Bronze Age Metalworking

This is the next in our series of posts on metal-working written by Dr. Kevin Leahy, PAS National Finds Adviser. The articles were first published in The Searcher magazine and are reproduced here with kind permission of Harry Bain, editor for The Searcher.

Typical Late Bronze Age copper ingot from Barham, Kent (KENT-14DDA6). Fragments of dish-shaped ingots are much more common than complete examples. Copyright: Kent County Council, License: CC BY.

In Britain we are highly fortunate in our mineral resources. A lot of geology is packed into these islands, which is why the principles of geology were discovered here. All of the main metal ores are present: non-ferrous metals in the hard rocks of the north and west, and iron in the south and east. Copper ores are found in Wales, Scotland and Ireland, and tin (needed to make bronze) is found in south west England. We have Bronze Age copper mines at Great Orme’s Head in North Wales and metal was transported in the bowl-shaped ingots, pieces of which are found in later Bronze Age hoards.

Copper working started in Mesopotamia in the 6th millennium BC but the first evidence we have for metalworking in Britain dates to around 2500BC when we find gold ornaments and copper daggers in graves with “Beaker” pottery, suggesting metal working was introduced into Britain at the same time as these distinctive pots. Archaeologists saw the arrival of Beakers along with metalworking, barb and tang arrowheads, round barrows and other bits and pieces, as evidence of an invasion but this “Beaker invasion” idea fell out of favour as it came to be seen as “Imperialist”, so everything was explained by cultural influence. However, recent DNA work on Neolithic and Beaker skeletons has shown that there was a massive change in population with the Neolithic people being largely replaced – not what we expected at all.

The first metal objects were made from pure copper which is soft, weak, difficult to cast and certainly no improvement on flint and stone. Later, the addition of arsenic to the copper gave a much stronger alloy. Ötzi, the 5000 year old mummified man found in the Alps, had an axe made from arsenical copper. Arsenic was eventually replaced by tin, about 10% being added to copper to produce bronze, a strong and useful alloy. The addition of tin also made the alloy easier to cast, reducing problems caused by gas and lowering its melting point from 1085ºC to 950ºC, with further additions making its melting point still lower. Another advantage of using alloys was the great improvement to the degree to which the metal could be “work hardened” by hammering.

1. Late Neolithic/Early Bronze Age “Beaker” from Manton Warren, Lincolnshire. Other metal objects sometimes found in Beaker graves are gold basket earrings and copper awls, both of which are present on the PAS database. 2. Copper dagger from Lancashire (LANCUM-3BEC10). Analysis has shown it to have the composition expected of Chalcolithic implements. It dates to around 2350-2150BC. 3. Early Bronze Age flat axe from Lancashire (LANCUM-874565). While probably cast in a flat mould, the cutting edge and butt were hammered to shape and harden them. Date 2250-1900BC. 4. These two Early Bronze Age axes are from Thornton Carr, Lincolnshire, and were found together but show two stages of the development of both axe design and manufacturing technique. The axe on the left is an improvement on the flat axe in that it has flanges running down its sides to prevent it twisting in the haft during use. The right hand axe has flanges but also has a transverse rib to prevent it being forced into the haft and splitting it. 5. Mould for casting Early Bronze Age flat axes from Llangwelyn, Radnorshire. 6 & 7. Stone moulds for a Middle Bronze Age rapier (left) and a spearhead (right).

As well as being worked by hammering, bronze was melted and cast into moulds – indeed all bronze objects start out as castings. It’s like that the earliest moulds for making flat axes were made from stone, although the use of a hollow in the ground cannot be ruled out. These early stone moulds are referred to as “open moulds”, although its highly unlikely that they were open when used as this would allow the top of the axe to oxidise leaving a layer of crud that would have to be scraped off. Covering the top of the mould with a flat piece of wood weighted down with a stone, would ensure that the axe’s upper face remained clean, carbon monoxide from the charring wood preventing oxidation.

The next great development occurred around 1650BC with the appearance of two part moulds which allowed objects with two shaped faces, such as flanged axes, to be cast. The use of clay “cores” made it possible to form hollow castings particularly spearheads and, later, socketed axes. Cores were made from a clay/sand mix and were fixed between the halves of a two part mould before the metal was poured in.

Stone mould continued to be used in the north and west (particularly Ireland) where suitable rocks were available. These needed to stand the heat of the molten metal and to be easily worked so that the matrix could be carved. It is likely that they were heated before the metal was poured in to prevent the mould surface from flaking due to thermal shock and the cold stone “freezing” the metal before the mould was filled. 

