Ingot casting andSouthern Africa

.wire

.In Iron Agedrawing

by R. H. STEEL* (Visitor)

SYNOPSIS

This paper describes the experiments that were conducted in 1974/1975 on two related aspects of Iron Agecopper technology in Southern Africa: ingot casting and wire drawing.

Three types of ingot were successfully cast: the St Andrew's Cross ingot, the marale ingot, and the musuku. It issuggested that the 'studs' on the musuku are not the remains of broken-off rods as previously proposed by otherinvestigators, but that the ridged pattern is an ornamental feature.

Copper wire was successfully drawn with similar tools and according to the procedures described in the literatureon African Iron Age wire drawing. It is concluded that these accounts are generally accurate and that the pre-Euro-pean metal workers are worthy of respect for the results they achieved with primitive methods.

SAMEVATTING

Hierdie referaat beskryf die eksperimente Wit in 1974/1975 uitgevoer is in verband met twee verwante aspektevan kopertegnologie van die Ystertydperk in Suidelike Afrika: die giet van gietblokke en draadtrekkery.

Drie soorte gietblokke is suksesvol gegiet: die St Andrew-kruis-gietblok, die marale-gietblok en die musuku.Daar word aan die hand gedoen dat die "knoppe" aan die musuku nie die oorblyfsels van afgebreekte stawe is soosvoorheen deur ander ondersoekers aan die hand gedoen is nie, maar dat die rifpatroon 'n ornamentele aspek is.

Koperdraad is suksesvol getrek met soortgelyke werktuie en volgens die prosedures Wit in die literatuur oordraadtrekkery gedurende die Ystertydperk in Afrika beskryf word. Die gevolgtrekking word gemaak dat hierdieverslae oor die algemeen noukeurig is en dat die voor-Europese metaalwerkers ons agting verdien vir die resultateWit hulle met primitiewe metodes behaal het.

INGOT CASTING

The copper ingots found atarchaeological sites in the Northernand Eastern Transvaal have beenthe subject of much discussion. Theunusual shapes of some of theingots, especially of the musukus-the 'miniature top hats' of theSoutpansberg (Figs. 1 to 3)-and themarale-'the miniature golf-clubs'of Palabora (Fig. 4)-have oftenintrigued collectors and archaeolo-gists. The literature suggests anumber of explanations, whichascribe the following to such ingots:(1) a religious, mythical, or cere-

monial aspect (Thompsonl),(2) a trade and currency value (Van

der Merwe and Scully2), and(3) an unusual shape due to casting

methods (Stanley3).I believe that the rod and stick-

like ingots, as well as the musuku,were used for trade if they were ofsolid copper. Some musuku arefilled with sand, and this type,according to Thompsonl, was alwaysused for ceremonial purposes.

Between October 1974 and Feb-ruary 1975, we conducted experi-ments to test the conditions andthe results of casting copper intomoulds patterned to the shape ofthe original ingots. We obtainedsome of the required copper frommalachite-azurite ore that wo

*University of the Witwatersrand

~32 NOVEM~!;R 1975

Fig. I-Musuku copper ingot from Soutpansberg, Northern Transvaal. Cat. No. 1/70.

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

0z.,;'"u

-=>..c'"..I-c..41...:;41

1:.....0zff'i.8~~~11.E0........0DOC

..410.0.0u:I

..It:I..:I:I:I...

DO

ii:

c..41

.c.....0

Z....000...41...

'"~"ClC

'"f,.:"'...:1:0;"-c'"g:o~z....41'",1:1'"GIU... ..iii-="'>E ~0

'".. ..':1-0DO.:..410.0.0u:I

..It:I..:I:I:~DO

ii:

NOVEMBER 1975 233

.smelted in an experimental smeltingfurnace similar to that of theVenda described by Stayt4. Thebalance of the copper used wasrefined commercial copper. In eachcase, the copper was re-smelted ina crucible furnace constructed onthe pattern of ancient cruciblefurnaces found in the WaterbergDistrict of the Transvaal5,6. A sand-stone crucible is shown in Fig. 5.

A ceramic crucible of 50 mlcapacity was filled with copper andwas placed on a charcoal bed pre-pared in the furnace. It washeated, by blowing air into thefire either:-twith hand-worked skinbellows or with an air compressor, to atemperature well above the meltingpoint of copper (1080°C). When themass of the copper had becomeliquid, the crucible was taken outwith very long iron tongs, and thecopper was immediately poured intothe prepared moulds. Details ofthe smelting are given in anotherpaper7 in thIS issue.

