The Age of Iron

his 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.

Socketed axehead from Middleham, North Yorkshire (AD800-600). Iron objects, particularly spearheads, have been found in Late Bronze Age hoards. The most commonly found iron objects in Britain are iron socketed axes. These were easy to cast in bronze but a real challenge to the iron worker. Iron socketed axes were replaced by the shaft-hole type which remains in use.

We all love iron, don’t we? Well perhaps not, many detectorists set their machines to discriminate against iron finds – out of 1.4 million finds on the PAS database, only 6,353 (less than half a percent) are made of iron. There are reasons for this: iron is usually poorly preserved, difficult to date, and there is an awful lot of it out there. If you dug every iron signal, you’d get nowhere fast. However, iron can be interesting and, like everything else, has its story to tell.

Iron was used in Egypt to make small beads around 3,200BC but their high nickel content showed them to be made from meteorite iron, a source used at an early date by other peoples. An iron dagger found in the tomb of Tutankhamun, who died in 1,323BC, has also been found to have come from a meteorite. Iron was first smelted from its ore in Anatolia, Turkey, around 2,200BC and by 1,400BC was in common use, at least amongst the aristocracy.

The iron dagger from Tutankhamun’s tomb – made from meteorite iron rather than smelted from iron ore. Copyright: The Egyptian Museum, Cairo.

Iron first appeared in Britain around the 7th century BC and there was a period overlap when both iron and bronze were used. This is not surprising as early iron objects were pretty useless. Iron is a weak, soft metal and was inferior to bronze. There is an account of Celtic warriors at the battle of Telamon (224BC) having to break of the action to stamp on their swords and straighten them! It was only with the development of steel (see below) hat iron became a strong and useful metal. 

So, if iron was so useless, why did it replace bronze? Well, it was more readily available – while copper is found only in the north and west of Britain, and tin only in Devon and Cornwall, iron is widespread. There are deposits of iron ore in the Weald, Lincolnshire, Northamptonshire, the Cleveland Hills, Cumbria and the Forest of Dean. In addition to these, there are many deposits of “bog iron”, easily smelted, which was an important resource in early times. 

After mining, the ore had to be dressed to remove as much of the non-ore material as possible, before it was roasted to around 500-800ºC, driving off water and turning it into oxides. The roasted ore was broken up and put into the furnace for smelting to convert rock into iron.

Smelting is based on the affinity that carbon has for oxygen at a high temperature: the carbon monoxide (MO) gas from the burning charcoal desperately wants another oxygen atom to become the more stable carbon dioxide (CO2) and grabs an oxygen atom from the iron oxide leaving the iron alone as metal. The reaction, CO + FeO –> Fe + CO2, creates the iron metal and caron dioxide gas.

Finding fuel was perhaps a bigger problem than getting the ore as the smelting process used charcoal in enormous quantities. 16 pounds of charcoal were needed to make one pound of iron, and as charcoal is very light, this represents quite a bag full. The process was slow, calling for six to twelve hours pumping the bellows to maintain the blast of air.

During this process the iron never melted but changed from ore to metal while remaining solid. While iron melts at 1,536ºC, smelting starts at around 800ºC and iron could be extracted at this temperature. However, iron is not the only thing to come from smelting. As well as iron oxide, ores contain other minerals which form slag and a temperature of 1,150ºC is needed to melt the slag so that it separates from the iron.

The final product from smelting was a spongy lump of iron known as a “bloom”, as well as large amounts of slag waste which still contained a lot of iron – early smelting was inefficient. After removal from the furnace, the bloom was consolidated by heating and hammering which forced out most of the slag to form wrought iron. Blooms were small and to make a large iron object such as anchor or a furnace bar it was necessary to forge together a large number of blooms.

1: While impossible to date, this iron “bloom” shows the typical product of early smelting (HESH-C26546). 2: An iron “hipposandal”. These elaborate objects were strapped to the hooves of Roman horses when they were used on paved surfaces. Fashioned from white-hot iron they represent a fine example of the smith’s art. AD50-400 (WILT-A3591B).

Although iron smelting was a slow and arduous task, large amounts of iron were made in the past. During the excavation of the Roman fort at Inchtuthil, Perth and Kinross, a hoard of iron weighing ten tons was found, including 875,000 iron nails weighing seven tons. These had been buried when the Roman army moved out in AD86 to prevent the local tribesmen using them to make interesting things.