11. Mis-cast spearhead from the Guilsfield Hoard. This was meant to be a Late Bronze Age spearhead but the core was left out leaving a solid casting. 12. Two part bronze mould for casting Middle Bronze Age palstaves (SF-2D55E2). The top of the mould is expanded to form a poruing basin for the molten metal. Date 1400-1100BC. 13. Part of a Late Bronze Age leaf-shaped sword which was either mis-cast or broken during use. An attempt was made to repair it by fusing-on a replacement hilt but it hasn’t worked. 14. One half of a bronze mould for casting socketed axes. The decoration on the back of this one is unusual. 15. Casting gates removed from Bronze Age implements (WREX-1BF26F and NARC-85E2F5). They are difficult to date because we don’t know what was being made but they are similar to what would have been produced by some of the moulds pictured here.

Many objects were cast in clay mould which disintegrated  as soon as they were used. Evidence for clay moulds and crucibles is rare even on excavations but it is worth looking out for them – they are highly friable with a black/dark grey inner surface and yellow/orange back.

Clay moulds were made using wooden models or “patterns”, examples of which were found at Tobermore in Co. Londonderry. Somewhat squashed by 3000 years in a peat bog, these patterns were for making moulds for casting two types of spearhead, two socketed axes and a socketed gouge. In use, one side of the pattern would have been covered by a layer of clay and turned over so that the other side could be covered. They would have resembled two-part bronze moulds. The clay would have been allowed to dry and harden a bit before the two halves were separated and the wooden pattern removed. The two halves were put back together with a core set between them. After thorough drying, molten bronze was poured into the mould and the casting made.

A still more sophisticated method of casting involved the use of bronze moulds – a technique which would now be known as “gravity die casting”, in which the two halves of the mould were made not of clay but from bronze. Most bronze moulds are for casting palstaves and socketed axes but we also have moulds for spearheads and a socketed gouge. Pouring molten bronze into a bronze mould isn’t as risky as it might sound as there is little chance of the casting fusing to the mould. There are occasions when the intention was to fuse two pieces of metal together to effect a repair (known as “burning on”) but this is difficult to achieve as the molten metal needs to flow over the solid casting so that it melts. The use of die-casting in the Bronze Age points to the production of axes being on what must have been an industrial scale.

16. Fragments of a clay mould for casting Late Bronze Age swords, and the hilt from an unfinished Ewart Park type sword. 17. Part of a stone mould for casting socketed axes, found at St. Keverne in Cornwall (CORN-031000). The use of stone moulds is a feature of the north and west of Britain. 18. Socketed hammer of typical Bronze Age type (NARC-5B738E). The PAS has recorded over 40 of these hammers. 19. A sheet bronze shield found in Brumby, Lincolnshire. Incredibly, this would have started as a small bronze ingot and was slowly hammered out to shape. It would have provided no defence against Bronze Age weaponry so can only have been used for display. 20. Bronze anvil from Chitterne in Wiltshire (HAMP-7C41DB). 21. This odd looking object from Norfolk (SF-832744) brings together both cast and wrought technology. It is a handle from a Bronze Age cauldron dating to 1200-650BC. 22. Early Bronze Age razor from Caistor in Lincolnshire. The ridges running around the edge were made by hammering the metal to thin, harden and sharpen it as well as having a decorative effect.

The evidence we have for Bronze Age casting includes finds of casting gates through which the metal flowed into the mould. Some of these we can feel confident are Bronze Age but many are impossible to date and could have come from castings of recent date. Defective castings are uncommon (they probably went straight back in the pot) but the fault that we see most often is miscasting where the metal has not full filled the mould. We also see some displaced cores and porosity caused by gas in the metal.

In addition to casting, Bronze Age metalworkers were also producing objects from sheet metal some of which, like shields and buckets, were impressive objects. Nowadays we take sheet metal for granted and can buy metal rolled to any gauge you want. Things were different in the past and if you wanted sheet metal you had to start with an ingot and hammer it to the required thickness, repeatedly stopping and heating the metal to anneal it, preventing it from becoming too hard and cracking. Some Bronze Age hammers and anvils have been found by detectorists and recorded by the PAS.

The work of detectorists and the PAS has revolutionised our knowledge of Bronze Age metalworking with a massive increase in finds and knowledge – we live in exciting times!

