spectroscopic studies of maya pigments - QUT ePrints

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, FTIRATR spectral imaging, Environmental scanning electron microscopy, ESEM-EDX, Pigments, Paint, Stucco, Ceramics, Maya, Copan

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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

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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.

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GLOSSARY OF TERMS AAS AD BC BP CCD EDX ESEM FT FT-IR FT-Raman GC-MS ICP ICP-AES ICP-MS IR MS NAA NIR PIXE SEM XRD XRF

Atomic absorption spectroscopy Anno Domini Before Christ Before present Charge coupled device Energy dispersive X-ray Elemental scanning electron microscopy Fourier transform Fourier transform infrared Fourier transform Raman Gas chromatography-mass spectrometry Inductively coupled plasma Inductively coupled plasma-emission spectroscopy Inductively coupled plasma-mass spectrometry Infrared Mass spectroscopy Neutron activation analysis Near infrared Particle induced X-ray emission Scanning electron microscopy X-ray diffraction X-ray fluorescence

Definitions Efflorescence The development of salt crystals on the surface after the evaporation of water Paint Pigment

Colouring mixture of materials use to impart colour to a surface. Usually finely ground matter suspended in a liquid for application. 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.

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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

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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

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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

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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.

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1.0 INTRODUCTION

This study of ancient Maya paint is the outcome of a joint investigation between the School of Physical and Chemical Sciences, Queensland University of Technology (QUT) and the School of Social Science, The University of Queensland (UQ).

The UQ is conducting a long-term archaeological field

research program at the MAYA site of Copan, in Honduras, Central America. I am working in collaboration with the program directors, Dr Jay Hall (UQ) and Dr Rene Viel, (Copan Formative Project, Honduras). This study is very much an applied one as it employs contemporary chemical analysis to investigate the nature of Maya paints and pigments. It is expected that development of a more complete understanding of the nature of the materials used by the Maya in their decorative pigments will lead to a deeper understanding of both the processes involved with their preparation and changes in these materials and processes through time.

1.0.1 Description of the research problem investigated Pigments have been used by humankind for thousands of years to paint representations of their environment, depict significant social symbols, to decorate and enhance the appearance of their surroundings or themselves. The earliest known paintings are found in South Africa and date to c.70,000 BP1. Representational figures were painted in the caves of France and Spain as early as 30,000 years2 ago and some art in Australia is estimated to be around 30,000 years old3. Paintings can be seen in many other parts of the world on cave and rock

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shelter walls as wells as on the surfaces of structures and dwellings. Many early buildings in Europe4, Asia5, Africa6 and America7 show residues of both paint and stucco and these early pigments were mineral based, utilizing materials that were readily available in the immediate environment. They had the advantage of being chemically stable and required little more processing than grinding and mixing with a liquid medium before they could be used. Typical mineral pigments include iron oxides, manganese oxides, clays, ochre and copper oxides but many others have also been utilized8. Iron oxides, one of the most commonly used pigments, are also one of the most commonly available minerals. Less common minerals were often highly valued by ancient peoples. Later, organic materials were utilized particularly in Europe for the production of oil paints1 and since AD 1704 many pigments have been chemically synthesized1.

Knowledge of pigment minerals, their composition and methods of utilization can provide important scientific information on a number of issues concerning our understanding of the human past. The origins of minerals can offer insights regarding possible trade routes and socio-cultural interactions between different cultures. An understanding of mineral type and composition is critical for the preparation of appropriate conservation and preservation of ancient artefacts. Understanding past paint production processes can inform not only on methods of pigment preparation and use but may also lead to inferences concerning technical abilities of artisans and their social position and interaction within broader society.

In the case of archaeological materials which are an irreplaceable cultural resource, it is crucial to seek analytical techniques that are non-destructive or at

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least only minimally so. Vibrational spectroscopy is such a technique: it provides information about the molecular composition of material and has been used extensively for the identification of both minerals9-11 and archaeological source materials, especially ancient pigments12-15. Raman spectroscopy also offers high spatial resolution with rapid, non-destructive analysis.

