Making a Silver Pot

Seuso silver situla or finger pot known as Hippolytus situla B, photo by Judit Andras-Kardos, Magyar Nemzeti Múzeum

In our last post, we were introduced by St. Augustine to the practices of fourth- and fifth-century Roman silversmiths. Augustine compares argentarii to pagan gods, who are all great at one thing. He would have preferred a single perfect artisan, competent in all areas. Let us now consider the production of a single object, created by many artisans during Augustine’s lifetime (CE 350-430).[1]

The object we have chosen is a situla, literally a bucket, in this case a small pale, surely a finger pot for washing hands at the dinner table. It is around nine inches (23cm) high. We have chosen it because there has been an excellent recent analysis of it, and objects with which it was found. It is part of a large hoard of silver, the Seuso Treasure – mainly highly decorated plates, jugs, and dishes – now displayed at the Hungarian National Museum, Budapest. This analysis allows us to make the observations that follow.

There are, in fact, two situlae showing complementary scenes from the story of Hippolytus and Phaedra. The situla we have chosen, Hippolytus situla B, comprises several elements, all of which required expert smithing.

Let us posit the following process of production: Silver was melted down, either from ingots or, far more likely, existing objects and coins were recycled; two silver sheets was formed by pouring the molten silver into a mould; a smooth inner liner, and the outer shell of the piece were formed from these sheets of silver by a vascularius. The inner liner was set aside, and the outer shell was then given its exquisite chasing, the scenes of Hippolytus and Phaedra, by a caelator. A flaturarius formed the lower and upper framing bands, the base, and perhaps the beaded rim. However, the beaded rim may have been made elsewhere since, as we shall see, it has a somewhat different silver content. In any event, it was formed with a punch. A crustarius formed the three feet in the form of gryphons, the two decorative handle ornaments, which are busts of emperors, and probably also the lozenged handle. This was done using the lost wax casting technique. The various elements – inner liner, outer shell, handle, feet, etc. – were soldered together. An inaurator then added gilding, including the golden sheen on the figures’ clothes, hair, and other features of the landscape, the bands at the base and upper rim. Finally a tritor buffed it to a high sheen.[2]

Each of these silver-workers worked in an atelier that was, let us imagine – excavations suggest we would not be far not wrong – hot, full of fumes, and had poor ventilation. The melting of metals released various toxins into this workshop, while other escaped through chimneys, spreading across the broader city, its hinterland, and many miles beyond. Silver itself is relatively benign. Repeated exposure to silver particles causes the skin and body tissues to turn grey or blue-grey, a condition known as “argyria.” Ingesting high levels of silver may cause the heart to enlarge and stomach irritation, and breathing in silver particles causes throat and lung irritation. Copper was added to a great deal of Roman silver plate, to improve its mechanical properties. That is, adding copper makes the silver harder, more durable, and easier to work mechanically (i.e. with a hammer, rather than casting). Today we know the silver-copper alloy as sterling silver (typically 92.5% silver, 7.5% copper).

XRF analysis of the Seuso situla shows that the body, handle and feet all contains between 2% and 3% copper, compared to around 95% silver. However, the upper beaded rim, has much less copper, no more than 0.5%, with 99% silver. This tells us that molten copper was added to the silver after it was refined to ensure it was better able to withstand hammering, shaping and chasing. Exposure to copper fumes “causes upper respiratory tract irritation, metallic taste, nausea, and metal fume fever.”[3]

The same XRF analysis shows that each piece of the situla contains very small amounts of lead, between 0.2 and 0.5%. All Roman silver contains lead, usually between 0.5 and 1%. It took a little effort to refine silver to that standard, by a process known as cupellation. It took a great deal more to refine it still further. Evidently, the silver in this situla was refined again to produce very high quality silver before the right amount of copper was added. This may have been done using a process known as liquation, whereby silver is melted together with lead, forming a lead-silver alloy that separates from other metals, including copper. This alloy is then subjected to further cupellation. Roman silver production, including recycling, always involved a great deal of lead. Melting lead releases lead aerosols that are highly toxic.[4]

