Manufacturing Processes
The Mining Process
A valuable starting point for gaining insight into medieval metalware processes is Georgius Agricola’s “De Re Metallica” (1494-1555). Recognized as one of the pioneering scholars to systematically examine the properties and characteristics of minerals and metals, he authored the comprehensive treatise “De Re Metallica,” which was published posthumously in 1556. This seminal work holds immense historical significance in the realms of metallurgy and technology, serving as a fundamental point of reference for contemporary researchers and scholars.
Though his work gives us insight into early mining techniques and aids with our understanding of the practices of late medieval metalwork, he writes little about the manufacturing process of early bronze and brass items. Nonetheless, he offers important insight for those interested in the metalwork processes of the late Gothic period.
TheManufacturing Process
Manufacturing in the Burgundian Netherlands
The production of Gothic socketed candlesticks within the Burgundian Netherlands was concentrated in specific regions distinguished by their skilled artisans and access to extensive trade networks, employing established metalworking methodologies.
- Key Production Centers and Craftsmanship
The Meuse Valley (Mosan region), particularly the urban centers of Dinant and Bouvignes, is preeminent as the principal locus for brass and bronze production during the late medieval period. The appellation ‘Dinanderie’ itself originates from Dinant, attesting to the high reputation of brassware emanating from this area. Archaeological investigations in these towns corroborate extensive foundry operations, including specialized candlestick manufacture. Flanders, encompassing major commercial hubs like Bruges, also hosted significant metalworking activity, and candlesticks are frequently attributed to Flemish workshops.
Artisans in these centers possessed exceptional technical proficiency, and their products were highly esteemed and exported throughout Europe. Metalworkers likely organized into guilds or analogous associations, ensuring quality control and the transmission of craft knowledge. These associations sometimes maintained close affiliations with major patrons, including the Church and its large-scale architectural projects. The concentration of specialized expertise and resources in regions such as the Meuse Valley underpinned the area’s dominance in base metalware production. However, a significant disruption transpired in 1466 when Philip the Good besieged and subsequently destroyed Dinant, precipitating the dispersal of many of its surviving bronze casters. This event may have exerted considerable influence, potentially augmenting production in other centers within the Burgundian Netherlands or further afield, and possibly contributing to the diffusion of Mosan styles and techniques during the latter part of the Burgundian era.
- Material Sourcing
Notwithstanding the high level of indigenous craftsmanship, the production of bronze and brass depended substantially on imported raw materials. Copper, the primary constituent metal, was principally sourced from mining regions in Germany, such as the Harz Mountains. Tin, indispensable for the creation of bronze, was imported from England. Calamine, the zinc ore required for brass production, was available more locally, supplied by the Principality of Liège, geographically proximate to the Meuse Valley production centers.
This reliance underscores the critical role of established trade networks, facilitated by the political stability and economic strength of the Burgundian state and its major commercial centers like Bruges. The manufacturing hubs were thus strategically positioned not merely for local skills or resources like calamine, but also within a broader network ensuring access to essential metals from distant sources. The viability and cost-effectiveness of the industry were therefore intrinsically linked to the operational efficiency of these long-distance trade routes. Any disruptions or fluctuations in these supply chains could potentially impact material costs and availability, consequently influencing choices regarding alloy composition (e.g., the observed shift towards brass).
- Casting Techniques
Archaeological investigations, particularly those conducted in Dinant and Bouvignes, have yielded substantial evidence indicating that foundry processes constituted the core manufacturing methodology. Numerous fragments of clay molds, fractured after the metal solidified, have been recovered, permitting the reconstruction of the casting process. Notably, fragments specifically identified as candlestick molds represent a significant proportion (approximately one-third by mass in some early 15th-century Dinant sites) of the foundry detritus, suggesting a considerable degree of specialization in candlestick production.
Several casting techniques were likely employed by Netherlandish founders:
- Lost-Wax Casting (Cire Perdue): This ancient and sophisticated technique, documented by medieval authors such as Theophilus and later by Cellini, permits the creation of complex and detailed forms. It entails sculpting a model in wax, encasing it within a mold material (typically clay-based), heating the mold to melt and evacuating the wax (hence “lost wax”), and subsequently pouring molten metal into the resultant cavity. Following cooling, the mold is broken away to reveal the cast object. This method was utilized for high-status items like the early 12th-century Gloucester Candlestick and was undoubtedly accessible to skilled Netherlandish artisans for finer or more intricate pieces.
