturdy. Its perforations include
circular holes of two sizes : larger ones of 4 cm diameter each of
which is surrounded by a number of smaller holes of 2.5 cm diameter.
Within the furnace, the composite terracotta plate was found to be
supported on a ledge in the furnace walls on all four sides and a
single solid terracotta pillar placed below the junction of its four
Up above the
perforated terracotta plate is the furnace chamber, in which 36 charged
retorts (Figs.1-2) were arranged, inverted vertically; it may be
presumed that 36 vessels were placed, one underneath each retort, to
collect the condensed zinc vapour. This arrangement of downward
distillation retort with the condensing unit underneath or
distillation per descensum , is precisely what had been described in
Rasaratnasamuccaya text (2,157-166, 9.48-50). The brinjal-like retorts
in Zawar (Fig.3) are also similar to the vrntakamusa described in
appears that a cylindrical reed of 1.5 cm diameter was inserted into
the retort after it was charged and the funnel part was luted on it
(Fig.3); this is evident from the central hole which is preserved in
many retort residues. The reed helped to keep the charge within the
retort when it was inverted and placed in the furnace. When the furnace
was fired, the reed burnt away leaving behind a cylindrical flow
channel for the zinc vapour to flow freely out of the retort. The ore
must have been roasted before smelting.
smelting charge must have included a small quantity of common salt (as
surmised from the chlorine and sodium contents in the retort residue)
and an adequately large quantity of carbonaceous matter, apart from the
calcined ore, and then rolled into pellets of 1 cm3 volume
Rasa Ratna Samuccaya or RRS 2.163-164 refers to the gutikakrti pellets
containing sodium bicarbonate and borax). The charge (about 1.5 kg per
retort) was loaded into clay retorts fitted with funnel like condenser
tubes, as described before (Fig.3). These were indeed the
brinjal-shaped crucible or vrntakamusa, as described in RRS(2.157,
2.163, 10.23-24, etc.). On heating in the furnace, zinc oxide was
reduced by a carbonaceous matter to zinc vapour. The reducing blue
flame of carbon monoxide was observed to be substituted by white flame
of zinc vapour, indicating that reduction had taken place (bhavet bila
sita yadi RRS 2.159-160).
a scanning electron microscope and observing the vitrification textures
of the Zawar retort and clay materials, Freestone estimated that the
temperature reached in the Zawar zinc distillation furnace was of the
order of 1150-1200oC, and that this temperature was
maintained for 5 hours ore more. The highly endothermic reduction of
zinc oxide must have been achieved at a very low partial pressure of
oxygen (less than 10-20 atm) to prevent re-oxidation of the metal. Zinc vapour condensed in the tube, the temperature being around 500oC,
and collected in the vessels placed below. This kind of downward
distillation or tiryakpatana of zinc vapour, produced under a highly
reducing atmosphere, has been described in RRS (2.163-168, 10.48-50).
A part of the zinc oxide was converted to well-identified silicate phases and thus could not be recovered as reduced metal.
et al. estimated that 200-500 g zinc was extracted per retort, or 7-18
kg per smelt of 36 retorts. Each retort weighs about 3 kg. Thus, the
debris of around 6 lakh tons of spent retorts corresponds to about 1
lakh ton of zinc, according to Freestone et al. which might have been
produced at Zawar during 13th-18th centuries AD. This has been indeed one of the most outstanding levels of industrial production in the medieval world.
PHASE STUDIES ON ZAWAR SLAGS AT IIT, KANPUR
lakh tons of spent retorts contain two lakh tons of residues within,
assaying about 3% zinc. Therefore, some 6000 tons of zinc metal remain
within the retort residue, and probably another 1000 tons in the lead
slag. Our research at the Indian Institute of Technology (IIT) Kanpur,
sponsored by the Hindustan Zinc Limited, was directed towards the
recovery of zinc from these two kinds of slags. The first step in our
world was characterization of these residues, which turned out to be
very useful and relevant to the archaeo-metallurgical problem.
The phases identified by X-ray and electron diffraction studies by Biswas et al. are summarized in Table 2.