Iron was worked in a markedly different way to bronze. Bronze could be hammer-worked to produce sheet metal objects like shields and buckets. This was done while the metal was cold  but with frequent reheating to relieve the stresses and prevent cracking. Iron on the other hand was worked as white-heat and, unlike bronze, was not cast in antiquity. New types of object were devised to take account of the different way in which iron had to be worked. For example, complicated shapes like a socketed axe could be easily cast in bronze but difficult to fabricate in iron.

3: Not all iron objects are large and rough. This Roman headstud brooch is a fine piece of work by any standard and shows what we might be missing. Roman iron brooches have been found on excavation and may have been common (NLM-9F8090). 4: Spearheads can be difficult to date but those of the Early Anglo-Saxon period have a highly characteristic split socket that was not used at other times (HAMP-B3DAC5). 5: Because of the difficulties of hammer-welding the intricate joints and angles on Early Anglo-Saxon shield bosses like this one were fashioned from a single piece of iron – there are no joints (FAKL-929576).

The properties of iron offered advantages: heated to white-heat, it becomes highly malleable; it can be shaped by forging; and, unlike bronze, pieces of it can be welded together. If two pieces of wrought iron are made white-hot and hammered together, they will fuse making a strong permanent joint. Iron is a poor conductor of heat making it possible to heat just a single area; the middle of a bar could be heated so that is could be bent or expanded or hammered from its ends.

It was the development of steel that made iron important. Steel is made by introducing carbon into the iron by a process known as “carburisation” in which iron bars were kept at around 900ºC in a charcoal fire, blown by bellows with charcoal being added. After about six hours the carbon would have penetrated 2mm into the iron producing steel. By “piling” – repeatedly folding the carburised bar along its length and hammer welding – the carbon was distributed in layers throughout the bar.

7: This large iron object is a plough-share. These can be difficult to date but as it was part of a hoard of three plough-shares, an Anglo-Saxon date is likely as hoards of iron tools are a feature of this period (NLM-F10454). 8: While most iron objects cannot be dated, this find is of a highly distinctive type. It is a “francisca” or Frankish throwing axe – a devilish weapon which if caught on the shield was designed to spin behind it (CAM-5D8F2E). 

Steel is harder than iron and offers the great advantage in that it can be heat-treated – heated until it is red-hot and plunged into water to rapidly cool it. This gives a hard but brittle steel and it is necessary to “temper” it by heating it to a lower temperature and allowing it to slowly cool, giving a tough, usable steel. Making steel was a slow process and alloy (steel is an alloy of iron and carbon) was used carefully. Often a strip of steel was welded along the edge of an iron tool for economy, or a layer of steel was incorporated into the core of a knife. It’s sometimes possible to see the line of the steeling on a corroded iron knife.

In the late 15th century a new type of iron was introduced into Britain in the form of “cast iron”. This was produced in a blast furnace which, unlike the earlier method, produced liquid iron that could be poured into a mould or cast into “pigs”. Cast iron picks up carbon from the charcoal or, in later periods coke, used in the blast furnace. While carbon is added to iron to make steel, cast iron contains too much carbon – more than 2.5% – which has a dire effect on its properties: cast iron is brittle and will snap if bent or placed under tension. Cast iron could be converted into the workable wrought iron in a “finery” where the carbon was oxidised from the molten iron. The development of the “puddling process” in the 1780s allowed cast iron to be converted on a larger scale. 

9: A fine iron helmet dating from the English Civil War. Few iron finds are as well preserved as this – the maker’s mark can still be read “HK”, for Henry Keene who was working in London (LIN-E0B301). 10: Cast iron cannon ball. We tend to be suspicious of “cannon balls” as many of them may have been used as ball-mill rather than in a gun. However, this iron ball has hit something with sufficient impact to break it in two, suggesting that it has been fired from a gun (NCL-950857).