Infrared spectroscopy

provides complementary information to Raman, often providing information on materials that are poor Raman scatterers. Another technique is scanning electron microscopy with energy dispersive X-ray micro-analysis, it provides elemental as well as morphological information. By employing all these techniques to the samples a detailed set of data can be obtained which will provide a comprehensive understanding of samples.

1.0.2 Study objectives The main objective of this study was to gain a comprehensive characterisation of the mineralogy and composition of the materials used in paints and stucco by the ancient Maya on artefacts and structures using a combination of non-destructive spectroscopic techniques. Then to assess any changes in the composition of these materials over time in order to understand any changes in artistic methodology, styles or production processes.

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1.0.2.1 Specific aims

The specific aims of this research were to:

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obtain the Raman and infrared spectra of the Copan pigment samples, and identify the individual minerals phases present

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extend the identification using non-destructive or minimally-destructive morphological and elemental analysis (ESEM-EDX)

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compare samples from different locations and cultural periods in order to assess temporal change in the materials used

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determine the production processes that created the paints and preparatory coatings from the raw minerals

1.0.3 The research progress linking the research papers The research presented here in chapters relating to published papers, embraces four stages of investigation into the pigments used by the Maya in Copan. To fully understand changes in each paint type across various applications and through time, surfaces of ceramics and buildings were sampled. Thus samples were taken from ceramics representing different Maya time periods, from external walls of structures from different time periods, from multiple paint and stucco layers of individual structures from a single time period and from the walls of a buried tomb. Each of these four sample types were investigated and separately published (see Chapters 2 -5). The organization of the thesis is outlined below.

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A descriptive overview of the archaeological context of the study is provided in this first chapter. It identifies the key factors of the physical and cultural setting from which the samples were taken. This context is critical to the understanding of the changes in production techniques and materials identified in later chapters and in understanding how these material changes relate to different building periods at Copan. Further, a literature survey serves to summarize the analytical methods applied by other researchers to obtain both structural and elemental information of other archaeological samples. The merits and disadvantages of these techniques and methodologies are compared to determine the best techniques to utilize in this study.

Chapter 2 investigates the pigments used to decorate the ceramics from two ceramic phases covering the Maya Classic period. Variation in paint composition is correlated with change in ceramic types, improvements in production processes and firing techniques.

Ceramic Samples Acbi Ceramics Coner Ceramics

Paint Samples

Time Period (AD) 400-650 650-900 Clavel Structure c450 Ani Structure c530 Rosalila Structure c520 Sub Jaguar Tomb c550 Structure 22 c730 Table 1.1 Paint and ceramic samples analysed and their approximate dates

Chapter 3 investigates samples from three structures in the Copan Acropolis. They cover three different temporal phases (and building styles) in the building of

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the Acropolis. The paint mixture variations identified on each structure suggest the use of different geological sources for red pigment minerals. Differences in the preparatory coatings indicated refinement of the production technique over this period (see Table 1.1).

In Chapter 4 the multiple pigment and coating layers found on a single structure are analysed as well as a range of differently coloured paints. Unique pigment types are identified in the mask samples on this building. A comparison of the layers of each pigment type shows a consistency in paint composition during the life of the building.

In Chapter 5 a new analytical technique, infrared micro-ATR spectral imaging, is applied to investigate the identity and spatial relationship of the mineral phases in the paint.

This technique made possible the identification of significant

differences in the Sub Jaguar Tomb wall sample from the previous building paint samples.

Chapter 6 compares the differences in pigment use across time periods and sample type at Copan. Then the final conclusions are draw from the data.

1.1 ARCHAEOLOGICAL BACKGROUND

The Maya are an ancient people numbering some millions that inhabit parts of Guatemala, Belize, Mexico, El Salvador and West Honduras, Figure 1.1. Their civilization began around 1600 BC, reached its zenith at about AD 800 and

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underwent decline and cultural change for some centuries until savagely subdued by Spanish conquest in the sixteenth century. At the height of their cultural development during the Classic period (AD600-800), they built large urban complexes within the Maya area, Figure 1.1.

These cities controlled large

populations and areas. Most were situated in strategic locations and hence could control not only local interactions but also trade routes. There is also evidence of complex political systems and interactions within their society16. Amongst their many achievements the Maya developed a written language, complex calendar and a mathematical system including the concept of zero.