We used three types of moulds.

1. A 'cross' pattern mould, similarto that used for the casting ofthe St Andrew's Cross ingotsfound at Zimbabwe and othersites in Southern and CentralAfricaB, 9. The mould was pre-pared by pressing a woodenstamp carved as a negativepattern into moulding sand,and the casting into such amould gave a satisfactory 'cross'ingot.

2. The mould for the lerale ingotwas prepared by thrusting awooden rod (190 mm long by10 mm in diameter) into asand-filled cylinder sunk intothe ground. The rod was with-drawn and, on top of the hole,a 'head' in the shape of a bent-over conical knob typical of themarale (e.g., Cat. No. 55/54Palabora) was carved. The cast-ing was successful when donerapidly. Occasionally, a castmarale ingot showed holescaused by air that was stilldispersed in the copper, butthis difficulty was overcomeby stirring the molten copperwith a green stick before pour-ing out. This is termed de-aeration by poling. The massof the molten copper in the

234 NOVEMBER 1975

3.

crucible defined the size ofa marale. We tried to fill alarger mould by successive pour-ings from two separate smelt-ings, but, once the first chargehad solidified, the second chargedid not join it.A musuku (Fig. 2) was usedto obtain the musuku mouldlo.At the bottom of the mould,equally spaced holes werepressed into the ground withpencil-shaped wooden rods (20mm long by 5 mm in diameter).Mter the copper had beenpoured and the cast had solidi-fied, the copper rods formeda continuation of the studs onthe ridges of the musuku head.These 'studs' were supposed tobe the remains of the copperrods that were broken off tobe used for wire drawing3.The casting of the musuku wasonly partly successful, as asection of the 'head' broke off.There is a feature of the musukuthat still needs explanationl, 4.On most musuku preserved, oneor two pouring lines can beobserved, showing that thepouring was effected in severalseparate stages. Why was thatso, if the copper rods werethe primary products desired?A fairly thin overflow slabwould have been sufficient as ahead. It has also been observedthat, on several musuku ingots(Fig. 2), no breaking-off markshave been preserved. For thesemusuku, we are inclined tothink that the 'studs' were notthe remains of broken-off rodsand that the cylinder-shapedmusuku ingot as we know itwas the only product manu-factured. The ridge-stud patternon the top of the musuku isprobably just an ornamentalfeature whose meaning is un-known to us at present.

IRON AGE WIRE ORA WING

Wire drawing appears to havebeen a craft practised by Mricanmetal workers for a very long timell.The Kikuyu of East Mricall believethat this craft is indigenous in theirtribal landsl2, but it is probablethat wire drawing, like other aspectsof African metal technology, is

part of the cultural heritage of theIron Age people who migratedsouthwards, bringing with themthe technological knowledge theyhad acquired by diffusion fromMediterranean shorelands or by tradecontacts with the East Coast.

The technique of copper wiredrawing demands, besides the coppersticks and copper rods used asraw materials, two essential tools:a drawing plate and a vice. Suchtools have been found at a numberof sites in Central and SouthernAfrica, and wore seen still in use bytravellers of the 19th CenturyI3-15.

The drawing plate (Fig. 6) appearsto be a simple implement-just aflat iron bar punched with holesof various sizes. However, we foundthat the punching of the holesis not quite so easy as one mightimagine. To draw wire properly, thehole (the die) should have a smoothconical entrance and a similarlyshaped exit. It seems that holespunched with an awl-like tool intoheated iron plate and reamed inare just as suitable for wire drawingas those drilled and reamed in themodern way.

The Iron Age vice (Fig. 6) thatclamps and holds the wire is actuallya fairly indigenous tool. It is astrong band of iron, bent back ontoitself to form a fork resembling atuning fork with the prongs pressedclosely together. A coiled iron ringis slipped over the open end of thefork after the wire has been clampedin, and is hammered upwards witha stone, being finally kept in positionjust below the wire by an ironwedge forced between the prongsand rings. A number of such wirevices that have been described andpictured in the literature come fromplaces as far distant as Kikuyuland16,Katanga12, the Zambesi Valley atIngombe Ilede9, and the NorthernTransvaal4, 17. The similarity of pat-tern and design of the vices is anindication of the basic uniformityof Iron Age metal technology.

