I. Craftsmanship Matters: The Medieval Silver-gilt Casket in the Cathedral Treasury of Trier and Its Goldsmithing Techniques in the Context of Cultural Entanglement

Introduction

The Cathedral Treasury in Trier, Germany, houses a unique silver-gilt casket decorated with high-quality ornaments in filigree and granulation on its corpus and lid, while the bottom plate is chased and shows medallions, scrolls, and fabulous creatures (Fig. 1–10).¹ Lacking figural scenes and inscriptions, to date the casket has received limited attention in research, and it has usually been mentioned only briefly in publications. Despite this relative neglect, over the course of the past 150 years, diverse suggestions have been made regarding the casket’s provenance, ranging from Byzantium, Moscow, the territory of the Golden Horde located along the Volga River, Mesopotamia, Syria, Egypt, Italy and Spain. As to the casket’s chronology, various suggestions have ranged from the eleventh to fifteenth centuries.²

The main aims of my research project were, first, to clarify the provenance and date of the object and, second, to explore the potential of these findings in relation to broader art historical discourse, especially on the topic of transcultural exchange during the Middle Ages. With these aims in mind, a research project was initiated that was funded by the Gerda Henkel Stiftung, Düsseldorf, Germany, and incorporated into the research programme of the Leibniz ScienceCampus Mainz/Frankfurt.³ In order to investigate the material composition and goldsmithing techniques, a collaboration was established with the Department of Scientific and Experimental Archaeology at the Leibniz-Forschungsinstitut für Archäologie Mainz (LEIZA) to analyse the casket’s materials, construction, and metalworking techniques.⁴

Since such in-depth investigations of material composition and technology are still the exception rather than the rule when it comes to goldsmiths’ works, it was a great opportunity to examine this contextless object. In this way, approaches from the perspective of art history, history, materials science, and technology complemented each other and together provided a dense chain of evidence to answer the question of the silver casket’s origin and date. In this contribution, I will present some of the research results with emphasis on the technical findings, which provide a crucial component in this investigation. Furthermore, this article generally aims to highlight the benefits of technical art history when it comes to understanding the medium of goldsmiths’ works, which were so often transmitted without historical context.

Description of the Casket

The silver casket consists of a rectangular corpus with a lid in the shape of a truncated pyramid and is closed with a silver peg that is crowned by a seated lion (Fig. 4).⁵ Additional features are the fragile handles on the sides and cast lion’s feet (Figs. 1, 7, 8). Weighing almost 4.5 kilograms and composed of high-carat silver, the gilded casket is constructed using a framework consisting of two layers of sheet silver for the corpus and the lid. On each side, openings were cut out from the double sheets of silver in the shape of rectangles and right-angled trapezesia, with the inner sheet left slightly broader. This way, the eighteen separately produced plates could be set into the openings and rest on the inner margins of the frame (see Fig. 9). An additional metal strip was attached to hold the plates in place as is typical for bezel settings. Small marks were incised on the inside of the plates to either indicate the exact location for each of the plates or to identify the maker, which were made separately, not in situ.

The eighteen plates are decorated with dense filigree and granulation, framed by a plait pattern that is interrupted in each corner by either a six-pointed star or a Solomon’s knot (Figs. 4, 5). The rectangular plates inserted into the front and back of the casket’s corpus are adorned with complex knots inscribed into round medallions with a double frame. Smaller knots arranged in roughly square shapes are placed in the corners on those plates inserted into the corpus, accompanied by Solomon’s knots. Variations of these complex knot motifs also decorate the plates inserted into the sides of the corpus and the lid (Figs. 1, 3). In addition, every space of the plates is filled with delicate spiral filigree and minuscule, flattened twisted wires bent in the shape of a little hook or worm (thus called “vermicular filigree”; Figs. 5, 6). The glittering, “pearly” surface was achieved through the addition of granulation work and the filigree by subtly varying heights of the decoration (Figs. 5, 6).

