Utrecht occupies a special place in medieval Dutch ceramic history. The earliest evidence for pottery production there dates to the late 12th century CE, and by the 14th century the town had joined Haarlem, Leiden and Breda as a major manufacturing centre supplying both local markets and wider regional trade. Its products have been recovered as far afield as Alkmaar, Haarlem, Dordrecht and Amsterdam. The workshops themselves clustered in the suburbs of Bemuurde Weerd and Tolsteeg, north and south of the town walls, and along the banks of the Vecht river, where excavations have uncovered nine vertical updraft kilns with brick or clay floors, round or oval in plan and measuring up to five metres long.

The excavated waste heaps tell a story of technological transition. The first production phase at Zeedijk, dated 1150 to 1175 CE, yielded almost exclusively grey, round-based jars. After an apparent hiatus of roughly a century, the second phase, from 1275 to 1350 CE, saw a wider repertoire including lead-glazed reddish tripod forms, jugs, bowls and pans, though grey jars remained dominant. By the third phase, represented by the Oosterkade workshop (1350 to 1400 CE) and riverside workshops such as Anthoniedijk, Hogelanden and Lauwerecht (1375 to 1425 CE), lead-glazed redware had become far more prominent, and unglazed and lead-glazed floor tiles were also being produced.

To characterise the raw materials and firing technology, the team subjected the 59 samples, plus one clay sample from a waste pit at Bemuurde Weerd, to a battery of techniques: polarised light optical microscopy, wavelength-dispersive X-ray fluorescence spectrometry, X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectrometry. Thin-section petrography revealed two main fabric groups, a Coarse Group with large, moderately to poorly sorted quartz inclusions and a Fine Group with smaller, better-sorted inclusions. The size, rounded shape and bimodal distribution of the coarse quartz grains suggest they were deliberately added as temper, most likely derived from fluvial deposits, consistent with the Holocene river clays of the region.

The chemical data, measured on 26 major, minor and trace elements at the Fitch Laboratory of the British School at Athens, showed a strongly homogeneous, silico-aluminous dataset pointing to local clay sources. Principal component analysis identified three compositional groups, with a large, homogeneous group A accounting for more than 70 percent of the samples. All the Utrecht products were made from calcium-poor, iron-rich clay, with calcium contents below 2.5 percent, and the chemical similarity between the fired clay sample and the pottery, despite differences in calcium, may itself be evidence of quartz tempering. X-ray diffraction confirmed the mineral assemblage of quartz, illite-muscovite, K-feldspar and plagioclase, with redware bodies generally containing more hematite than greyware.

Firing temperatures emerged as consistently low. Most of the ceramics, 44 of them, were fired below 800 degrees Celsius, while a handful containing the high-temperature minerals gehlenite, diopside and mullite may have reached roughly 850 to 900 degrees or slightly above. The co-occurrence of surviving calcite and dolomite with these high-temperature phases implies short soaking times in the kiln. The glazes told their own story: single-layered, transparent coatings up to about 250 micrometres thick, of very high to high-lead type, with lead oxide contents between roughly 51 and 69 weight percent. Comparisons of corrected glaze and body compositions indicate that potters mixed lead oxide with silica before application, and that the yellowish-brown to greenish colour came from iron in the glaze over the reddish ceramic body.

The most novel element of the study was the application of small-angle neutron scattering, or SANS, to the question of how the vessels were formed. Measured non-destructively at the YS-SANS instrument of the Budapest Neutron Centre, 38 jar samples yielded data on the orientation and alignment of nanoscale domains in the ceramic fabric, which record the forces applied during forming. Thirty-two samples showed high isotropy values, indicating disorganised internal structures characteristic of percussion-building techniques such as pinching, moulding or tamper-and-concave-anvil forming. Combined with the wheel-made traces on rims and necks, this points to a two-stage strategy the authors call percussion-wheeling: the body formed by percussion, then the neck and rim refined on a rotational device.