The Maya decorated

their buildings with painted stucco, moulded masks, carving and elaborated murals, using a range of coloured pigments.

Copan is an important Maya centre on the southern periphery of the Maya Region, Figure 1.1, and was constructed over some 400 years during the reigns of some 16 successive rulers of the Copan dynasty17. This dynasty was founded by K'inich Yax K'uk' Mo' in AD 426 and ended with the demise of the 16th ruler in 822 AD, at the hands of a warring neighbor, Table 1.2.

Time periods in Mesoamerican archaeology are also related to the sequence of ceramic phases found at each site. Ceramic chronology is used as a rapid and inexpensive way to approximately date structures and floor levels in archaeological excavations, particularly where other dating techniques are unavailable. Table 1.2 shows the relationship between ceramic traditions mentioned in the text and the reigns of the Copan rulers. Two ceramic phases cover the period of construction of the Copan Principle Group, the earlier Acbi

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and the later Coner phase18. Both the ceramics and the architecture of this developmental period reflect the changing cultural influences on the Copan polity from both the local area and wider region, particularly the Maya centre of Tikal in the Peten and Teotuachan in Mexico. Dates (AD) of Reigns Ceramic Phase Rulers Ejar (AD900-1400) Postdynastic 16 Yax Pasaj Chan Yoaat 763-822 Coner 15 K'ak Yipyaj Chan K'awil 749-763 Coner 14 K'ak Joplaj Chan K'awil 738-749 Coner 13 Waxaklajun Ub'ah K'awil 12 Smoke Imix 11 Butz Chan 10 Moon Jaguar 9 Sak Lu?

695-738 628-695 578-628 553-578 551-553

Coner Coner (AD650-900) Acbi Acbi Acbi

8 Wil Ohl K'inich 7 B'alam Nehn 6 Muyal Jol?

532-551 524-532 c.510-524

Acbi Acbi Acbi

5 Yuku? 4 Ku Ix

c.500-510 c.480-500

Acbi Acbi

Structure 11

Structure 16

10L-11

10L-16

Northeast Court Structures 10L-21A 10L-21A 10L-22a

10L-22

Structure 26 Tombs 10L-18 (empty) 10L-26 1st 10L-26 2nd Esmeralda

10L-20 Chorcha

Scribes Galindo

Red Olive

Rosalila

3 Ya…?

c.470-480

Tan

Azul

Ante/Ani

Celeste

Aguila Toucan Loro

Marisha Maravilla

Acbi

2 K'inich Popal Hol

c.437-470

Acbi

Cobalto

1 K'inich Yax K'uk' Mo' Predynastic

426/27-437

Acbi (AD400-650) Bijac (AD50-400)

Urano

Chilan Margarita

Papagayo rededicated

Mascarones Papagayo

Clavel Yehal Hunal Cab

Sub-Jaguar

Margarita

Tartan Cominos Motmot Yax Hunal

Table 1.2 Chronological list of Copan rulers correlated with ceramic phases and building construction sequence. (After Sharer et al.17 page 152)

1.1.1 The Copan Valley The Copan site lies on a fertile floodplain of the Copan River which runs through a steep and narrow valley to the nearby Guatemalan border.

The valley is

restricted by the surrounding mountains but is linked to other regions and sites through mountain passes.

Today crops including maize, beans, tobacco and

cacao all grow well on the valley floor20. The geology of the region mainly comprises ancient volcanic deposits of rhyolitic ash-flow, tuffs, biotic tuffs and some basalts21. Limestone outcrops are also found and can be seen in the road

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This figure is not available online. Please consult the hardcopy thesis available from the QUT Library

Figure 1.1 Map of the Maya Area of showing the location of Copan and other major Maya centres16 (p21)

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cuttings entering the valley today. Small pockets of clay have been identified in the valley and at least two of these are used by local potters today20,

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. The

distinctive green stone used in Copan’s ceremonial building complex is a rhyolite tuff quarried from hill overlooking the Principal Group. Other imported raw materials such as obsidian (used for cutting blades) and jade (a precious material used in ceremonial activities) were sourced from outside the valley, in nearby Guatemala20.

