-1IRON AGE SMELTING AT MELVILLE Koppies
Contents
1) Discovery
2) Origin of iron making
3) Types of furnaces
4) Bellows
5) Firing
6) Chemical process
7) Forging
8) Recent records of iron firings
8.1) Klaas’ firing
8.2) 1936 Empire celebration firings
8.3) Tshovote brothers
8.4) Wits experiments 1977
9) Black art
1) Discovery.
Prof Revil Mason of the University of the Witwatersrand Archaeological Research
Unit anticipated that there would be furnaces in the area because the ridges,
from Linksfield to Northcliff, are rich in iron ore. This can be seen fromthe reddish
colour of the shale, into which ferruginous fluids (iron rich) have seeped and
coloured it red. Many of the furnaces have been built over, but the ones at
Melville koppies had been saved because the Council bought the land in 1940s.
The lecture hut was supposed to be built where the protected furnace and shed
are now. A sharp eyed builder noticed a funny circular rim on the ground and
contacted Wits. There were also slag pellets on the surface, which were a good
indicator of a possible furnace A more recent furnace which had been at ground
level had been swept away by erosion. Pottery sherds and slag were found
banked up against the rim of the retaining rocks of the ridge
Revil Mason began to dig there in 1963 (site 7/63) and found the furnace, dated
1050 AD. The furnace that was excavated probably had a dome-shaped roof with
a chimney. The openings for the tuyeres may have been closed except for a
circular opening for the tuyeres. Erosion may have washed away the dome and
opened the sides openings more. The present shape is round with two openings
for the tuyeres (blow pipes)
Mason was also helped by the SA Defence Force, which was stationed at
Auckland Park. They used mine sweepers to look for further sites but were
unsuccessful. Aerial photos of the area were also not successful in revealing any
more sites.
-2Mason excavated two levels further down and found late Stone Age and Middle
Stone Age artefacts. These are all kept in a providenced collection at Wits
because MK cannot guarantee their security at the Koppies. However, donations
of similar artefacts are in display on the furnace.
The vandalized furnace on the lower northern slope was site 28/64. This is a
much more recent one, probably 1860’s. Bone fragments, teeth, pottery sherds,
slag, charcoal were found here. The remains of kraals to the north west of this
furnace are still there but they are well concealed by the bushes in the area. This
furnace was totally vandalized in 2000. The MKMC decided not to restore this
one because of the expense. The upper furnace was also vandalized at the
same time, but not so badly. The South African Ceramic Restorers repaired the
upper furnace. The bill was R20 000 but they only charged the MKMC R2000
because it is a non-profit organisation.
The cave, site 9/65 was excavated by J.D. Seddon in 1971. This was a shelter
used by traders who brought grain and cattle from the south, Klipriviersberg, and
traded with the metal makers of Melville koppies, Lone Hill and Panorama. They
used the natural fault between the koppies, which Beyers Naude runs through,
as a route. The cave area was declared a National monument because of the
remains found there, viz. bone fragments of sheep, domestic fowls, birds, ostrich
eggs, mice, hares. jackals, mongooses, dassies, Burchell’s zebra, buffalo, eland,
kudu, steenbuck, blesbok, hartebeest, .
2) Origin of iron making.
It probably started by accident in the Tigris-Euphrates area, the Fertile Crescent.
A fire that was very hot may have had some iron ore in it. The molten lump could
have been idly toyed with, beaten into a shape, and it’s properties discovered.
The knowledge and skill was a closely guarded secret, but nevertheless it got
passed on. It seems to have reached North Africa, and then traveled down south
along routes to the west and east of the Rift valley. As the iron makers came,
they brought with them their culture of crops and husbandry. Crops were millet,
sorghum. Maize, or corn, was only introduced in the 1760’s, and the better
nutrition it gave caused a population explosion, the same as happened in Europe
during the agrarian revolution which preceded the industrial revolution. The iron
makers seem to have traveled down the East Coast and fanned into the
Transvaal as well. A site at Amamzimtoti is dated to 850A .D. and a site at
Broederstroom in Gauteng is also dated to 850A.D. These earlier iron makers
moved away, climatic change perhaps? And then another wave swept into the
Transvaal later. In the northern Transvaal, Mapungubwe is dated to 1060 AD,
and thereafter the iron sites in the Transvaal are all in the 1500s AD
-33) Types of furnace.
1) Round furnace, domed with a chimney, with two openings for tuyeres. Melville
Koppies
2) Oval domed furnace with chimney and two openings. Buispoort NW of
Zeerust
3) Loole type. Round, domed, chimney with one opening from Loole in
Phalaborwa.
