15 Early Iron Metallurgy

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  • 1. FIRST YEAR ARCHAEOLOGY TUTORIAL 15 EARLY IRON METALLURGY
  • 2. THE IRON AGE IN IRELAND Definition of term ‘IRON AGE’ TECHNOLOGICAL MEANING Iron-using societies
  • 3. THE IRON AGE IN IRELAND Definition of term ‘IRON AGE’ TECHNOLOGICAL MEANING First contact with iron 700 – 500 BC Adoption of iron technology 300 BC onwards Influence of Roman technology from 1st century AD Expanded use of iron in early medieval period ( 500 – 1200 AD ) Technological influence of Viking World after 900 AD
  • 4. THE IRON AGE EARLY IRON WEAPONS IRON SWORDS
  • 5. Drumlane iron cauldron Co. Cavan
  • 6. Drumlane iron cauldron Co. Cavan Influence of Late Bronze Age metalworking traditions on the first ironworking in Ireland
  • 7. Lough Mourne iron axehead, Co. Antrim Can see this also in case of earliest iron axeheads > copies of bronze axeheads
  • 8. Sources of Iron in Early Ireland Pure iron: very rare. Use of meteoric iron by some early cultures, but not in Ireland. Early Ireland: probable use of 2 sources: bedrock ores & bog ores. Examples: Haematite (Fe 2 O 3 ) and Limonite Fe 2 O 3 H 2 O). No early iron mines discovered in Ireland. Probably surface extraction of bog ores, leaving little archaeology. Ore Preparation Cleaning (washing) and concentration (hand-picking) of ores Roasting of ores to expel water
  • 9. SMELTING OF IRON ORES Early iron workers were not able to melt iron to be able to cast it into moulds > required the development of the blast furnace in later medieval times. In earlier times, iron was produced by the Bloomery Process, in the same 1200 ˚C temparature range as bronze casting. This involved the solid state conversion of iron ore to iron metal, without the iron ever entering the liquid stage. This produced Blooms of impure iron This happens through the production of carbon monoxide gas in The furnace, which reduces the iron ore: Fe 2 O 3 + 3CO  2Fe + 3CO 2
  • 10. IRON SMELTING REQUIRED THE USE OF A FURNACE Excavation evidence of a early furnace Slag Pit Furnace Tuyere
  • 11. IRON SMELTING SMELTING SLAG Converting the bloom of iron into pure iron Heating it and hammering it hot to squeeze out impurities
  • 12. THE IRON SMITH FORGING IRON OBJECTS
  • 13. CASTING BRONZE OBJECTS IS DIFFERENT ! Involves pouring molten metal into Crucibles and Moulds
  • 14. IRON SMITHING TOOLS Iron is a pure metal; Steel is an alloy of Iron (that has absorbed carbon) All iron produced in prehistory was impure > Wrought Iron This impure iron can be converted to Steel by a process called Carburization
  • 15. HOW EARLY IRON AXEHEADS WERE MADE IN IRELAND Forging the Feerwore axehead from Co. Galway
  • 16. Lough Mourne iron axehead, Co. Antrim
  • 17. VIKING IRON OBJECTS
  • 18. PRESERVATION OF IRON OBJECTS IN ARCHAEOLOGICAL CONTEXTS