- Clay and Sand Molds: The archaeological prevalence of clay mold fragments confirms their widespread application. For simpler geometries or components, sand casting, involving the mixture of sand with clay or other binders to form a mold, was also developed during this period and may have been utilized. Another method evidenced in the Meuse Valley is direct imprinting, wherein a non-fusible pattern (e.g., wood or metal) is impressed into clay plates to create the mold cavity; this was deemed particularly suitable for producing the slender shafts of candlesticks.
The selection of techniques likely depended on the specific object’s complexity, the desired level of detail, production volume, and economic considerations. Lost-wax casting offered the highest fidelity, whereas direct imprinting or sand casting might have proven more efficient for simpler forms or larger production runs. The sheer volume of candlestick mold fragments discovered suggests that their production constituted a routine and possibly standardized aspect of foundry operations in the region. Advances in furnace technology, such as the blast furnace employing water-powered bellows to achieve higher temperatures, were occurring in Europe, potentially enhancing metal quality and casting efficiency, although their specific application to brass and bronze casting versus iron smelting in the Low Countries during this precise period necessitates further nuanced investigation. Traditional bellows-assisted hearths remained in use.
- Construction and Finishing
Gothic Netherlandish socketed candlesticks were typically constructed from multiple cast components. The most frequent configuration involved two primary parts: one section comprising the socket and stem, and a discrete base section. These components were subsequently joined mechanically. A common method involved casting the stem with an integral extension (tang) that passed through an aperture in the base; this tang was then hammered flat (peened) on the underside of the base, securely affixing the two parts. Screw threads may also have been employed in some instances, and soldering or brazing were established joining techniques for metalwork. More complex forms, such as certain pricket candlesticks or figural examples, could involve additional cast components.
After casting and assembly, finishing processes were crucial for achieving the final aesthetic appearance. Lathe turning was employed to refine the shapes of stems and bases, create crisp moldings, and produce smooth surfaces. Evidence of lathe tool marks, often discernible on the less-polished undersides of bases, confirms the utilization of this technology. Surfaces were then meticulously polished to remove casting flashes, file marks, and other imperfections, resulting in the clean lines and reflective finish characteristic of well-preserved examples. While extensive surface decoration was uncommon, some finer pieces might receive minimal engraving. This multi-stage process—casting in discrete parts, mechanical joining, and meticulous finishing including lathe work and polishing—represents a pragmatic and efficient approach to manufacturing these characteristic forms, balancing production exigencies with the aesthetic standards of the era.
The production of bronze and brass candlesticks in the Meuse Valley heavily relied on imported components. Copper, primarily sourced from the Hartz Mountains, and tin, essential for bronze production, was imported from England. Similarly, the Principality of Liège supplied calamine, the zinc ore crucial for brass manufacturing. Considering the substantial distance between the Meuse Valley and these vital sources of raw materials, one might question the logic behind establishing the valley as a hub for metalware production had it not been due to the remarkable skill and craftsmanship exhibited by the artisans inhabiting the Meuse Valley, who, for centuries consistently demonstrated their expertise in the field. Their exceptional proficiency was so highly regarded that their products were sought throughout Europe.
We are fortunate for the work of Nicolas Thomas, Jean Plumier and Marie Verbeek in conjunction with Maison du Patrimoine Médiéval Mosan, Public Service of Wallonia and the National Institute for Preventive Archaeological Research (France) whose archeological excavations of Bouvignes and Dinant, reintroduced us to the workings and manufacturing processes of these early metalworkers long since forgotten.
Through these excavations and sifting through numerous waste materials found in the various sites in Bouvignes and Dinant, Public Service of Wallonia and the National Institute for Preventive Archaeological Research (France) uncovered numerous items that give us insight into the extraordinary accomplishments of the craftsman of Dinant and Bouvignes.