There was, however, something even worse than lead in the workshop, and its immediate vicinity: Mercury. The XRF analysis has identified mercury in the thin layer of gold applied by the gilder. This proves he used a method known as fire gilding, whereby liquid mercury is mixed with gold and then heated, releasing the mercury into the atmosphere and adhering the gold. Mercury is a powerful neurotoxin, ultimately deadly to the fire-gilder. It is “toxic to the central and peripheral nervous systems. The inhalation of mercury vapour can produce harmful effects on the nervous, digestive and immune systems, lungs and kidneys, and may be fatal.”[5] Like lead aerosols, mercury was carried away by the wind and deposited by rain, contaminating the soil and vegetation many miles from its source. A recent study of Roman age skeletons in Spain, over a 70-year period, consistently had more than twice as much mercury and lead as bones of those who lived in the same place afterwards.[6] There is no indication that these were metalworkers. Rather, abundant evidence makes it clear that Roman-age metallurgy had a massive deleterious effect on human health and the environment.[7]

[1] The choice of the Seuso situla was entirely due to the excellent new publication: V. Mozgai et al., “Non-destructive handheld XRF study of archaeological composite silver objects – the case study of the late Roman Seuso Treasure,” Archaeological and Anthropological Sciences 13:83 (2021), 20 pages.

[2] D. E. Strong, Greek and Roman Gold and Silver Plate (Ithaca, NY: Cornell University Press, 1966), 7, 14-16. On silver beaded rims see Richard Hobbs and Laura Perucchetti, “Beaded rims on silver plate vessels in late Roman Britain and beyond,” Britannia 53 (2022), 385-401.

For an instructive video on the creation of a Roman silver cup:

[3] CDC:

[4] Very generally, see Paul Stephenson, “Ancient Roman Pollution,” Lapham’s Quarterly, February 23, 2022.

[5] The approach to this sad fact to date is captured in a sentence by a scholar of silver-smithing: “[Fire-gilding] is a durable and economical use of gold, and the health hazards of mercury were not given the consideration that they are today.” See The Hoxne Late Roman Treasure: Gold Jewellery and Silver Plate, ed. Catherine Johns (London: British Museum Press, 2010), 186.

[6] O. López-Costas et al., “Human bones tell the story of atmospheric mercury and lead exposure at the edge of the Roman world,” Science of the Total Environment 710 (2020), 136319 (7 pages). Here bones from two adjacent cemeteries at A Lanzada in northwestern Spain showed that Romans (first to fifth centuries CE) absorbed twice as much lead and mercury as those who came later (fifth to seventh centuries). Isotopic analysis suggests that 70- 80% of this came from atmospheric lead pollution (and the remainder from local geogenic lead sources).

[7] J. Montgomery et al., ‘“Gleaming white and deadly”: using lead to track human exposure and geographic origins in the Roman period in Britain’, Journal of Roman Archaeology, supplementary series, 78 (2010), 199-226, at 209: “From the 1st c. A.D., some individuals exhibit enamel lead concentrations of up to 30 mg kg-1. These individuals have a level of lead that is 10,000 times higher than that of the least polluted individual in this study: the Early Bronze Age skeleton from Gristhorpe (Yorkshire) (3 μg kg-1; Table 11.3). According to the ratio above, an enamel lead concentration of 30 mg kg-1 would arise from a blood lead level of c.300 μg dL-1, which is far higher than the ~100 μg dL-1 associated with “very severe poisonings”. J. Moore et al., ‘Death Metal: Evidence for the impact of lead poisoning on childhood health within the Roman empire’, International Journal of Osteoarchaeology 31 (2021), 846-56: “This study includes 173 individuals (66 adults and 107 non-adults) from five sites, AD 1st–4th centuries, located throughout the Roman Empire. Results show a negative correlation between age-at-death and core tooth enamel lead concentrations.

This is the third and last of three posts that formed part of a short lunchtime lecture delivered at the Humanities Institute, Pennsylavania State University, in February 2023.

Pewter in Late Roman Britain

Pewter jug in the Ashmolean Museum, Oxford

Pewter in Late Roman Britain       

Tin was less abundant and more expensive than lead in late Roman Britain, but it was still mined and widely available. Objects manufactured in tin-lead alloys, called pewter in English, were increasingly common. Of the more than 400 pewter vessels known from Roman Britain, most have been dated to the fourth century. Moreover, the high tin alloys are dated earliest, with increasingly leaded alloys predominating in the late third and fourth centuries. A higher proportion of lead than tin made pewter vessels both more durable and less expensive, but also to most purchasers less desirable. Pewter ingots were made and circulated. However, there is clear evidence for conscious choices made by pewter smiths, with different alloys employed in the casting of parts of vessels, for example the base of a dish having a higher lead content, whether for hardness and support or because the upper part with higher tin content would be more apparent to a viewer. The distribution of pewter finds suggests an active industry in the east of England, near Cambridge, where there are no tin or lead mines, but also activity in and near Bath, the Mendips, and further southwest, where there are both.[i]