Silver and Silver Working

This is the next in our series of posts on metal-working written by Dr. Kevin Leahy, PAS National Finds Adviser. The articles were first published in The Searcher magazine and are reproduced here with kind permission of Harry Bain, editor for The Searcher.

The Mildenhall Treasure is one of the high points of British archaeology. Apart from the artistry and the classical decoration, it is worth reflecting on the skill of the 4th century metalworkers who raised the repousse from flat sheets of silver. Copyright: The Trustees of the British Museum.

Of the 1.4 million objects recorded by the PAS to date, almost 180,000 (around 12%) are made from silver, representing a respectably high percentage. However, 78% of these are silver coins, either as single finds or as part of coin hoards which, while greatly adding to the total, are dealt with as groups to keep things in proportion.

Along with gold, silver is one of the “noble” metals; the other noble metals such as platinum were not known in antiquity and don’t concern us. These metals are known as noble because, unlike base metals, they don’t corrode – although silver does have its problems. I once excavated an Anglo-Saxon silver toilet set which, on first appearance was silver but, as we watched, it turned violet, then purple, then black. This was a photo-chemical reaction as the silver chloride covering the tweezers reacted with sunlight. Most disappointing. Silver is a lovely metal; bright, lustrous and highly workable, it is both easily cast and wrought giving craftsmen a superb medium on which to apply their skills.

Finds from around the Aegean Sea show that silver was being used as early as the 4th millennium BC but we have no evidence for its use in Britain before the later Iron Age, around 100BC, when we then see a substantial use of silver coins (there are over 17,000 Iron Age coins on the PAS database).

The Romans loved silver and some of their work, both in coins and tableware, has never been surpassed. Claims (perhaps exaggerated) of its mineral wealth may have played a part in the Roman’s decision to conquer Britain.

1. Only a few of the thousands of Roman brooches recorded by the PAS are silver. This gilded example (LVPL-80B2F2) is of “Polden Hill” type and is identical in form to many of the copper alloy brooches we see. 2. A Roman dress pine from Leicestershire in the form of a woman’s hand holding a scent bottle, AD50-200 (NARC-2D8651). 3. There has been some debate over the dating of this cheerful silver-gilt bird from Lincolnshire, but an Early Medieval date seems most likely, AD700-800 (NLM-78C696). 4. A Middle Anglo-Saxon  silver pin with the typical gilding below the head, from Lincolnshire and dated AD700-900 (LIN-4C7679). 5. A Middle Anglo-Saxon silver-gilt pin head from Lincolnshire, AD750-800. Up to the 8th century gilding was commonly applied to silver objects. This pin head formed part of a set of linked pins (NLM-028751). Copyright: Portable Antiquities Scheme, License: CC-BY.

Most silver is found in combination with lead. Lead is easily extracted from its ore but separating the silver from the lead was laborious and time-consuming.  It was done by a process known as cupellation where the lead was placed in a shallow hearth at a temperature of around 1000-1100ºC and a blast of air played over it. This oxidised the lead converting it to litharge (lead oxide) which was skimmed off or absorbed by the bone ash that lined the hearth. The silver, unaffected by the air blast, remained untouched as a pellet in the middle of the hearth. 

This sounds simple but imagine treating tons of lead in this way. The litharge was then re-smelted to turn it back to lead, which was a by-product. Over-production meant that the market was saturated with more lead than anyone needed.

The trouble here is the silver content of most British ores is disappointingly low and it’s not really worth the trouble extracting it. The Derbyshire ores contained around 2 to 6 ounces per ton which stands in stark contrast to the great silver mines at Laurion, which paid for the ships that defended Athens, and contained about 600 ounces of silver per ton.

The Romans seem to have limited themsleves to ores containing more than 20 ounces of silver to the ton of lead. Despite claims made on Roman lead ingots that they are “EX ARG” or “EX ARGENT” (from the silver mines), analysis of ingots showed that they still contain a low level of silver – no attempt had been made to extract the silver as it was simply not worth the trouble. But why are British ingots marked “EX ARG BRIT” when argentium (silver) wasn’t there? Was something dodgy going on? It all seems rather odd.

6.  A Middle Anglo-Saxon strap end decorated with Trewhiddle style inlaid with niello, AD800-900 from Staffordshire (WMID-4462B7). 7. Silver ingots like this are difficult to date but they are found in Viking hoards. This one was found in Essex and is dated to AD800-1000 (BH-7253E7). 8. This brooch was found in Norfolk as part of a hoard of 23 coins, four brooches and two strap ends. This fragment of a disc brooch shows the use of niello inlay (NMS-972E58). 9. Heavy stamp marks like these are a feature of many pieces of Viking silver (ESS-9CB5B8). 10. This silver ingot fragment from Lincolnshire shows the single chisel cut often seen on Viking ingots (NLM-1B15F9). Copyright: Portable Antiquities Scheme, License: CC-BY.

