Materials used for the Smelting

Materials provided for the smelting included tuyeres, calabash, and white cloth, chemical and iron ore. The workshop and the furnace were reconstructed and smelting took place thereafter.

Each of the smelting materials is discussed hereby.

3.3.1 (a) Tuyeres

Materials used for making tuyeres included clay, palm kernel shells, water, a stick and a rope. Clay was mixed with ground palm kernel shells and water. The mixture was used to coat a stick which served as an inner core (channel) for tuyere. When the clay on the stick was still wet the rope tied on the stick was pulled and the stick removed, thus, creating the tuyeres channel in the clay pipe. The tuyeres were left to dry for three days and were then fired for about two hours in order to make them stronger.

Long and short tuyeres were made for th demonstration. The long ones had an average length of 34cm. While the short ones were 25cm long. The two types had an outside diameter of about 3-5cm.

We used 28 tuyeres in the furnace for the demonstration.

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3.3.2 (b) Calabash

A medium sized calabash was used for collecting and pouring iron ore into the furnace. It was preferred to a pot because it was light. The washed ore was collected in the calabash and spread on a white cloth before it was collected and poured into the furnace.

3.3.3 (c) White Cloth

The calabash and a square metre of white cloth (teru: Yoruba) used were bought at Oje market in Ibadan. The market is noted for selling various types of woven cloths (Aso Ofi: Y oruba). It was on the white cloth that the iron ore washed in water was spread. It is the belief of the smelters that iron ore would "copy" the colour of the cloth which is good for their expected iron product.

3.3.4 (d) Charcoal Preparation

Charcoal serves as fuel for making fire for smelting iron ore.

The charcoal is not from just any wood but it is specifically from the tree called Afromosia laxiflora which was used in this demonstration (plate 4).

In the remote past, the smelters used hoes, cutlasses and axes to uproot and cut the trees. It took them 2 or 3 days to uproot and cut the trees into logs. They later used handsaws which was a little easier than the former method. For this demonstration a mechanical-saw was hired from the Department of Forestry, University of Ibadan, to fell the Afrormosia laxiflora tree used for preparing charcoal in the Godogodo district of Isunndunrin. The wood was cut into short logs and these, together with the branches, were arranged in a trench about 60cm deep. The logs were burnt when wet to produce charcoal. Afrormosia laxiflora is a plant that can bum when wet. It. does not bum to ashes in its wet condition when the burning is controlled. To control the

burning, the logs and branches arranged in the trench were covered with the leaves of the plant and soil. A little opening was created in the western side of the log to let in oxygen. Fire was set to the logs and branches in the trench. After the third day, a section of the fire was uncovered to find out how well it had burnt to form charcoal. In this case not all the logs had burnt . Fire was rekindled and it was covered with earth to repeat the operation (plate 5).

Charcoal which could be got from the fire pit was collected. Two and a half baskets of charcoal were collected to which were added two other baskets stored inside the workshop. In the event, it was shortage of charcoal which was curtailed the demonstration not shortage of ore.

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Normally, burning wood to make charcoal is ajob which is

performed in the dry season, and had that been the case, all the cut wood must surely have been transformed into charcoal in time. The rainy season clearly was not ideal for this task which was carried out at my request. The experience of the researcher revealed that charcoal is a vital component of the operation. Vast quantities of wood in the past have been consumed in this way.

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5.3.5 (e) Iron Ore

The iron smelter used iron ore from his reserves for the smelting and we did not witness iron mining (for information on iron mining, see Adeniji 1977, Aremu 1990b). Gabriel Oyeyode used muscovite iron ore (afuye Yoruba) for the smelting during the demonstration. The other types of ore he used for smelting are sagodo (Y oruba: meaning big ore) and agunwinwin(Yoruba: meaning small ores).

The muscovite iafuye; Yoruba) ore had been ground into powdery form.

It was washed from 8.am on our arrival that day and was spread out to dry. The ore cannot be used in a completely dry powdery form because if so it would be wafted away by the air current in the furnace. Hence the preparation of slurry was sufficiently dry. At the end of the operation, in which the smelting stopped due to lack of charcoal, there was still one inch thick slurry on the cloth.

3.3.6 (I) Workshop

The furnace was built inside a house, which also served as the

smelters' workshop. The workshop is built of mud walls covered with corrugated iron sheets. It was 15 metres (east west) long, and 8 metres north south) wide. The walls of the workshop at the east and the west had collapsed while part of the ones at the north and the south were standing. Where there were walls, wooden poles were used to support the roof as a temporary measure. The roof was made high so that it could not catch fire when the tongues of flame from the furnace. In addition, a special protective plate was placed immediately above the furnace at roof level which controlled the effect of the flame.

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Tarpaulins were used to cover the four sides of the workshop when smelting was in progress. The walls of the workshop and the tarpaulins prevented air from rushing into the furnace during smelting. The feature of the construction is of great importance, walls acting as a windbreak.

Originally windows up to eight in number were inserted in the walls of the house, for the convenience of those working there. There were also originally two entrances at the west and the south.

3.3.7 (g) Furnace

The furnace was located at the eastern end of the workshop. It was built of clay a circular form (Plate 6). The circular wall of the furnace was about 30cm thick and had an external circumference of 40cm at the top, with a narrow opening at the top about 30cm wide into which iron ore and charcoal were poured at different times during the smelting operation. (It was expected that the charcoal would bum to ashes while the impurities in the iron ore burnt off and the metallic iron be left). The domed furnace is about one metre high (Aremu 1990:2.15. Tylecote 1975:1-9: Williams 1974:60).

The furnace was sited over a shallow basin in which the bloom was formed. From the centre of this basin a tap-hole about 4cm in

diameter passed down into an underground slag pit(about 1-2 metres high) with a separation access 1-8 metre away from the furnace at ground level at the western end of the workshop. The slag was collected in the underground pit during reduction ofthe ore.

At the base of the furnace to the east, an aperture (the mouth of furnace) about 60cm square existed.

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Around the base of the furnace structure, six large holes, each accommodating two or three tuyeres provided a forced draught.

During the smelting one of the holes took two tuyeres and the remaining fiv e took three each. The interstices between the tuyeres were filled with clay. Through the tuyeres allowing free draught the heat in the furnace is regulated so that an iron bloom could be produced. It was interesting to observe during the smelting

operation that the externals of the tuyeres remained quite cool, due to the inrush of air, while the inside of the tuyeres was very hot.

Seven small platforms were built around the furnace at the base.

These occurred in the spaces between the tuyeres. The smelter stood on the plate form when he wanted to pour charcoal and iron ore into the fire in the furnace.

The tap-hole was blocked at its lower end by means of conical plug made from a mixture or powdered charcoal and clay. Williams

(1974:58 - 60) noted that during reduction the smelter from time to time . removed the plug and allowed a run of liquid slag into the underground pit. The slag might thus be tapped six to eight times during a smelt.

Slag successive tapping around the aperture drip down slowly from the bottom of the basin to the passage. The first product of such tapping (high in silica and low in iron content) was discarded, as were the products of all subsequent tapping to the last two or three. These last were collected by the smelter before the furnace "door" was forced open. They were crushed and stored to be used as a flux in further smelting (Williams 1974:59-60, Oyeyode 1989: Pers. Comm.). In our

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own case they kept testing whether slags were formed at the tap-hole, using a piercer ogbagbara: Y oruba) and replacing the charcoal balls with new ones. The slags formed in the basin were recovered after the furnace "door" was opened.