            The increased number of metal objects, including those in lead and pewter, may indicate increasing wealth in Roman Britain in the fourth century, and perhaps even a wealthier middling sort, beneath those who built ever more and larger villas in that century, frequently with beautiful mosaics. However, it is most clearly an indication of the abundance of lead available, whether from new smelting or the recycling of existing materials. This lead, and pewter, made its way to northwestern Europe, where it has been identified in numerous contexts from the fourth century until the tenth, including pewter mounts from the Viking ship burial at Gokstad (dated CE 895-903).[ii]

[i] N. Beagrie, ‘The Romano-British pewter industry’, Britannia 20 (1989), 169-91; R. Poulton and E. Scott, ‘The hoarding, deposition and use of pewter in Roman Britain’, Theoretical Roman Archaeology Conference 4 (1993), 115-32; J. Hall, ‘Public, personal or private? Roman lead-alloy ingots from Battersea’, in ‘Hidden histories and records of antiquity’: Essays on Saxon and Medieval London for John Clark (London, 2014), 116-21; Bayley, ‘Roman non-ferrous metalworking’, 332, 334, 336-7. A new study is promised based on the British Museum collection: L. Smith, Pewter in Roman Britain (London, forthcoming).

[ii] U. Pedersen et al., ‘Lead isotope analysis of pewter mounts from the Viking ship burial at Gokstad: On the origin and use of raw materials’, Archaeometry 58, suppl. 1 (2016), 148-63. For Roman-period finds in France, Belgium, and the Netherlands, see Beagrie, ‘Romano-British pewter’, 179-81.

Slave Makers

inscribed pot made by enslaved potter dave (david drake)

Hear Me Now, an exhibition at the Metropolitan Museum of Art, opened this month. A wonderful video allows us to hear the thoughts and reflections of the curators. More importantly, through the art they have curated we are able to hear the voices of the makers, enslaved potters of great skill, put to work at Edgefield in South Carolina. As slaveholders and their enablers tightened laws aimed at restricting literacy, these makers spoke eloquently in local clay, the same kaolin (porcelain clay) that they and their families had worked, or still worked, in West Africa. More than this, they wrote on the pots they threw. Dave, a potter of immense talent, also wrote poetry.

In highlighting the reliance on highly skilled slaves in artisan production, the exhibition reminds us that the antebellum South was far from unique. Slavery has been ubiquitous in human history and we have no way of knowing, in almost every case, whether a work of pre-modern art was produced by an enslaved person.

It was certainly the case in the Roman world that skilled slaves made almost everything, frequently alongside those who had been freed and those who were born free.[i] Private slaves and freedmen were also employed in countless artisanal contexts.[ii]

Enslaved artisans led hard lives, but typically did so in far better conditions than those endured by industrial and agricultural slaves. I highlight here metal communities, since they extracted and smelted the ores to produce metals worked in countless smithies and workshops by artisans. Miners and smelters were frequently imperial slaves, perhaps criminals or prisoners-of-war condemned to their profession, but also those who happened simply to born to miners, and therefore were bound to the mines. A section of the Theodosian Code (CTh.), a compilation of laws produced in the 430s, entitled De metallis et metallariis, addresses the regulation of mines and miners, metals and metal-workers, and stone quarries. A law of 424 (CTh. 10.19.15) ruled that “if any person should be born from a miner and from any other stock, he shall necessarily follow the ignoble birth status of a miner”. Moreover, if miners should “seek to migrate to foreign parts, they shall be recalled to the family stock and the household of their birth status”. There was by then an established body of law relating to the flight of indentured miners, starting with a ruling of 30 April 369, which instructed provincial judges to provide support in identifying and apprehending vagrants (CTh. 10.9.5).[iii]

[i] The vast bibliography can be entered via N. Lenski, ‘Violence and the Roman slave’, in The topography of violence in the Greco-Roman world, eds. W. Riess and G. Fagan (Ann Arbor, 2016), 275-98.