Only six samples showed the low isotropy and significant tilting angles diagnostic of other techniques. One redware jar from the second phase at Zeedijk proved to be coil-built and wheel-shaped, while five jars, from both Zeedijk and Oudenoord, were genuinely wheel-thrown, three with clockwise and two with anticlockwise wheel rotation. Notably, all the wheel-thrown examples date to the second production phase after about 1275 CE, confirming a previously observed typo-technological shift from grey hand-formed jars to reddish tripod forms. Contrary to common expectations, the potters did not favour fine fabrics for wheel-throwing; nearly all the wheel-thrown jars were made from the coarse fabric. The persistence of percussion-wheeling across the 100-year hiatus between the first and second phases suggests a conservative, culturally embedded technological tradition, one perhaps also suited to producing the round-based jar shapes that were difficult to throw on a wheel.

The study also cautions against reading forming techniques from surface features alone. Interior depressions often interpreted as fingertip impressions from moulding appeared on wheel-thrown vessels too, and may instead reflect hands supporting the vessel wall during brushing, while interior ridges below the neck, sometimes taken as evidence of added coils, also occurred on wheel-thrown jars and may result from clay displacement during wheel work. The reasons for discarding the wasters were largely firing failures: warping and cracking from overfiring, loosened tripod legs and handles, and glazes accidentally fired in a reducing atmosphere. Taken together, the results portray a production tradition defined by both continuity and change, in which local potters favoured iron-rich, calcium-poor clay, tempered it with river sand, fired at low temperatures, and gradually adopted wheel-throwing and lead glazing, offering archaeologists a new quantitative template for reconstructing medieval craft knowledge and its transmission.

Subject of Research: The production technology and chaîne opératoire of medieval greyware and redware ceramics from 12th to 15th century Utrecht, the Netherlands

Article Title: Advancing the chaîne opératoire analysis of medieval greyware and redware ceramics: A case study from 12th to 15th centuries CE Utrecht, the Netherlands

Article References: Borgers, B., Gait, J., Bajnok, K., Allepuz, E. T., Bajnóczi, B., Len, A., & Griffioen, A. (2026). Advancing the chaîne opératoire analysis of medieval greyware and redware ceramics: A case study from 12th to 15th centuries CE Utrecht, the Netherlands. Archaeological and Anthropological Sciences, 18(9), Article 194. https://doi.org/10.1007/s12520-026-02554-x

Image Credits: AI Generated

DOI: 10.1007/s12520-026-02554-x

Keywords: medieval pottery, Utrecht, chaîne opératoire, ceramic technology, greyware, redware, small-angle neutron scattering, lead glazes, petrography, X-ray fluorescence, pottery workshops, the Netherlands

An international team led by Alejandro G. Sinner of the University of Victoria, together with colleagues from the University of Barcelona, the Catalan Institute of Classical Archaeology, and the University of Cincinnati, analyzed 57 ceramic individuals dated between the late fourth and early first centuries BCE. Crucially, the samples came not only from domestic consumption contexts but also from production areas within Pompeii itself, allowing the researchers to compare presumed local wasters and workshop debris with the fine tableware Pompeians actually used.

The team employed a three-pronged analytical battery. Wavelength-dispersive X-ray fluorescence, or WD-XRF, measured the elemental chemistry of each vessel, while powder X-ray diffraction, PXRD, identified the crystalline mineral phases preserved in the fired clay. Scanning electron microscopy coupled with energy-dispersive spectroscopy, SEM-EDS, then zoomed in on the famous black slip itself, revealing its microstructure and composition at the microscopic scale. Together these techniques provide chemical fingerprints that can distinguish clay sources and reconstruct ancient firing practices in ways that visual typology never could.

The chemical results revealed a polygenic assemblage, meaning the pottery found in Pompeii did not come from a single source. Instead, the material separated into several distinct compositional groups. One major group was interpreted as local or regional production associated with Pompeii or its immediate surroundings, lending quantitative weight to the idea that the city supported its own black gloss industry. Other groups corresponded to additional Campanian productions, including the celebrated Campanian A ware from the Bay of Naples, and one widely distributed group documented across the Italian peninsula and the western Mediterranean that shows striking compositional similarity to the Pompeian group. The data also identified a production compatible with materials linked to the Etruscan city of Chiusi in Tuscany, underscoring Pompeii’s connections to trade networks stretching well beyond Campania.