The structural framework holding the plates is decorated on the outside with a geometrical design of overlapping circles that form lanceolate intersections, punched into the metal surface (Fig. 4). This pattern is only interrupted by metal fittings around the lock at the front and the three hinges at the back (Figs. 1, 2, 4). The horizontal front fittings show winged, fire-breathing dragons, while the vertical counterparts show birds and cats of prey. The sole humanoid figure on the corpus and lid is the tiny leopard sphinx with a height of only 1.5 centimeters (Fig. 10), situated behind the lion on the closing peg. The fittings along the casket’s back are decorated with various birds (center) and floral motifs (sides).

Although usually not visible, the very thin bottom plate of the casket is also richly decorated with five large medallions filled with elegant scrolls and inhabited by animals and mythical beasts (Figs 7, 8), such as monocephalic double lions, griffins, three hares arranged in a circle and sharing three ears, and two crowned human-headed sphinxes with tails ending in dragons’ heads. This superbly chiselled plate is framed by a plaited band, visually linking the bottom plate with the plates of the corpus and the lid (Fig. 4).

Written and Visual Sources

Historical information on the silver casket in Trier is scarce. The first written source that can be related to it with confidence is a list of objects in Trier’s Cathedral Treasury dating to 1429. It contains an entry referring to an “exquisite” silver-gilt shrine with head relics of Saint Lazarus and Empress Helena, the latter’s skull surrounded by two gold bands and decorated with precious stones and pearls.⁶ This description is important for the history of Trier, as Helena was the revered mother of the Roman Emperor Constantine I the Great (r. 306–37 CE). Her palace in the Roman city of Augusta Treverorum, today Trier, was part of a large endowment to the church and laid the foundation of the architectural ensemble of the Church of Our Lady (Liebfrauenkirche) and the cathedral we see today. Relics of Lazarus of Bethany, who had been resurrected by Jesus according to the Gospel of John (11:1–44), are also mentioned for the church of Saint Paulin in Trier in an inscription dating to 1088, although it is not clear at what date the skull relic entered the cathedral.⁷

The reliquary mentioned in the list of 1429 is likely to be the silver-gilt casket in question, a depiction of which appears later on the Heiltumsblatt, an etching dating from 1655 (Figs. 11, 12).⁸ Although deviating in some details, the depiction clearly shows the same casket, labelled here as the reliquary for the skull of Saint Lazarus (Caput S. Lazari resuscitatia). In the Heiltumsblatt, the object is part of the distinguished group of relics in precious reliquaries surrounding the most revered of them all, the Holy Robe of Jesus Christ.

The cathedral treasure suffered considerably in the late eighteenth century, when many of the objects depicted in the Heiltumsblatt were melted down and the metal repurposed in order to finance the war against France. One of the surviving reliquaries depicted in the etching is the silver casket, which according to a list dating from 1794 was thought to be of no particular value and consequently saved from the furnace.⁹ Today, the material value of the massive silver casket becomes obvious when the lid of the casket is opened (Fig. 9). In the eighteenth century, however, the inside must have had a different appearance. Based on comparisons with other caskets, we can hypothesise that it was lined with textiles, obscuring its actual value.¹⁰ This could have led to the assumption that the silver casket’s core was made from wooden panels that accounted for its considerable weight, and that the amount of metal was not worth melting down. In any case, today, the object appears to be the only one of this kind that has survived.

Art Historical Evidence

Decontextualized from its original function, the casket is today an empty, somewhat dusty museum object that has left art historians puzzled regarding the questions of its origin and production date. Neither inscriptions nor iconographical themes provide intrinsic information, and the exact date of the casket’s arrival in Trier is unknown. As mentioned above, the only indication that the silver casket had already migrated during the Middle Ages is the 1429 inventory list, suggesting a terminus ante quem for the object.

Comparing the casket and its decoration with other artworks requires a consideration of European, Byzantine and “Islamic” art from a wide geographical area and broad chronological time span. ¹¹ Many of the ornaments on the silver casket were common in the medieval Mediterranean and far beyond. Interesting examples include the “Three Hares’’ motif (Fig. 8, top left), which can be traced back to sixth-century China¹² and illustrates the enormous popularity and longevity of certain motifs represented on the Trier casket. Others appeared as early as Roman antiquity, such as the “Solomon’s Knot” (see the small medallion in Fig. 5), but can also be found in twelfth-century art of the Mediterranean, such as the ivory covers of the Melisende Psalter, made between 1131 and 1143.¹³ The versatility of some of these ornaments is astonishing but understandable since they can so easily be adapted and reinterpreted beyond religious or political frameworks, thus extending their meaning towards archaeologist Oleg Grabar’s concept of a “shared culture,”¹⁴ especially with regard to the period under consideration here.