Henry VII introduced blast furnaces and cast iron from the continent to produce cannon balls, guns still being made by the “stave and hoop” method. Cast iron took quite a while to really catch on. Later, guns were cast, as were fire-backs, but it’s not until the 18th century that things really took off with the large-scale use of cast iron in building, machinery and household goods. Cast iron is capable of taking incredible detail, and be cast into thin and intricate shapes. Most of the iron we see today is “mild steel”, a cheap but entirely satisfactory material.

Iron Age and Roman Mirrors from East Anglia

Iron Age Mirrors

Iron Age mirrors were elaborately-decorated discs of polished bronze with decorative handles, such as the famous Desborough mirror. In 2010, Jody Joy catalogued 58 examples, mainly from southern England. The earliest mirrors from East Yorkshire date from about 400 BCE, but most others are 1st century BCE-1st century CE.

Decorated Iron Age mirror, Desborough, Northants. (©Trustees of the British Museum 1924,0109.1, used under CC BY-NC-SA 4.0 license).

Mirrors are very rare in East Anglia (Norfolk, Suffolk and Cambridgeshire), home of the Iceni people, although the area has one of the highest recovery rates of Iron Age artefacts nationally. Mirrors are unknown from Norfolk or Cambridgeshire, except for a possible handle from Thetford (NHER: 5853). Three handle fragments have been found in eastern Suffolk: at Akenham (SHER: AKE006), Badingham (SHER: BDG033) and Westerfield (PAS: SF6712). This may reflect the lack of Iron Age burials, the most common location for mirror finds. By contrast, Essex, which is richer in Iron Age burials, has at least ten mirrors. The absence of mirrors in this period suggests that local communities may have been selective about adopting their near neighbours’ artefacts and practices, as well as more exotic imports from Gaul and the Mediterranean, which began to be available through contact with the Roman Empire in the 1st century BCE.

Distribution of Iron Age and Roman mirrors in East Anglia (source: Author).

Mirrors have often been described as important status symbols, buried with wealthy women for the afterlife. However, some skeletons have been interpreted as female based on the presence of mirrors in graves, rather than scientific analysis, and many burials were poorly recorded during antiquarian excavations. No mirrors have yet been categorically associated with a male individual, but occasionally have been found in graves that also contained weapons, considered male belongings. Mirrors can also be regarded as marking ‘difference’ rather than status.

Finds relating to personal adornment and grooming practices greatly increase in the Late Iron Age. Mirrors could be part of both private acts of grooming and public performance. Looking at your own reflection in a mirror is a natural response to greater interest in the body. Social norms and ideals were changing and this could have affected relationships between people.

Mirrors may have had uses beyond personal grooming, perhaps used in rituals of divination. A mirror can be used to see behind or beyond the person, even to communicate over large distances. It can catch and reflect light outwards. The surface may also replicate the otherworldly, shimmering boundary of water, relating back to an earlier prehistoric tradition of depositing metalwork in watery places.

Changes over time and space can be seen. These may reflect different groups’ responses during the early contact period with the Roman empire. In East Anglia, as we have seen, they are extremely scarce. Large, intricately-decorated mirrors were abandoned by people in the southeast, yet continued in more westerly parts of Britain. A few Roman mirrors were already in use during the Late Iron Age, suggesting that some people had a range of options. The deliberate choices of material, size, style and decoration perhaps signalled identity, group allegiance or exchange networks.

Roman Mirrors

Roman mirrors were small, circular or rectangular, sometimes set within ornamental cases. They often have moulded decoration or punched ring-and-dot patterns around the outer edge of one face. Roman mirrors were made from ‘speculum’: a brittle, highly-tinned copper alloy. This material fragments easily and is often found in small straight-edged chips. Mirrors with handles date to the mid-1st to early 2nd century CE. Like many other forms of material culture, they fade from the archaeological record in the 3rd century CE.

Roman mirror fragment showing tinned surface and ‘snapped’ edges (source: PAS LEIC-111FE3, Leicestershire County Council, under CC BY 2.0 licence).

It is thought that all Roman mirrors were imported, suggesting local manufacture ended after the conquest, although some people continued to use and be buried with their Iron Age mirrors. Perhaps imported mirrors were superior in reflectiveness, or were less valuable and more available than the ornate one-off Iron Age types. The two types of mirror may simply have been used in different social situations.

CountyQuantity
Cambridgeshire3
Norfolk104
Suffolk49
Total156

Table: Roman mirror fragments by county.