Cinnabar was used as a pigment, in ceremonial contexts and

particularly in the painting of skeletal remains. Deposits of cinnabar have been found in the neighboring department of Santa Barbara, Honduras and in Guatemala23.

A source of the iron oxide pigment used in abundance on both the ceramics and buildings has not been identified in the valley, however a US geological survey in the 1950s by Roberts and Iving23 identified two main iron oxide deposits in Honduras. One at Mt Agalteca near Tegucigalpa is predominately magnetite with some hematite. The Mt Agalteca ore is hard but in weathering zones is a soft red earthy material which would be easier to collect. The second deposit, Aramecina, is near the Pacific coast on the slopes of Mt Cerro Colorad. Both sources are some distance from Copan but could easily have been traded from their localities. It is more likely that the bulk of the raw material used was found closer to Copan. Small-scale workings from the historic period were also identified across the Central American region and Honduras in particular. Iron ore boulders in soil are found in the neighboring department of Chiquimula, Guatemala and these are collected today for small-scale requirements.

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Thus, the Maya were possibly

utilizing material found closer to the Copan Valley for construction materials and pigments.

1.1.2 Development of the Principal Group of Buildings The ruins of Copan cover an area of 600x300 meters and consist of an elevated series of structures making up the royal complex at the southern end, the Acropolis, and a series of plazas and lesser structures to the north17, Figure 1.2. The Acropolis comprises two courts, the East and West Courts surrounded by groups of elevated structures believed to be temples, shrines and royal dwellings. The Copan River has eroded the eastern side of this complex exposing a huge vertical section that permits unique insight into the sequence building construction over some 400 years. This Acropolis construction history is quite complex with each layer built over previous structures. The result is that the latest structures sit at a considerable elevation above the original level of the floodplain above the Great Plaza to the north. Archaeological tunneling under and into the Acropolis revealed the earliest building levels and all those above them17,24,25. Construction styles and methods have varied throughout the 400 year construction period, external influences in style sitting along side local architectural designs.

At the basal level on the sterile river bottomland are found small scale cobble structures covered by extensive terraces and platforms all predating AD 40026. Above these are large earthen platforms with earth filled structures dating to Bijac/Acbi ceramic traditions ca AD 400. Archaeological evidence of post holes indicates that these buildings may have been protected by larger timber superstructures26,27. These earthen structures are built generally in the local styles

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and traditions of the Maya highlands from local materials without significant preparation, suggesting at this stage, that the centre was built by local inhabitants of the valley rather than the Maya themselves27. The surfaces of these well preserved earthen structures are coated with “a thin surface of red pigment mixed with clay”27.

This figure is not available online. Please consult the hardcopy thesis available from the QUT Library

Figure 1.2 The Principal Group of buildings Copan, Honduras. The samples come from the Clavel building under the northern edge of building 10L-16, building 10L-22 at the northern end of the East Court, the Ani structure below building 10L-20, Rosalila structure below building 10L-16 (yellow spots), Sub Jaguar Tomb below the steps north of building 10L-16 (blue spot). (Fash et al. 1998, page 11)28

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Around AD 426 a large-scale platform expansion ran from the Great Plaza to the southern limits of the site, covering these early platforms. This new platform has been given the working name Yune27. At this stage some of the buildings began to be replaced by masonry structures of styles and traditions resembling those

Figure 1.3 Copan’s Great Plaza looking south to the Acropolis. Photo S. Goodall

found in the Lowland Maya region (Peten) or in the Mexican city of Teotuachan. These changes coincide with the arrival of the first ruler in the Copan dynasty, K’inich Yax K’uk Mo’, and are accredited to his influence and that of his son. Isotopic studies of the bones found in the Hunal Tomb believed to be those of this first ruler point to the Tikal in the Peten region as his likely homeland, thus connecting him to the styles of that region29. These early masonry structures were raised in three main locations across the Principal Group setting a design plan and layout that was to be followed for the next 400 years. According to Sharer et al., “each building and location had meaning for the people who created and used