Pure silver melts at 962ºC but was rarely used as such: adding other metals to silver to form an alloy reduces its melting point. Sterling silver, the most commonly used silver alloy, contains 7.5% copper and melts at 893ºC. Not only is the melting point reduced but Sterling silver is harder and stronger than the pure metal. This lowering of the melting point is also the principle behind solder where an alloy of two parts silver to one part copper will have a much lower melting point than pure silver making it possible to join pieces together without risk of melting them. The surfaces to be joined were cleaned carefully and the solder applied along with borax which acted like a flux preventing the surfaces from oxidising. When heated, the solder flowed into the joint making a strong and almost invisible bond. Soft solder, an alloy of lead and tin has a melting point of around 300ºC and was much easier to use, but after burial objects can fall apart.

The watlington Hoard found in Oxfordshire contained 186 coins, 7 items of jewellery and 15 silver ingots (SUR-4A4231). Copyright: The Trustees of the British Museum.

Silver  is easily cast. The method used to produce many small objects was the “cire purdue” (lost wax) process, a method so clever and ingenious that it still invites wonder. The first step was to make a model of the required object using beeswax, a material that is soft and easily worked. Once this was done the necessary channels for the metal to flow into the mould were added, also made of wax. The whole thing was then covered in clay. To ensure that the full detail was captured this would be done by repeatedly dipping the wax model into a clay slurry to build up the mould thickness. When this was dry, it was turned upside down and heated in a kiln. This fired the clay and melted the wax which ran out to leave a hollow mould which was filled with molten silver. Intricate objects with fine detail could thus be easily made.

Silver is also highly malleable and the ease with which it could be shaped by hammering led to the production of the plate and table vessels that adorned Roman and Medieval aristocratic tables. Breath-taking hoards of Roman silverware have been found such as the Mildenhall TreasureSilver vessels can be made by “sinking” in which a disc of silver is hammered into a hollow cut into a block of wood. Soft and malleable, silver can be cold worked but, as work progresses it becomes increasingly work-hardened so it is necessary to “anneal” it – heating it up to soften it and prevent it from cracking. This may need to be done repeatedly. After “sinking” the silver vessel was placed over a round-ended iron stake from planishing – using concentric light taps from a smoothly polished hammer to further shape the object.

11. A silver brooch or badge made from a penny of Edward the Confessor, found in Hampshire. These brooches are an odd phenomenon as only one face was gilded (usually reverse) and fixings look too weak for use as a brooch (WILT-C94353). 12. A Medieval silver seal matrix bearing the figure of St. Peter and the inscription + SIGILLVM PETRI DE BARASTRE. An American professor contacted us to identify the man as Peter de Barastre, a canon of Wherwell Abbey (HAMP-4E0317). 13. A silver gilt Medieval finger ring found on the Isle of Wight (IOW-9F11B3). 14. A gilded Medieval brooch found in Worcesterhire, AD1270-1350 (WMID-EF7056). 15. A Medieval silver-gilt finger ring bearing the inscription “AVE MARIA” – a popular inscription as the Virgin Mary was greatly venerated (NMGW-115DBC). Copyright: Portable Antiquities Scheme, License: CC-BY.

Repoussé decoration was much used to decorate silver plate. This involves the design being raised by hammering. One can imagine the difficulties of hammering out fine decoration on a thin sheet silver plate. The answer was ingenious: the top of the surface to be raised was covered in a thick layer of pitch and, working from beneath, the design was hammered down into the resilient pitch. When complete the pitch could be sharpened up by “chasing” using fine, flat-ended tools to hammer down from the upper surface.

Silver could be further embellished by gilding or by the application of niello or enamel. Gilding was carried out by dissolving gold into mercury to form an amalgam which was painted onto the surface to be treated. The object was then heated so that the mercury boiled off, leaving a thin, fine layer of gold on the treated surface. Niello was a black silver sulphide which was applied to the surface of silver to give a bold contrast.

