Spectroscopic Studies of Maya Pigments
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SPECTROSCOPIC STUDIES OF MAYA PIGMENTS By Rosemary Anne Goodall B.App.Sci (App. Chem), M. App. Sci. School of Physical and Chemical Science Queensland University of Technology A Thesis submitted for the Degree of Doctor of Philosophy of the Queensland University of Technology 2007 KEYWORDS Micro-Raman spectroscopy, Micro-ATR infrared spectroscopy, FTIR- ATR spectral imaging, Environmental scanning electron microscopy, ESEM-EDX, Pigments, Paint, Stucco, Ceramics, Maya, Copan ii ABSTRACT The Maya of Central America developed a complex society: among their many achievements they developed a writing system, complex calendar and were prolific builders. The buildings of their large urban centres, such as Copan in Honduras, were decorated with painted stucco, moulded masks, carving and elaborate murals, using a range of coloured pigments. In this study the paints used on the buildings of Copan and some ceramic sherds have been investigated, non-destructively, using micro-Raman spectroscopy, micro-ATR infrared spectroscopy, environmental scanning electron microscopy with energy dispersive X-ray analysis (ESEM-EDX) and FTIR-ATR imaging spectroscopy. The paint samples come from four buildings and one tomb covering three time periods in the four hundred year history of Copan. The main pigment used in the red paint on these samples was identified as haematite, and the stucco as a mixture of calcite particles dispersed throughout a calcite-based lime wash stucco. The composition and physical nature of the stucco changed through time, indicating a refining of production techniques over this period. A range of minor mineral components have been identified in each of the samples including rutile, quartz, clay and carbon. The presence and proportion of these and other minerals differed in each sample, leading to unique mineral signatures for the paint from each time period. Green and grey paints have also been identified on one of the buildings, the Rosalila Temple. The green pigment was identified as a celadonite-based green earth, and the grey pigment as a mixture of carbon and muscovite. The combination of carbon and mica to create a reflective paint is a novel finding in Maya archaeology. The iii high spatial resolution of the micro-FTIR-ATR spectral imaging system has been used to resolve individual particles in tomb wall paint and to identify their mineralogy from their spectra. This system has been used in combination with micro-Raman spectroscopy and ESEM-EDX mapping to characterize the paint, which was found to be a mixture of haematite and silicate particles, with minor amounts of calcite, carbon and magnetite particles, in a sub-micron haematite and calcite matrix. The blending of a high percentage of silicate particles into the haematite pigment is unique the tomb sample. The stucco in this tomb wall paint has finely ground carbon dispersed throughout the top layer providing a dark base for the paint layer. Changing paint mixtures and stucco composition were found to correlate with changes in paint processing techniques and building construction methods over the four hundred years of site occupation. iv GLOSSARY OF TERMS AAS Atomic absorption spectroscopy AD Anno Domini BC Before Christ BP Before present CCD Charge coupled device EDX Energy dispersive X-ray ESEM Elemental scanning electron microscopy FT Fourier transform FT-IR Fourier transform infrared FT-Raman Fourier transform Raman GC-MS Gas chromatography-mass spectrometry ICP Inductively coupled plasma ICP-AES Inductively coupled plasma-emission spectroscopy ICP-MS Inductively coupled plasma-mass spectrometry IR Infrared MS Mass spectroscopy NAA Neutron activation analysis NIR Near infrared PIXE Particle induced X-ray emission SEM Scanning electron microscopy XRD X-ray diffraction XRF X-ray fluorescence Definitions Efflorescence The development of salt crystals on the surface after the evaporation of water Paint Colouring mixture of materials use to impart colour to a surface. Usually finely ground matter suspended in a liquid for application. Pigment Colouring agent. Usually added to paint to impart colour. Slip liquid for of clay used as an outer coating on ceramics, giving a smooth surface and often coloured, sometime base for decoration Stela A stone slab erected for commemorative purposes, often highly carved and decorated in the Maya area. v TABLE OF CONTENTS 1.0 INTRODUTION………………………………………………………………1 1.01 Description of the research problem………………………………………….1 1.02 Study objectives………………………………………………………………3 1.0.2.1 Specific aims………………………………………………………….4 1.0.3 The research progress linking the research papers…………………………..4 1.1 ARCHAEOLOGICAL BACKGROUND……………………………………..6 