Jede Menge Kalkstein – Archäometrische Untersuchungen an mittelalterlichen Gussformen aus Magdeburg

Stone moulds from the late Romanesque - early Gothic Magdeburg. Archaeometric and experimental archaeological studies of medieval pewter casting on selected artefacts

"Of the approximately 500 different stone moulds which came out of a high medieval goldsmiths from Magdeburg/Germany, 45 pieces could be examined in detail. The primary goal of the archaeometallurgical and experimental archaeological examinations was to determine the use of the moulds as well as the sort and provenance of the rock material used. Therefore it was possible to extract wedge and powder samples of the rock as well as remains of metal. Moreover all moulds had to be checked with regard to traces of use. Additionally casting and glowing tests were carried out with the potential mould material to study its behaviour under different casting and temperature conditions. The petrographical examination of thin sections from 15 stone samples with transmitted- and direct-light microscopy and the examination of rock powders has shown the use of a fine-grained Jurassic and/or Cretaceous marly limestone. For it the so called »Plänerkalkstein« of the northern foothills of the Harz Mountains is most probable. But also the »Solnhofener limestone« of the southern part of the Franconian Jura has to be considered. Because there are no discolorations within the pouring system of all moulds it is clear that they cannot have served for the founding of bronze, gold and silver, which is confirmed by the results of the casting experiments. With energy dispersive X-Ray fluorescence analysis, light and scanning electron microscopy it could be shown reliably that 23 metal specimens of the cast system and several registration holes were made of pewter. Sometimes small amounts of copper might have been added to these tin-lead alloys. Because metal residues were available in the cast system at only six moulds, you cannot conclude on the general use of these metals for all of the 500 moulds. With discolorations outside the cast system and bright, powder like coatings on the complete surface at 60 % of all moulds an indirect reference to their use is given. Both observations indicate a heating of the whole mould. This is reinforced by scanning electron microscopic examination of thin sections and diffraction analysis of powder samples which revealed the »burned« character of the coating. Glowing tests with the Plänerkalkstein and Solnhofener limestone demonstrated that discolorations arise from 300 °C upwards, however, decomposition of calcium carbonate starts at around 700 °C. Thus all moulds with a bright surface coating must have been heated at temperatures of at least 700 °C. Such a measure can only be explained plausibly in connection with the metal cast and furthermore with the casting of pewter under consideration of the missing discolorations in the cast system. According to the results of the casting experiments it is quite improbable that the moulds had been heated at high temperatures like 700 °C before their use. However, a general explanation for the motives of a possible heating after founding cannot be given with the performed examinations. So some questions are still unanswered."

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Veröffentlichungen des Landesamtes für Denkmalpflege und Archäologie Sachsen-Anhalt – Landesmuseum für Vorgeschichte 76, 2020