2 - Phases Identified in Zawar Retort (Content), Wall and (Lead) Slag
by X-ray and Electron Diffraction Studies (Biswas et al.)
|X-ray diffraction ||Electron diffraction|
Esperite Ca2Pb (ZnSiO4)4
Sphalerite Zns, Chalcopyrite
CuFeS2, larsenite, PbZnSiO4
|Zn2P2O7.5H2O, goslarite, |
or aurichalcite Zn5(CO3)2(OH)6
|Goslarite, hardistone, hemi- |
|Goslarite, hemimorphite, |
|Quartz, goslarite, |
Sphalerite, chalcopyrite, hardistone
|Hemimorphite, goslarite, |
The results show that in the roasting operation prior to retort
distillation, a small part of sphalerite was not converted into oxide
and remained in the retort as ZnS and ZnSO4. The presence of goslarite or ZnSO4.7H2O
(hydrated at a later stage) was confirmed by the endothermic DTA peaks
apart from X-ray and electron diffraction studies. Some ZnO might have
remained unconverted in the retort to undergo atmospheric conversion to
basic carbonate at a later stage. While most of the ZnO was reduced to
metal, a part of it must have been converted at a high temperature to
phosphate and silicates from which the metal could not be recovered.
Biswas et al. detected a number of zinc, calcium-zinc, lead-zinc,
calcium-lead-zinc and magnesium-aluminium silicates. Later, Freestone
et al. reported that lead slag contained iron, calcium-iron,
calcium-zinc, magnesium and calcium-magnesium silicates. The only
silicate phase that Freestone et al. could report in the retort residue
was CaMgSi2O6 or diopside.
et al obtained secondary electron images of retort residue samples and
found that the particles have a variety of morphology : plates, needles
and spheres. Scanning electron microscopy and X-ray microanalysis
showed characteristic peaks of many elements, the most prominent being
those of silicon and calcium. Scanning was done a fine electron probe
on the zinc-containing particles in the size range of 0.5 40 m m.
Several of the small particles (0.5-8.0 m m)
show approximately constant values for the ratio of intensities
corresponding to the elements Si, Ca, Mg, Fe, Al, Zn, Pb, Mn, Na, K and
S (in decreasing order of occurrence), indicating that these particles
containing a few of the above elements are homogenous in nature. The
larger particles show wide variation in intensity ratios and hence
variation in the chemical composition of the grains from point to
point. Thus, the approximate size of the zinc containing and other
homogenous grains in the retort residue is in the range 0.5-8.0 m m.
size of the particles in the lead slag sample was found to be lower
than that in the retort residue. The size of the zinc-containing grains
was estimated to be in the range 0.5-6.0 m m. m m,
by carrying out point to point analysis. The X-ray spectrum showed the
presence of titanium apart from the other elements noted in the retort
The work at IIT
Kanpur was directed primarily towards the recovery of zinc from the
siliceous retort residue and slag at Zawar. We found that the
non-silicate phase, such as hydrozincite Zn5(CO3)2(OH)6 could
be easily leached by acid. A special fast leaching technique, making
use of the water-starved nature of the silicate-sulphuric acid system,
could recover more than 80% of the zinc contained in the silicate
phases, such as hemimorphite Zn4(OH)2Si2O7H2O, willemite Zn2SiO4 etc.
characterization work done at IIT, Kanpur, has established the
existence of complex zinc phosphate-silicate phases in the slag which
could have been produced only by the above 1000oC pyrometallurgical smelting process. This corroborates the conclusions reached by Craddock et al.
large scale manufacture and widespread use of zinc and brass in
medieval India need to be fully chronicled. Table 3 records a few brass
icons of India for the period 1350-1752 AD; the high zinc content,
sometimes in the range 35-40%, in these icons is particularly not
worthy. Item No.9 in Table 3 is dated 1752 AD five years before the
War of Plassey, and eight years before the Zawar production was slowed
down on account of the Maratha invasions. During the medieval period,
the Moghuls had used brass (as well as bronze) for manufacturing guns
and artisans of Bidar (83 km from Hyderabad) used high zinc (84%) brass
or bidri alloy for ornamentation over it by gold or silver ware.
