An Introduction to Early Bronze Age Metalworking
It is impossible to understand early metal working without looking at the early Bronze Age itself. Only in recent years we have started to get a glimpse of how rich and complex the early Bronze Age was. Not only did they build stone circles, but they also built huge ceremonial landscapes, often incorporating henges, avenues, barrows and stone and timber circles. They marked some important points in the calendar with alignments, built huge timber enclosures, but the biggest single use of the ceremonial landscape was for the rituals of the dead, the passage from this world to join the ancestors. It is thought that Stonehenge was only the end of a journey that started at Woodhenge, (Timber circle) timber for the living, stone for the dead, with rituals and feasting on pigs on a mass scale, a huge wake, with a great procession escorting the dead, travelling down the river Kennet to the beginning of the avenue that leads to Stonehenge, to deposit the remains or bury them in one of the many barrow that surround Stonehenge.
Over the 800 years of the Early Bronze Age in Britain we see an intensive building of stone circles, and the embellishment of several henges with stone circles, and later additions of avenues. Barrow cemeteries spread and became part of the ceremonial landscapes we see around Stonehenge and many other prehistoric sites. On the archaeological record in Britain the first objects made of gold and copper appear around 2300 BC, at a time of rapid growth and development. There is a slow, but marked change in the burial practices from a few centuries earlier, family or clan burials in long barrows with little if any grave goods. The use of the long barrows with groove ware pottery, being slowly abandoned in favour of single burials in round barrows, with a new type of pottery, a style imported by a migrating people from the Rhine area of Europe.
The arrival of this new pottery and people have a profound effect on the archaeological record and appear to take over and dominate all burial practices and from the arrival of Beaker pottery 2500 BC it spreads across Britain to be found at nearly every ceremonial site and most burials during the early Bronze Age. From here on most graves are furnished with grave goods: archaeologists call them the Beaker package, which included one or more of the following: a beaker, flint tools, arrowheads, daggers, flat axe of copper and gold work in the form of disks and basket earrings.
It is in these Beaker barrows that the first metal objects arrive, and were most probably powerful symbols of status of the new ruling social elite. Until a few years ago it had always been generally accepted that the first metal work arrived with the beaker people, but more recently some archaeologists have realised that early metal work in Britain must have been heavily influenced by earlier metal work, being imported from Ireland, where the earliest copper mining dates from around 2400 BC on Ross island and possibly earlier. Beaker pottery was found in connection with the site.
In Ireland the earliest form of copper axes date from around 2500BC. These are called:
(castletownroche) (each group of metal work is named after the area in which it was first found) very simple shape, straight sides and thick butts, shallow curved cutting edge.
(knocknagur) typically have broad thick butts, with the Loughravel type having curving sides and more deeply convex cutting edge.
(frankford) bronze axes start here but copper axes are still being made. with a new type (Ballybeg) axes, which have curved sides and tightly curved cutting edge. Excavation in Ireland of Bronze Age tract ways, (Corlea 6) in a peat bog have produced timbers that show stone and copper axes being used simultaneously, carbon dating puts them at around 2259 BC running parallel with Ballybeg axes.
(Killlaha) copper axes end here, bronze axes with much narrower butts than the early copper axes the sides splay out the middle of the blade is usually only slightly curved, one of this type of axes was found deposited in a pit at New Grange and carbon dated to around 2000BC,also there is a close comparisons, with (Milecross) axes 2000BC in Britain.
(Ballyvally) noticeable change from earlier axes, low edges were put on the faces, creating slight flanges and the slightly later development of (Inch island-derrtniggin) axes with narrower blades and half-flanged bodies, to add to the confusion, the earliest dated metal work in Britain 2300 BC comes from the recently discovered Beaker grave of the Amesbury archer. The copper for his blades came from two different sources in southern Europe.
As the evidence of metal working is so limited in Britain, almost nonexistent, it seems that it may have taken quite a while for anyone to develop metal working skills outside the beaker network, and possibly taken several centuries before we had indigenous metal-smiths in Britain. As the first artefacts are quite simple, people are unaware of the extraordinary effort the early metalworkers went to, maybe as much as two weeks work to make a copper dagger. It was a triumph of human ingenuity over a new complex science and material with limited equipment, -charcoal, clay, sticks and stones. It is hard to imagine the impact that those first metal implements had, but objects of the finest workmanship were soon taken up as symbols of power. In a time when society would have been very ritualistic, smelting ores, turning stones into metal, and even pouring molten copper the colour of the sun, must have had a deep magic attached to the metalworking process.
Why did they go to all the effort of decorating an axe when the haft would have covered a large area of it? Maybe it is the creation of the object, with all the ritual attached, which gives it its importance.
There are carvings of bronze axes on Stonehenge, all with the blade upwards with no handles. Could this be a veneration of the bronze axes to the sun or an axe cult? Remember the metal axe must have had an impact on every day life. All early furnaces used crucibles to hold the metal during melting, finds from the Middle East show that early clay crucibles were open and shallow and the heat was applied from above. This reduced the thermal stress to the crucible by passing the heat straight to the metal. Furnaces were probably a simple clay retaining wall about 10 inches high to contain the charcoal fire, with the crucible sitting on the floor and the air being blown with bellows through holes in the walls, possibly via clay tubes.
