ARC 1010 - Pyrotechnology and Metallurgy

1. Can be hard – or soft

2. They can be shaped, and re-shaped

3. They drawn into wire

4. They can be sharpened to a cutting edge

5. They have colour and lustre

6. They can ring and have tone

7. Some are rare and some are common

Two-stage process

1. making metal – irreversible process

2. making artefacts from metal – reversible process

Understanding the technology

Smelting and the archaeological record

• generally takes place near sources of raw materials (ore and charcoal fuel)
• generally away from habitation sites
• produces large quantities of waste (more waste than metal)
• waste is left on site and metal goes into circulation

• Many different types of mining
• Not all require underground work
• Streaming mineral-bearing river deposits
• All require specialist tools

Examples: 

• Great Orme, Wales - copper mine
• Kestel Mine, Turkey - copper and tin mine

Ore = a mixture of desirable metal minerals, unwanted minerals and ‘country’ (surrounding) rock

Ore Deposit = bodies of rock containing sufficiently high concentrations of desirable metal minerals to be ‘economically viable’ to exploit (‘economically viable’ can mean many different things at different times in history)

Remember – an ore is not a metal, it is a mineral, and it does not behave like a metal Ore has to be chemically converted into a metal in a process called smelting

Smelting:

• Thermo-chemical conversion of mineral to metal
• Physical separation of metal and unwanted minerals
• This is done in a purpose-designed furnace (1200oC) using charcoal fuel
• **** waste in lrg quantities, funace remains, ore and charcoal

Furnaces

• wide range of shapes and sizes dependent on technology, date, and region/culture

Copper smelting:

• Malachite ore in crucible
• ore covered with fine charcoal
• placed on hearth with charcoal and heated (1200oC)
• prills of copper produced (raw metal)

Charcoal fuel: 

• needs planing, skills, and knowhow
• labour intensive (social investment)

Metal-making needs expertise therefore master craftsmen had social status and power (sometimes perceived as magical power)

Making the best metal: 

• refining
• alloying

Making the artefact

• casting
• forging (hot and cold)

Refining

• raw metal needs to be refined into useable material for object making
• first steps in refining include removing remaining **** waste (bloom smithing to form billets of iron or re-melting of raw ingots to separate ****) and consolidation to bar/ingot
• refining generally at workshop scale and takes place in or near habitation (customers, end-users) and produces less waste
• most important process for non-ferrous and ferrous metals is alloying
• form bronze by mixing copper w tin by remelting

• Alloying lowers the melting point below that of the base and sometimes below that of both metals
• Alloys melt over a range of temperatures not a single temperature. This increases workability
• Alloying increase hardness (by introducing different size atoms into the regular crystal lattice of the pure metal movement in the lattice is inhibited)
• Alloying changes the colour of the metal. This is used to greatest effect in jewelry and decorative metalwork
• Alloying can change the tone or ring of a metal. (This is used in musical instruments and musical strings)

• casting: crucible using molten metal and mould 
• crucible: ceramic (gets hot but doesn't melt during casting)
• casting: oldest method in metallurgy
• cold working: traditional, smithing e.g. gold smiths
• hot working: approach melting point, e.g. smiths of iron, heated in a forge

• The metallurgical process is multi-staged and requires planning, group activity as well as specialist knowledge
• The metallurgical process is ‘energy’ expensive and needs social/collective investment in advance of the output
• There is therefore an imperative that it succeeds and the metal produced thus has integral value even before the artefact is produced
• Therefore, being a person who can make metals or owns metals gives a distinctive place in society (good or feared)

The importance of the advent of metallurgy is no better demonstrated than in the continuing persistence of the Three-Age-System:

• The Stone Age
• The Bronze Age
• The Iron Age

Not

• the hunter-gatherer era and the farming era
• the cave and camp age and the city age

Only other durable nomenclature division is prehistoric and historic

From this we might conclude that metals had a major transforming impact on human society BUT did the use of metallurgy divide society? 