EXPERIMENTAL WIRE-ORA WING

We made some experiments todemonstrate working with a drawingplate and a vice for drawing wire.We ordered a vice to the size and

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALl,URGY .

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

as*"0;-N

1$Z.w11

UQ.0

~....cuIII>E0.....IIIC0...VI

"C11VI

'0III

:i:i'u::I..uIIIDO

cCC0..

TIII

~ii:

1$Z

~u';11>VIC11..I-c..III.c.....0z~III-eO;~Q.,.,'=0.-o~en

E0.::...0DO.5..IIIQ.Q.0uIII

';..III

...

J~ii:

NOVEMBER 1975 235

Fig. 6-lron Age style vice and drawing plate made from modern~5teel in IngombelIede pattern, with copper wires pulled through the drawing plate to show decreas-

ing diameters.

\

shape of a vice found at IngombeIlede9 to be made in a Johannesburgworkshop, and this vice was usedfor the drawing of copper rods thathad been cast at the Department ofArchaeology of the University ofthe Witwatersrand (Fig. 7).

One end of a copper rod (approxi-mately 5 mm in diameter) wasground to a point .mall enough topass through the appropriate holein the drawing plate, which wasfastened to a stout pole. The pointof the rod was clamped into thevice as described above, and thevice was drawn away from the plate,pulling the wire through the die.This process was repeated a numberof times, successively smaller plateholes being used until the rod wasreduced to the required thickness(2 to 3 mm in diameter). Not all theexperimental runs were successful,since the wire had a tendency tobreak when pulled too strongly,or to seize up in the drawing plate.The results became better when,after each stage, the drawn wirewas softened by annealing (heatingup in a small fire for half an hour).Lubrication of the plate holes withfat also facilitated the process.

Our lack of experience and tradi-tional knowledge made our experi-mental wire drawing rather slowand cumbersome-quite differentfrom the efficient and apparentlyeasy working of the Iron Age metalsmiths described in the reports ofthe early travellers and ex-plorers13-15. However, we were suc-cessful in repeating the Iron Agemethod of wire drawing.

The reports on copper casting andwire drawing found in the literaturehave been proved to be generallyaccurate. Our practical experiments

236 NOVEMBER 1975

Fig. 7-Method of wire drawing 1975, showing drawing plate, stabilizing pole, andvice held in hands. The 1974/1975 copper-smelting and forging furnace is in the

background.

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

on the smelting and extraction ofmetal from ores have increased ourrespect for the pre-European metalworkers, who achieved excellentresults with primitive technicalmethods, and have confirmed theopinion of other investigators inthis field, who, like the famousarchaeologist, G. Caton-Thompson18,recognize the 'innate and receptivemetallurgical talent of Africanpeoples' .

ACKNOWLEDGEMENTS

My thanks are due to the manypeople who assisted me in variousways in this work, including Dr R. J.Mason, Dr H. Friede, Edwin Han-isch, Messrs P. Wallace, M. A.Veimstra, M. Evers, R. Welbourne,and M. Taylor, and Mrs T. Mostert.

REF~lrENCES

1. THOMPsON, L. C. The mu-tsuku. S.Afr. J. Sci., vol. 35. 1938. pp. 396-398.

2. VAN DER MERWE, N. J., and SCULLY,R. T. K. The Phalaborwa story.Wld Archaeol., vol. 3, no. 2. 1971.pp. 190-192.

3. STANLEY, G. H. Primitive metallurgyin South Africa. S. Afr. J. Sci., vol.36. 1929. p. 739.

4. STAYT. H. A. The BaVenda. London,1931. pp. 62-68.

5. WAGNER, P. A., and GORDON, H. S.Further notes on ancient bronzesmelters in the Waterberg District,Transvaal. S. Afr. J. Sci., vol. 26.1929. pp. 566-567.

6. STEEL, R. A furnace from the Water-berg. Unpublished report, 1973.

7. FRIEDE, H. and STEEL, R. Notes onIron Age copper-smelting technologyin the Transvaal. J. S. Afr. Inst. Min.Metall., vol. 76, no. 4 Nov. 1975 (thisissue). pp. 221-230.