From a scientific point of view, archaeologists succeeded in finding a real »treasure trove« in 2005: During an archaeological excavation in the old town of Magdeburg, about 450 mostly completely preserved stone moulds from the 13th century were unearthed in a single rubbish pit. This find thus represents the largest of its kind in Europe to date and is considered an important pivotal find for the study of medieval realia as well as of the history of technology. In addition to this, the image of Magdeburg’s foundry craftsmanship, which was well-known in the Middle Ages, takes considerable shape, having previously been characterised almost entirely by the »Magdeburger Gießhütte« (Magdeburg foundry). Besides the enormous amount of casting moulds, however, it is precisely also the high-quality elaboration of the cast motifs which is rather remarkable. At the same time, a high degree of standardisation of production and a mass of shapes and motifs can be observed. Among the motifs, dress accessories such as fibulae (brooches) and ornamental fittings predominate, but jewellery, toys, and mounts are also represented in greater numbers. The find of casting moulds belonged to a workshop that was situated in the backyard of a townhouse plot on the old road »Goldschmiedebrücke« (today the northern end of Regierungsstraße) between Magdeburg’s cathedral precinct and the civil town. The property was located only three house numbers away from the former goldsmith’s guild and was demonstrably used from 1284 onwards for church construction purposes. This precise date is thus a terminus ante quem, because the workshop that had probably been in operation since the 11th century had to be removed for this purpose. Despite several ground-level furnace plates of burnt loess and other features, it was not ascertainable whether the workshop had been used for casting the entire time. The furnaces were repeatedly renewed during the long operating period, which resulted in the floor level being raised by more than 1.5 m. In addition to the furnace structures, rectangular borrow pits and pits with wooden bracing had been set up, reaching down into the loess soil almost as far as 2 m. Remains of two pithouses originate from the early period of the recorded area and date before the commissioning of the workshop. Here, remains of bone carvings and pigments were discovered. The casting moulds themselves were found in a rubbish pit specially set up for their disposal at the time of the abandonment of the workshop. Since not all pieces were located in the pit, it can be assumed that originally more rubbish pits existed, which however remained undocumented due to the rather small excavation area. The moulds were sampled for petrographic analyses and consist of fine-crystalline limestone that was presumably mined in the northern Harz foreland near the town of Thale. Due to its low heat resistance, this particular type of limestone was not suitable for casting non-ferrous or precious metals; however, it was proven by extensive casting experiments that it could be used for casting pewter and lead. By casting pewter and lead, it was possible to use the moulds several, if not countless times, since they were designed as permanent moulds. At the same time they are products of serial manufacturing: Apparently, standardised raw moulds with even mating surfaces were delivered to Magdeburg and used for certain motifs or groups of motifs depending on size, thickness, and shape. Apart from flat moulds, there are also a number of vaulted exemplars for casting objects of a more sculptural shape, like miniature figures and vessels. Moreover, many of these finds have been worked on both sides and could thus be used alternately for the sequential manu-facturing of objects. Stacking moulds for rationalisation, as they are known in England, are however not represented. Quite a number of pieces show nothing but engraved preliminary drawings or fragmentary motifs, which indicates that these were the back parts of multi-piece casting moulds that did not have to be worked in such great detail. In addition to fine cutting tools divider calipers, engraving needles, various kinds of drills (e.g. spoon or spotting drills), milling tools as well as a lathe were standardly used. The fine-grained rock material of the limestone allowed for a highly precise and detailed cutting of the motifs’ mould cavities, which resulted in very complex and elaborately designed objects. The casting moulds were mainly constructed from two or three components; however, there are several finds that consisted of four, five, or even eight parts. To ensure the accuracy of fit, holes were drilled in the mating surfaces of each matching moulding which then took up tin-lead dowel pins. For a secure fixation additional wires or bandages had to be wrapped around the moulds. The casting material was poured through a sprue into the assembled moulds and runners or feed sprues led the material directly into one or multiple cavities. In this manner a large number of objects were serially mass-produced. Engraved vent holes or – in the case of complex objects – internally drilled vent channels, which were connected to the mating surfaces, facilitated the escape of air or gases trapped in the mould cavities. The Magdeburg foundry documents the earliest evidence of this venting technology so far, which was then apparently adapted by other foundries across the whole of Europe. Apart from two moulds for a pilgrim’s amulet and a badge depicting the Crucifixion, motifs of profane nature predominate in the find material. It can thus be assumed that the foundry produced items for common bourgeois households. The range of motifs is extremely extensive and can be divided into following subject groups: 1. Small- and large-sized fibulae or brooches 2. Decorative fittings and mounts 3. Belt and strap buckles 4. Rings 5. Pendants 6. Buttons and beads 7. Toiletry (e. g. mirror cases) 8. Toys (miniature vessels and figures) 9. Spoons and bowls/plates1o. Chapes for the scabbards of knives or daggers 11. Micro scale or candlestick components 12. Box hardware and fittings 13. Miniature hatchets 14. Religious themes There is a large variety of shapes within the individual groups, especially with the numerically predominant fibulae/brooches and fittings that together make up a total of c. 60 % of all moulds. The remarkably extensive range of motifs, which presumably was even larger originally, demonstrates that in the 13th century almost everything was cast, which was technically feasible and according to the customers’ desires. In doing so, there seem to have been hardly any technical difficulties, since it was possible to even produce the most complicated and sculptural objects by means of chill casting. Here, one was able to draw on long established and well practised techniques like full-mould and core casting, but more rarely used technologies like slush casting were also mastered. What is furthermore notable is that a lathe was used for creating and developing individual motifs (e. g. scale pans). Of particular importance is the detected casting material, since it enables statements on a commercial orientation of the workshop. Besides a large number of dowel pins, corroded relics of tin-lead metal were also found in the casting cavities or sprues of several mouldings. In addition to this, a particularly high amount of residues was found in the vent channels, where the metal was pressed in during the casting process. Here, too, scientific analyses have revealed alloys of lead and tin, which were occasionally admixed with a little copper for an increase in hardness. In view of this fact it can be assumed that the entire find complex is associated with pewter casting and previously belonged to a tin foundry. This would thus be the earliest evidence of a presumably independent tin moulder. Even if the workshop produced tin objects (or white metal in general) it is still highly likely that many objects, especially the most elaborate and decorative ones, were modelled after precious metal realia. This is indicated among others by the reper¬toire in itself, but also for example by the imitated granulation works, filigrees, and gems at the finds, and the location of the foundry in a district otherwise charaterised by gold- and silversmithing. It may be suggested that all these workshops were part of some kind of pre-industrial production and trading system of a larger scale, which was made pos-sible by or required a correspondingly large urban market like the one in Magdeburg. This means that we are looking at an exclusively commercially oriented craft, which emerged in a completely different environment than the monastic goldsmithery described by Theophilus Presbyter in the early 12th century. In contrast to a serial and profane mass production, the monastic smithery focused on the manufacturing of elaborate and individual objets d’art for ecclesiastical demands. In this context, the above mentioned cast objects contribute to a change of our point of view regarding day-to-day life in the 13th century by means of their quantity as well as their professional, serial standardisation and compilation within a time horizon before 1280. They indicate a much richer everyday material cul¬ture in the urban milieu than was sometimes suspected. At the same time the Magdeburg foundry with its mass production both for a regional and presumably for a supra-regional market, marks an important step in the history of the development of the town and towards the guild-dominated trade structures of the late Middle Ages. Without doubt, this find of casting moulds thus represents a »treasure trove« in various aspects.

