IRON 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.
Mason 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
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
3) Types of furnace.
1)
Round furnace, domed
with a chimney, with two openings for tuyeres. Melville Koppies
2)
O
3)
Loole type.
Round, domed, chimney with one opening from Loole in Phalaborwa.
4)
Most of the
furnaces are sunk into the ground, from 15cm deep to the equi
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
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
5) 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
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.
6) Chemical process.
The first chemical
reaction to take place is the remo
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
8) 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
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.
The 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 li
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
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.
8.2) 1936
firing demonstration for the Empire Celebrations.
Unfortunate, no
record was kept of this firing!
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
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
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
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.
Because 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
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 in the Melville Koppies collection)