In the present work we report the systematic studies of Maya blue paint using High Resolution Electron Microscopy, Electron Energy Loss, Scanning Electron Microscopy and Related Techniques.

A model to explain the well known properties of the paint such as: acid resistance is piesented

This report to the congress “Materials issues in Art and Archaeology IV Cancun 1994”, deals with the materials that intervene in the construction of our traditionalbuildings, basically of those of the viceregal epoch. It is to clarify the term viceregalbecause most of you are familiarized with the noun “colonial” that is usually applied, inappropriately, to that epoch and to its architecture, word derived of the used term, now used accurately, in the architecture and in the culture of the north neighbour countries, due to the circumstances of their historic-political development. The culture of Mexico is of crossbreeding. What Mexico is today was never a“ colony ”of anybody, it was called Viceroyalty of New Spain until it became an independent nation. And although you have noticed I am not an expert in the English Language, so I apologize, it seems to me that the equivalent terms are Viceregal Period and Viceregal Architecture. We can now start with the introduction.

The most direct ways in which materials science has contributed to material culture Studies are dating, provenance and conservation. For material culture studies materials science is unique in evaluating material properties which leads to inferences about performanceand characterizing the internal structure which leads to inferences about processing. As a guide towards planning for the future, we have considered the essential nature of objects and devices and what this may suggest for prospective studies. Artifacts are created as purposeful objects; the essential nature of objects is related to their purpose and theoperational principles of how they achieve that purpose. Designers are constrained by these essences of objects and devices; looking at the way in which design tools are used cantell us about human relationships with purpose, operational principle and design. Objectshave both utilitarian and signifying operational principles and normal configurations as well as aesthetic sensibilities. In addition to their purposeful content, objects have non-purposeful unconscious attributes that are related to their cultural origins. The essential nature of objects must always be in the forefront of material culture studies of purposeful artifacts.

In recent years there has been considerable progress in archaological excavation in various parts of the world. However, and especially in developing countries, much of the newlyexcavated and culturally significant antiquities deteriorates, often precipitously, irreversibly and unexpectedly, soon after excavation is completed. By analyzing opinions of specialists concerned with these deteriorations it is concluded that the discipline of practical conservation is structured in such a way that it can provide, at least for the present, only limited care for much of the recently excavated cultural heritage. This occurs to a significant degree because the discipline of archceologicalf ield conservation (which deals with the preservation of archaological sites and monuments situatedon these sites) is still in its infancy. The development of the discipline of field conservation can be considerably enhanced by efforts of environmental scientists because most of the deterioration is due to some adverse impact of the environment. This task is now the goal of the subdiscipline of environmental archaological science, often abbreviated asecoarchaeometry, which deals with the physics, geology and chemistry (be it biological, inorganic, organic or physical) of the deterioration of our cultural heritage. Eco-archwuometry is in a position to develop cost-effective shortcuts to the efficient salvage of deteriorating antiquities. Examples of eco-archwometric studies in Egypt, which already produced constructive results, are provided.

Molecular preservation in the archaeological record has been recognized and documented inseveral cases. The association of protein, lipid and DNA remnants on artifacts requires anew level of care in the excavation and conservation of materials. The removal of blood from a series of experimental tools made of quartzite and obsidian is shown by a simple water washing procedure. Attempts at stabilizing the blood with time and temperature did little to alter its removal. It is suggested that the normal procedures utilized onsite andin postexcavation treatment can be detrimental to the recovery of information at the molecular level.

The Central Library murals were finished in 1952. They cover the outside of the building, totalling a surface of over four thousand square meters. Their design conveys the historyof Mexican culture through visual symbols. They were constructed by assembling one meter square, metal framed panels with cement mortar in which naturally colored stones gathered throughout Mexico, were inlaid, as well as fragments of man-made blue glass.

Environmental agents have severely damaged the stones, especially the green ones; the iron and steel support elements show exfoliative corrosion; as some panels have warped, the stones have been projected out of their seats, many of them falling down.

