Bronze in Iron Age Britain
These artefacts can help us understand us how people worked bronze in Iron Age Britain. Bronze is an alloy, a mixture, of two metals, copper and tin, and can be used in two ways. Sheets of bronze can be hammered and bent into a shape, often held together with rivets. This is how cauldrons, scabbards and shields were made. Other items were made by pouring molten bronze into clay moulds. This technique was used to make complete objects including horse bits, terrets, massive armlets, and parts of objects, for example, parts of scabbards and the handles of mirrors.
To cast bronze, gold or silver, a full size model of the object was first made in beeswax: the bone tools shown here were used to make these models. The wax models were covered in clay and baked; the melted wax was poured out of the hardened mould. Care was taken to remove the wax completely as any residue might spoil the casting. With the mould prepared, the metal was melted in a crucible over a fire: on the left is an ingot of bronze in front of three triangular crucibles. The hot, liquid metal was poured into the clay mould, filling the void left by the wax model. This technique is called lost wax casting.
After the metal cooled and had become solid, the mould was broken to release the new casting: a pile of broken moulds for making horse bits and terrets can be seen in the centre. After casting, bronze objects could be trimmed and finished off using iron files, similar to those shown bottom right. Some artefacts might also be decorated with coral or coloured glass: two cakes of unused red glass can be seen on the right.
Most of the objects shown here were found when a large Iron Age farmstead was excavated at Gussage All Saints in Dorset and are on loan from the Dorset County Museum. The broken moulds, tools and crucibles were used to make at least fifty sets of horse harness in the first century BC. The objects were placed in a disused grain storage pit, along with part of a human skull. The bronze ingot and cakes of red glass are from Essendon, Hertfordshire and London. The ingot was given to the Museum by C.R.H. Crosland.