The mineralogical and microstructural analyses opened a window onto the potters’ kilns. Most of the productions used calcareous clays, rich in calcium compounds, and were fired at roughly 900 to 950 degrees Celsius, precisely the temperature window required to produce a durable, well-sintered ceramic body for this class of fine ware. By contrast, the low-calcareous Campanian A pottery had been fired at temperatures below or around 800 degrees Celsius, a distinctly different technological recipe that reflects the particular properties of the volcanic Bay of Naples clays used in that tradition.

The black slip itself, the defining feature of the ware, told an equally nuanced story. All of the slips proved to be iron-rich and illitic, consistent with the established Black Gloss manufacturing tradition in which a fine, iron-laden clay slurry is applied to the vessel and reduced in firing to produce the characteristic metallic black surface. But the study revealed considerable variability in slip thickness, vitrification, and adhesion, particularly within the Pompeian group. That variability reflects differences in technological control from workshop to workshop, and perhaps even from potter to potter, offering a rare glimpse of quality differences within a single production tradition.

Perhaps the most consequential finding concerns the mismatch between archaeological classification and chemical reality. Typological attributions, such as assigning a vessel to the famous Cales production on the basis of its shape and style, did not correspond to single production units in the compositional data. In other words, similar-looking vessels were being made in multiple places. The results therefore support a model of decentralized production in Campania, in which numerous workshops exploited similar calcareous clay resources while maintaining distinct compositional and technological identities. This picture replaces the older notion of a few dominant production centers flooding the market with a monolithic product.

The study forms part of the broader MedConTaCCt project, Mediterranean Connectivity: Economy, Trade and Commercial Circuits in the Roman West, funded by the Social Sciences and Humanities Research Council of Canada. As part of that project, nearly 600 Black Gloss samples have now been analyzed from consumption centers across the Italian peninsula, including Populonia, Pompeii and Gabii; from Sicilian sites such as Monte Iato and Morgantina; from southern French sites including Narbo, Loupian and Lattara; and from a string of Iberian ports and inland towns from Emporion to Valentia. The Pompeii dataset thus plugs into a vast comparative framework that allows individual vessels to be matched against reference groups spanning the entire western Mediterranean.

For archaeologists, the implications extend well beyond ceramics. Black Gloss pottery is one of the most common dating and diagnostic artifacts in Hellenistic and early Roman sites, and assumptions about its origin underpin reconstructions of trade routes, market systems and economic integration. Demonstrating that Pompeii participated actively in production, not merely consumption, positions the city as a node in regional supply networks decades before it became the famous Roman colony of the imperial era. The results also refine interpretations of how technological knowledge, particularly the demanding reduction-firing technique behind the black slip, spread among workshops that shared raw materials yet preserved their own manufacturing signatures.

The full dataset is being released in open access through the SMART database, the Server for Mediterranean Archaeometric Roman Tableware, ensuring that future researchers can test and extend these compositional groups as new samples accumulate. As the chemical atlas of Black Gloss pottery grows, the humble black-slippered cup on an ancient table is proving to be one of the most informative tracers of economic life in the Hellenistic and early Roman Mediterranean, and Pompeii, it turns out, was making its mark on that world long before the eruption preserved it in stone.

Subject of Research: Archaeometric provenance and technology analysis of Black Gloss pottery from Pompeii

Article Title: Made in Pompeii? New insights into the production, consumption and distribution of black gloss pottery

Article References: Made in Pompeii? New insights into the production, consumption and distribution of black gloss pottery. (n.d.). https://doi.org/10.1007/s12520-026-02542-1

Image Credits: AI Generated

DOI: 10.1007/s12520-026-02542-1

Keywords: Pompeii, Black Gloss pottery, archaeometry, WD-XRF, PXRD, SEM-EDS, Campanian A, ceramic technology, provenance studies, Hellenistic trade, decentralized production, Roman ceramics