Charles S. Tumosa's research while affiliated with Smithsonian Institution and other places

Publications (29)

Article
As linseed oil ages, hydrolysis and oxidation produce acid groups on the polymer chain that may lead to ionomeric behavior. The effect of these changes is difficult to determine in old paints because of the lack of records of environmental and treatment histories that can alter the physical properties significantly. A series of paints were made tha...
Article
This study examines the methods for determining the effects of temperature and relative humidity (RH) on the dimensional and mechanical properties of artists' materials. Using both of these properties, typical cultural objects, such as paintings and photographs can be modeled on the computer to correlate the magnitude of developed stresses to envir...
Article
The mechanical properties of strength, modulus, and elongation to break were studied for artists' acrylic and alkyd paints under varying conditions of temperature and relative humidity (RH). In the ambient environment, 23° C, 50% RH, acrylic paints are very flexible and are able to sustain large deformations (>50%). Alkyd paints are much stiffer an...
Article
Full-text available
The effect of different tanning and fixing processes on the mechanical prop- erties of taxidermy skins was investigated using a screw driven tensile machine. Tanning treatments were potash alum powder, salt and a bath (salt, potash alum, and water) used at the Museum National d'Histoire Naturelle in Paris. Fixing was with formalin or alcohols (meth...
Article
Lead compounds or pigments alter the drying behavior and physical properties of oil paints and varnishes, enabling artists and craftsmen to tailor the properties most suited for their purposes. Investigations into the mechanism of these changes have, however, often been contradictory or misleading. Using modern theories of driers, the behavior of l...
Article
Oil paints dry by polymerization. This 'drying' process may be substantially complete and the surface of the paint film dry to the touch within weeks, but measurable changes continue for years. Other, slower processes also continue, primarily hydrolysis of glyceride esters. This produces carboxylic acid groups as either free fatty acids (in the cas...
Article
Full-text available
The stiffening and embrittlement of oil paints over time has been a real concern for those responsible for the long term care and preservation of paintings. This paper examines the effects of time, pigments, relative humidity (RH), temperature and solvents on the mechanical properties of traditional oil paints. In this way it is possible to determi...
Article
Concentrations of soluble sugars including glucose and xylose in papers produced over a range of 500 years were determined. Extraction of samples from the unprinted areas of the paper was followed by concentration, derivatisation, and analysis of the extracts by gas chromatography. The identification of the sugars was made by comparison of retentio...
Article
Although preserving museum collections is vital, it is equally important to consider the failure mechanisms of the build- ings that house those collections. A combination of research, survey, and experience with high-profile buildings at the Smithsonian Institution has led to broadening the indoor environmental guidelines. The new environmental gui...
Article
Full-text available
In the fall of 2001, anthrax-contaminated letters were sent to public figures in the United States. Chemical and radiation treatments were employed to decontaminate exposed buildings, objects, and materials. These treatments are effective, but potentially damaging to exposed objects and materials. The recommended surface chemical treatments include...
Article
One aspect of the response to a biological attack using anthrax spores sent through the mail has been to use electron irradiation to treat the mail. This irradiation procedure has altered the materials and objects in ways that were probably not anticipated. The mail was damaged by both thermal and radiation processes. Business, government, and pers...
Article
—Objects in ethnographic and ancillary natural history collections contain many types of vegetable oils as components of varnish coatings, paints and lubricants. Tests were performed on thin oil films dried in a laboratory environment. These oils, composed of the glycerol esters of unsaturated fatty acids, will oxidize through a free radical proces...
Article
Full-text available
Natural history museum collections are incomparable storehouses of geological, biological, and genetic resources throughout the world. Some of the materials composing the specimens in these collections are vulnerable to deterioration when stored in fluids. Samples were taken from liquid storage media surrounding mammal specimens in the National Mus...
Article
Some of the most important cultural icons in the world are oil paintings. Preserving them for future generations requires a fundamental understanding of the long-term chemical, mechanical, and physical behavior of their components. If the properties are understood, modeling and even predicting the effects of exposure to changes in temperature, rela...
Chapter
An understanding of the chemical and physical changes that occur in cellulosic materials is crucial to the preservation of many objects in museums and archives. Decisions regarding care, treatment, and appropriate storage environments are based on their effects on the permanence and condition of the objects. Because many of the changes that occur i...
Chapter
The photographic record of the twentieth century is rapidly being lost. The gelatin of the image emulsions is relatively stable, but the silver salts and dyes that form the image, and the principal photographic film bases, cellulose nitrate and cellulose triacetate, have been found to be chemically unstable within the time frame of historical signi...
Article
The chemical and physical state of naturally aged samples of oil paint were examined. Results were compared to those for samples of oil paint subjected to various conditions of accelerated aging. As a result, it was possible to account for the thermal aging at different relative humidities.
Article
Processes that occur in oil paints after the initial drying stage include the hydrolysis of glyceride ester linkages, the formation of soaps, and the volatilization of low molecular weight compounds. The nature, amounts and distribution of the soluble components of paint films serve as indicators of the relative rates and extent of these processes....
Article
The mechanical response of objects having a complex composite structure can be accurately modeled if the material properties of the individual components are characterized using the approach briefly described in this paper. The three dimensional surface of the equilibrium stress-strain state and the methods required for its determination were the s...
Article
The comprehensive review of the biochemical forensic literature by Gaensslen covered much of the subject until about 1980. This review focuses on two aspects of forensic serology and reports on the progress and research in the identification of blood and its species determination during the period 1980 to 1995. The development of ELISA techniques a...
Article
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...
Article
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...
Article
The environmental effects of temperature and relative humidity on the mechanical response of paintings and photographs were examined using numerical methods and computer analysis. The basic mathematical approach is introduced that defines the material parameters necessary to conduct such an analysis. Methods of determining the material and dimensio...
Article
Full-text available
Acrylic paints are commonly found in modern art. The mechanical properties of strength, modulus, and ability to elongate of a large sampling of artists' acrylic paints were studied in the temperature range of -8° C to 33° C, and from 5% to 50% relative humidity (RH). Data derived from the stress-strain curves suggests that acrylic paints lose the a...