[ii] A related law, issued just a month or two later, suggests miners had absconded to Sardinia by ship, and that ships’ captains were liable for a fine of five solidi for each miner they helped to escaped. Evidently, the practice continued, and a further law of 378 returned to the matter of miners absconding to Sardinia, notably gold miners. There were certainly fewer slaves working the mines than in earlier centuries.

[iii] C. Hawkins, Roman artisans and the urban economy (Cambridge, 2016), passim, especially 84-5, 87, 89, 91-2, 97, 126-8, 130-91.

Lead pollution, modern and ancient (1 of 2)

A recent study has demonstrated that lead pollution has damaged the health of half the population of the USA. Lead can be inhaled or ingested. Between 30% and 50% of inhaled lead particles remain in the body, compared to 5-10% of lead particles that are ingested by adults. Lead is equally toxic however it enters the body, and it is especially dangerous for the growing bodies of children, which absorb far more ingested lead (40-50%). For more than a century, lead in paint and later in gasoline has exposed children to a lethal toxin in their homes and streets. (We shall look at lead in paint in another blog post.)

Every person alive today who was born before 1980 has suffered known or unknown effects from breathing the fumes of the gasoline additive tetraethyl lead (TEL). Millions have lived with or died from conditions without knowing that exposure to historical lead pollution may have contributed to them, including cognitive impairment, intellectual disability, and cardiovascular disease.

Despite knowing from soon after its introduction in the 1920s that burning leaded gasoline was deleterious to human health, the fuel additive, which boosts octane and reduces the likelihood of pre-ignition (“knocking“), was only fully banned for regular automobiles in the USA (and Germany) in 1996, following similar bans in other countries. It was only last year, in July 2021, that the last leaded gasoline was used in automobiles in Algeria. Moreover, leaded fuel is still used in aviation and in motorsports. Aviation (the use of “avgas”) emits more than half of the annual lead pollution in the USA, and children who live near airports suffer disproportionately. Although the most popular motor-racing organizations in the USA, NASCAR and ARCA, switched to unleaded fuels in 2007, it remains in common use.

A recent study has suggested that a single three-hour track race can release as much lead into the atmosphere as an average airport does in a year, causing atmospheric lead pollution to jump more than 20% in locations up to 50 miles from the track and persist for up to four weeks. The same study argues that the “social cost” of a burning a gallon of leaded racing fuel, which retails for $10-$20, is $110,000 per gram of TEL added (which varies, and is hard to identify precisely, but appears to be between 4 grams [medium, 110 octane] and 6 grams [high, 116 octane or more] per gallon).

The UK was a laggard in cleaning up its petrol, implementing a full ban only in 2000. Due to lead’s ability to persist in the environment, it has been shown that two decades later “lead deposited via gasoline combustion still contributes significantly to the lead burden in present-day London”. Likewise, in the USA, many studies in smaller and larger urban centers, from Appleton, WI, to Durham, NC, to New Orleans, LA, have shown the persistence of lead pollution in urban soils and argued for necessary remediation.

Cleaning up historical lead contamination, which is expensive and whose costs generally fall on communities and municipalities rather than state and national governments, has rarely been a priority, and therefore historical lead contamination remains a feature of urban environments. The same holds in rural settings.

The use of leaded fuel to run agricultural equipment was phased out less quickly than for regular automobiles in the USA. A presidential report published in 1986 recognized that a great deal of expensive farm equipment would have been damaged (“valve-seat recession“) if run on unleaded fuel. A shift to diesel-powered equipment — diesel was never leaded — took off at that time, but it has not been without significant health consequences for farmers. A further shift to electrification may be slower still because of the high power-to-weight ratio required to run of heavy farm equipment.

Lead from historical pollution remains a minor threat to our soil and food supply. Furthermore, lead (and other heavy metals), which was present in widely used commercial fertilizers, is now less of a problem. However, one must imagine that crops grown near sources of lead pollution, which today include airports and racetracks, remain problematic. Lead fixes in the top 2-5 cm of soil, but regular cultivation will drive it lower into the soil. Unfortunately, this is the root zone for many crops. Lead is drawn from the soil into these crops, and hence is ingested when eaten. There is more to do, therefore, but also an increasing recognition that it must be done even where local resources are inadequate.

Despite the foregoing gloom, there has been amazing progress in removing lead from urban and rural contexts, improving the health prospects of today’s children. Today, children ingest far less lead in their food even as they inhale far less than their parents and grandparents did as children. If lead in water and paint remain issues, modern governments have the knowledge and capacity to regulate and legislate necessary change. University and commercial researchers, large corporations and small businesses have embraced that change and taken it forward through innovation and investment. There are, of course, still local, regional, and national challenges, but the level of environmental lead pollution measured globally has fallen precipitously since reaching a global peak in the 1970s.