Table 3 - Brass Icons in India (1350-1752 AD)
|S.No.||Site ||Item||Elemental percentages||Impurities|
|68.4||1.6||18.5||9.5||-||Fe, Ag, Bi|
|2.||Gujarat, 1480 AD||Model Temple with four doors 10 x 24.5 cm||68.6||0.2||28.9||1.6||-||Fe, Mg, Bi|
|3.||Gujarat 1485 AD||Vishnu-Narayana||58.9||0.5||36.8||2.1||-||Fe, Al, Ag, Si, Mg, Bi|
|Rajput Prince on Horse||72.9||0.4||21.8||2.7||1.0||Al ).3, Ag, Mg|
|5.||Gujarat 1554 AD||Kal Bhairava||76.7||1.2||13.8||6.3||1.5||Al, Mg|
|Chauri-Bearer||58.3||1.5||35.5||2.3||-||Fe, Ni, Al, Ag, Cd, Si, Mg|
|Dipalakshmi Rajput Girl||58.8||0.9||33.2||4.5||0.8||Al 1.6, Mg|
|Tirthankara-Seated||62.3||-||36.0||0.5||-||Fe, Ag, Bi|
|10.||Nepal||Sadakasari Lokesvara Form of Avalokitesvara||60.5||2.75||35.3||2.37||-||Fe, Ni, As, Au|
etymology of the words denoting zinc became clearer. Madanapala
Nirghantu of 1374 AD mentioned yasadam vangasadrsam or the zinc metal
(yasada) like tin (Table 4). Yasada means that which gives yasa or
fame; the connection was clear in so far as zinc was known to produce
the famous gold-like yellow alloy of brass (vide 2nd century
AD text Rasaratnakara 1.3). The European word zinc was probably
derived from yasada; the Sanskrit word became jast (Abdul Fazl) and
dasta in several Indian languages.
1597, Libavius (AD 1545-1616) received Indian zinc, which he called
Indian or Malabar lead . He was uncertain what it was. Although
Paracelsus (1616 AD) is generally credited to have given the name
zinc to the metal, large scale export of the metal from India to the
West started later in 17th century, and according to Roscoe,
the identification of zinc as the metal from blende or calamine was
accomplished by Homberg in 1695.
Table 4 Some Literature on Zinc
Nighantu refers to Yasam vangasadrsam (zinc tin like) : Yasada
means that which gives yasa or fame, converts copper into yellow
|1597 AD||Libavius receives a sample and calls it Indian or Malabar lead|
|1616 AD||Paracelsus calls it zinc from Yasada, in several Indian languages : dasta|
|1695 AD||Homberg identifies Indian zinc as the same metal from European calamine|
|Before 1730 AD||An Englishman transmitted Zawar technology to the West identity not known|
Champion s experiment at Warmley near Bristol; patent in 1738. Cost of
metal £ 260 a ton, whereas calamine cost only £ 6 a ton|
starts manufacturing zinc by distillation per descensum process
notoriously close to the Zawar process (Morgan and Craddock)|
s Disctionary of Trade and Commerce admits ignorance about zinc
technology. India continues making high Zn brass statues|
|1800-1820 AD||Zawar zinc industry devastated by famine and Marhatta invasion|
|1886 AD||V.Ball quotes Beckmann s History of Inventions (Bohn s Edition, ii.p.32) : "An Englishman went to India in the 17th century
to discover the process used there in the manufacture of zinc, and
returned with an account of distillation per descensum. I have not yet
been able to identify this Englishman".|
BIDRI AND OTHER ART WORKS IN PRE-MODERN INDIA
pre-modern India several traditions of art works based on metals,
alloys, gems and stones flourished and became internationally famous.
Many of these traditions started in ancient India and continue
vigorously in modern India.
ware, the sleek and smooth dark coloured metalwork with intricate
eye-catching designs on its glossy surface, is famous all over the
world. This metalwork as well as the technique to produce it are found
in India alone.
an alloy which contains 76 to 98 % (normally in the neighbourhood of 95
%) zinc, 2 to 10 % copper, upto 8 %. lead, 1 to 5% tin and trace of
iron (vide Table 5). Occasionally high percentage (19.9) of lead and
(11.4) tin have been noted. However mostly it is high zinc low copper
alloy. Up to 1 % copper in the zinc forms the terminal solid solution h ; above 1 % copper the Î phase
precipitates at the grain boundaries in this phase field. The usual
yellow brass may contain not more than 40-50 % zinc, often less; copper
constitutes the remainder or the predominant phase. Thus brass and
bidri represent the two opposite ends of the zinc- copper phase diagram.
