Large Roman Bronze Statues from the UNESCO World Heritage Limes

Frank Willer, Roland Schwab & Kati Bott Large Roman Bronze statues from the UNESCO World Heritage Limes Summary Introduction Fragmented bronze sculpture is an important category One of the important categories of finds from the Roman of finds from the provinces in the north of the Alps at border provinces between the north of the Alps and the the frontier of the Roman Empire. Portraits and statues North See are large roman bronze sculptures. Portraits of the emperors and their families were raised in a great and statues of the emperors and their families were number in the military camps and civil settlements along raised in a great number in the military camps and civ- the Limes. Numerous fragments of these statues are il settlements along the Limes in Germania inferior, in still preserved, but they have never been systematically Germania superior and in Raetia. Though also in ritual registered. The paper introduces the project and the first contexts, there must have been bronze statues in con- results. Three different techniques of gilding have been siderable numbers. Many of these statues are likely revealed: besides leaf and fire-gilding, the unusual tech- destroyed by invading German troops in the middle of nique of diffusion gilding has been observed. Also vari- the 3rd century AD when the Limes was abandoned or ous repair techniques, different to those already docu- in case of Damnatio memoriae when the emporer fall mented for Mediterranean statues have been exposed. out of favor. (Fig. 1). Fig. 1: Fragments of bronze statues from Aalen. Archäologisches Landesmuseum Baden-Württemberg. Scale 33 x 353 cm 239 Frank Willer, Roland Schwab & Kati Bott Even if the fragments are often difficult to characterize and to categorize, they do constitute an important source for the reconstruction of imperial representation in the Limes forts and thus the importance of the imperial image in the Roman army. Therefore, it is astonishing that they have never been compiled systematically. More than 4300 fragments from 124 different sites have been identified so far. Most of them have been archived for undefined old finds in museums and other collections. Only a few significant fragments have been published in the serial “Der Oberger- manisch-Rätische Limes des Römerreiches” of the Reichslimeskommission since the end of the 19th century (see Sarwey et al. 1892). They were briefly reviewed in the works of Gustav Gamer (1969) and Oliver Stoll (1992). Only a few better preserved pieces like a horse head from Augsburg (Bakker 1985; Bergemann 1990), the portrait of Gordian III from Niederbieber (Fig. 2) (Lahus- en & Formigli 2001), or the so-called “Trajan” from the Rhine near Xanten (Schalles 2010) have already been presented in individual articles. Comprehensive publica- tions are available of scrap fragments from Colonia Au- gusta Raurica in Switzerland (Janietz Schwarz & Rouill- er 1996; Janietz 2000) or recently of the well preserved statue of so called “youth from Xanten” (Schalles & Peltz 2012). The project: aims, strategies and methods Fig. 2: Picture of the life-sized head of Gordian III from Nieder- bieber. Landschaftsverband Rheinland-LandesMuseum Bonn. The research project “Roman bronze Statues from the UNESCO World Heritage Limes” (2010-2014) is funded by the German VolkswagenStiftung and is initiated by the Archäologisches Landesmuseum Baden-Wuerttem- the public comprises an archaeological-historical ap- berg, the Institut für Archäologische Wissenschaften proach as well as the technological aspects. Casting of the Goethe Universität in Frankfurt a. M. and the techniques, alloy compositions and surface working like LVR-LandesMuseum Bonn (see Wessler 2011). Within gilding, chiselling, repair and joining are investigated by the initiative „Research in Museums“, the project is fur- different scientific methods. thermore supported by numerous partners of museums, universities and specialized research institutes in Ger- A lot of the technological details like casting flaws, re- many, Netherlands and Switzerland. pairs, joints and the positions of chaplets can be revealed by carful optical surface observations and conventional Scientific investigations are performed by the Bunde- radiography. Computed tomography (CT) provides 3-D sanstalt für Materialforschung und -prüfung in Berlin, the information (Fig. 3) of more complex casting techniques Institut für Gießerei of the RWTH Aachen, the Instituut and makes it possible to investigate the interior surface. Collectie Nederland in Amsterdam, the Institut für Che- Based on the 3-D models casting simulations will be mie, Biochemie und anorganische Chemie of the Freie performed to visualize the entire process of casting, in- Universität in Berlin and the Curt-Engelhorn-Zentrum