Unlike Iron Age examples, Roman mirrors are widespread in East Anglia. Using data from the PAS and the county Historic Environment Records (HERs), 156 Roman mirror fragments were recorded (original database including HER records closed April 2017, PAS records updated January 2019). Norfolk produced 104 fragments, with clusters from parishes with religious and/or urban centres of the period, including Caistor St Edmund (6), Walsingham (22), Wicklewood (26) and Wighton (5). At the important local capital of Venta Icenorum (modern Caistor St Edmund), a decorated circular mirror was found pre-1894 just outside the walls (Norfolk Museums Service: 1894.76.717, for image see http://www.norfolkmuseumscollections.org/collections/objects/object-3654695206.html/#!/?q=Caistor) and part of a hinged bronze mirror was excavated in 1957 at the nearby temple (NHER: 9787), which may suggest ritual use. Two joining fragments were excavated within the town itself during Donald Atkinson’s investigations in 1929.

Joining fragments of a circular mirror, Caistor St Edmund (source: Norfolk Museums Service 1929.152.M17, Author’s photo).

In Suffolk, there were finds from the Romano-British small towns at Pakenham (6) and Wixoe (5), along with Scole, on the modern border with Norfolk (6). There were several mirrors recorded in the late 19th and early 20th centuries, including a ‘speculum’ from Felixstowe (SHER: FEX092) and circular mirrors from Long Melford (SHER: LMD020) and Herringswell (SHER: HGWMISC). Cambridgeshire has very few records of either Iron Age or Roman mirrors, which may be due to historical differences in reporting practices between the counties.

Distribution of Roman mirrors (source: PAS 2019).

Roman mirror finds on the PAS database are highly concentrated in the Eastern counties. The lack of Iron Age mirrors in the region makes this concentration even more unusual. Recovery bias is an important factor to be considered. During data collection in the Norfolk HER, I noted that a small number of metal-detectorists regularly reported speculum fragments. Plotting mirror fragment findspots confirmed this. The distribution is skewed heavily in favour of three key detectorists. Almost one third of mirror finds reported in Norfolk were made by Finder 1, another third by Finder 2, while Finder 3 found seven pieces all in the same parish. The concentrations reflect their search areas and ability to recognise mirror fragments by their distinctive sharp ‘snapped’ edges and the highly-tinned metal. The Suffolk and Cambridgeshire finds did not show any notable recovery bias.

Roman mirror finds showing detectorist hotspots in Norfolk (source: Author).

This demonstrates that the knowledge of individual metal-detectorists has an important effect on the artefacts recovered and reported. Training for other finders (and recorders) would surely increase the known quantities and coverage. This pattern, while unusable for distribution analysis, other than to confirm that people were using Roman-style mirrors in Norfolk, is telling of the processes of recovery for metal-detected finds. It is worth remembering that one mirror can shatter into many fragments, so the numbers of whole mirrors would be considerably smaller. This finding may also have a bearing on excavated and museum finds: mirror fragments are hard to recognise, although once you know what to look for, they are unmistakeable!

Roman mirror case with bust of Nero, Coddenham (©Trustees of the British Museum 1838,0331.1, used under CC BY-NC-SA 4.0 license).

Representations on Roman tombstones often show women holding a mirror, with attendants helping them dress or doing their hair. However, two circular cases containing convex mirrors were found in a cremation urn at Coddenham in Suffolk in 1823. On the outside are motifs based on a coin of Nero. One case shows the emperor’s head in profile, and the other an ‘imperial Adlocutio’, an image of the emperor addressing his assembled troops. This ‘male’ and military symbolism indicates that the use of mirrors in the Roman period was not restricted to women. Adlocutio imagery is also found on brooches deposited at the Romano-British shrine at Hockwold-cum-Wilton, suggesting a religious connection.

Stanley Avenue, Norwich

In continuity with Iron Age funerary practices, there are very few early Roman burials in northern East Anglia, although the southwestern area, particularly Cambridgeshire, shows a different tradition had taken hold. Perhaps some local communities were resistant to the practice of burial in the early part of the occupation, while others embraced it. Interestingly, a few early Roman burials do include mirrors.

Density of Late Iron Age and early Roman burials in East Anglia (source: Author).