Bidri ware s surface is first made smooth and a solution of copper
sulphate applied to it to darken it temporarily for engraving. The
engraving tools cut the intricate but delicate tapestry of design into
the metal which is then lighter in colour than the darkened surface and
enables the pattern to be seen clearly.
Table 5 Results of Atomic Absorption Spectrometry Analysis of Birdi Ware (Taken from La Nilece et al)
|Victoria & Albert Museum|
|Description||Percentage by weight content|
|Zinc||Copper ||Lead ||Tin||Iron|
|I.S. 46 1977||Weight||92.6||4.7||1.4||5.7||0.1|
|1479 1904||Ewert||89.3||4.8||0.8||< 0.1||0.8|
|I.S. 10 1973||Bowl||92.1||3.6||1.4||0.3||0.1|
|I.S.131 1958||Pan box||95.0||3.1||1.5||0.1||0.1|
|I.S. 181 1965||Huqqa||76.1||10.1||8.2||11.4||0.6|
|I.S. 31 1976||Bottle||98.6||2.6||1.0||0.4||1.2|
|I.S. 17 1 1970||Pan box||81.3||2.0||2.0||< 0.1||0.5|
|I.S. 4 1977||Huqqa||83.6||3.7||0.8||< 0.1||0.6|
|I.S. 19 1978||Huqqa||85.3||4.6||3.0||1.3||< 0.1|
|I.M. 224 1921||Bottle||91.7||3.6||0.7||0.7||0.7|
|I.S. 11 1973||Vessel||97.6||3.4||1.8||< 0.1||0.1|
|I.S. 39 1976||Huqqa||89.2||3.4||0.5||0.7||0.7|
|I.S. 19 - 1980||Huqqa||80.6||3.6||7.3||6.4||0.9|
|856 - 1874||Huqqa||77.4||4.4||0.9||0.4||0.1|
piece is then handed over to the inlayer. The inlay may be of silver,
brass or occasionally gold. The final stage after the inlay has been
burnished, is to blacken the surface of the piece so that the inlay
stands out. This is done by applying a paste of ammonium chloride,
potassium nitrate, sodium chloride, copper sulphate and mud which
darkens the body by producing a characteristic black patina while
having no effect on the inlay. The paste is later washed off and
finally oil is rubbed into the piece to deepen the blackness of the
patina. The result is a lustrous dense black body to contrast with the
shining lining white (silver) or yellow (brass or gold).
REPLICATION EXPERIMENTS AND CHEMICAL HYPOTHESIS
Niece and Martin performed some replication experiments to show that
the black colour of the patina was due to copper. The recipe for
blackening the bidri metal has the main constituents in a warm solution
of potassium nitrate (one part) often substituted by well-urinated
soil, and ammonium chloride (four parts).
a replication experiment a clean pure zinc sheet was immersed in the
above solution, when a pale grey patina of zinc oxide and chloride was
produced. When the experiment was repeated with the addition of copper
sulphate, a reasonably good but superficial black patina formed almost
instantaneously. Again only zinc oxide and chloride were the main
crystalline products. XRD analysis identified Zn5(OH)8Cl12H2O,ZnO and Cu2O
(cuprite) as the crystalline phases. None of these explains the
blackness of the patina which was amorphous and contained copper.
experiments were performed with a specially prepared alloy of zinc
containing 3 % copper. When this alloy was dipped in a warm solution of
potassium nitrate and ammonium chloride, it turned as deep black
instantly and the patina was even and adhered well to the metal
surface. This was found to be non-crystalline. Scanning electron
microscopy showed the patina to be about 10 m m thick assaying 30 % copper as a contrast to 3% in the bulk. Zinc and chlorine were the other elements detected.
niece and Martin have postulated that ammonium chloride preferentially
dissolves the zinc from bidri and the resulting copper-enriched surface
or the copper-rich Î phase precipitate gets
oxidised by potassium nitrate producing the black colour. The use of
clay does not seem to be crucially important. It could merely serve as
a source of alkali nitrate and as a poultice to absorb the unwanted
zinc chloride formed during the process. The matt black patina is
easily damaged by the standard cleaning techniques designed to remove
the white decomposition products from the zinc.