It is beyond the scope of this article to discuss all of the ornaments, let alone trace their origins, development, and distribution, which is only productive and relevant in some cases.¹⁵ Without additional contextual evidence, ornaments, animals, and hybrid creatures can be difficult to pinpoint¹⁶ and cannot per se yield solid information on the provenance and date of an object. However, it is not the single ornament, but the combination of the motifs on the Trier casket that helps in the reconstruction of the object’s origins. This evidence can be found in the arts of Sicily dated to the twelfth/early thirteenth centuries.¹⁷ For example, in the Cappella Palatina in Palermo, built by the Norman King Roger II (r. 1130–54), the interior combines Byzantine mosaics with a wooden Muqarnas ceiling. In both we find many relevant ornaments, such as complex knots and spiral scrolls (Fig. 13), lanceolate “petals,” as well as rows of intertwined medallions similar to those on the casket’s underside. Furthermore, the Muqarnas ceiling is decorated with star-shaped medallions (Fig. 14) that are again reminiscent of the medallions on the casket’s underside (Figs. 7, 8). Other comparanda are found in ivory works from Sicily and southern Italy, such as the group of c. ninety oliphants (ivory horns) that are often decorated with intertwined medallions and a similar range of animals and fabulous creatures.¹⁸ Further examples of medallions comparable to those on the silver casket’s bottom plate are found on representatives of the even larger group of so-called Siculo-Arabic ivory caskets (Figs. 15, 16).¹⁹ While these comparisons only provide part of the story relating to the Trier casket’s origin, it is remarkable how well the combination of motifs on the casket fits into the cultural sphere of Norman and Hohenstaufen Sicily. The suggested Sicilian origin for the Trier silver casket can be complemented and consolidated by materials science and especially the analysis of techniques.

Scientific Analyses of the Trier Casket

Earlier researchers’ difficulties in pinpointing the Trier casket’s origins are not surprising for several reasons: lack of opportunities for inspection, insufficient photographic documentation, and a far less comprehensive state of research. In particular, the first led to misunderstandings regarding the appearance of the solid-silver casket: for example, it had been assumed previously that the bottom plate was attached to the Trier casket at a later date due to supposed stylistic differences with the object’s corpus. It was further assumed that the casket was made from wood and only revetted with metal plates.²⁰ As discussed above, the misinterpretations had probably saved the casket from the furnace in the late eighteenth century .

Taking this previous lack of material information into account, it became essential to investigate the casket’s materials and goldsmithing techniques in order to answer the questions of whether the object is indeed an authentic, intact object and whether it shows signs of losses, additions, and repairs. To this aim, the object was analysed with different methods at the LEIZA: X-radiography was used to illuminate the casket’s structural components and production methods. X-ray fluorescence spectroscopy (XRF) yielded information on the chemical composition and revealed the metal alloys used in its creation. The object was studied further with photomicrography (see Fig. 10).²¹

The analytical methods cannot provide reliable information with regard to the age and the provenance of metals—at least not for the Middle Ages.²² However, the LEIZA analyses confirmed that the composition of the silver used for the casket is consistent throughout the entire structure of the object except for two brass nails used to repair a broken hinge at the back and a later copper nail in the bottom plate.²³ The silver content in all areas of measurement was shown to exceed 90% (all measurements were taken from spots where the gilding had been abraded). For example, it was found to be 98.04% in the bottom plate and 97.19% in the frame. Adding to this, the fire gilding used throughout was shown to contain a mercury content of c. 10–12%, a concentration that is also consistent throughout the object.²⁴ The analyses did not reveal any signs of later repair/re-gilding, as such changes would have been reflected through differences in the gold/mercury contents of the gilding. The latter result in particular provides very strong evidence that the whole structure of the casket was manufactured and completed as part of a single production campaign. In other words, the results indicate that all parts of the casket are contemporary to one another, with the possible exception of the lion peg, which offers some room for doubts.²⁵ The complete lack of visible traces of repair along the edges of the bottom plate—for example, one would expect solder remnants, loss of original gilding, or traces of re-gilding—speaks convincingly for the casket, including the handles, being intact.