Copper has a high melting point of 1086C, but to get it to stay molten long enough to pour, it needs to be heated to near 1300C. Due to the shallow crucibles and the small volumes of metal the heat loss was very rapid, maybe they had as little as twelve seconds to recover the crucible and pour the metal before it chilled. Recovering the crucible from a fire of 1300°C is no mean feat. The heat radiated is so intense that anything nearby will ignite. It seems most probable that they used a wooden paddle to lift the crucible out of the fire, and then picked it up with green sticks for pouring.
Colour can be used as a temperature guide, but it is often overlooked that the caster with experience will use time as a means of knowing his bronze has melted. he will know that if he repeated the same process at the same pace and using the same amount of time he will repeat the success. He would know that a slow steady temperature rise would not harm his fragile crucible; so bellowing at a steady rate will increase his chances of success.
When enough time had passed he would see bright yellow in the heart of the furnace, this would indicate a high enough temperature. It is impossible to see the colour of the flames in daylight, and one wonders if they would have done all metalworking under cover in darkness or at night.
The earliest casting method used was a simple ingot mould, with the shape carved in a block of sandstone. Quite a few examples exist, especially in Ireland, but there are also some in Britain.
As a result of this casting method, the mould would have been preheated to get a better casting.
In Ireland it has been possible to trace several groups of axes, and the moulds they were cast in, showing a surprisingly wide distribution across the country with some in Britain. Early copper axes are often less than symmetrical when looked at side on. Although simple stone moulds survive, and the earliest clay mould is dated to around 1300BC, it is most probable that they mastered some form of clay impression moulding especially for later flanged bronze axes, this would have needed to be fired simultaneously. Copper, when molten, will absorb gasses from the atmosphere, which appear as holes when it solidifies. The longer it is exposed, the more holes there are in the casting. Leaving charcoal floating on the metal can counteract this. This presents no problem with an open mould but could spell disaster for a closed mould, either by blocking the entrance to the mould or getting trapped in the casting.
Copper doesn't lend itself to casting interesting shapes so the moulds are more like simple billets, far from the desired shape. After casting, the first step would be to remove the surface debris before forging. To obtain the basic shape, it would be necessary to forge the copper, hot using a heated stone anvil, and stone hammers, to achieve a basic shape, and the final shape through cold hammering, this would require constant annealing (softening through heat). Once the finished shape has been cleaned of marks, by grinding with a wet stone, decoration could be applied to copper axes and the recesses forged behind the edge of the blades of copper daggers before the final hammer hardening. The last stage would be to polish out the last hammer marks and apply the decoration with hammer-hardened copper punches.
Sometime around 2300 BC, metal smiths begin to alloy tin with copper and this first appears in a group of metalwork called Brithdir 2150 BC in Wales, this is strange because all tin and a plentiful supplies of cooper are available in Cornwall and some in Devon, I think it is more likely that the first alloying happened in Cornwall. Tin must have been hailed as a gift from the gods by the metalworkers, for the miraculous effect it had on copper. By alloying just 10% tin with copper would lower the melting point by 100C. It also made metal flow and cast better so you could cast nearer the final shape and create new shapes. It reduced the oxygen absorption, thereby forming fewer holes and better castings. The resulting alloy was much harder when cast, instead of the dull thud of copper; it was hard enough to ring straight from the mould. With cold hammering it went even harder but could be annealed in the same way as copper. They soon worked out that 10-12% tin was the optimum: any more and the alloy became too brittle, any less and it was too soft. Unlike copper, bronze is brittle when hot, and they took advantage of this, making it easy to break off the casting debris.
Even though bronze was much stronger, forging and hammer hardening were still important in finishing bronze axes. This is visible in Mile cross metal work 2000BC but quite noticeable in Willerby metalwork 1900BC; being heavily forged along the narrow edge to make slightly raised flanges, and highly decorated with blades that flare out quite noticeably. Bronze daggers of this period have also changed to riveted handles, with three to six rivets, instead of tangs. Instead of forging behind the edge of the blade, as with copper daggers, they moved further into the blade with three or four lines for decoration. So accurate is the forging that you could be forgiven for thinking that it was cast in and some daggers being decorated inside the lines with hundreds of regularly spaced dots. The finest examples are from the Wessex I Culture barrows1900BC.
The most fabulous burial of this period is the Bush Barrow one kilometre south of Stonehenge.
Among the many gold and bronze objects is a dagger with a handle decorated with thousands of gold pins to form a zigzag pattern on the pommel. It must have taken hundreds of hours of painstaking work, with each pin being 0.2 mm in thickness. Arraton Down metal work1700 BC follows on from Willerby. Some examples being highly decorated but the flanges are even more pronounced, possibly cast in and then forged to shape, with the cutting edge even more flared than before. Now you can see the bronze-smiths moving towards casting nearer the finished shape, and not going through some of the time consuming forging processes of their predecessors.
Bronze daggers and spears also start to take a simpler form, with the lines being cast in. There is the trend towards longer blades that become dirks and rapiers of the middle Bronze Age, and similarly with the raised flanges and stopping ridge on the axe developing to become the palstave axe.
After the early Bronze Age, metal work develops with better casting techniques, which save a lot of labour, and maybe because of this, one can sense that the metal work is losing some of its magic with items becoming more utilitarian in the middle Bronze Age. Maybe ritualised metalworking carries on in the production of rapiers, being cast in stone moulds. Could this have given rise to the sword in the stone of Arthurian legend?
© Neil Burridge 2004
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