Getting Bronzed

The Smeltery At West Brandon, Durham by Marion K. Pearce from Northern Earth 65

A major technological innovation of prehistory was of course the creation of bronze. The technology took such hold that the metal characterises the second of the three great age classifications of antiquity (unsatisfactory though these terms are to describe a process that was continual and dependent on local circumstances and technological achievement), and it is moreover the Bronze Age that saw a marked change in the sacred landscape and traditions of Britain, albeit developing gradually from forms established in the Stone Age. Round barrows of various types were the primary funerary feature of the 1300 or so years that bronze dominated both weaponry and religious ritual, as society moved steadily away from the more communal mode of the Neolithic towards a more hierarchical structure. Many votive offerings found at religious sites throughout the Bronze and Iron Ages are of bronze; this may reflect a belief that the more valuable an offering the greater its magical potency, or that some special quality adheres to bronze that makes it more apt as a ritual item, certainly when compared with iron, whose sacred value has long been and remains in folklore ambivalent at best. Some places, indeed, seem to have persisted in making bronze implements for ritual purposes even when more advanced technology was available, which suggests that to some extent at least it was seen as an inherently special substance. So where was bronze actually made? Here, Marion Pearce introduces us to a site in Northern England.

Two metals make up the alloy bronze; tin and copper. Copper is more plentiful than tin and in fact was used to such an extent in Europe that on the continent it is thought that a Copper Age preceded the Bronze Age. This stage in the evolution of metals was omitted in Britain, which is considered to have moved from the Stone through to the Bronze Ages; although copper was used here, it was not to the same extent as in Europe.

Furnaces used to smelt metal in the Bronze and Iron Ages are very rare. Vital in the production of copper, only two are known in Britain; one at Kestor on Dartmoor and another at West Brandon in Durham.

The West Brandon furnace was discovered by George Jobey in 1961 at a wooden roundhouse, a type of building common for its period. The roundhouse was surrounded by a double wooden palisade and an external ditch as defence. At the time of discovery, the building was dated from the 2nd or 3rd centuries BCE, but since then similar-type constructions have been found, dating from around the 6-7th centuries BCE.

The actual process of smelting is interesting. First, the ores would have to have been roasted to remove the sulphur present in the mineral. This would have been achieved by interlaying the ore concentrate with wood charcoal. This was then lit, and the whole pile kept at a low temperature for several days. This was a highly skilled operation. The pile would have had to be constructed with adequate ventilation and air holes. The roasted ore would then be placed in a charcoal-burning furnace to be smelted. In Ireland, cakes of raw copper which would have been obtained from such furnaces have been found, though not an actual smeltery. Cakes found at Carrickshedoge, Co. Wexford, vary from 4-8" in diameter and are around l/2" in thickness.

The furnaces in which the metals were fired are thought to have been generally shallow round bowl-shaped hollows dug in the ground and lined with clay. The ore and charcoal would have been layered and placed into these holes. On the side of the bowl would be placed a tuyere, a funnel shaped nozzle. A charge would have been lit, and a dome-shaped clay cover, with an air vent to release the gases, would have been placed over it. The air blast would have been controlled through the tuyere with a pair of bellows. The metal would become molten and separate from the rock in the ore, dropping through the charcoal before settling in the bottom of the furnace in a cake or ingot of pure metal.

The West Brandon furnaces themselves were bowls cut into the rock, and were quite small at around 12" in diameter and 8" in depth. There was a slight groove in the bowl of the furnace which would have held the tuyere for the bellows. At the base of the bowl was found a saucer-shaped layer of oak charcoal fragments and droplets of slag. The clay lining of the furnace was up to 2" thick. The domed covers would have been destroyed when the smelting process was complete, and do not survive.

This seems to me to be a very elaborate structure to be in use by the Bronze Age, but it produced ingots that, worked by smiths, became the fine metalwork that we know from this period of history.

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