Research and data collection are under way. They will eventually produce an accurate diagnosis which will enable the technical committee to establish the basis for the conservation project.

Efforts to preserve this masterpiece are fully justified, be it from the point of view ofits artistic value, its importance within the framework of plastic art applied to architecture or for its worldwide renown.

Recently many US Federal Cultural Agencies have reevaluated the preservation responsibilities required by any comprehensive program to preserve research collections. There appears to be consensus about core responsibilities with specific action steps and targeted goals, that can be achieved by addressing seven key responsibilities:

1. preservation administration;

2. reformatting/duplication;

3. environmental control (storage & exhibits, disaster & integrated pest management);

4. collections maintenance (handling & housing);

5. conservation treatment;

6. conservation research;

7. preservation education.

In this paper we describe the analysis of ceramic artifacts with a new type of three dimensional x-ray microscopy which can have micron spatial resolution. The x-ray microscopy is based on a microtomographic technique which reconstructs the three dimensional structure of millimeter sized specimens from high resolution digital radiographs of the specimenstaken from several hundred different view angles. When the high resolution radiographs are taken with a monoenergetic x-ray beam from a synchrotron source, each volume element (voxel) in the reconstructed data set is quantitatively the x-ray opacity of the equivalentvolume in the specimen. Typical reconstructed data sets contain more than 106 voxels and are rendered using computer visualization techniques. Specimens can be nondestructively analyzed so long as they are small enough to fit into the area of the x-ray beam imaged by the detector. We have applied x-ray microtomographic analysis both to a shardspecimen taken from a Jun bowl and to a modern ash glaze and show examples of the structure of glazes on these ceramics; interfaces between the glaze and underlying ceramic bodies; and the porosity of ceramic bodies.

During the past four and a half years this group has been involved in a programme of development and testing of methods for the study of organic residues in archaeological ceramics. The analytical approach used is based on solvent extraction of powdered potsherds to release lipids absorbed in the ceramic fabric, with gas chromatography (GC) and combined gas chromatography/mass spectrometry (GC/MS) being used to characterise andquantify the individual components of the residues. Our most recent work has focused on an assemblage of more than sixty reconstructed vessels of Late Saxon/early medievaldate for which full or partial profiles were available. Analysis of potsherds sampled from different parts of these vessels, e.g. rim, body and base, have shown that different concentrations of lipid can exist in different parts of a vessel. This observation has important consequences for the sampling of potsherds for organic residue analysis. More significantly, these results indicate that the variation in the concentration of lipid in different parts of a vessel may reflect the way in which the vessel was used in antiquity. This paper discusses the results obtained from preliminary laboratory simulation experiments which have been carried out using replica vessels to provide supporting evidence for this potentially new approach to interpreting vessel use. Consideration will also be given to the possibility of using potsherds from these replica vessels in laboratory experiments aimed at simulating the decay of absorbed lipids during burial.

Infrared microspectroscopy is useful for characterizing media in very small cross sectionsamples using both transmission and reflection modes of analysis. In a direct comparison of the two methods, reflection techniques produce poorer quality spectra than the transmission methods. However, many of the problems of reflection spectra can be mitigated by looking at the variations that occur between spectra obtained under similar conditions. An excellent venue for such a study is the use of infrared mapping. Mapping studies compare the intensities of absorption bands versus their location in the sample to generate an image of compositional differences in a region. Several examples are shown in this paper for the application of infrared mapping to the determination of components in thin section and cross section samples. The technique for infrared mapping was also used as a direct, nondestructive method for the characterization of colorants and binders on a small painted manuscript leaf. Compared to the paint cross sections, four relatively large areas (1 cm2) were mapped with the infrared microscope then joined together using a mosaic technique.