Craftsmanship Matters: Comparing Goldsmithing Techniques

Having established that the Trier casket is, in fact, an intact, complete object, we now turn to its goldsmithing techniques, with the aim of further narrowing down its possible date and origin. For this, it is necessary to take into account the movement and exchange between crafts and the craftsmen who were active during this period and can thus be viewed as “agents of cultural entanglement.”²⁶

In discussing these cultural entanglements and the issue of craftsmanship, comparisons with artworks securely ascribed to this period of Sicilian history are essential.²⁷ Although no other caskets with filigree and granulation from Sicily appear to have survived from this date, details of the ceremonial sword of Frederick II (Figs. 17, 18) and the so-called Kamelaukion of Frederick’s wife Constance of Aragon are comparable. These two objects are decorated with pearls, enamels, and filigree, the latter characterised by wires shaped like little worms. This particular kind of decoration, referred to as vermicular filigree, is in turn characteristic of the Palermitan workshops from this period and was also used earlier on several objects from Sicily, such as the frames of the enamels on the coronation robe (1133/34) of the Norman King of Sicily Roger II.²⁸ Thus, vermicular filigree would have remained in fashion for about a century during the Norman and Hohenstaufen rule. More importantly, the same kind of filigree decoration is also found on the Trier casket (Figs. 4–6) and is in that detail remarkably similar to the works mentioned above.

Also worthy of mention is that the style of the granulation on the Trier casket is executed in a particular fashion: lines of granules are set into the grooves between two upright flattened wires, reminiscent of a so-called “marble run” (Fig. 6). This technique represents a very particular method of keeping the tiny gold spheres in place while soldering, but also raises the line granulation above the level of the spiral filigree, producing an undulated, glittering surface. A group of small belt fittings from Sicily (Fig. 19) match the casket’s style of granulation and filigree very well, including a strikingly similar glittering surface.²⁹ This fitting was attached to a blue silk belt (cingulum), which probably belonged to the coronation insignia of Roger II, dating from 1133/34, and thus would have represented the highest level of craftsmanship and taste at the Palermitan court. Although the star-motif on the belt fitting is different from the ornaments on the casket, the granules are set within a comparable “marble run.”

Generally, lines of round shapes, such as pearls, granules, and painted dots are visual hallmarks of twelfth-century Sicilian art, seen, for example, in the rows of tiny round holes on a rock-crystal lion’s head that can be attributed to Sicily (today in Karlsruhe, Germany).³⁰ Further examples are the rows of white pearls in Palermitan textiles³¹ and other pearl-embroidered objects (including a ceremonial sword of Frederick II; Figs. 17, 18), as well as the aforementioned painted, Fatimid-style Muqarnas ceiling in the Cappella Palatina, where lines of white indicate pearls to visually enhance the ceiling’s structure, adding to its layered morphology (Fig. 20).

The idea of placing granules in grooves is further characteristic of eleventh- to twelfth-century jewellery from the Fatimid Caliphate in Egypt (tenth to twelfth centuries), where the tiny gold granules are also set into a groove, usually between two parallel twisted wires (Fig. 21).³² This additional technical detail in turn provides vital clues relating to the Trier casket, revealing, through its miniscule details, a connection to Fatimid craftsmanship traditions. This is not surprising, since Sicily was under Fatimid rule during the tenth century and also became de facto an independent emirate in the eleventh century until the Norman Conquest (c. 1060–90).³³ Thus, the technical details discussed here fit well into the transcultural atmosphere of the Palermitan court, where Arabic craftsmen worked alongside artisans of Christian and Jewish backgrounds.

