Modem rubber is a nightmarish material in a museum collection because it is highly susceptible to oxidation, and will slowly crystallize at room temperature, the combination of which can make the rubber inelastic after only a few decades. Recent studies by the author have shown that the rubber in modem spacesuits can be preserved against oxidation by cold storage, but only at the cost of considerably accelerating crystallization.

Natural rubber from ethnographic artifacts, produced by less consistent and less documented technology (as well as from different botanical sources), presents similar problems. A rubber sample from a Mexican artifact, for example, was found to be both highly oxidized and highly crystalline. It also appeared to have been filled with an inorganic material and may be crosslinked, offering striking similarities between its physical and chemical properties and those of the degraded modem rubber found in the spacesuits.

This paper discusses the results of the present research on crystallization/decrystallization of rubber artifacts, and the effects of storage environments on their degradation. These results are then applied to the problem of preserving the chemical and physical integrity of both older and modem rubber collections.

There are very few quantitative tests suitable for measuring the degradation of historic wools and silks. Most tests are qualitative and results are confounded by variations in fiber diameter. The ninhydrin test, in which ninhydrin (triketohydrinene hydrate) reacts with primary amino groups and produces Ruhemann's purple, is a well known test for amino acids in solution. The test has been modified by researchers in order to give a quantitative measure of primary amino groups in wool and silk fibers. The primary amino group content of new wool is compared with wool degraded by moist heat and several archaeological wools. Some of the advantages of the ninhydrin tests include 1) an analytical procedure for quantitative work 2) small sample size and 3) equipment commonly available in an analytical laboratory. One limitation of the test is the fact that ninhydrin reacts not only with (α + ɛ) amino groups but also with ammonia nitrogen and other free amines. In addition, archaeological and historic protein fibers are often contaminated with soil residues which are difficult to remove and will influence tests results.

This paper discusses the kinetics of aging and its implications for the evaluation of changes in the aging process, especially as applied to accelerated aging. The problem of comparing accelerated aging conditions is shown to be separate from that of evaluating changes occurring under one specific set of conditions. Thus tests and measurements that can be used to evaluate the results of a specific accelerated aging experiment are not necessarily valid for use in determining whether two sets of aging conditions are comparable. This distinction is crucial in trying to determine whether a set of aging conditions is comparable to, or accurately simulates, natural aging. The criteria for comparing two sets of aging conditions are defined, and applied to the problem of evaluating accelerated aging conditions. Data from the analysis of individual reaction products of artificially aged paper samples are used to determine the effects of temperature and relative humidity (RH) on the rates of individual reactions. Changes in the distribution of reaction products are used as indicators of changes in the aging process. The aging process of cellulose under the conditions studied (60–90°C, 30–80% RH) is shown to be RH dependent, but relatively temperature independent. Thus raising the temperature at constant RH speeds up the aging process without significantly altering it. If the RH is changed, then the aging process is altered and equivalent states of aging cannot be reached. Accelerated aging should be conducted at the same relative humidity as the conditions to which the results are to be applied. The data also indicate that lowering the relative humidity from 50% to 30% slows the rate of hydrolysis by a factor of three to five times.

Characterization of paper provides information vital to the preventive care and conservation of vast collections of paper-based materials in museums, libraries, archives and research repositories. Tracing papers, a relatively cheap material used abundantly by folk artists and architects, pose particular problems because of reactivity and instability inherent in their compositions and structures. Previous research published in MRS investigated the aging properties and the impact of conservation treatment on natural, prepared, vellum, and imitation vegetable parchment tracing papers [1, 2]. An additional group, that of genuine vegetable parchment papers, needs particular evaluation with respect to other tracing papers, since they are made by controversial production methods which while considered to be economically advantageous, are environmentally questionable. This technical study characterized three types of genuine vegetable parchment papers, assessing their relative degree of deterioration after aging and their reactivity to solvents commonly used with tracing papers to remove mounts and repairs. The parchment papers were compared optically (fiber, surface, and cross-section morphology; colorimetric, opacity, and gloss properties), chemically (FT-IR, SEM/EDS, and pH), and mechanically (tensile measurements) to provide baseline information on aging properties important to preventive care storage, and relative reactivity important to conservation treatment protocols. The effects of solvents used for conservation treatments (deionized water, ethanol, acetone, toluene, and ammonium hydroxide) were evaluated by comparing relative degrees of reaction (absorption).

The structural degradation effects of temperature (T) and relative humidity (RH) are important considerations in the setting and maintaining of museum environments. An approach to determining the acceptable values for this environment would be useful if a general model could be developed from simple physical (mechanical) measurements. In this paper, a general model is developed in which the mechanical behavior of materials composing museum objects can be described using the easily determined parameters, stress development (force), environmental conditions and dimensional change.