HISTORY OF THE ART TRADITION
mystery of the black patina is not yet fully solved. The inventors of
the tradition did not have any ideal about the underlying scientific
principles; they merely hit upon the arts and crafts aspect of the
The craft of
bidriware is a kind of damascene work which has defined by sir George
Birdwood as the art of encrusting one metal on another, not in crustae ,
which are soldered or wedged, but in the form of wire, which by
undercutting and hammering, is thoroughly incorporated into the metal
which it is intended to ornament. The original tradition at Damascus
was to encrust gold wire, and sometimes silver wire, on the surface of
iron, steel or bronze.
group of the damascene craftsmen moved from Syria or Iraq to india.
Some of them were at Ajmer in Rajastan and hit upon the idea that
damascening could be done on the base of high zinc low copper alloy.
Zawar in Rajastan was the major zinc production center in the medieval
world. the said craftsmen moved down south during the 15th century A.D.
and settled at Bidar (17 o55 N and 77o3 E) near Hyderabad. when the art flourished in that place for centuries, it became known as Bidriware crafts.
earliest known craftsmen like Abdullah-bin-khaiser and his pupil
Sivanna worked at Bijapur. Historical evidences indicate that the
beautiful articles presented to Alauddin Bahamani II (1434-1457 A.D.)
on the occasion of his coronation impressed him very much, and he
invited the craftsmen of Bijapur to settle at Bidar itself. The workers
used to prepare beautiful huqqa base, ewer bowl, pan box, basin,
bottle, slabchis, cot legs etc. The varieties of workmanship of the
design consisted of tarakashi (inlay of wire), taihnishan (inlay of
sheet) zaranishan (low relief, inlay levels with surrounding area),
zarabuland (high relief, for examples silver over a lead pad, aftabi
(design in overlaid sheet) etc.
russian traveller Althanasins Nikitin, who visited Bidar during
1470-1474 A.D., took with him some of the early Bidriware specimens for
presentation to the Russian Emperor. A large number of articles of
Bidriware were made for presentation to the prince of Wales when he
visited India in 1875. These now adorn the collection of the Victoria
and Albert Museum which has published a comprehensive bibliography and
illustrated catalogue on the subject. Bidar and Hyderabad museums also
have beautiful collections of this kind of ware.
has given some details about this craft under specific heading such as
raw materials, tools, implements, process of production, preparation of
alloy, mould making, casting (such as goblet ) etc. The manufacture of
Bidriware has been carried on under a system of division of labour. The
moulder prepares the alloyed metal, casts the vessel and turns it to
its proper shape by his lathe. The carver engraves the patterns on the
surface of the vessel, and the inlayer designs the patterns, inlays the
ornament of gold, silver or brass, and finally polishes the article. In
the pre-modern India there have been four seats of Bidriware
manufacture: Bidar, Lucknow, Purnea (Bihar) and Murshidabad (Bengal ).
Arun Kumar . The primacy of India in Ancient Brass and Zinc
Metallurgy.Indian Journal of History of Science , 28,(4), 1993, pp.
- Biswas, Arun Kumar and
Biswas, Sulekha; Minerals and Metals in Ancient India, 2 Volumes, U.K.
Print world ( P ) Ltd. 1996. Chapter 18 in Vol .1 ( pp. 351-384 ) is
entitled : Antiquity of Zinc and Brass in Ancient India
- Werner.O., Spektralanaivusche and Metallurgische Untersuchangen an Indischen Bronzen. Lerden.. Brill.,1972.
- Haedecke.K, Glerchgewichtsverhailtnisse bei der Messingherstellung nach de Galmerverfahren. Erzmetall. 26, 229-233.1973.
Lothal - A Harappan Port-Town ( 1995-62 ) in 2 Volumes. Archaeological
Survey of India, New Delhi. Vol.II. 1985 p.660. Chemicals analyses of
the Harappan Level samples were provided by B.B.Lal
- Swarnakamal, Metallic Art and Technology of Gujarat, Museum and Picture Gallery,Baroda.1978. pp. 36-37. 56-57. 56.104-105.
R.C., Excavations at Atranjkhera - Earlv Civilisation of the Upper
Ganga Basin.Aligarh Muslim University and Motilal Banarasidass. Delhi.