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it…(buildings) were rebuilt on the same location over time, the buildings became higher but kept the same function” 17 [p145]. There was a continuity of use with each phase of construction even with changing styles, construction techniques and materials. Fash et al.24 found masonry buildings at the base of Structure 26, built by the first ruler and his son. The earliest, Yax structure has the remains of a stucco panel on its back wall24. Floors were also filled and then covered in a thick layer of stucco, a practice that also extended to the Plaza surfaces. The masonry Hunal building was constructed in the area that was to become Structure 16 and is believed to be the house of the founder K’inich Yax K’uk Mo’. Fragments of stucco and paint found in the demolition debris of this building indicate that the interior was painted with decorative murals30. The tomb in this building is also believed to be that of the founder. During the reign of the second ruler from AD 437, this building was covered by the Yenhal building which was decorated with sun god masks painted in red, green and blue. To the northwest was the Clavel building, a masonry structure from this early period AD450-550 that was covered with stucco and red paint.

During the reigns of the third to sixth rulers further consolidation of the area was carried out with platforms raised and earthen structures replaced by masonry structures including residential buildings. Ruler 8 renovated the complex in two stages, extending the northern end of the Acropolis platform to cover the royal palaces then extending the platform to Structure 26 later in his reign. This later platform completely covered all previous constructions except the three major structures, re-establishing the Acropolis plan which was then followed for the next

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Figure 1.4 The Clavel building showing the painted wall surface and a later stucco floor in section on the left.

Figure 1.5 Wall paint and stucco on the Ani building. Multiple layers of paint are visible in some sections.

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250 years30. The predecessor of the East Court was formed with a series of new buildings on the eastern side. The Ante substructure was decorated with stucco masks and topped with the Ani structure. On the northeastern corner was located an earlier version of Structure 22 with mosaic corner masks.

The imposing Rosalila Temple also built around this time (cAD520) in the southwest corner of the East Court. This building was preserved with a thick coating of stucco before being buried and not partially destroyed as was the practice with other buildings31. Ruler 8 is most likely buried in the Sub Jaguar Tomb which is situated under the western side of the East Court.

Figure 1.6 A painted mask on side of the Rosalila building. The surface of the building was covered in a thick layer of stucco before burial. The samples for this study were taken from the red and green painted areas. 16

Rulers 9 and 10 carried out similar construction, probably only one or two buildings around the East Court and some Stelae. Ruler 11 filled in this court and covered some of the structures around it around AD600. Ruler 12 began the construction of the final version of the Acropolis in several stages. Sharer et al.17 suggest that the pace of construction over the final 200 years was much slower than previously, indicating a change in amount of labour and resources controlled by the rulers. During this time Rulers 12 -16 built new versions of Structures 26, 21, 22 and 22A. Ruler 16 built the final version of Structures 11, 16 and 18, the latter is believed to be his mortuary temple but the tomb was empty when discovered.

Figure 1.7 Structure 10L-22, on the northern side of the East Court. Photo S. Goodall The construction of the Copan’s Acropolis was thus carried out in a series of stages with the first 100-150 years seeing the majority of construction. This was a

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time of expansion and consolidation of the dynasty, when rulers appear stronger and able to call on considerable resources. Around AD600 a series of buildings were added and then the final versions of structures were completed during the final 200 years. During these last years after the death of the 13th ruler by the neighboring city of Quiguira less construction was carried out.

Figure 1.8 Section of Corner Masks on 10L-22 showing the residue of multiple layers of paint and stucco. Photo S. Goodall These rulers also created more carved stone stela with images of themselves and carried texts which linked the ruler to his ancestors. The buildings constructed throughout the dynastic period were used by the rulers to emphasise their connection to the cosmos and their control over it32. The size and imposing designs were intended to show both the ruling elite and the populace the power of the ruler.

Changing designs and techniques from the early earth structures,

masonry with stucco relief, to the later carved masonry structures all carried the symbols of power and control. How these changes reflected the changing power of the rulers and their interaction with the elite ruling class can only be surmised. 18

The collection of information from archaeological excavations, the interpretation of hieroglyphic texts and function of architectural remains17 provide a combination of information that allows the interpretation and formulation of hypothesis of these interactions. It allows some degree of understanding of the social and political structure that was in place during the Classic period Copan. In this study I have characterized the pigments and stuccos from architectural structures to determine if there are any changes in production techniques and materials used, over time and between groups of structures. In time as more samples are analysed it is hoped that this information will add to that already established and help to extend the knowledge of the Copan polity.