The Sicán Archaeological Project (under the direction of I. Shimada) is centred inthe Batán Grande region of the La Leche Valley in northern Peru. One of the major topics of investigation is Middle Sicán (A.D. 900-1100) metallurgy within its broader cultural and environmental contexts. Results of the investigation of copper-arsenic alloy production have been published [1,2]. Two major Middle Siádn elite tombs excavated during the 1991-2 season yielded large quantities of diverse preciousmetal and arsenical copper objects. In particular, the twelve-metre deep shafttomb at thenorth base of the pyramidal temple of Huaca Loro contained some 1.2 tons of grave goods with about 75% of them in weight being metal [3-6]. Samples of precious metal artifacts are being studied using metallographic techniques and electron probe microanalysis (EPMA). At this stage of the investigation, over 40 samples of gold-silver-copper alloy, sheet-metal objects have been analyzed using over 200 EPMA data points on depletiongilded surfaces and multiphase compositions of the centres. The metallographic structuresof the objects are extensively coldworked, but variable in composition including single and multiphase alloys. Surface enrichment is characteristically on the order of 10-20 microns, but several examples are observed with greater thickness. Depletion gilding is documented even in some of the most corroded metal samples. Object types studied include crowns, headdresses, “feathers”, hanging ornaments, wire and foil as well as several exceptional objects. Additional analyses are presented for a gold-silver-copper alloy ingot and standardized copper-arsenic alloy objects called naipes. Due to the archaeological significance of this assemblage of artifacts as well as the quantity, there are several research groups working co-operatively, using different analytical techniques. Compositional results are used to explore issues such as selection of precious metal alloys by surface colour and mechanical properties.

872 metal rubbings, each weighing about 10 micrograms, were taken from 364 gold objects from an unlooted Middle Sicin (ca. 1000 A.D.) Peruvian burial site and the gold, silver, and copper contents were determined by neutron activation analysis. Almost all objects have contents that are in the range: 35-65% gold, 25-45% silver, and 10-30% copper. Objects of similar style were more uniform in content; for example, the 28 bangles and 90 feathers from the main headdress have gold contents that range only from 46-56% and 37-45%, respectively. Some objects have contents markedly different from the rest of the objects; ear-spools, for example, have very low copper (1-6%) and high gold (56-75%). A high degree of control of the alloy content is evident, with each alloy mixture probably being chosen to have desired color and mechanical properties. The data indicate that very consistent 1.0-1.1 mixtures of gold:silver were used for 136 of the 142 feathers whereas gold:silver mixtures closer to 1.3-1.9 were used for most of the 96 bangles.

The scanning proton microprobe and electron microprobe/microscope are used to characterise overglaze painting on 18th and 19th century Japanese porcelain. The first objective was to distinguish between two apparently different types of gold painting in terms of particle size, composition and application. The multi-element X-ray mapping and analysis using proton-induced X-ray emission and the depth profiling possible using Rutherford back-scattering on the scanning proton probe make simplify the analysis of the structure of complex decorative schemes involving several pigments. First results and future developments are presented.

The use of fiber optics reflectance spectroscopy (FORS) in the near IR is proposed as a simple, fast, and totally non destructive method to detect alteration products. Indeed gypsum and calcium oxalates show very distinctive absorption bands in the near IR due to theovertones and/or combination bands of the 0-H and C-O vibrational modes. The present communication reports the results obtained on laboratory samples and on actual artworks.

Moreover it will be stressed that the FORS procedure, being quite safe for artworks, allows to record a large number of spectra in order to give the possibility of building up a map of the alterations and to perform a statistical analysis of the data.