Two cremation burials from Stanley Avenue, Norwich (NHER: 550) date to around 65-70 CE, a few short years after the turbulent time of the Boudican revolt. In one, the cremated remains of an adult human (interpreted as female) and bones from the right-hand-side of a pig were accompanied by coins of Nero (64-66 CE), a blue glass bead, and a circular copper alloy mirror. The latter had a highly-polished surface, a decorative border and handle, and was found with the remnants of its wooden case. The mirror had been deposited while the bones were still hot from the cremation pyre, and the case, despite being charred, retained traces of Pompeiian red paint.

The second cremation also included adult human and pig bones, and a fragmentary Thistle brooch, dating from the early to mid-1st century CE. With both cremation burials were flagons and platters. Do these materially wealthy burials show us that people in the Iceni territory were adopting the traditions and belongings of their conquerors?

These burials may represent a hybrid ceremony which combined elements of both local Iron Age and imported Roman traditions. The inclusion of the mirror in a cremation burial with pig bones was an Iron Age practice, but the material culture is distinctively Roman and probably imported. In this scenario, the mirror may be understood as an indicator of difference rather than status. This woman and her companion were being marked in death by their community, for despite the introduced materials, there is nothing to suggest that they themselves were not local. The revived practice of burial and the imported objects would have been distinctive, perhaps representing the ‘otherness’ of those individuals, or a way for their community to rationalise the political turbulence of the invasion and rebellion.

Natasha Harlow, University of Nottingham, 2019.

Further Reading

For more information on sites with NHER codes see Norfolk Heritage Explorer http://www.heritage.norfolk.gov.uk/, SHER codes see Suffolk Heritage Explorer https://heritage.suffolk.gov.uk/ and PAS object records see https://finds.org.uk/database.

Allason-Jones, L. 1989. Women in Roman Britain. London: British Museum Press.

Anon. 1951. Roman Britain in 1950. Journal of Roman Studies 41(1-2): 120-145.

Davies, J. 2011. Closing Thoughts, 103-105 in J. Davies (ed.) The Iron Age in Northern East Anglia. BAR British Series 549. Oxford: Archaeopress.

Davies, J. 2014. The Boudica Code, 27-34 in S. Ashley and A. Marsden (eds.) Landscapes and Artefacts. Oxford: Archaeopress.

Eckardt, H. 2018. Writing and Power in the Roman World. Cambridge: Cambridge University Press.

Eckardt, H. and Crummy, N. 2008. Styling the Body in Late Iron Age and Roman Britain. Montagnac: Monique Mergoil.

Gregory, T. 1991. Excavations in Thetford 1980-1982, Fison Way. East Anglian Archaeology 53. Gressenhall: Norfolk Museums Service.

Gurney, D. 1986. Settlement, Religion and Industry on the Fen-edge. East Anglian Archaeology 31. Gressenhall: Norfolk Museums Service.

Gurney, D. 1998. Roman Burials in Norfolk. East Anglian Archaeology Occasional Paper 4. Gressenhall: Norfolk Museums Service.

Harlow, N. 2018. Belonging and Belongings: Portable Artefacts and Identity in the Civitas of the Iceni. Unpublished PhD thesis: University of Nottingham.

Hutcheson, N. 2004. Later Iron Age Norfolk. BAR British Series 361. Oxford: Archaeopress.

Joy, J. 2007. Reflections on the Iron Age. Unpublished PhD thesis: University of Southampton.

Joy, J. 2009. Reinvigorating Object Biography. World Archaeology 41(4): 540-556.

Joy, J. 2010. Iron Age Mirrors. BAR British Series 518. Oxford: Archaeopress.

Whimster, R. 1979. Burial Practices in Iron Age Britain. Unpublished PhD thesis: Durham University. http://etheses.dur.ac.uk/7999/.

Figures

All maps credited to the author contain OS data © Crown Copyright and Database Right (2017) Ordnance Survey (Digimap/Opendata Licence). Roman road and coastline map layers were kindly provided by Katherine Robbins (adapted from Ancient World Mapping Centre 2012, DARMC Scholarly Data Series 2013, English Heritage, Fenland Survey 1994, and Norfolk Archaeological Trust 2012–6).