Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC
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Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC - the influence of composition on the susceptibility for detachment Fiep Korstanje BA 11741686 [email protected] MA Thesis Conservation and Restoration of Cultural Heritage Specialisation: Glass, Ceramics and Stone University of Amsterdam, Amsterdam Supervisor: Kate van Lookeren Campagne – Nuttall 21-06-2019 Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Table of Contents Introduction 1 1. The Case-Study Objects 3 1.1 Context of the Objects: From Excavation to Museum 3 1.2 Object Description 5 1.3 Object Condition and Surface Coating 8 1.3.1 Standing Woman with Chiton and Himation (APM00257) 9 1.3.2 Head of Woman (APM00277) 9 1.3.3 Standing Woman with Hand on Side (APM00394) 10 1.3.4 Lower Part of Walking Woman (APM01145) 10 1.3.5 Eros (APM01161) 11 1.3.6 Incense Burner (APM14207) 11 2. State of the Art: Greek Terracotta Figurines 13 2.1 Production of Ancient Terracotta Objects 15 2.1.1 Forming the Object 19 2.1.2 Coating Materials 21 2.1.3 Coating Application 24 2.2 Factors Influencing the Loss of Surface Coatings 25 2.2.1 Production 25 2.2.2 Morphology and Chemical Composition of Ceramic and Coatings 26 2.2.3 Coating Composition 28 2.2.4 Burial Conditions 29 2.2.5 Treatment on/after Excavation 29 3. Experimental 33 3.1 Methodology 33 3.1.1 Hirox Optical Microscopy 34 Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC 3.1.2 pXRF Analysis 34 3.1.3 X-ray Diffraction 34 3.1.4 SEM-EDX 35 3.2 Results and Interpretation 36 3.2.1 Hirox Optical Microscopy Results and Interpretation 36 3.2.2 pXRF Results and Interpretation- Major Elements Measured 38 3.2.3 XRD Results and Interpretation 41 3.2.4 SEM-EDX Results and Interpretation 42 4. Conclusions from the Analysis 54 Conclusion 58 English Summary 62 Dutch Summary 64 List of Figures 66 Bibliography 71 Acknowledgements 74 Appendix I: Images 76 Appendix II: Images Objects from Museum Database and Literature 84 Appendix III: Indicating Coating Layer, Hirox Images, XRD Measurement Points of 88 SEM-EDX Samples Appendix IV: XRD Results of Case Study Group 102 Appendix V: SEM-EDX Results of Case Study Group 110 Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Introduction From the Bronze Age, terracotta objects were produced on a large scale in Ancient Greece. These objects were decorated with different organic and mineral pigments that were applied on top of a light-coloured surface coating.1 The composition of these surface coatings often remains unclear, being referred to for instance as slip layers or as surface coatings containing, or mixed with, calcium carbonate.2 Because it is unknown what type of coating is present, it has been decided in this research to refer to this layer as a ‘coating’. The application of a surface coating on terracotta was done from the fifth century BC onwards.3 At the Allard Pierson Museum, an important collection of these Greek archaeological terracotta sculptures is stored. On some objects, a much larger percentage of the surface coating remains than on others. The exact factors that have led to this difference in loss of surface coating are unknown. Probable causes for the loss of surface coating are the composition of the coating, burial conditions as well as how the objects were treated on or after excavation. This thesis discusses the research undertaken into the possible reasons for the variation in percentages of loss of the coatings and the way in which loss occurs on these terracotta objects. The main research question is: ‘In how far does the composition of the surface coating on ancient Greek terracotta figures influence the susceptibility of the coating layer?’, with focus on a specific region and period. For this research, six terracotta objects with varying conditions of surface decoration were selected from the collection of the Allard Pierson Museum. Three originate from Boeotia (in Greece) and three are from Taranto (now Italy). All objects date between the fourth and the second century BC.4 It is hoped that the results of this research will aid the preservation of Greek terracotta figures, by giving greater insight in susceptibility of the coating layer for damage. 1 Robert A. Lunsingh Scheurleer, Grieken in Het Klein: 100 Antieke Terracottas (Amsterdam: Allard Pierson Museum, 1986), 9. & Paula G. Leyenaar-Plaisier, Griekse Terracotta's: Uit De Collectie Van Het Haags Gemeentemuseum (Den Haag: Haags Gemeentemuseum, 1986), 12-21. & Herman Brijder, "Griekse Godinnen En Meisjes in Het Klein," in Kleur! Bij Grieken En Etrusken, ed. Vincenz Brinkmann and Herman Brijder (Amsterdam: Allard Pierson Museum, 2006), 57. & R. A. Higgins, "The Polychrome Decoration Of Greek Terracottas," Studies in Conservation 15, no. 4 (1970): 273. 