4) Venda type. A cylindrical-shaped furnace with a wide chimney and three
openings for tuyeres at equidistant intervals, i.e. 120* intervals
Most of the furnaces are sunk into the ground, from 15cm deep to the equivalent
of half of the furnace height. This was to prevent the walls from cracking during
firing. Cracks would let in oxygen which would stop the smelting process. The
furnace was prepared from anthills and clay. It was fired to dry it out before use.
Some furnaces were lined with clay at the bottom, others were not.
4) Bellows.
At Melville Koppies, smelters used bellows made of goatskin. The goat was
skinned alive because it was believed that this helped the iron-making process.
The skin was loosed at the hind quarters then dragged to the neck. The cut ends
were neatly sewn together. A thin awn-like needle made tiny holes, just enough
to pull the sinew thread through, so that no air could escape. The skin was bent
and rubbed to make it flexible. Tannin bearing leaves or cattle dung were also
rubbed into the skin to preserve it. The one end of the bag was firmly attached to
a straight horn, eg cow horn, and this was inserted into the tuyere. The other end
was attached by lashing with thongs to two sticks, which the smelter would open
and close as a valve. The capacity of the bags was about 5l of water. A bundle of
grass was put in the bellows to plump it out. The art of leather making of these
bags is also lost.
Further north, people used drum bellows. These are made from a hollowed out
log and skin is attached over the rim. The skin is lifted up and down with a stick
inserted through the skin and air is forced out of a hole in the drum. The
availability of large trees favoured drum bellows. The goatskin bellows seem to
have been superior even though they were more fragile.
Women used drum bellows to make copper (a women’s’ metal). They stood in a
circle and carried out a rhythmic dance while blowing.
Women used straws to blow gold in a crucible over a fire. Gold was also a female
metal but was only used for ornaments by royalty.
The tuyeres were made out of clay by women
-45) Firing.
This is what probably happened.
Charcoal was used to smelt the ore. The ratio of charcoal to ore was 1:10. At
Melville Koppies they probably used the Acacia caffra and A. robusta.
To make charcoal, cut down the tree and wait for it to dry. Then set the wood
alight and when it forms coals, rake the coals out and bury them in sand to
exclude the oxygen and so make charcoal. A slow burning charcoal is best.
(Nowadays, exotic invaders are used to make charcoal) If no charcoal was
available, it could be obtained by trading. One bag charcoal for one bag
sorghum or, millet, grain, and after 1760, maize.
A flux was also used to get the fire going. It was probably crushed quartz,
regarded as ‘medicine’ to improve the extraction. Fat was also used.
The iron ore was probably found in a few localities close to Melville Koppies i.e.
the contorted banded iron stone beds along Jan Smuts Ave near Wits, and the
squashed quartzite formation along the arboretum. The iron ore was broken into
pigeon egg sized nuggets. The iron ore was probably haematite, which has a
high ration of iron, or geetite or magnetite. There were other impurities in the iron
ore as well!
The fire was lit at about 4pm on a full moon night. Perhaps for visibility, or for
omens. First a fire was made at the bottom of the furnace with some charcoal.
When this was red-hot, alternate layers of iron ore nuggets and charcoal were
dropped on top through the chimney, keeping the ratio of 1 part ore to 10 parts
charcoal.
Tuyeres were placed in the openings at an angle so the wind did not blow directly
into the centre of the furnace, but was directed at the side so that the cold air
swirled around the inside perimeter first and got warm.
A team of smelters would work through the night. Each smelter had two bellows,
which he would pump at up to 120 beats per minute. The smelters were kept
hydrated with water and beer, brought by old women. Menstruating women were
not allowed near the furnace as it was believed that it would jinx the process. The
extraction of iron was seen as a birthing process, hence the womb-like shape of
the furnace and the phallic shape of the tuyeres. A woman of child bearing age or
a man whose wife was pregnant could not come near the furnace. The furnace
could not give birth to iron at the same time as another human birth
It took the charcoal from about two trees to do one firing, which might produce
iron for a hoe head, spearhead, and a chisel or two.
-56) Chemical process.
The first chemical reaction to take place is the removal of one atom of oxygen
from each oxygen molecule in the furnace and the bonding of C (Carbon) from
the charcoal with one molecule of oxygen to form carbon monoxide.
Heat + C + O2 = CO (+O which disappears)
Then the carbon monoxide combines with the haematite to form iron crystals and
carbon dioxide.
CO + Fe2O3 = Fe2 + 3CO2
Sponge iron or bloom is iron crystals, slag, bits of unburnt charcoal and bits of
iron ore.
Slag is iron with lots of impurities.
In modern blast furnace, slag is the scum which rises to the top of the molten
iron.
Tempering is heating and then fast cooling with water, oil or fat, to make the iron
hard. Tempering with blood, urine, breast milk were believed to impart human
qualities to the iron
Annealing is heating and then slow cooling
Melting is turning a solid to a liquid state.