16. A small silver-gilt Post-medieval dress hook found in Buckinghamshire (BUC-C09A34). 17. Silver gilt dress hook decorated with filigree wire and granulation both fused onto the surface of the silver. Once rare, metal-detecting has shown that these fittings must have been relatively common during the Tudor period (IOW-6CD1A5). 18. At one time, pins like this one were considered to be Viking but they are now known to be Post-medieval, AD1500-1600 (KENT-CE8D6B). 19. Post-medieval pin found in Surrey (SUR-C52692). 20. A silver spur, probably for attaching to a fighting cock. Not a nice object but still interesting (SWYOR-B06054). Copyright: Portable Antiquities Scheme, License: CC-BY.

While gold is the premier metal, I often think that we see a higher level of craftsmanship on silver objects where, using a workable material and not having the WOW factor of gold, the artisan had to try that bit harder.

Prehistoric Gold

This is the first in a series of posts on metal-working written by Dr. Kevin Leahy, PAS National Finds Adviser. The articles were first published in The Searcher magazine and are reproduced here with kind permission from Harry Bain, editor for The Searcher.

Gold is, perhaps, the strangest of the metals not through its inherent properties (interesting as they are) but through gold’s social role. Here we have a metal grubbed from the earth at great cost and labour, and because of which countless people have died, but which is effectively useless. Tools and weapons were made from stone, bronze and iron but, until recently, when high-tech applications appeared, gold’s only use was decorative and as a high level means of exchange.

Britain is lucky in having its own sources of gold. These are all in the north and west – Ireland, Wales and Scotland. The gold is present in the ancient hard rocks of these areas to which it was brought, from deep with the Earth, by volcanic and hydrothermal activity. However, these rocks have been eroded and so redeposited gold can be extracted from streams by “panning”, swirling sand around in a shallow, water-filled dish so that the sand is washed away, hopefully leaving a smudge of gold dust in the centre.

What is it about gold that gives it its allure? Soft and weak its mechanical properties are hopeless but it does offer the advantage of being very easily worked. It is highly malleable and can be beaten so thin that it becomes transparent. It can also be cold-welded by hammering and offers a craftsman almost unlimited possibilities. 

Then there is its colour. Most metals are either grey or white; only gold and copper are coloured. But unlike copper, gold does not tarnish – even after long burial it remains lustrous and bright yellow, the colour of the sun. Gold is also dense and has “heft” – if you toss it in your hand you can feel it landing on your palm. Finally, gold is scarce and scarcity makes it desirable to those with the power to obtain it.

Image of three gold archaeological objects.
(1) Beaker period “Basket ornament” found in Oxfordshire (BERK-0D1A05) and dating to 2400-2200BC. These ornaments were made from thin sheet gold decorated with raised dot. They may have been worn as earrings but it has been suggested they were actually worn in the hair. (2) Drawing of DUR-02828D from Northumberland showing how a “basket ornament” was fitted, if not how it was used. (3) Gold lunula made from thin sheet gold and found in Dorset, dating to 2400-2000BC (DOR-2198F8).

By about 5000BC gold was being used to make trinkets in Eastern Europe. Its early use was due to it occurring in a “native” state, not as an ore that needed to be smelted but as metallic gold which just needed to be beaten to shape and cold-welded to form small objects.

Gold working appears in Britain around the middle of the third millennium BC when “basket ornaments” were placed in Late Neolithic/Early Bronze Age “Beaker” graves; that of the celebrated Amesbury archer was dated to 2470BC. In this period we find small gold discs (about 30mm in diameter) with raised decoration and also gold “lunulae”. Lunulae bear incised, zig-zag linear decoration similar to that seen on beaker pottery suggesting that they are of similar date, although there are no examples from graves or anything else that might date them. We also don’t know who wore them or how they were worn – were they around the neck or inverted on the head? Most lunulae have been found in Ireland where they must have originated but a few stray into Britain and onto the European mainland.

Similar in shape, if not in decoration, to Bronze Age beakers is the wonderful cup found at Ringlemere, Kent, in 2001. Beaten from a sheet of gold, its corrugated sides more than compensate for the lack of an incised pattern.

(4) The Ringlemere Cup from Kent (PAS-BE40C2), dated 1700-1500BC. The strip of metal forming the handle was attached using distinctive diamond-shaped washers, a feature which also appears on continental gold cups. (5) Composite finds like this twisted bracelet threaded through gold rings from Berkshire (BERK-A5FFE5) date from the Middle Bronze Age, 1300-1100BC. (6) This massive twisted gold torc (CAM-E5D871) from Cambridgeshire dated 1300-1100BC would have encircled the wearer’s neck multiple times or may even have been worn around the body.