A final comparison with regard to the Trier casket’s goldsmithing techniques is with the large group of Siculo-Arabic painted ivory caskets, many of which also have a lid in the shape of a truncated pyramid.³⁴ Around three hundred of these objects are preserved in various museum collections and church treasures (see Fig. 15). They display the “profoundly Arabicized milieu of their production,”³⁵ again demonstrating how embedded Arabic traditions were in the arts and crafts of Sicily during this period.³⁶ This group is of special relevance for the Trier casket in one detail: some of the ivory caskets and other painted ivories bear painted decorations with large medallions similar to those on the bottom plate of the Trier casket (compare Figs. 8 and 16). To use a specific example, the ivory casket in the Benaki Museum in Athens (Figs. 15, 16) is decorated with medallions, the backgrounds of which are stippled with miniscule dots.³⁷ The medallions on the bottom plate of the Trier casket have similarly structured backgrounds made of tiny punched circles (Fig. 8).

This final observation further strengthens the arguments for the Trier casket deriving from the Palermitan royal workshops, while also shedding light on the large group of Siculo-Arabic ivory caskets and their production. It also shows that goldsmiths and ivory painters used a similar repertoire of motifs during this period, and that both would have been strongly connected with monumental art, such as the Cappella Palatina and its Muquarnas ceiling with the scroll-filled medallions. Furthermore, the technical detail of the Benaki ivory casket’s dotted areas in the medallions seems to indicate that the painters of ivory caskets looked towards metal prototypes for their inspiration. However, unlike ivory objects, metal pieces can easily be melted down and the materials reused, which is why few such objects remain.³⁸

The construction of the Trier casket is well thought out—including the assembly marks on the inside—and the indication that more than one goldsmith was involved in the making of the silver object hints towards a larger serial production of metal caskets.³⁹ With the Trier casket, it becomes possible to trace the remnants of a group of medieval luxury goldsmiths’ works that has nearly been lost.

Conclusion

Based on the analyses presented in this article, the available evidence strongly points towards the Trier silver casket originating from the cultural sphere of Palermo, sometime between the mid-twelfth to early thirteenth centuries. The analyses of the casket’s metal composition confirm that the physical structure of the object is intact, that is, complete and original to its initial production context. The comparisons of the motifs with other artworks attributed to Sicily and especially the particular execution of technical details (granulation and filigree) provide strong links with the craftsmen and workshops that were active within this particular artistic climate.

Sicily was one the most affluent regions of the period, enabling ambitious patrons to commission top-tier craftsmen with various religious and cultural backgrounds, including Christian, Jewish, and Muslim, to produce exceptional artworks. The multicultural, multivisual, and multilingual society is a hallmark of Norman Sicily, a characterisation that includes the craftsmen and artists working for the Norman rulers.⁴⁰ Amongst the masterpieces are objects in different media, such as silk, rock crystal, pearls, and precious metal.⁴¹ The Trier silver casket represents one such masterpiece, which as discussed can be linked to the Nobiles Officinae, the royal court workshops in Palermo, on the basis of comparisons with other artworks, especially its notable similarities with the shape and decoration of the large group of Siculo-Arabic ivory caskets dating from this period.⁴² These royal workshops at the Palermitan court were active for eight decades at least, from 1133/34 to 1190,⁴³ during the Norman Kingdom of Sicily (1130–1194; Roger II was crowned King of Sicily in 1130). In addition, these workshops are also likely to have remained active under the succeeding Hohenstaufen rule, at least until c. 1220 (and probably much longer than hitherto thought, to at least c. 1300⁴⁴). This is demonstrated by prominent objects discussed in this article, such as the ceremonial sword (Fig. 12) of Emperor Frederick II of Hohenstaufen (King of Sicily, 1198; King of Germany, 1212; King of Italy and Holy Roman Emperor, 1220–1250) and the so-called Kamelaukion of his wife Constance of Aragon, as well as fragments of her robe, all made around 1220.⁴⁵