1.2 LITERATURE REVIEW

1.2.1 Ceramic analysis The physical and chemical investigation of ceramics has an important standing in the archaeological investigation of ancient peoples. In the words of Tite, the data obtained can be used to,

“Better understand the behaviour of people who produced, distributed, or used the pottery and, thus, achieve the final goal of such studies, which is not to describe microscale prehistoric activities, but to understand microscale social processes”33

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For this reason, ancient ceramics have been the focus of intense investigation for many years.

It many archaeological contexts they are the major surviving

artefact. Early investigations focus on the physical attributes of the individual pieces such as shape, decoration and functionality but in the early twentieth century more scientific methods were employed such chemical analysis and petrography studies34. Ethnographic comparisons35,36 and field trials have played a large role in the establishment of production procedures such as clay processing, pot forming and firing technology37-39. These early investigations relied heavily on the physical appearance of ceramics to group them: a practice which lead to misleading assumptions regarding the origins of some ceramics and in turn to a misunderstanding of social and political interactions. As instrumental methods of analysis developed and became more readily available these were applied to the investigation of ceramic samples.

Early studies in the American region focused primarily on the provenancing of ceramics. Using neutron activation analysis (NAA) to analyze the paste, limited success has been achieved in grouping similar styles of ceramics. NAA results seem to provide limited confirmation of production centers and groupings tend to identify with regional geology rather than local clay deposits40-45. Bishop et al.46 used NAA to examine the likely origin of the Copador polychrome ceramics found in the Copan region. Using trace elemental concentrations they concluded the materials were most probably produced in the Copan area. More specific provenancing was not possible. The use of mineralogical analysis, for example petrology, in some of the above studies has enhanced the separation of groups prior to statistical analysis and has reduced the amount of overlap and outliers in

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each group. This combining of chemical and mineralogical analysis has proved to be more successful.

ICP-AES and ICP-MS analysis have been predominately applied to European ceramics47-49 achieving some success in differentiating samples from different provenances as well as separating samples from different ages. Although a high degree of sensitivity is obtainable with these techniques they are completely destructive, time consuming and involve the use of aggressive chemicals in the sample preparation. The introduction of laser ablation ICP-MS has removed some of these problems while reducing accuracy. The increased spatial resolution, with the ability to examine small sample areas provides some advantage over other elemental techniques. Surface treatments in particular can be examined with less contamination from the main paste body. Neff50 found that provenance studies utilizing surface analysis agreed well with previous analysis using only paste. XRF provides similar elemental information.

The chemical results can be

analysed by statistical methods to establish groups, while matching stylistic determinates can identify where these were made at unique production centers51. Chemical analysis although providing broad scale information regarding the geological region of production, provides little information regarding clay processing and firing techniques.

Investigations utilizing SEM-EDX in combination with XRD obtained significant information regarding the provenance of the samples and aspects of material processing and firing technologies. The high spatial resolution of SEM-EDX enables the analysis of individual grains as small as 1-2 µm 52. In an analysis of

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both clay and inclusions by Wells52 they were able to match samples to specific areas of procurement in the valley of Malpaso, Mexico, confirming that the ceramics were locally made. Garcia-Heras53 matched chemically distinct groups to production centres and used minerals remaining post firing to determination four separate firing regimes and processes. SEM-EDX has also proved useful in the examination of black ceramics and black painted ceramics. These dark hues are usually the product of iron or iron and carbon based mixtures. These have been detected using the C/Si ratio in painted and unpainted sections of the surface54 or by a combination of SEM-EDX and Mossbauer spectroscopy55. Although in the latter case carbon was not successfully detected. When XRD analysis is also used, predictions of firing temperature and atmosphere can be made from the remaining mineralogy in the samples56. A reducing atmosphere is required to obtain the black/grey colouration in the paste and pigments.