The importance of the advent of metallurgy is no better demonstrated than in the continuing persistence of the Three-Age-System:

• The Stone Age
• The Bronze Age
• The Iron Age

Not

• the hunter-gatherer era and the farming era
• the cave and camp age and the city age

Only other durable nomenclature division is prehistoric and historic

From this we might conclude that metals had a major transforming impact on human society BUT did the use of metallurgy divide society? 

1. First encounters – Minerals (as pigment materials or for bead making) – colour; weight/density; hardness/brittleness

2. Native metals – occur in nature as metals - found in association with minerals e.g. Cu, Au, Ag 

3. Zoomorphic forms in native metals – natural forms that can be enhanced by cold shaping and hammering leading to embrittlement of the metal and cracks/breakages

4. Annealing – gentle heating to soften the native metal and counteract embrittlement, allows repeated cold working and forming of the metal

5. Melting – combining separate fragments of native metal by melting them together in a container or hollow (6th millennium BC?)

6. Shaping – deliberate shaping of melted metal by pouring into a shape - casting into ‘moulds’

These steps are hard to fully identify as there are very few objects (trinkets), they are small and very corroded – and the technical features are difficult to unequivocally identify Sites – Cayonu Tepesi; Yarim Tepe; Catal Huyuk (Anatolia and Mesopotamia)

7. Accidental smelting – in melting container (crucible) with accidental inclusion of mineral with native metal (6th -5 th millennium BC)

8. Intentional smelting – abandon search for rare native metals and collect more abundant minerals (4th millennium BC - Chalcolithic) – in crucibles and small furnaces

9. Alloying – combining metals or minerals to change properties, e.g. colour, hardness, lustre (Early Bronze Age) Sites – Feinan; Timna; Goltepe (Jordan, Israel and Anatolia); Ain Bunar; Rudna Glava (Balkans)

From 3 rd millennium BC onwards evidence for copper smelting begins to appear in Balkans, Iberian peninsula, Mediterranean, Indian sub-continent, China, South-East Asia – i.e. widespread

• Early Neolithic in Mesopotamia and Anatolia Trinkets and zoomorphic forms – no evidence of working
• 8th mill BC Cayonnu Tepesi – 50 copper awls, sins of annealing
• 7th mill BC Tell Mayzallia, Iraq – annealed native copper awls
• 6th mill BC – annealed copper objects from Yarim Tepe, Ali Kosh possible ‘****’ at Catal Huyuk ‘****’ at Feinan, Jordan
• 5th mill BC – ambiguous evidence for smelting at several sites across Turkey, Iraq and Iran
• 4th mill BC – increasing good evidence for smelting at many locations, smelting in crucibles and the beginnings of the use of alloys
• 3rd mill BC Early Bronze Age – alloying with tin, smelting in furnaces producing **** and smelting in SE Spain and Balkans
• 2nd mill BC – copper metallurgy widespread but at different stages of development
• 2000-1500 BC – first evidence for smelted iron

What makes a precious metal?

• Rarity
• Resistance to corrosion
• Colour and lustre
• plasticity? render of fine detail
• Qualities of the metal combined with quality of the craftsmanship – aesthetic 

What makes a precious metal?

• Rarity
• Resistance to corrosion
• Colour and lustre
• plasticity? render of fine detail
• Qualities of the metal combined with quality of the craftsmanship – aesthetic 

GOLD

• Only occurs as native metal and doesn’t require smelting
• Generally earliest exploitation is from alluvial placer deposits extracted by panning.
• Lighter minerals washed away from denser gold particles by gravity separation.
• Particles then melted together to form ingots that can be remelted and cast or hammered into thin sheet.
• Despite its attraction and ease of use GOLD is not exploited as early as copper in Near East and is not used by other cultures (e.g. North American) that exploit native metals
• Earliest evidence for regular use of gold is from the Neolithic cemetery at Varna, Bulgaria (4600-4200BC) where hammered sheet and cast gold are in abundance.
• Varna – c. 300 graves discovered 1972 with c. 3000 gold artefacts weighing total of 6kg.