Archäologie Baselland, Jahresbericht, 2021

29 Gussmarken, gefunden am Fuss des Wartenbergs, Muttenz BL, Schweiz. Darunter gussgleiche Stücke und nicht überarbeitete Rohgüsse aus Holzformen. Datierung 15. Jh.? im Kontext ökonomischer Prozesse in den Wartenberg-Burgen?

Between 1998 and 2001 and in 2010, two mass finds from the first half oft the 16th century were excavated in Augsburg. They are thought to consist of waste material from all over the imperial city. Although cleaning oft he ceramic finds is not yet complete, the special importance oft the two find complexes is already clear.

Siedlungs- und Küstenforschung im südlichen Nordseegebiet (SKN) 46, 2023

Untersuchungen der letzten Jahre zur Siedlungslandschaft des Allermündungsgebietes zeigen, dass die Region während der ersten Hälfte des ersten nachchristlichen Jahrtausends als ein wichtiger Kommunikationsraum zu bewerten ist. Insbesondere der Zugang zu den Wasserwegen von Aller und Weser führte dazu, dass die ansässige Bevölkerung an überregionalen Handels- und Austauschverbindungen partizipieren konnte. Um nähere Erkenntnisse zum Fundinventar der Region zu erhalten, wurde das Keramikmaterial des Fundplatzes Holtorf-Lunsen 23, Ldkr. Verden, mithilfe von typologischen Vergleichen und naturwissenschaftlichen Methoden analysiert. Da sich das Allermündungsgebiet in einer Kontaktzone verschiedener überregionaler Formenkreise befindet, bildet die kulturelle Einordnung der Funde anhand ihrer stilistischen Merkmale einen Schwerpunkt der Untersuchungen. Dabei ist von besonderem Interesse, inwiefern das hohe Maß an kultureller Diffusion in der Region die lokale Töpfereitradition beeinflusst und geprägt hat.

Vor-und Frühgeschichte, Frühmittelalterarchäologie Institution:

C. Rauhut/K. Wagner/M. Wemhoff/G. Döhner/L. Grunwald (Hrsg.), Keramik in Berlin, Brandenburg und Europa – Produktion, Innovation, Handel und Sammlungsgeschichte. 53. Internationales Keramik-Symposium 2020. Beiträge zur Denkmalpflege in Berlin, Sonderband (Berlin 2022), 33-42., 2022