Citations

... For example, the use of long immersion times for leaching studies may yield highly accurate data on extractables, but the results may be less easily translated into conservation strategies because of the short contact times encountered in cleaning practice. Finding the optimal balance between theoretical and practical relevance of cleaning experiments has led to many discussions [24][25][26][27]. We will attempt to highlight the practical relevance of the literature discussed throughout this review. ...
... Considering amber's susceptibility to deterioration when exposed to a variety of environmental factors, a stable storage environment is essential for any collection of these fossil resins, including amber specimens that are embedded in epoxy. To create and maintain a suitable indoor environment for most types of fossil collections, including amber collections, the overall range for RH should be between 37 ±2% and 53 ±2% (Mecklenburg et al., 2004;Pastorelli et al., 2013b). Even so, the ideal RH range for each specific type or deposit of amber appears to differ to some extent. ...
... The acidic hydrolysis of b-glycosidic bonds of cellulose, often associated to oxidation, can induce reduction in the polymerization degree of cellulose and consequently structural weakening of paper (Erhardt and Mecklenburg 1995;Erhardt et al. 1999Erhardt et al. , 2000Margutti et al. 2001;Whitmore 2011). To overcome acidity and prevent such degradation processes, different deacidification treatments were studied based on the use of aqueous and non-aqueous systems (Baty et al. 2010;Hubbe et al. 2017). ...
... Long-existing awareness of the correlation between climate stability and the preservation condition of wooden heritage objects was a motivation for adopting general environmental specifications for museums as decorated wood is the key representative of objects composed of humidity-sensitive materials most vulnerable to RH and temperature fluctuations. Grounds for evidence-based environmental specifications were laid in 1990s when the key mechanical parameters-stiffness, moisture expansion coefficient, strength, strain at break and yield point were quantified for a broad range of materials relevant for cultural heritage (Mecklenburg and Tumosa 1991;Mecklenburg et al. 1998;Mecklenburg 2007), However, most of the predictive models (Mecklenburg et al. 1998;Rachwał et al. 2012) assume equilibrium of object with the surrounding environment, which is valid for slow RH variations producing little gradient of moisture content in bulk wood. In consequence, most environmental specifications to ensure the preservation of valuable collections do not take into account the environmental specificity of churches and historic houses. ...
... In turn, it is convenient to study the glass transition temperature (Tg) of each material, based on the surface measurement references that some authors have collected on this type of cleaning. Failing to take this consideration into account could cause severe fractures in the material to be preserved since exceeding the Tg of a structure causes a notable loss of flexibility, reaching a completely irreversible glassy state that will compromise its future preservation [48]. The loss of flexibility increases the risk inherent in any momentary drop of temperature, added to the lack of resistance to the vibration produced during impact. ...
... In different studies, a negligible to slight decrease in EMC was observed with increased aging of wood [33,34]. In contrast, Erhard [35] observed an increased sorption behaviour of scots pine with increasing weathering. In our own experiments, an increase of the EMC was also observed, both for natural and artificial weathering. ...
... Depending on the ambient RH the material cycles of moisture adsorption and desorption is the dominant process for a material to maintain equilibrium with its environment; a process considered as most critical for physicochemical and structural alterations [4][5][6]. Organic materials based on carbon and hydrogen molecules are porous and characterized as hydrophilic. When the pores are of the order of thousands of a cm, as in the case of wood and cellulose, they have a large internal surface area allowing through capillary rise significant water absorption and moisture transmission. ...
... Much of the present knowledge surrounding the mechanical properties of artist paints comes from the body of research by Mecklenburg and coworkers [1][2][3][4][5][6][7]. Tensile data are published for oil, alkyd and acrylic artist paints, primarily as a function of temperature, humidity and age. ...
... Results in literature have demonstrated that moisture-induced fractures in wood have been studied in building industries and sawmills [1,2] as they are creating an issue in prediction during the kiln-drying process; building condition monitoring and structural health monitoring [3][4][5] as building envelopes are subjected to transient climate conditions which can ultimately lead to poor hygrothermal behavior, wood decay, and structure deterioration [6]; andmore extensivelyin the heritage science field [7,8] for a broad category of cultural heritage objects [7][8][9][10][11]. ...
... For the papers discussed in this section, all use a linear elastic model as their material model unless otherwise specified. Mecklenburg's work using FEA focused on the understanding of the response of paintings to T or RH fluctuations, out of plane bending of the canvas due to vibrations from transport, and an impact force on the side and corner of a painting to simulate a painting being dropped, comparing the resulting simulated craquelure patterns to ones observed in painting mock ups [29,61,117]. Further studies of vibrations affecting canvas paintings have been carried out to assess the vibrational modes that are most relevant to consider [118]. ...