Raw materials

Copper ores 

• numerous viable deposits across Europe important sources include Balkans (Bulgaria, Serbia, Albania), the Alps, the Carpathians, central Europe (Germany), Iberian peninsula, France, North Wales, Ireland, Cornwall North Wales (Great Orme) and Ireland EBA mining sites

Tin ores (for bronze alloys) 

• very few in Europe Largest deposits in Cornwall, also small amounts in Spain, Brittany, Sardinia and eastern Europe. Tin sources for BA metallurgy remains a puzzle, little sound evidence for exploitation where did they get it from?

Smelting 

• primary smelting of ore to metal generally took place near ore sources. EBA **** from Mount Gabriel, Ireland but no unequivocal EBA ****s identified in Britain. Middle and Late BA **** deposits in Mitterburg, Alps and throughout Balkans

For production of bronze, tin was needed, but with few available sources in UK, trade emerged across Europe and the West --> therefore value of bronze went up!

Primary smelting would produce ingots of metal

These then become important drivers of trade across Europe

Ingot shapes 

• plano-convex ‘buns’ formed by molten metal collecting in rounded base of furnace or crucible
• axe-shaped ingots
• ‘ox-hide’ ingots – eastern Mediterranean to Sardinia, also recently fragments found in Germany

Ulu Burun, Turkey – LBA (1400BC)

• shipwreck off coast of Turkey found in 1982
• 10 tonnes of cargo included 354 ox-hide ingots of copper and tin, 121 plano-convex ‘bun’ ingots of copper and tin (over 1 tonne of tin in total, sufficient for 11 tonnes of bronze). Cargo also included glass ingots and many finished artefacts.

• With quantities of metal ingots being transported and traded metalsmiths could be flexible in working practices.
• Could use and mix primary smelted metal ingots, scrap metal from mis-casting and recycled artefacts.
• Most artefact producing workshops situated in or near settlements.
• Circulation of scrap metal and recycled artefacts demonstrated by founders hoards and traders hoards.
• Workshops saw lots of objects from lots of places, demonstrates collection and trade

• ubiquitous distribution of useable sources of ore meant less valued-added long distance trade in raw materials/metal
• increase in locally smelted metals
• increase in use of iron for implements and tools of everyday use – agricultural, domestic, craft specialists
• increase in availability of iron across all strata’s of society
• increase in demand for metal-workers (blacksmiths) to make, mend and supply tools increasing competition (for reputation/status as much as income) between blacksmiths probably led to development of technical skills
• dev. of techniques to treat iron to give sharper /harder cutting edges and superior tools
• inevitable development of more effective weapons that gave real advantage in battle
• development of edged weapons and ballistic weapons – swords, spears, arrows, shot
• need to develop ‘defence’ to counter ‘offence’ – armour, shields
• scaled up to mass warfare from bands or groups of followers to armies

• ubiquitous distribution of useable sources of ore meant less valued-added long distance trade in raw materials/metal
• Iron is one of the most common elements in the earth’s crust
• Few regions of the world do not have some concentrations of the mineral sufficient to smelt the metal
• increase in locally smelted metals
• Reduced need to transport ore or trade primary metal ingots (as with copper and tin) over long distances
• Trade iron only becomes important in major economies (Roman) or if quality of iron is superior and sought after (high-carbon steel)
• increase in use of iron for implements and tools of everyday use – agricultural, domestic, craft specialists
• Digging tools, ploughs, vegetation cutting, harness, domestic knives, butchery, carpenter’s tools, stone-masons chisels, architectural fittings
• increase in availability of iron across all strata’s of society
• Social economies function more profitably if tools are available to everyone so all tasks become more efficient. Mass use of iron