A series of graphs showing levels of historical atmospheric lead pollution as measured in ice cores
Graphs showing historical levels of atmospheric lead pollution as measured from deposits in ice cores. Reproduced from Longman, J., Ersek, V. & Veres, D. High variability between regional histories of long-term atmospheric Pb pollution. Sci Rep 10, 20890 (2020).

Historical levels of lead pollution are preserved in glaciers and revealed in extracted ice cores. These show that globally lead pollution reached increasingly higher peaks at various points over the past 2000 years. Alas, although falling rapidly, global lead pollution is still at historically high levels. Until the advent of leaded gasoline, each peak was associated with an increase in smelting and metallurgy. Conversely, the only return to something like a “background level” of atmospheric lead pollution has been associated with the demographic and economic catastrophe of the fourteenth century. Ancient Roman lead pollution reached its peak between 100 BC/BCE and CE/AD 100, which period marks the rise and fall of the Roman silver denarius.

Although recycling of lead was common, remediation of lead contamination was unknown in the pre-modern world. Hence, each additional peak in emissions added to environmental lead accumulation, which was far greater the closer one lived to a center for smelting. A good deal of evidence suggests that the Romans did not establish large settlements near mining/smelting facilities. However, recent research in Britain suggest this sensible rule was not universally observed. As yet to be published excavations near Charterhouse-on-Mendip in Somerset, one of the principal lead mining and smelting areas in Britannia, have uncovered a settlement of some size and wealth. It recently featured in a BBC archaeology show, Digging for Britain (season 9, episode 5).

Earlier field surveys at Charterhouse-on-Mendip had identified a substantial settlement, encompassing between 27 and 36 hectares (67-89 acres), which was continuously occupied until the fourth century CE, after which ceramic finds end. For some of the period of occupation it boasted an amphitheatre improvised from an existing earthwork. Clearly, this was not a peripheral mining colony occupied only by imperial slaves supervised by soldiers. It was, however, wholly reliant on imported food and fuel. Most significantly, there is no evidence for local agriculture to support the substantial settlement and related settlements at Priddy and Green Ore. This suggests clearly an awareness of the consequences of smelting on the local environment. [i]

Charterhouse-on-Mendip, where thin seams of galena (lead sulphide ore) exist near the surface of a limestone landscape, sits above a complex cave system. Mining is known at this site from pre-Roman times, and Roman slags contain up to 25% lead, more than a third of the original lead content before smelting. Whereas unprocessed galena is not soluble in water, roasted ore slag is more soluble and atmospheric fallout from smelting is highly soluble. Water permeating through the surface limestone into the caves has left clear indications of surface contamination in speleothems, mineral cave deposits formed from dripping water. One speleothem, in this case a stalagmite, suggests a peak in lead contaminants between CE 50 and 150, followed by a further and higher peak between CE 400 and 500, which falls away rapidly afterwards. This may relate to leaching from slag deposits after smelting activity had ended. However, it is also likely that mining and smelting continued in the Mendips for far longer than elsewhere, since it was known that these mines yielded the most silver. This is consistent with the continued but far lower levels of pollutants after CE 200 at bogs hundreds of miles to the north of the Mendips. There is no evidence for medieval reoccupation of the settlement at Charterhouse, which remained contaminated, but there was medieval mining activity. [ii]

If the most contaminated sites in Roman Britain were not used for arable or pastoral farming, still substantially increased levels of lead aerosols deposited across a broad region by precipitation will have affected bees and birds, fish and shellfish in polluted rivers and bays, cattle and sheep eating grass growing in contaminated soil. Lead entered the food chain and affected human health across northern Europe, hundreds of miles from smelting facilities. Consequently, many Roman children will have suffered in similar ways to modern children exposed to elevated levels of lead pollution and no efforts were made to remediate the environmental damage done by Roman-age smelting.

[i] M. Fradley, ‘The field archaeology of the Romano-British settlement at Charterhouse-on-Mendip’, Britannia 40 (2009), 99-122.

[ii] D. McFarlane t al., ‘A speleothem record of early British and Roman mining at Charterhouse, Mendip, England’, Archaeometry 56 (2013), 431-43.