1.1.1 The Copan Valley……………………………………………………………8 1.1.2 Development of the Principal Group of buildings…………………………..11 1.2 LITERATURE REVIEW……………………………………………………...19 1.2.1 Ceramic analysis……………………………………………………………..19 1.2.2 Ceramic surface decorations…………………………………………………22 1.2.3 General pigment analysis…………………………………………………….26 1.2.4 Vibrational spectroscopy in pigment analysis……………………………….29 1.2.5 Iron oxides……………………………………………………………………38 1.2.6 Lime based stucco……………………………………………………………42 1.2.7 FTIR spectral imaging and micro-ATR spectral imaging…………………...46 1.3 SUMMARY……………………………………………………………………50 1.4 REFERENCES…………………………………………………………………51 2.0 A SPECTROSCOPIC INVESTIGATION OF PIGMENT AND CERAMIC SAMPLES FROM COPAN, HONDURAS……………………………………….61 3.0 RAMAN MICROPROBE ANALYSIS OF STUCCO SAMPLES FROM THE BUILDINGS OF MAYA CLASSIC COPAN…………………………………….77 4.0 RAMAN MICROSCOPIC INVESTIGATION OF PAINT SAMPLES FROM THE ROSALILA BUILDING, COPAN, HONDURAS……………………………87 5.0 MICRO-ATR SPECTRAL IMAGING IN ARCHAEOLOGY: APPLICATION TO MAYA PAINT AND PLASTER WALL DECORATIONS………………….95 6.0 GENRAL DISCUSSION……………………………………………………..103 6.1 CONCLUSIONS……………………………………………………………...109 6.2 FUTURE DIRECTION……………………………………………………….113 6.3 REFERENCES………………………………………………………………..113 vi LIST OF TABLES Table 1.1 Paint and ceramic samples analysed and their approximate dates …..…...5 Table 1.2 Chronological list of Copan rulers correlated with ceramic phases and building construction sequence……………………………………...8 Table 6.1 Mineral identification and elemental analysis results for the red pigment samples……………………………………………………………104 Table 6.2 Mineral identification and elemental analysis results for stucco layers..108 LIST OF ILLUSTRATIONS Figure 1.1 Map of the Maya Area of showing the location of Copan………………9 Figure 1.2 The Principal Group of buildings Copan, Honduras…………………...12 Figure 1.3 Copan’s Great Plaza looking south to the Acropolis…………………...13 Figure 1.4 The Clavel building showing the painted wall surface…………………15 Figure 1.5 Wall paint and stucco on the Ani building……………………………..15 Figure 1.6 A painted mask on side of the Rosalila building…………………….....16 Figure 1.7 Structure 10L-22, on the northern side of the East Court………………17 Figure 1.8 Section of Corner Masks on 10L-22……………………………………18 Figure 1.9 Heat induced transformations of iron oxide minerals………………..…40 Figure 1.10 Reactions in the production of lime stucco……………………………43 Figure 6.1 Raman spectra of haematite from all buildings……………………….105 Figure 6.2 Close up of the cross-section of the Clavel building sample……….....109 vii STATEMENT OF ORIGINALITY The work contained in this thesis has not been previously submitted to meet the requirements for an award at this or any other higher education institution. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference in made. Rosemary A Goodall January 2008 viii ACKNOWLEDGEMENTS I wish to thank the following people for their support and encouragement throughout the course of this study, Peter M. Fredericks, for his continual support, inspiration and understanding. His guidance ensured that I kept focused through many years of part-time study. Jay Hall, for his support of this study from the outset, his help in obtaining samples and support in the field. He also provided invaluable support in understanding the complex nature of the Maya civilisation. Llew Rintoul, who shared his great knowledge of vibrational spectroscopy and instrumentation and who was amazingly patient with my obscure questions and requests. John Bartley, who has provided encouragement throughout and some interesting discussions on the beauty of the Maya complexes of Mexico and Guatemala. Rene Viel (Copan Formative Project, Honduras) who as the man on location, negotiated with the Honduran authorities and obtained permission for the removal of samples and laboratory analysis. He also provided invaluable guidance in understanding the Maya ceramic phases study here. Howell G.M. Edwards for technical advice and assistance with FT-Raman analysis. Bob Sharer and Loa Traxler, University of Pennsylvania Museum, ECAP Project for their samples and support Thor Bostrum, Loc Doung and the staff of the AEMF for their support and help with the recording of images and spectra. Flor de Maria Leon Flores who was kind enough to translated a number of documents from Spanish to English and visa versa. The many students at QUT and UQ who have added their encouragement and advice to the mixture. My son Christopher for his understanding and support. Sherlock, who has been my constant companion through many hours of computer time. But most of all I wish to thank my husband, Stephen Goodall, for your constant support, love and understanding I will be forever grateful. ix 1.0 INTRODUCTION This study of ancient Maya paint is