1.2.2 Ceramic surface decorations The materials used to decorate the surfaces of ceramics differ from those used in the main body (paste) of the vessel, consisting of mineral pigments, organic liquids, carbon and slips of different clay minerals. These materials form very thin layers on the surface of the ceramics and are difficult to analyse separately from the vessel body. Surface decoration can be applied in a number of ways, the addition of a coloured slip and paint prior to firing, the addition of coatings and paint post firing, and incising through the outer slip to expose the colour of the inner paste. It should be noted that the use of glazes was not developed by the Maya and hence glaze analysis has not been reviewed here. The raw materials used for slips and paints were not available in many locations and were more

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likely to be traded across larger distances50 and because of this movement these materials have the capacity to tell us more about inter-regional interactions than the ceramics pastes. Coatings and pigments were finely ground uniform materials and their analysis suffers less from the contamination of natural and added inclusions. Given this advantage it is interesting that few studies have focused on this area. Sample preparation procedures for techniques such as NAA, ICP and XRF make it difficult to achieve the removal and separation of the surface material without including contamination from the underlying paste.

In a study

by Cecil and Neff57, the analysis of paints and slips when compared to results of the paste analysis showed similarities between groupings in both cases. However, results form the surface coatings provided further information regarding differences in paint mixtures. The authors used this to postulate on the production of different quality wares for different socio-economic groups within the local area. Salamanca et al.58 carried out an external beam PIXE analysis of surface pigments on early Mexican ceramics. Although this is a surface technique it is expensive and limited, requiring specialized facilities. Portable micro-XRF has been applied with some success in identifying the general paste composition of ceramics59. However, the full value of the results was restricted by the limited elemental range of this technique.

More readily available surface techniques such as SEM and vibrational spectroscopy can provide comprehensive results of external coating while avoiding contamination from the body. The combination of SEM and XRD has proven successful in identifying surface material. This combination of elemental and mineralogical composition has enabled the differentiation of similar red

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coatings60. When combined with thermal analysis studies, the differentiation of firing conditions, coating thickness and degree of vitrification is also possible61. Micro techniques such as SEM and micro-FTIR when applied to sample crosssections can also facilitate the characterization of individual paint layers62. This combination of SEM and FTIR causes little damage to the sample if the preparative SEM coating can be avoided and the cross-sections can be kept for later analysis.

Over the last ten years the use of vibrational spectroscopic

techniques has moved from a purely supportive role to the primary method of analysis providing information on firing regimes63,64, homogeneity of materials and production practices. With FTIR it is possible to detect materials in lower concentrations than with XRD65. Micro-Raman spectroscopy adds still further information with the characterization of minerals that have not decomposed during firing and subsequently point to firing temperature66. Barilo et al.67 in a study of pottery from Sicily, were able to identify inclusions as well as determine paint composition and hence identify changing paint mixtures through time.

Raman spectroscopy has been shown to be useful for identifying mineral paints on ceramic samples. Clark and Curri68 showed how useful the technique was in differentiating the different minerals used to create red pigments as well as yellow pigments. Similarly Zuo et al.69 identified the pigments used to paint ancient Chinese ceramics including the very early use of anatase as a white pigment. In a more recent study Zuo et al.70 used Raman spectroscopy to identify a range of pigments used on painted pottery figurines. In this instance XRD was used to confirm the characterization of some of the pigments including a synthesized barium copper silicate purple pigment. Bordignon et al.71 used micro-Raman

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spectroscopy to identify a range of pigments used on painted terracotta samples and Akyuz et al.72 used FTIR and micro-Raman spectroscopy in the identification of the pigments used on decorated ceramics. Raman was shown to be effective in identifying paste components particularly minerals used for the determination of firing temperatures73. In each of the studies Raman spectroscopy has been show to be highly successful in the identification of carbon-based paints and pastes. Carbon is difficult to detect by most other techniques but is a good Raman scatterer with a distinctive spectrum.

Van der Weerd et al.74 compared the

effectiveness of ATR-FTIR and micro-Raman spectroscopy in identifying the iron/carbon based paints. The spectral range available with ATR-FTIR is limited and excludes much of the region of interest for iron oxide minerals,