1983. p. 497
- Marshall.J., Taxila. 3 Volumes. Cambridge.1951
M., Smith. C.S., and Rodda. J.L., Metallographic Examination of a
sample of Mettalic Zinc from Ancient Athens.Hesperia (Suppl. 3. ).
- Tiwari .R.K., and
Kavdia N.K., Ancient Mining activity around Agucha Village.Bhilwara
District, Rajastan. Man & Envir . 8, 81-87, 1984
- Neogi.P., Copper in Ancient India,1917 reprinted in 1979 by Janaki Prakashan,Patna.10-42.
- History of Chemistry in Ancient and Medieval India, edited by P.Ray, Indian Chemical Society, Calcutta, pp.94-95, 1956
- Lo Bue, E.Statuary Metals in Tibet, in Reference 21, p.38
- Werner, O., Spectro-chemical Analysis of Antique and Modern Bronzes, Material Prufung.7 (12). 463-470, 1965
- Lal, B.B., An Examination of some Metal Images from Nalanda, Anc. India, 12, 53-57,1956
- Schroeder, U. Von., Indo-Tibetan Bronzes. Visual Dharma Publications Ltd., Hong Kong 1981
A.K., Biswas, S. and Chakraborty, N.A., Archaeo-material studies in
India and Literary Evidences in Historical Archaeology of India, edited
by A.Ray and S.Mukherjee, Books and Books, New Delhi, 1990, pp.49-66.
Lynn, Ancient Zinc-lead-silver Mining in Rajasthan, Interim Report,
Bull.Peak Dist. Mines. Hist. Soc. Ltd. 10(2), Winter 1987, pp.81-123
P.T., The Composition of Copper alloys used by the Greek, Ertuscan and
Roman Civilization The Origins and Early use of brass, J.Archaeol.
Sci., 5, 1978, pp. 1-16
P.T. et al, Hellenistic Copper-Base Coinage and the Origins of Brass,
in Scientific Studies in Numismatics edited by W.A. Oddy, Occasional
Paper No.18, British Museum, 1980, pp. 53-64
P.T., The Copper Alloys of Tibet and their Background, in Aspects of
Tibetan Metallurgy, Occasional Paper no.15, British Museum, 1981,
- Biswas, Arun Kumar, Annual
Reports to Hindustan Zinc Limited, Udaipur. Studies on Recovery of Zinc
form Floation Tailings and Ancient Slags. Indian Institute of
Technology, Kanpur, 1981-84
Arun Kumar, Gangopadhyaa, A. and Ramachandran, T.R., Phase Studies on
Zinc Residues of Ancient Indian Origin, Trans. Indian Inst. Metals, 37
(3), June 1984, pp. 234-241
P.T., Goat Path Discovery Unlocks Secrets of Medieval Zinc. IAMS
Newletter, No.6, Institute of Archaelogy, London, 1984
I.C., Craddock,P.T., Gurjar, L.K.Hegde, K.T.M. and Paliwal, H.V.,
Analytical Approaches to the Interpretation of Medieval Zinc Smelting
Debris from Zawar, Rajasthan, J.Archaeol. Chem., 3, December 1985,
- Hegde, K.T.M., Craddock, P.T., and Sonavane, V.H., Zinc Distillation in Ancient India, Proceedings of the 24th International Archaeometry Symposium, Smithsonian Institution Press, Washington, 1986, pp. 249-258
K.T.M., An Introduction to Ancient Indian Metallurgy, Geological
Society of India, Bangalore, 1991. A special chapter on Zinc and Brass
Production in Ancient India , pp. 56-83
Sayed Jafar, Metal Technology in Medieval India, Daya Publishing House,
Delhi, 1988. Chapter 14 (pp.115-126) is devoted to Bidri Metallurgy
- Gairola, T.R., Bidri Ware, Ancient India, 12, 1956, pp. 116-123
- Agarwal ,O.P., Bidri, Museum XXVII, 1975, p.193
- Stronge, S., Bidri Ware, Inlaid Metal work from India, Victoria and Albert museum, London, 1985
- La Niece, S. and Martin, G., The technical Examination of Bidri Ware, Studies in Conservation, 32, 1987, pp.97-101