8. GARLAKE, P. S. Great Zimbabwe.London, 1973. p. 114.

9. FAGAN, B. M. et al. Iron Age culturesin Zambia. vol. 2. London, 1969.pp. 92-99, 102, 103.

10. HANtSCIt, E. O. M. Copper workingin the Messina District. J. S. Afr.Inst. Min. Metall., vol. 74. 1974.p.252.

11. LINDBLOM, K. G. Wire drawing,especially in Africa. Stockholm, 1939.pp. 17, 19.

12. CLINE, W. Mining and metallurgyin negro Africa. 1939. pp. 97-110.

13. LIVINGSTONE, D. Missionary corres-pondence 1841-56. London, 1961.p.95.

14. MOFFAT, R. Missionary labours andscenes in Southern Africa. London,1842. pp. 466-467.

15. BURCHELL, W. Travels in the interiorof Southern Africa. London, 1822-24.

16. ROUTLEDGE, S. K. With the pre-historic people. London, 1910. pp.92-95.

17. VAN WARMELO, N. J. The coppermines of Musina. Pretoria, Depart-ment of Native Affairs, EthnologicalPublications, vol. 8. 1940. Plate V.

18. CATON-THOMPSON,G. The Zimbabweculture. Oxford, 1931. p. 190.

19. VAN RIET LoWE, C. Preliminaryreport on the stone huts of Vechtkop.J. R. Anthrop. Inst., vol. 57. 1927.pp. 217-233.

Company AffiliatesThe following members have beenadmitted to the Institute as Com-pany Affiliates.

AE & Cl Limited.Afrox/Dowson and Dobson Limited.Amalgamated Collieries ofS.A. Limit-

ed.Apex Mines Limited.Associated Manganese Mines of S.A.

Limited.Blackwood Hodge (S.A.) Limited.Blyvooruitzicht G.M. Co. Ltd.Boart & Hard Metal Products S.A.

Limited.Bracke.1 Mines Limited.Buffelsfontein G.M. Co. Limited.Cape Asbestos South Africa (Pty) Ltd.Compair S.A. (Pty) Limited.Consolidated Murchison (Tvl) Gold-

fields & Development Co. Limited.Deelkraal Gold Mining Co. Ltd.Doornfontein G.M. Co. Limited.Durban Roodepoort Deep Limited.East Driefontein G.M. Co. Limited.East Rand Prop. Mines Limited.Envirotech (Pty) Ltd.Free State Saaiplaas G.M. Co. Limited.Fraser & Chalmers S.A. (Pty) Limited.

Gardner-Denver Co. Africa (Pty) Ltd.Goldfields of SA Limited.The Grootvlei (Pty) Mines Limited.Harmony Gold Mining Co. Limited.Hartebeesfontein G.M. Co. Limited.Highveld Steel and Vanadium Corpo-

ration Limited.Hudemmco (Pty) Limited.Impala Platinum Limited.Ingersoll Rand Co. SA (Pty) Ltd.Kinross Mines Limited.Kloof Gold Mining Co. Limited.Lennings Holdings Limited.Leslie G.M. Limited.Libanon G.M. Co. Limited.Lonrho S.A. Limited.Loraine Gold Mines Limited.Marievale Consolidated Mines limit-

ed.Matte Smelters (Pty) Limited.Northern Lime Co. Limited.O'okiep Copper Company Limited.Palabora Mining Co. Limited.Placer Development S.A. (Pty) ltd.President Stern G.M. Co. Limited.Pretoria Portland Cement Co. limit-

ed.Prieska Copper Mines (Pty) limited.Rand Mines limited.

Rooiberg Minerals Development Co.limited.

Rustenburg Platinum Mines Limited(Union Section).

Rustenburg Platinum Mines Limited(Rustenburg Section).

St. Helena Gold Mines Limited.Shaft Sinkers (Pty) limited.S.A. land Exploration Co. Limited.Stilfontein G.M. Co. Limited.The Griqualand Exploration and Fi-

nance Co. Limited.The Messina (Transvaal) Develop-

mellt Co. limited.The Steel Engineering Co. ltd.Trans-Natal Coal Corporation Limic.

ed.Tvl Cons. land & Exploration Co.Tsumeb Corporation limited.Union Corporation limited.Vaal Reefs Exploration & Mining Co.

limited.Venters post G.M. Co. limited.Vergenoeg MiningCo. (Pty) Limited.Vlakfontein G.M. Co. limited.Welkom Gold Mining Co. limited.West Driefontein G.M. Co. limited.Western Deep levels limited.Western Holdings limited.Winkelhaak. Mines limited.

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY NOVEMBER 1975 237