cluding solidification and shrinkage formation. For the Archäometrie in Mannheim. determination of the chemical compositions by energy-dispersive x-ray fluorescence analysis (EDXRF), 370 The aim is to reappraise these important relicts of ancient samples were taken until now. Initial investigations of bronze casting to make them open for research and to the microstructure, corrosion, gilding and other surface 240 Large Roman Bronze statues from the UNESCO World Heritage Limes that the prevalent alloy in Roman times is brass, one would expect most of the statues being of gunmetal. Actually the large statues are all of bronze (see also Caley 1970, Scott & Podany 1990; Oddy et al. 1990; Janietz Schwarz & Rouiller 1996; Janietz 2000; Lahus- en & Formigli 2001). Therefore we can follow Caley’s (1970) supposition, that most scrap used for casting statues is foundry waste or scrap coming from statues in turn. Figure 4 shows the alloying components of samples analyzed so far and it attests the published data that Roman large statues are mostly made of leaded or even of highly leaded bronze. Consequently the well known leaf gilding (Fig. 5 a, b) is the predominately observed gilding technology of the statues (see Oddy et al. 1990; Oddy 2000). Only one fragment of an arm shows a pre- vious fire-gilded layer which was regilded by gold leafs (Fig. 6 a, b). A very unusual and hardly observed technique of diffu- Fig. 3: Computed tomography of the head of Gordian III as shown sion bonding has been revealed at a back fragment from in figure 2 with a view inside. III Bundesanstalt für Material- a life size statute of a naked male deriving from an Ale- forschung und -prüfung, Berlin (BAM) mannic scrap depot of the early 4th century from Gross-Gerau in Hessen (Wenzel 2003; 2009), which were recently conserved in the LVR-LandesMuseum decorations are performed by metallography with optical (OM) and scanning electron microscopy (SEM) with at- tached energy dispersive spectroscopy equipment (EDX). Apart from the categorization of the bronze fragments themselves, the reconstructions of the original statues, their locations and functions as well as aspects of pro- duction techniques will become more interpretable. The results are documented and recorded in an internet da- tabase, which is available to all participants during the whole project and which will also be available for every- body at the end of the project. a) In addition to the research on bronze fragments, the compilation and analysis of all known statue bases with inscriptions is in progress. They are, as far as they are no bases for stone statues, directly and functionally as- sociated with the bronze statues. They can provide important information on the source for the assembly and disassembly, and they are essential for the historical context. Alloy compositions, surface decorations, experiments and exceptional casting techniques b) Fig. 4: Histograms showing the lead (a) and tin concentrations According to a recipe given by Pliny, it is thought, that (b) of statues analyzed so far. Landschaftsverband Rhein- a third part of the bronze used for statues was scrap land-LandesMuseum Bonn and Curt-Engelhorn-Zentrum Archäo- (Caley 1970; Gazda & Hanfmann 1970). Bearing in mind, metrie, Mannheim 241 Frank Willer, Roland Schwab & Kati Bott Fig. 5a: Fragment of a garment (17 x 13 cm) from Groß-Gerau, Fig. 7a: Fragment of a gilded human back (60 x 42 cm) from with repair which has been done direct after casting. Groß-Gerau. 7b) Scanning electron image (backscattered mode) 5b) Leaf gilding with adhering lead corrosion. Landschaftsverband shows phase formation on the gold-base metal interface. Land- Rheinland-LandesMuseum Bonn and Curt-Engelhorn-Zentrum schaftsverband Rheinland-LandesMuseum Bonn and Curt-Engel- Archäometrie, Mannheim horn-Zentrum Archäometrie, Mannheim Fig. 6a: Fragment of a gilded live-sized bronze arm (23 x 12 cm) of a statue from Bonn. 6b) Scanning electron image (backscattered mode) shows porous fire gilding with two outer layers Fig. 8: The X-ray dot map from the interface of the gilded back of gold leaf from regilding. Landschaftsverband Rheinland- from Groß-Gerau (see figure 7) illustrates the interdiffusion of LandesMuseum Bonn and Curt-Engelhorn-Zentrum Archäo- gold from the gold leaf and copper of the bronze. Curt-Engel- metrie, Mannheim horn-Zentrum-Archäometrie, Mannheim (Fig. 7a , b). The surface beneath the gilding is heavily been done only to lead free bronzes, but several exper- corroded, but figure 8 clearly shows that interdiffusion iments showed that there is already a good adhesion of of gold and bronze has taken place. It is not clear if this the gold coating on leaded bronze after polishing a leaf technique is an accidental or an intentional

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