The archaeological excavations of Bouvignes and Dinant yielded a substantial amount of waste, which could be categorized into two distinct production types based on the employed shaping techniques. The first method involves a foundry process, wherein liquid metal is poured into a mold, while the second technique relies on plastic deformation, primarily achieved through hammering. Identification of the foundry process used was facilitated by the discovery of clay mold fragments. These fragments, fractured after the solidification of the cast metal, enable the recovery and reconstruction of the manufactured objects by bearing the characteristic hollow imprint of the cast items. The foundry technique was prevalent in numerous workshops, in Bouvignes and Dinant. Among these sites, a remarkable quantity of approximately 24,000 mold fragments, weighing a total of over 730 kg (1,600 lbs), were meticulously recognized, identified, and cataloged. Tripod cauldrons constituted more than 64% of the total mass, with minimal variation in shape observed between the 13th and 17th centuries. Concurrently, the presence of candlestick mold fragments attests to the extensive production of candlesticks, particularly prevalent in the Dinant sites during the early 15th century.
These candlestick fragments account for approximately one-third of the foundry waste by mass. Nevertheless, the fragments of foundry molds that do not fit into these two production categories represent a mere 2.5% of the overall waste. This finding suggests a relatively limited and homogeneous production pattern, although some variability can be observed in the candlestick base designs. However, insufficient justification exists for constructing a chrono-typology solely based on these candlestick bases.The identified types predominantly exhibit contemporaneity, and any differences observed likely stem from the aim to offer a certain variety to the market, rather than indicating an evolutionary typology over time. Furthermore, it does not appear that the various types correspond to specific workshops.
The manufacture of candlesticks experienced a surge in popularity during the late 14th and throughout the 15th century, gaining prominence on the tables of affluent households. Notably, the production of these candlesticks exhibited a heightened emphasis on meticulous craftsmanship. Although sharing similarities in molding techniques with cauldrons, candlesticks showcased greater diversity in shape, often necessitating the employment of intricate mold production methods. The alloys predominantly used in their fabrication were brass, known for its vibrant yellow color, which conveyed a sense of luxury. However, to ensure accessibility and affordability, foundries commonly incorporated lead into the alloys. The finishing touches on these candlesticks were executed with great care, and extensive polishing was carried out to achieve refined surfaces.
In light of the question surrounding potential differentiating factors between the workshops situated in Bouvignes and Dinant, archaeological evidence fails to substantiate substantial distinctions.
Despite the backdrop of intense industrial and commercial competition, occasionally escalating into political conflicts and resulting in cannonball exchanges along the Meuse River, identifying specific differentiating characteristics between the workshops in the two cities proves challenging. Material findings contradict any narrative of divergence, as the materials employed and techniques utilized remained strictly homogeneous across workshops. Exclusive recipes, artisan secrets, or closely guarded techniques were not attributed to any specific workshop. Perhaps the only discernible indication of specialization, based on the analysis of foundry mold fragments, lies in the prevalence of cauldron production in Bouvignes and candlestick manufacturing in Dinant.
Within the realm of casting techniques, numerous intricate methods exist, encompassing two opposing yet occasionally complementary approaches: those utilizing a positive model crafted from a fusible substance, such as wax, and those employing non-fusible materials for the models. One of the most ancient techniques, known as the lost wax method, involves the creation of a wax model, subsequently encased in clay. Following the drying of the clay mold, it undergoes heating and firing. Due to the relatively low melting point of wax, it liquefies and escapes the mold, leaving behind an impression of the model within the clay. Into this cavity, liquid metal is poured, and upon solidification, the mold is fractured to retrieve the metal object, now bearing the shape of the original model.
The lost wax technique, a prevalent method employed in metalworking, is not without its limitations and costs. A significant proportion of the wax material utilized in this process seeps into the porous clay and undergoes evaporation, resulting in notable expenses. As an alternative, craftsmen resort to employing non-fusible materials for their models. Given favorable geometric characteristics, the model can be directly impressed between two clay plates. Subsequently, the plates are carefully separated to extract the model, which is then repositioned and meticulously reassembled along the parting line using clay. The actual casting occurs subsequent to the drying and firing of the mold. The direct imprinting technique, specifically the utilization of a positive model between clay plates, is commonly favored by Mosan founders, particularly in the creation of slender candlestick shafts.