We do not know precisely when and on what occasion the silver casket came to Trier, but the precious object fits well within the context of Hohenstaufen political diplomacy, which often involved valuable gifts for loyal allies. Frederick II in particular had the reputation of being very generous, which is considered a decisive factor in his success as a ruler.⁴⁶ That being said, it is tempting to assume that the casket was a gift from Frederick II to the Archbishop of Trier, Theoderich II (Dietrich von Wied, r. 1212–42), who was one of his loyal allies during the German throne controversy. This controversy ended in favour of Frederick II, who went on to become Emperor of the Holy Roman Empire in 1220.⁴⁷ However, this cannot be more than a hypothesis as explicit sources are not available. In any case, the silver casket has changed its function from what was very likely a secular object, perhaps a vessel to lock up valuables, to a reliquary, which in Trier contained important relics.

Beyond these specific technical and art historical results, this case study of a precious- metal object can further emphasise the importance of interdisciplinary collaboration between art historical, scientific, and technological methods and approaches. This is particularly important for mobile objects that have shifted over time in terms of their place and ownership—often already in the Middle Ages—as trade products, diplomatic gifts, or war booty. Many mobile objects that have survived until today are not infrequently contextless in museum collections and church treasuries, as well as the art market. Without intrinsic information helping to specify an object’s date and provenance (such as iconography or inscriptions), clarifying the origin and date can be difficult.

In the case of the Trier casket, art historical research from the past 150 years can be said to have reached a wall with regards to clarifying its origin and age. The extremely diverse suggestions that have been made for the Trier casket’s provenance particularly illustrate some of the limitations of traditional art historical approaches towards such an object. Art history as a discipline has historically tended to focus on so-called major or fine art (often represented by painting, sculpture, and architecture), as opposed to minor art, referring to artefacts and craft-based works in an often depreciative sense. Adding to this, art historians of the twentieth century and earlier have all too often demonstrated a preference for visual culture instead of material culture, on iconography instead of ornaments, thus creating certain hierarchies within mainstream research. These dichotomies—although challenged especially in recent decades—provocatively highlight problems encountered when studying objects belonging to the sphere of material culture, such as the casket presented in this article.

It is hoped that the collaborative approach demonstrated through this case study serves to highlight the benefits of interdisciplinary research, particularly within the context of art historical investigation. The result has been the rediscovery of a masterpiece belonging to the medieval art of goldsmithing from the court at Palermo during its heyday, while also adding another object to the landscape of transcultural entanglement, emphasising the significance of the medium of goldsmiths’ works within this discourse. The complexity of cross-cultural exchange in the premodern era has been demonstrated by many different studies, extending across various disciplines and research perspectives. Cross-media analyses have led to a deeper understanding of such exchanges, entanglements, and processes of globalisation on different levels: through mobile objects, their shape and function, iconography and style, as well as agents, such as gift-giving rulers, travelling traders, craftsmen, and pilgrims. An important differentiation must be added to these complex patterns of exchange between the decoration of objects and the specifics of its execution, something which can be observed in the details of the tradition of and the particular execution by the craftsman, in other words: craftsmanship matters.

AUTHOR BIO

Antje Bosselmann-Ruickbie studied art history and archaeology at Bonn University, Germany. Her MA focused on style and techniques of Byzantine architecture, and her PhD thesis on Byzantine jewellery won her two academic awards (Byzantinischer Schmuck des 9. bis frühen 13. Jahrhunderts, Wiesbaden: Reichert, 2011). Antje has been assistant professor at Mainz University and is currently at Gießen University, at the Institute of Art History. She is a fellow of the Royal Historical Society and an associate member of the Leibniz Science Campus Mainz/Frankfurt: Byzantium between Orient and Occident. Her research was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Fund), Deutscher Akademischer Austauschdienst (DAAD, Germany Academic Exchange Service), Gerda Henkel Foundation, Dumbarton Oaks Research Library and Collection, and others. Currently, Antje is working on a book project focusing on the object biography of the silver casket in Trier within the context of cultural entanglements in the Mediterranean and beyond. She has published extensively on Byzantine jewellery, goldsmiths’ works and enamels, on aspects of cultural entanglement in the Middle Ages, on Byzantine magic, and on the Middle Ages in popular culture, especially in Heavy Metal music.