The use of a particle accelerator to measure the 14C content of carbon-containing materials is briefly described. The application of the method to the determination of the age of some artistic artifacts is discussed.

Historical archaeologists investigating early American production and trade must work with the written record as well as the evidence from controlled excavation. Both kinds of data have their place in the inquiry, yet the details they furnish are not necessarily congruent or applicable to the solution of all historical questions. To illustrate, artifacts were not always manufactured in the places where they are found, but in order to resolve this uncertainty accurately and directly, the origins of excavated materials must often be determined by means that are independent of historic documentation. If sources can be shown to be distant, then despite any similarity to items of known local manufacture or written evidence suggesting otherwise, long-range exchange structures must have been present. The interpretation of archaeological and historical data can then be guided by more informed judgment.

The principles of Environmental Scanning Electron Microscopy (E-SEM) are explained and discussed. The performance of the E-SEM compares favorably with the performance of traditional SEM instruments. This new technology has significant advantages in art conservation and archaeology. In this paper we describe several pilot studies which explored potential uses of the E-SEM. Electron micrographs recorded from moist, outgassing, and difficult to coat samples are presented, together with X-ray spectra recorded from uncoated samples of electrically nonconductive materials.

Dynamic studies allow the observation of microscopical changes of materials over time as various factors alter an object. Using this methodology, processes important in art conservation and archaeology such as the wetting and drying of consolidated and unconsolidated building materials or the corrosion of metals from air pollutants can be studied in situ and in tempora. The development of the Environmental Scanning Electron Microscope has made it possible to videotape these dynamic processes at nearly the same resolution limits as traditional SEM technologies without elaborate sample preparation. Experiments examining salt crystallization, shrinkage in adobe, and lead corrosion illustrate the value and applicability of the new E-SEM technology.

Tracing artifacts to ore sources is different from assigning ore samples to time epochs. Until now, archaeometrists working with lead isotopes have used the ratio methods developed by geochronologists. For provenance studies, however, the use of composition data (the fraction of each of the four isotopes) leads to fewer arbitrary choices, two standard types of plots (labelled ternary and canonical variable), and a consistent method of discriminant analysis for separating groups of samples from different sources.

Industrial computed tomography was used to study eight Chinese bronzes from the collection of the Cincinnati Art Museum. With industrial CT two different types of images can be formed, the digital radiograph (DR) which produces a twodimensional image of the object and computed tomography (CT) which takes a crosssectional slice. A further advancement discussed is the use of General Electric's Digital Replica™ method to create a three-dimensional reconstruction of the object which enables one to view interior surfaces and to dissect joins. The paper discusses the numerous advantages of the industrial CT over conventional radiography.

Recent advances in x-ray imaging and image processing are providing new options for the nondestructive physical evaluation of archaeological artifacts and works of art. Traditional film-based methods have played an important role in this field for many decades1, but digital modes developed for medical and industrial applications have been gaining ground2 and can be expected to become more important as they become more accessible and less expensive. Modes such as digital radiography (DR) and computed tomography (CT) have many advantages in terms of information content, quantitative analysis options, and image display options (including some that make image publication easier). CT, in particular, provides structural information which cannot be obtained through any other nondestructive means. From a technical point of view, the only real drawback to digital methods has been spatial resolution that hasn't compared favorably with the best available from film. That situation is changing3.

The objective here is to discuss a few of the important characteristics peculiar to digital images, to show examples of how high-resolution digital images can provide important structural information, and to illustrate useful types of image processing. The use of experimental CT and DR systems, with spatial resolution as fine as 50 microns, is illustrated in studies of three objects: an ancient terracotta sculpture, a Japanese assembledwoodblock sculpture (ca. 17th century), and an oil painting on canvas (ca. 18th century).

Crown ethers, cryptands, polyphenols, and several other reagents are known to have high specificity for various cationic species. These reagents have great potential for application in general conservation problems of selective cleaning, desalination, stain removal and reversal of treatments in conservation. They are remarkably more effective in metal ion complexation than the more common chelates (usually only EDTA is used for conservation applications) which are used generally with little regard for selectivity.