Smelting is a chemical process of extracting iron
Forging is beating the iron into shape.
Too much oxygen and the process stops. Too little oxygen and the process
doesn’t start.
The carbon content was difficult to control. Too much carbon and the result was
cast iron which is brittle and not pliable enough for tools. Too little and wrought
iron was produced. The right mix and the beating afterwards resulted in a type of
steel, so the quality of some tools was very good.
7) Forging.
Nuggets of iron from several smeltings were placed in a clay envelope to reduce
the oxidation in the next firing. The clay envelope was then broken and the
nuggets beaten and forged into the required shapes, e.g. hoe, chisel, pin,
scraper spear head, arrow head.
Microphotography of Iron Age tools shows that nuggets of varying carbon content
were successfully laminated together
-68) Recent records of Iron Age firings.
There are very few written records of actual firings.
8.1) KLAAS ‘S FIRING
(This account appears to be a myth. The temperatures reached in the
furnaces were not likely to be high enough to melt the iron to a runny state)
“ The Afrikaans naturalist, poet and author, Eugene Marais, had the privilege to
have seen an expert iron smelter at his craft. This was sometime during the
period 1907 to 1917 when Marais was stationed in the Waterberg district as
Justice of the Peace. He was introduced to ‘old Klaas’, as he was known, by a
farmer, Jan Nel. Klaas was also one of the last Vaal pense, the now extinct
Transvaal Bushmen. Klaas lived in the Waterberg Middleveld on the watershed
between the Magalakwena and the Palala rivers.
His kraal was hidden away between huge boulders and thorn trees. His garden
was about three hectares in extent. Crystal clear and ice-cold water emerged
from a fountain between the rocks.
Klaas was about 135cm (4.5ft) tall. He must have been very, very old, judging
from the condition of his skin, which was 100% wrinkled. He had the widest and
flattest nose Marais had ever seen, with a gigantic mouth, and monstrous lips.
His head was abnormally big. He had broad shoulders, but poorly developed
legs, which accentuated his outward-pointing feet. He wore a necklace from
which were suspended various small tools – a strange pair of pliers, knife, snuff
spoon, tweezers and a porridge spoon. On his back he carried a small bag
containing a pipe and tinderbox, as well as a few extra tools. All these tools were
hand-made, as could be seen from the marks of a stone hammer. He pointed out
that the blade of his spear was fastened to the haft with wire, which he had made
himself.
As a youth, Klaas was a slave of a Mapela tribesman, from whom he learnt the
art of iron smelting. It is interesting to compare Klaas’ technique with that of the
Tshvote brothers. Klaas’s furnace was built against a huge rock. It was of the
Loole type and consisted of a clay chimney about one metre tall. The ore
consisted of reddish pebbles mixed with earth of the same colour. This was
mixed in a carefully measured ratio with powdered glassy quartz, which was the
flux. The fuel was charcoal made from a specific tree. Thick branches were
ignited in a sandpit and then quenched with sand after one hour.
The ore was mixed with the charcoal in a specific ratio, and packed in the
furnace on a layer of dry dung. Through a 10cm diameter hole at the base, the
charge was lit. The hole was then closed with wet clay. Klaas’ twelve-year-old
son operated the bellows, which consisted of two goatskins stitched together with
sinew. A clay pipe connected the bellows to the furnace.
-7The smelting was a tedious process. Every now and then charcoal or ore-flux
mixture had to be added through the chimney. In the meantime, Klaas showed
his visitors his tools. The anvil was a smooth black rock. The hammers were
fashioned from stones made of a white sandstone which “came from very far”,
and which Klaas considered as treasures. But the greatest treasure of all was the
wire making tool, which consisted of an iron plate 18cm by 10cm by 2.5cm in
dimensions with holes of various diameters. Klaas inherited this tool from hid
Mapela master. It was passed down from one generation to the next, and must
have been hundreds of years old, judging from its degree of wear. How the holes
were made through such thick metal was a mystery, which even Klaas could not
guess at.
Unfortunately Klaas did not give a demonstration of wire-making, but he told his
visitors that the red hot wire, as it is drawn through the hole and wound round a
stick, must be tempered in a grass fire and then coated with lizard fat, which was
the only compound capable of preventing brittleness. (Perhaps copper wire for
ornaments and fastenings??)
Klaas then produced a bag containing magic powder. This was made from a very
special type of stone, and was essential to lower the viscosity of the molten iron
to nearly that of water. In front of the clay-covered hole, Klaas made a mould of a
pickaxe in moist sand. Everything was carefully measured off using a long stick
with notches.