One of the known contributors to the physical failure of coating or adhesive applications is the shrinkage stress which develops as a solid film is formed from a solution, dispersion, or reactive mixture. As a first examination of the magnitude of such shrinkage stresses in art and restoration materials, we have determined the stresses which develop in films of thermoplastic polymers cast from toluene solutions, by measuring the curvature of a flexible substrate coated on one side with the polymer solution. The polymers studied include several poly (vinyl acetates) and poly (methacrylates), chosen to include several common coating materials and to span a range of physical and chemical properties. The results have been compared with a theory on the development of internal stress in films of solvent-based thermoplastic polymers. The theory correlates the magnitude of internal stress in the film with the amount of solvent which evaporates from the film after it has 'solidified'.

Wood is common as a structural material throughout Art and Archaeological collections. While there is a considerable amount of information on the behavior of wood in the longitudinal direction, failure is often perpendicular to the grain direction. This study concentrated on the cross-grained mechanical behavior of several woods and their response to changes in relative humidity. The mechanical behavior of these woods coupled with the dimensional response to relative humidity can be used to assess the potential for damage to restrained wood objects as well as determine allowable museum environmental fluctuations.

A modified biaxial flexure format is developed for testing the strength of archaeological ceramics. Laboratory experiments demonstrate the reliability of this approach. Two archaeological examples are presented, using pottery from the site of Tikal in Guatemala, and several sites in the northern Southwest region of the United States.

This paper reports three aspects of an ongoing building archeology project at the MacPheadris-Warner House (ca. 1716–23) in Portsmouth, N.H., U.S.A. One is the use of a portable moisture meter to map rising damp levels and areas of water infiltration through brickwork. The second is the mapping of crack patterns and other defects on exterior elevations. We will also refer to a second site, the Juliette Gordon Low House in Savannah, Georgia, in discussing the problem of crack mapping. The third project is an ongoing attempt to replicate a shell lime mortar.

FT-IR spectroscopy was used to study the nature of the interface between silanes and stone. Methyltrimethoxysilane (MTMOS), 3-aminopropyltriethoxysilane (APS), and vinyltrimethoxysilane (VTS) were applied to three kinds of stone: limestone, sandstone and khondalite (a metamorphosed sandstone). Infrared spectra of silanes on the stone surfaces were obtained throughout the spectral region studied (4000–450 cm-1) by a digital subtraction technique and were compared with spectra of pure polymerized silanes. APS, VTS have been shown to interact with all three types of stone, however, interaction of MTMOS was observed only with sandstone and khondalite stone.

A metallurgical and corrosion study was undertaken on early eighteenth century cast-iron cannons to determine the extent and nature of the deterioration of the cannons. This study aided the development of a suitable conservation treatment in order to minimize further corrosion of the cannons. The cannons have been exposed for over 250 years to atmospheric corrosion in a coastal subarctic climate and marine environment. Due to high humidity, both damp and wet atmospheric corrosion was prevalent, resulting in loss of surface detail. The overall corrosion damage is limited, as thickness loss at bore and weight loss of cannons indicate. The structure and composition of the sound metal and the corrosion scale were examined. The metal structure is that of a phosphoric grey iron with a mixed pearlite and ferrite matrix, and the composition is typical for a cold-blast charcoal iron smelted from high-phosphorus ores. The structure of the corroded metal and the morphology of corrosion occurring in the cannons are common in grey iron. The role of atmospheric-corrosion factors in the deterioration of the cannons is discussed.

While living in Los Angeles in political exile in 1932, Mexican artist David Alfaro Siqueiros painted Amirica Tropical. The mural, 24 meters long and five meters high, is painted on the exterior south-facing wall of the Italian Hall building on Olvera Street, part of the historic monument of El Pueblo de Los Angeles. For this mural, Siqueiros used an experimentalfresco technique in which he painted on fresh cement using an airbrush. Shortly after its execution, the mural was covered with white paint because of its controversial political message. The mural's exposure to harsh environmental conditions, under direct sunlight and heat as well as the painting technique used, resulted in its deterioration. Since the late 1980s, the Getty Conservation Institute has been involved in a project to conserve the only surviving public mural by Siqueiros in the United States. In order to develop an appropriate conservation treatment it was necessary to understand the causes of its deterioration through the study of the original materials and the painting technique used, and the history of the mural.

In this article, historical information and scientific evidences are combined to discuss Siqueiros' innovative technique -fresco on cement - and the mural's deterioration. Contemporary and historical sources provide information on the materials and the technique used in this mural; but give also contradictory evidences regarding the type of paint used. Scientific investigation was carried out on samples of the mural to identify the materials used to paint America Tropical. The pigments were identified using polarized light microscopy and x-ray fluorescence analysis. The identification of the binder was carried out using Fourier transform infra-red spectroscopy, organic elemental analysis and gas chromatography. Scientific investigation, in particular infrared analysis, seems to suggest that cellulose nitrate was the principal component of the binder. The deterioration of the mural is discussed in the light of these results.