The advantages of a selective reagent are both its minimal effect on other species and its maximal cost-effectiveness. Most of the macrocyclic chelates are noutral specion that are lipophilic and solubilize metal ions (of the correct size) in non-aqueous media as well as water. Therefore, polar organic solvents may be used for water-sensitive treatments.

Research has been designed to assess the use of cationselective materials both in the laboratory and in situ. The potential of these compounds to expand the range and the safe execution of existing and new conservation treatments is excellent.

Paint layers on a stretched canvas or solid support present complicated behavior and failure patterns. The cracks, cups, blisters, and sagging commonly found in paintings give ample evidence of the detrimental effects of environmental changes on a composite of mechanically dissimilar materials. Under variations in stress caused by environmental conditions, the materials are inelastic and non-linear individually and collectively are anisotropic. The authors have conducted extensive biaxial tests on dozens of painting samples under variable stress, strain, relative humidity, and temperature [1,2,3,4].

The effect of titanium white, zinc white and lead white on the drying properties of poppy, walnut and linseed oil are analyzed by differential scanning calorimetry (DSC). All of the fresh films undergo complex thermal transitions between -100 and O°C. For some of the dried films subambient transitions that resemble glass transitions occur at about -30 O°C. After exposure to certain solvents, these sub-ambient transitions disappear or are reduced significantly. It is suggested that samples with diminished sub-ambient transitions become more brittle as a result of the loss of materials that act as plasticizers.

Much of the damage found in cultural and artistic objects is not chemical in nature but results from mechanical responses to stimuli such as changes in temperature, relative humidity, impact, and vibration. Analytical tools of engineering mechanics are available that allow us both to diagnose existing problems as well as to predict the effects of future potential hazardous conditions for many objects. A systematic approach of applying engineering principles to cultural objects requires two fundamental steps: 1, determining the mechanical properties of the constitutive material found in objects, and 2, developing analytical procedures that determine the overall effect of the individual material responses to various stimuli on the object as a whole. The individual material properties are typically defined as the yield and ultimate strengths, the elastic modulus, and the strains to yield and failure.

For the vast proportion of cultural objects, the materials are organic, and their mechanical properties are dramatically altered by environmental factors such as changes in temperature and relative humidity.

One of the most successful analytical techniques is Finite Element Analysis (FEA) using the digital computer. This method will allow one to numerically model an object, to mathematically induce environmental changes as well as determine the mechanical effects of these changes on the object modeled.

We have analyzed single and multiple layer paint samples to evaluate 3 MeV external beam proton induced X-ray emission (PIXE) for elemental analysis of inorganic pigments. The results are compared to those from energy dispersive electron microprobe analysis and Rutherford Backscattering Spectrometry (RBS). The advantage of PIXE is that the protons' penetration depth of 100 microns is more than 25 times greater than that of 20 keV electrons and 10 times greater than 3 MeV alpha particles, thus allowing analysis of relatively thick samples of up to 100 microns. The proton beam is passed into the atmosphere (external to the vacuum system) through a thin polymer film, and the beam area on target is 1 mmz. Electron microprobe and RBS require vacuum compatible samples; therefore, the pigments were painted on silicon wafers. Calibration was obtained from metallic thin-film samples of known thickness. The cross calibration of the three analytical techniques allowed evaluation of external PIXE analysis of paint films. We suggest that this nondestructive method is suitable for elemental analysis of drawings and paintings provided that further studies indicate no long term damage is caused.

A wide variety of natural resins, waxes, gums, drying oils and proteinaceous materials used on paintings are photoluminescent. The photoluminescence spectra of these materials are reported and discussed. The application of this technique towards the identification of these materials is considered. Both bulk materials and films prepared from selected bulk materials were studied and a comparison is made between the bulk and film samples. Temperature and excitation wavelength studies are reported and discussed for several of the samples.