The boy was then instructed to renew his efforts with the bellows. The sweat
poured down his naked body and he panted for breath. As Klaas added the
magic flux, an unbearable stench of hydrogen sulphide emerged from the
chimney. Klaas said this was a good sign. He then took a sharpened stick, and
with one deft movement, pierced the clay hole. The boy jumped out of the way,
dragging the valuable bellows with him. Witha dull rumble, a pure stream of
white-hot iron emerged from the furnace and flowed into the mould, sparks flying.
Klaas’ measurements were exact. Not a drop of metal was wasted.
A thin layer of moist sand was spread over the red-hot pickaxe, and then water
blown over it by mouth. This was to temper the metal. After cooling, the pickaxe
was finished off using hammer and anvil.
Klaas admitted that the “white man’s pick-axe” which had a hole for the haft was
superior to his product, which had a peg which must pass through the haft. Klaas
was famous throughout the north, and he must have been a true metallurgical
genius to have been able to produce molten iron with apparently little effort.
Sometime later, Klaas spent two weeks with Marais, who recorded that Klaas
was an absolute treasure house of knowledge.
POSTSCRIPT.
In our old uncle Pierneef’s collection on the farm Rietvlei, district Lydenburg,
there is a hand made axe as described above, which was unearthed during
ploughing operations. What a treasure that is!
(Unfortunately the article I have has no author)
8.2) 1936 firing demonstration for the Empire Celebrations.
Unfortunate, no record was kept of this firing!
-8-
8.3) Tshovhote Bothers
Two half brothers, Piet and Andries Tshovhote, who still practiced as blacksmiths
and whose father was an iron smelter, were prepared to demonstrate the whole
process as far as they remembered it. The demonstration included the mining of
ore, the building of the furnace, the making of the bellows and tuyeres, the
burning of the charcoal, the smelting process itself and the erection of a typical
Venda smithy. They used cape beech (Rapanea melanophloeos), water berry
(Syzigium garrardii) and wild syringa (Burkea africana) to obtain charcoal. The
highest temperature reached was only 1140 degrees C. No sponge iron was
present. This demonstration showed that the art of iron making has been lost. It
was not a primitive art at all, but a highly specialized technique which is far more
complicated than most authors make it out to be.
8.4) Wit’s experiments 1977
A study of prehistoric metal technology was part of the experimental research
programme of the Archaeological Research Unit at the University of the
Witwatersrand. Revil mason, Dr Heinrich Friede, Robbie Steel were some of the
researchers involved.
In their conclusions, they found that the raw materials, airflow system,
temperatures, gas composition varied very much from batch to batch of sponge
iron. Success or failure depended largely on the aptitude, training and experience
of the operators. The researchers were only able to forge small pieces. The more
complicated forge-welding techniques that the African smiths used when making
large implements could not be reproduced. The researchers found that they
could not get the layers to forge together. (Photomicrographs were taken of
original Iron Age implements. These photographs revealed the lamination
process of making implements. It also revealed the different chemical
composition of the layers. Nuggets of iron from several firings in the smelting
furnaces were heated in a forge and then laminated together by beating)
“The smelting and forging of iron were complicated processes, and it is much to
the credit of the smelters of that time that they could turn out, with the simple
means available to them, relatively uniform, high-grade products in quantities
sufficient for their needs.”
(Acknowledgements to Mason who initiated the project, the Human Sciences
research Council who subvented it, the Research laboratories of the SA Iron and
Steel Corp, Steele and H.Toch of the National Institute for Metallurgy and others.
Journal of the South African Institute of Mining and Metallurgy June 1977)
9) Black art
In the early days of iron making in Europe it was called the ‘Black art”. There
were two possible reasons; the smiths got very dirty from the charcoal. Secondly,
the art was so secret and the firings so attuned to a specialist ‘feel’ that only
experts could produce iron.
-9Because there were so many factors that could influence the outcome, the
smelters tried to eliminate known problems. According to Credo Mutwa,
menstruating women were not allowed near the firing because the iron had to be
pure and they could contaminate it. Only old women who were not menstruating
could attend the smelters during the smelt. Men who had had sex the night
before and men whose wives were pregnant could not attend the smelting either
because a person could only give birth to one offspring. The production of iron
was a birthing process.
Once the iron bloom had been obtained, the next process of forging could take
place in the kraal where women were, because this was not a magical process.
He said that body fluids, eg urine, breast milk, were sometimes also used to
anneal the iron tools and to give them strength. Iron was considered a ‘male’
metal.
In modern day iron making, computers are used to regularly test the chemical
composition of the iron and to test the tensile strength etc. It is still an art, but
technology is there to assist.
The so-called very complicated ‘primitive’ art of iron making has been lost. The
demand for this iron fell after iron goods from Europe flooded South Africa in the
19th Century. Gradually the art died out, as there was less and less demand.
Compiled by Wendy Carstens from various sources 2003
(Papers by H.M Friede, R. Mason, U.S Kusel, R.H. Steele and other papers
without authors)