From the Spanish tradition of tubular organ building, it is possible to detach an important branch that has its origins in México, country that owns a rich array of historic organs that were built in a period of approximately three hundred and fifty years embracing a good part of the colonial period and the XIXth century.

We studied mural painting samples from Bonampak (790-792 AD), Chiapas, Mexico, by several analytical methods: gas chromatography/mass spectroscopy (GC/MS), optical microscopy and X-ray diffractometry.

The GC/MS suggested an original use of natural organic materials on both, the painting layers and the mortars, leading to the identification of a specific a Mayan technique of painting murals.

In the Southwestern United States, adobe buildings comprise a significant portion of our architectural heritage. The recognition of this fact has led to research to devise better methods to preserve buildings constructed of adobe, however, many of the new methods are not appropriate for buildings in-use or are to costly to implement in communities or organizations with limited means. In an effort to devise cost-effective preservation methods based on traditional plastering techniques, aged plasters of varying durability have been analyzed using modern materials characterization techniques in order to determine what factors lead to durable plasters. In addition, the laboratory work has been supplemented by oral histories and practical experience in the field.

Synthesized glasses and glazes provide an opportunity to study natural corrosion processes which are intermediate in time span between geological examples of natural glasses, such as obsidians and tektites, and relatively short-term laboratory tests lasting a few hours to several decades. Study of these glasses also avoids the question of having to validate artificial aging experiments. Like natural glasses, the synthesized glasses are sufficiently abundant that laboratory studies can be conducted to study the processes, mechanisms and rates of corrosion. In addition, synthesized glasses can usually be tracked to particular archaeological find sites with known dates of production and, often, of burial. Environmental conditions are routinely measured at archaeological sites as a part of the excavation process, so that information is available on the yearly cycling of temperature and relative humidity, sometimes at the depth at which the artifact was found. Whether the artifacts were excavated in an air enclosure, such as a tomb, or in the soil can also be reconstructed. One can also determine whether aqueous or atmospheric corrosion was involved in the degradation process. Because so much glass has been excavated from well-documented contexts, it is inadvisable to study glasses that have no context. For instance, socalled “Roman glass” may span a time period of production of 800 years and a geographical range from Germany to North Africa and from Britain to Afghanistan.

Late thirteenth to early fourteenth century glasses of the so-called “Aldrevandin” group, are believed to be among the earliest enamelled products of the Venetian glass industry. Enamel colours and glasses from Aldrevandin-type vessels excavated in England have been analysed using energy dispersive X-ray analysis in the scanning electron microscope. The enamels are closely similar to those on Islamic glass of about the same period. The early Venetian techniques are inferred to have derived from the Near East, perhaps via a trade in enamel colours.

The excavations of an Abbasid (late 8th - early 9th century) industrial complex at Raqqa in northern Syria has revealed the first comprehensive evidence in the Islamic world for the manufacture of glass. This paper presents a summary of the results of two seasons of excavations and of the scientific investigations of the two phases of production on the site. The study has included a range of glass colours, glazed surfaces, furnace fragments, slags and a flit-like materials. By using electron-probe microanalysis and scanning electron microscopy the results have indicated that three distinct compositional types of glass were in use there and that glass was probably being fused from primary raw materials with the evidence of fiitting. Since this is the first Islamic workshop of its kind ever found, the excavations at Raqqa have produced seminal evidence for ancient glass production, including the discovery of some almost complete examples of the three-chambered ‘southern’ type of furnace within a complete planned workshop.

Few archaeological sites have drawn, and held the imagination and attention of the range of scholars as the prehistoric settlement of Akrotiri on Thera in the southern Cyclades, currently excavated by Athens University and the Greek Archaeological Society [1,2]. The archaeological significance of Akrotiri can hardly be overstated from any perspective. With respect to the controversial question of a Minoan hegemony, it lies on a particularly strategic point in Bronze Age trading routes between the mainland, the Cycladic islands and Crete [3\. By the sixteenth century BC the many Minoan features present in Theran material culture (such as fresco iconography, Linear A tablets, ceramic motifs and architectural details) continue to provoke debate concerning the existence, or extent of a Minoan thalassocracy. Thus characterizations of what may be distinguished as truly “local” attributes of Theran crafts in the earlier periods are increasingly important.

Hasanlu Tepe and Dinkha Tepe are located in the Ushnu-Solduz valley system of northwestern Iran. A comparison of the pottery assemblages of the Late Bronze Age (Has VI and Din IV) and the Early Iron Age (Has V and Din III) at each site shows that there was an abrupt stylistic change from one period to the next, that change being attributed to the migration of a new people into the region, circa 1450 B.C. INAA and petrographic analysis indicates that this cultural change influenced only stylistic aspects of the local pottery tradition: no new clay sources were exploited, no novel tempering practices were introduced. Rather, all the technological differences we can detect relate to variations within the internal organization of pottery production at each site, suggesting the presence of some workshops which specialized in certain ware types. There is also evidence for appreciable movement of finer painted wares from Dinkha to Hasanlu during the Bronze Age.