From later in the Early Bronze Age (up to c.1700BC), we get a series of small amber pendants covered, at least in part, by thin gold sheet; also dagger pommels decorated with hundreds of tiny gold nails. These are found in graves of the so-called Wessex Culture but so far none have been recorded on the Database.

Although important technical advances continued to be made in bronze working, gold seems to disappear with the end of the Wessex graves, or perhaps they were putting it somewhere where we can’t find it. Gold reappears big-time around 1400BC as part of the Middle Bronze Age “Ornament Horizon” which included gold bracelets, neck rings and ornaments often made from twisted bars. These objects aren’t based on earlier British Bronze Age types but are new forms introduced from the Continent. Some hoards of this period were enormous – the Mountfield, Sussex, hoard contained 13lb of gold.

(7) Fragment of a Middle Bronze Age torc from Hampshire (HAMP-C8DC02) dated 1300-1100BC. This fragment shows how they were made – the square rod was grooved to form a cross-shaped section which was then twisted. (8) An example of a “ribbon torc” found in Buckinghamshire, dated 1400-1150BC (BUC-C07E88). (9) A Late Bronze Age ribbon bracelet with buffer terminals from the Isle of Wight, dated 1150-750BC (IOW-7477D4). (10) A gold buffer-ended bracelet of Late Bronze Age type found in Hampshire and dated 1150-750BC). (11) Bronze Age bracelet with C-shaped section from the Isle of Wight, dated 1000-750BC (IOW-FA17F8). (12) A hoard of five Bronze Age gold bracelets found in a pottery vessel found in Milton Keynes and dated 1150-800BC (PAS-833958).

After 1100BC we have another gap in our knowledge of British gold working. Things start to pick up again with the production of gold bracelets. Most of these are found in hoards, usually of around three bracelets, sometimes with bronze objects. These come in a range of simple shapes with round, flat, D-shaped and hollow C-shaped sections. Most had expanded buffer terminals although the flat type had scrolled ends.

Of similar date is the so-called “ring money” consisting of small penannular rings sometimes decorated with bands of different coloured alloys. The function of these rings is unknown but it is unlikely that they were any sort of money. Lock rings represent another enigmatic object. The two faces and inner edge were fixed together with binding strips to form a hollow triangular section. Lock rings are in Britain, Ireland and north-west France but we have no idea of how they were used.

One of the emblems of the Iron Age is the gold torc. These splendid objects are, like so much else in archaeology, mystifying. They don’t stand at the apex of any deep tradition of gold working but represent, with the exception of coins and a few late brooches, the totality of Iron Age gold working. Made using techniques drawn from copper-alloy working these objects stand alone.

(13) This piece of “ring money” found in Kent (KENT-FF00A6) appears to be gold but many of them consist of a gold plated bronze core. (14) A feature of gold is that its alloys can come in a range of colours including pink, white and even green. This penannular ring from Buckinghamshire dated 1150-800BC, was analysed and found to have a content of approximately 78% gold and 18% silver. (15) A Late Bronze Age lock ring decorated with incised lines, found in Sussex and dated 1000-750BC (SUSS-5EA230). (16) This buffer ended torc from Lincolnshire (NLM-605352) dated 400-300BC is of continental type and must have been imported to Britain. (17) A torc from Nottingham dated 110-50BC, made with gold wire with terminals decorated in Iron Age style. (18) An Iron Age bracelet made up of two gold ropes plaited together. Each rope is made up of two twisted wires. It is made from an alloy containing 55% gold, 38% silver and 7% copper. Dated 100-50BC, it was found in North Yorkshire (SWYOR-681CE4).

Some of the discoveries have been amazing: excavations at Snettisham, Norfolk, revealed at least 12 hoards packed together into pits. Some of these torcs showed signs of wear and others look like continental imports. The alloys from which they were made became increasingly debased with the later torcs contained less than 25% gold. Mercury gilding, in which gold is dissolved in mercury for application to a silver or copper-alloy object appeared for the first time.

The Iron Age saw the large-scale use of coins, many of which were made from gold or “electrum” (a gold/silver alloy). This is not the place to discuss the massive and complex topic of Iron Age coins but one aspect of them is interesting from a technical point of view: we find tray-like slabs of pottery which bear rows of hollows. These may have been used to ensure the alloy composition of the coins was correct. Into each hollow was weighed the correct amount of gold, silver and copper, and the tray was then placed into a furnace so that the scraps of metal fused together to form a pellet of the right weight and composition ready for striking coins.