2 Anne Rinuy and Francois Schweizer, "Analysis of the White "ground" and Ancient Adhesives Found on Canosa Vases (south Italy) of the Third Century B.C.," in Proceedings of the 18th International Symposium on Archaeometry and Archaeological Prospection, Bonn, 14-17 March 1978; Archaeo-Physika, Band 10, Rheinisches Landesmuseum Bonn (Köln: Rheinland-Verlag GmbH, 1978), 255. & Riemer R. Knoop, Antefixa Satricana: Sixth-century Architectural Terracottas from the Sanctuary of Mater Matuta at Satricum (Le Ferriere) (Assen/Maastricht: Van Gorcum, 1987), 21. 3 Gloria S. Merker, "Corinthian Terracotta Figurines: The Development of an Industry," Corinth 20 (2003): 234. 4 Allard Pierson Museum Archeologische Collectie, December 2004, accessed February 1, 2019, http://dpc.uba.uva.nl/archeologischecollectie. 1 Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC 2 Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Chapter 1. The Case-Study Objects For this research an assemblage of six terracotta objects from the Allard Pierson Museum in Amsterdam, The Netherlands, was analysed (appendix I fig. I.1-I.21). The group was selected based on several criteria. The main criterion for selection was a variation in the condition of the white coating layers to enable comparison of objects. In addition, the provenance and date of the object needed to be known and literature about the specific objects available. In order to enable comparisons between the objects, the object’s dates needed to be as close as possible. Two different places of origin were chosen to see whether a correlation between a production region and coating composition could be made. Based on these characteristics, a pre-selection of fifteen objects was made and handheld XRF analysis (see chapter 3) was carried out to get an overview of the type of coating present on the objects in order to make sure that the objects would provide a balanced range. The selection of six suitable objects was made based on the percentage of aluminium, silica or calcium in the coating which suggested the presence of either clay minerals or chalk. In this chapter the archaeological context of the objects will be discussed. In addition, an overview of the six objects is included and the condition of the objects is described, including a detailed description of the surface coating (table 1 & 2). 1.1 Context of the Objects: From Excavation to Museum Three of the objects were produced in Taranto. This city, which is currently in Italy, was a Greek colony during the fourth and third century BC. The other three objects originate from different cities in Boeotia, a region in central Greece (fig. 1). The place of production has been based on the stylistic characters of these objects. Five out of six objects used in this research were part of the collection of C.W. Lunsingh Scheurleer, who was professor of classical archaeology at the University of Leiden. Lunsingh Scheurleer was a collector of ancient artefacts who bought objects from dealers and collectors often at international art fairs. Most items were acquired by Lunsingh Scheurleer between 1900 and 1932. Between 1912 and 1920 many objects from Boeotia and Taranto were acquired, which make up a large part of the collection nowadays. The objects were acquired by the Allard Pierson Museum in Amsterdam when the collection was up for sale and at risk of being separated.5 One object, the altar/incense burner (APM14207), was donated to the Allard Pierson Museum in 1998. No further information is known about who donated this object. 5 Leyenaar-Plaisier, Griekse Terracotta's, 3. & Lunsingh Scheurleer, Algemeene Gids, ed. L.J. Elferink (Amsterdam: Allard Pierson Museum, 1937), VIII. & Lunsingh Scheurleer, Grieken in Het Klein, 7. 3 Korstanje, UvA, 2019 Surface Coatings on Terracotta Objects from Boeotia and Taranto 400 - 200 BC Furthermore, the date of production and place of production is known as defined by the museum conservator or curator.6 In the beginning of the twentieth century, little emphasis was put on preserving information regarding the context and history of such objects in collections. Often hardly any information exists about where objects were found or excavated and who the objects were sold to. For this research, only objects of which the provenance and a production date are determined by the conservator or curator, are included.