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A common problem in art conservation is the reconstruction of fragmented objects. The fragments need to be assembled to produce the overall original shape of the object. This process includes the estimation of their relative positions (fragmentation problem), and the testing of their fractured surfaces for whether they match. These problems become more difficult when a great number of large and heavy fragments (or small and fragile ones) need to be physically manipulated in order to test potential matches. This increases the risk of damaging the objects while performing unsuccessful tests. So far, the process of selecting candidate matches has relied on access to the real fragments and/ or photographic and manual records. The success of the process is dependent on the experience of the conservator and the quality of the records. Here, a new methodology for solving this problem is proposed using digital tools, which introduce minimal risk to the object. Modern photogrammetric and laser scanning equipment can be used for the remote accurate recording of objects. These methods produce groups of 3D points collected from the surface of the object (called point clouds). The point clouds are triangulated to form a 3D model, from which the outward surface normals for each triangle can be computed. These normals are then analysed in Riemannian space (spherical surface) by calculating the Mahalanobis distance for each normal. This analysis allows the division of the models into their facets (the procedure is called segmentation and the facets identified are called segments) by setting a fixed maxirnum distance value, as the criterion for normals belonging to the same segment. The identification of a pair of potentially matching segments, can be achieved using a combination of parameters including conservation-related criteria and quantitative data from surface analysis. The conservation-related criteria originate from the visual study of objects and models and are related to the structural and decorative features of the objects. The surface analysis parameters come from the calculation of the eigenvalues of a normals' dataset, which allows the characterisation of the isotropy, spread and size of the surface. The results of the analysis are plotted in a 3D chart and are combined with the conservation-related criteria in a specialised database. In this document, several case studies of the application of this methodology to fragmented archaeological objects are presented. These case studies show the advantages of the proposed recording techniques against the traditional ways of recording. They also demonstrate how it is possible to segment a model using the proposed analysis, to determine whether a surface is a fracture or not, and to identify the style of carving of an object by analysing the tool-marks. Most importantly, the results of the case studies demonstrate the vast potential of the method in identifying matching fragments from a group, without any physical contact with the object. The risk introduced in the procedure is minimal and the reconstruction takes place after all the original locations of the fragments have been found using the digital models.

Im Mittelpunkt der Arbeit stehen sieben Flügelretabel, die nach ihrer Entstehung um das Jahr 1500 als Hauptaltarretabel in Dorfkirchen im Umkreis der Hansestadt Rostock sowie auf der schwedischen Insel Gotland fungierten. Ausgangspunkt der Dissertation ist die T­hese, dass diese Retabel, die heute sehr unterschiedliche, teils fragmentarische Erhaltungszustände aufweisen, in ein und derselben spätmittelalterlichen Werkstatt in Mecklenburg entstanden sind. Um die These zu belegen, wurde gemäß des kunsttechnologischen Forschungsansatzes eine systematische Befunderhebung der Flügelretabel durchgeführt. Umfangreiche kunst­technologische und dendrochronologische Untersuchungen sowie naturwissenschaftliche Analysen liefern für die sechs Retabel und ein Madonnenfragment zahlreiche holz-, schnitz- und fasstechnische Befunde, auf deren Grundlage sich Erkenntnisse zur Datierung und der Herstellung der Retabel, der verwendeten Ma­terialien und Techniken ableiten lassen. Den Schwerpunkt der Arbeit bildet der Vergleich der kunsttechnologischen Befunde. Die dabei heraus­gearbeiteten Übereinstimmungen sind geeignet den Werkstatt­zusammenhangs zu belegen. Für den Nachweis werden, erstmals in der Kunsttechnologie, die Vergleichsmerkmale kategorisiert und Befundüberein­stimmungen in Anlehnung an die Methode der „qualitativ vergleichenden Analyse“ (QCA) mittels Vergleichstabellen dargestellt. Mit dem Nachweis des Werkstattzusammenhangs für die Retabel­gruppe lassen sich Charakteristika dieser Werkstatt, deren serielle Arbeitsweise und allgemeine Werkstattorganisation aufzeigen, die den derzeitigen kunsthistorischen Wissensstand zur mittelalterlichen Werkstat­ttätigkeit in Mecklenburg sowie zur Kunstverbreitung im Ostseeraum erweitern. Die Verortung der Werkstatt in die Hansestadt Rostock ist nach kunsthistorischem Forschungsstand wahrscheinlich, lässt sich jedoch anhand der kunsttechnologischen Befunde nicht belegen. / Seven winged retables dating from around 1500 that served as main altarpieces in village churches around Rostock and on the swedish island Gotland are the focus of this work. The dissertation proceeds from the thesis that these retables – which are in differing, sometimes only fragmentary, states of preservation today – were all produced in the same late medieval workshop in Mecklenburg. In accordance with the art technology-oriented approach used to prove this thesis, a systematic analysis of findings on the winged altarpieces was carried out. Comprehensive art-technological and dendrochronological investigations as well as scientific analyses of the six retables and one Madonna fragment provided numerous technical findings regarding the wood, the carving and the paint. These were the basis for deductions concerning dates, materials, techniques and the production process. The main emphasis of the dissertation is a comparison of all the findings. The affinities identified among the retables are suitable evidence for proving the thesis of their connection to a single workshop. For the first time in art technology, the line of argumentation uses a “qualitative comparative analysis” (QCA), which makes it possible to depict the frequency of common factors in the findings. Based on evidence connecting the retable group to a s­ingle workshop, it is possible to establish characteristics of the workshop, its serial methods of work, and its general organization, thus furthering the current state of art historical knowledge of medieval workshop activity in Mecklenburg and of the dissemination of art in the Baltic Sea region. Art historical research makes placement of the workshop in the Hanseatic city of Rostock likely, but it is not possible to prove the workshop’s location on the basis of the art-technological findings.

Le musée des Antiquités nationales (MAN) a été créé sous l'impulsion de l'Empereur Napoléon III en 1862. Avec le projet de création du musée s'est imposée la nécessité de le doter d'ateliers de moulage et de restauration. Abel Maitre, sculpteur de formation, est le premier chef d'atelier de 1866 à la fin du 19e siècle. Rouage Indispensable du MAN, Il s'est avéré être un véritable précurseur de la restauration des objets archéologiques telle qu'on la conçoit de nos jours. Son successeur, Benoit-Claude Champion, dirige les ateliers durant toute la première moitié du 20e siècle et œuvre à la professionnalisation de cette discipline, à une période où la question de la formation des restaurateurs est au centre des débats. A travers l'exemple concret des ateliers du MAN, cette recherche se propose de montrer comment a émergé la spécialité archéologie dans l'univers très artistique de la restauration, et comment le développement de cette activité en discipline est Intimement lié à la politique Internationale de sauvegarde du patrimoine, qui prend toute son ampleur après la première guerre mondiale. / The National Museum of Antiquities (MAN) was created at the instigation of Emperor Napoleon Ill in 1862. With the proposed creation of the museum has become the need to equip the workshops of molding and restoration. Abel Maître, a sculptor by training, is the first leader of workshop in the late 19th century. Indispensable part of the MAN, Il proved to be a !rue precursor of the restoration of archaeological objects as it conceives today. His successor, Benoit-Claude Champion, leads workshops throughout the first half of the 20th century and works to professionalize the discipline, at a time when the Issue of training for restorers is central to the debate. Through concrete example of MAN workshops, this research alms to show how archeology has emerged as a specialty in the highly artistic restoration, and how the development of this discipline is closely linked to International politics Heritage Preservation, which comes into its own after World war 1.