The red/near-infrared emission spectra of alizarin (1,2-dihydroxyanthraquinonone), the potassium salt of alizarin and the aluminum and zinc complexes of alizarin in the solid state are reported. The emission is assigned to an alizarin localized transition from an in-plane nonbonding orbital delocalized over the anthraquinone rings to a predominantly π* C=O acceptor orbital (nπ* ligand localized excited state). The cobalt, nickel and copper complexes do not emit from their nπ* excited state. In these complexes, metal centered d-d excited states which lie lower in energy than the ligand localized state effectively deactivate the luminescence.

In 1984, archaeologists discovered an important group of mural paintings at the site of Cacaxtla, Mexico. Research has been undertaken to analyze the Prehispanic pigments and the painting techniques employed in these paintings. The present work is focused on the use of colors in these paintings by means of optical microscopy (OM) and transmission electron microscopy (TEM). The stratigraphic structure of painting layers support the presence of an organic binding media. In addition, Maya blue is for the first time described physically by TEM.

During conservation, The Detroit Institute of Arts' late Gothic carved wooden sculpture, Madonna and Child, was found to have extensive, though fragmentary, remains of the original polychromy and at least four subsequent “restoration” overpaints. The materials present in the original and overpaintings were probed by polarizing microscopic and X-ray diffraction analyses of individual paint specimens, and scanning electron microscopic/energydispersive X-ray analyses of cross sections prepared using an ultramicrotome. Several sections were also studied using ultraviolet fluorescence microscopic staining techniques to determine the nature of the media used.

The pigments identified include azurite, lead white, calcite, vermilion, red lead, hematite, red lakes and glazes, smalt and Prussian blue. Gold and silver metal leafs were also detected. The deteriorated remains of the late Gothic pressed brocade technique, and the use of “bronze” paint to approximate genuine gold leaf on a later addition to the sculpture, are also discussed.

An overview on the causes and methods of treatment of stone deterioration is presented. The reasons for and prejudices against epoxy resins for stone consolidaton are described in terms of achieving deep penetration, improvement in mechanical strength and good water repellancy without the inhibition of water vapor transmission. Early work which failed to understand the nature of epoxy curing in solution is outlined, and more recent research, where this problem has been solved, is discussed.

The present paper reports investigations on the application of surfactants in the stone conservation. It is found that alkyl ammonium chlorides reduce the hygric dilatation of clay-rich sandstones to half of the original value. Polysiloxane films can be tightly bound to clay mineral basal planes using aminoalkyl silane as primer. The water uptake as well as the hygric swelling are markedly reduced. Well defined mixtures of ethanolic alkyl silane and aqueous aminoalkyl silane solutions form stable microemulsions. They can be used as commercial conservative products which are compatable with the environment.

The use of commercially available chemical consolidants (hexamethylene diisocyanate (HDI) - derived polymers and silane esters) has been shown to increase the compressive strength of adobe and other natural building materials. Laboratory and field testing of chemically-treated adobe and sand-clay mixtures have also revealed an enhanced resistance to disintegration by water.

In HDI-treated materials this resistance to disintegration is attained without a significant loss of porosity. Because porosity is not lost and the adobe can still transmit water, the uptake of water by capillary rise is less destructive than for an adobe whose surface is sealed against moisture penetration.

B72 acrylic resin/methyltrimethoxysilane (YMTMOS) mixtures are frequently employed as consolidants for deteriorated limestones, sandstones and marbles- The addition of B72 to MTMOS imparts adhesive properties to the consolidant but it is not known to what degree the B72 affects the reactions which MTMOS must undergo to form a solid polymer network. This paper examines the following chemical, physical, and mechanical properties in order to better understand B72/MTMOS systems: 1. viscosity 2. vapor pressure 3. reaction mechanism and kinetics 4. chemical nature of polymer solids 5. rupture moduli of polymer solids and 6. rupture moduli of stone/consolidant composites.