Current techniques for removal of varnish (lacquer) and other organic protective coatingsfrom paintings involve contact with the surface. This contact can remove pigment, or alter the shape and location of paint on the canvas surface. A thermal energy atomic oxygen plasma, developed to simulate the space environment in low Earth orbit, easily removes these organic materials. Uniform removal of organic protective coatings from the surfaces ofpaintings is accomplished through chemical reaction. Atomic oxygen will not react with oxides so that most paint pigments will not be affected by the reaction. For paintings containing organic pigments, the exposure can be carefully timed so that the removal stops just short of the pigment. Color samples of Alizarin Crimson, Sap Green, and Zinc White coated with Damar lacquer were exposed to atomic oxygen. The lacquer was easily removed fromall of the samples. Additionally, no noticeable change in appearance was observed after the lacquer was reapplied. The same observations were made on a painted canvas test sampleobtained from the Cleveland Museum of Art. Scanning electron microscope photographs showed a slight microscopic texturing of the vehicle after exposure. However, there was no removal or disturbance of the paint pigment on the surface. It appears that noncontact cleaning using atomic oxygen may provide a viable alternative to other cleaning techniques. Itis especially attractive in cases where the organic protective surface cannot be acceptably or safely removed by conventional techniques.

We have investigated successfully the hydrogen concentration of samples of modern roof tile from the Shanghai Roof Tile and Brick Works. The intent of the investigation is to determine the applicability of ion beam analysis in the form of Forward Recoil Energy Spectrometry (FRES) to the analysis of the hydrogen content of the samples. We can measure hydrogen introduced during firing in modern bricks that we know were fired using hydrogen reduction. Completion of this feasilibity test allows us to propose sampling and testing ancient Chinese ceramics and to use the modern roof tile samples as a baseline for comparison.

Scanning electron microscopy with simultaneous energy dispersive x-ray analysis was used to characterize microdots to assess their suitability for the identification and trackingof artifacts. They were found comparable to commercial state-of-theart microfilm and microfiche which are known to be durable for about 20 years without postprocessing treatment to stabilize them.

In the area of Greek and Roman ceramics, it is now generally agreed that the forms of various fine wares are derived from metalwork. There is less harmony among scholars, however, regarding the surface colours of different fabrics, some maintaining that the colours we have were simply predicated by what it was possible to achieve in clay, while others invoke the hierarchy of materials and argue that precious metals, gold and silver underlie red, orange and black and grey colour schemes on Greek and Roman ceramics. On such a view, white would relate to alabaster or ivory, green and yellow to bronze, and clear glass to rock crystal. This paper will explore some of the issues involved, and present some newdata relating to Greco-Roman ceramics that seem to evoke various kinds of marble, including porphyry.

Venetian glass has long been admired for its quality workmanship and overall visual appearance. Beginning in the 17th century, Venetian glassmakers at Murano made a glass, in imitation of naturally occurring opal, called “girasole”. The historical and cultural background of this unique glass was examined using information from Venetian archival sources. An assortment of Muranese recipes for girasole spanning almost 150 years provided additional data regarding the raw materials used by Muranese glassmakers in the 17th-19th centuries. These recipes also allowed us to evaluate the continuing evolution of the Venetian glass industry.

A sample of Venetian girasole glass was analyzed using XRD, ICP-AES, SEM, and TEM. The compositional information obtained from these analytical techniques was correlated to the various recipes for girasole glass as well as to glass properties that would have been behaviorally significant to a glassmaker at Murano. Finally, the analyses indicate that small crystallites of a lead-arsenate compound were nucleated and grown in the glass to achieve the desired visual effects. These crystallites cause Rayleigh scattering of the light, thereby producing Tyndall blue colors.

Many ancient Chinese bronze mirrors have survived with their original surface decorationsintact, particularly those with “glassy” black surface coatings. The microstructures and compositions of cross-sectional samples from ancient mirrors have been analyzed with optical and electron microscopy and synchrotron x-ray fluorescence. The core has a two-phase metal structure while the surface shows evidence of selective dissolution of copper from the α (Curich) phase. The ci phase regions are replaced pseudomorphically by a mineral product with the δ (Sn-rich) phase remaining metallic. A fundamental study of the electrochemistry of the copper-tin system has given information on theconditions under which selective dissolution of copper takes place. Electrochemical polarization has been used to drive the copper dealloying process in cast high-tin bronze. Theresulting microstructure is similar to the dealloyed microstructure observed in the ancient samples.