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The Effects of Temperature and Relative Humidity on the Mechanical Properties of Modern Painting Materials
Abstract
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 and stronger, and they cannot sustain deformations nearly as dramatic as the acrylics. Acrylic paints at 5% RH are stiffer and stronger than at 50% RH and their ability to stretch is lessened. At temperatures below 15° C at 50% RH, the strength and stiffness of acrylic paints begin to rise rapidly. Some were found to be brittle at 5° C, and by −3° C, all were brittle. At a lower RH, some acrylic paints became brittle at a temperature near 11° C. These temperatures and relative humidities may be found in the transport environment of art objects, and may render them subject to possible damage.
... Inorganic pigments also tend to be much stiffer than the binding media, also leading to a significant increase in the stiffness of the sample. Many of the studies focused on the effects of temperature [18,29,30,36,37,41,43,46,50,54,57] and relative humidity [15,29,30,34,36,37,41,43,44,46,52,57,59] on the stiffness of the sample. There is a general trend across all three binding media classes of increasing stiffness as the temperature of a paint decreases, shown in Fig. 6, which would indicate that the increase in stiffness is controlled more by the properties of the binding medium than the particular pigment used. ...
... Inorganic pigments also tend to be much stiffer than the binding media, also leading to a significant increase in the stiffness of the sample. Many of the studies focused on the effects of temperature [18,29,30,36,37,41,43,46,50,54,57] and relative humidity [15,29,30,34,36,37,41,43,44,46,52,57,59] on the stiffness of the sample. There is a general trend across all three binding media classes of increasing stiffness as the temperature of a paint decreases, shown in Fig. 6, which would indicate that the increase in stiffness is controlled more by the properties of the binding medium than the particular pigment used. ...
... For all these general classes of binding media, −10 • C is below their T g , which leads to a glassier, more brittle response from the samples. When the RH is increased for a paint system, researchers observed a general softening phenomenon occur since water can act as a plasticizer in most paint films, leading to a decrease in the stiffness that can range from 30-90%. 2 [15,29,30,34,36,37,41,43,44,46,52,57,59]. When the RH is decreased, the paints become stiffer as less ambient water is present, showing anywhere from 40-300% increase in the stiffness. ...
While the chemistry of artists’ paints has previously been studied and reviewed, these studies only capture a portion of the properties affecting the response of paint materials. The mechanical properties of artists’ paints relate to the deformation response of these materials when a stress is applied. This response is dependent on many factors, such as paint composition, pigment to binder ratio, temperature, relative humidity, and solvent exposure. Here, thirty years of tensile testing data have been compiled into a single dataset, along with the testing conditions, to provide future researchers with easy access to these data as well some general discussion of their trends. Alongside the more commonly used techniques of tensile testing and dynamic mechanical analysis, new techniques have been developed to more fully investigate the mechanical properties, and are discussed along with salient results. The techniques have been divided into two categories: those that are restricted to use on model systems and those that are applicable to historic samples. Techniques applied to model systems (tensile testing, dynamic mechanic analysis, quartz crystal microbalance, vibration studies) require too large of a sample to be taken from art objects or focus on the mechanical properties of the liquid state (shear rheometry). Techniques applied to historic samples incorporate the use of small sample sizes (nanoindentation), optical techniques (laser shearography), computational simulations (finite element analysis), and non-invasive comparative mechanical properties (single-sided nuclear magnetic resonance) to investigate and predict the mechanical properties of paints.
... It was determined that even in the absence of RH or temperature variations, cumulative shrinkage, particularly when constrained by a stable substrate, can surpass paint strain at break and result in fracturing. In parallel, Jonah et al. [34] examined the mechanical properties of modern painting materials, specifically artists' acrylic and alkyd paints, across different temperature and relative humidity (RH) conditions. In ambient conditions, acrylic paints showed high flexibility and were able to sustain large deformations, whereas alkyd paints were stiffer and stronger but less capable of deformation. ...
Oil paintings represent significant cultural heritage, as they embody human creativity and historical narratives. The preservation of these invaluable artifacts requires effective maintenance practices to ensure their longevity and integrity. Despite their inherent durability, oil paintings are susceptible to mechanical damage and chemical deterioration, necessitating rigorous conservation efforts. Traditional preservation techniques that have been developed over centuries involve surface treatment, structural stabilization, and gel-based cleaning to maintain both the integrity and aesthetic appeal of these artworks. Recent advances in artificial intelligence (AI)-powered predictive maintenance techniques offer innovative solutions to predict and prevent deterioration. By integrating image analysis and environmental monitoring, AI-based models provide valuable insights into painting preservation. This review comprehensively analyzes traditional and AI-based techniques for oil painting maintenance, highlighting the importance of adopting innovative approaches. By integrating traditional expertise with AI technology, conservators can enhance their capacity to maintain and preserve these cultural treasures for future generations.
... Besides antifouling paints, PMMA is also widely used in marine paints that are applied on the outboard and superstructure of hulls to maintain beauty and gloss. It is noteworthy that acrylic paints are prone to dehiscing and cracking at low temperatures [55], and it has been verified that some acrylic paints become brittle at 5 • C with 50% relative humidity (RH) and even at 13 • C with a lower RH [56]. Therefore, these PMMA marine paints on upper hulls are also prone to becoming brittle and then falling off from the ship structure when navigating, especially in winter, which can result in abundant white PMMA fragments and fiber residues (shown in Figure S4) in the S-SML. ...
The abundance, distribution, and composition of microparticles (MPs) in the sea-surface microlayer (S-SML, less than 100 μm of sea surface in this experiment) and in bulk water (1 m under the sea surface) were investigated to evaluate the pollution level of MPs in Osaka Bay in Japan. Both seawater fractions were collected at eight sites including ship navigation routes, the coastal area, and the center of Osaka Bay for 2021–2023. MPs were filtered for four size ranges (10–53, 53–125, 125–500, and >500 μm) and then digested with H2O2. MPs’ abundance was microscopically assessed; and polymer types of MPs were identified by a Fourier transform infrared spectrometer (FTIR). For the 22 collections performed along eight sites, the average MPs’ abundance was 903 ± 921 items/kg for S-SML, while for the 25 collections performed along the same sites, the average MPs’ abundance was 55.9 ± 40.4 items/kg for bulk water, respectively. MPs in both S-SML and bulk water exhibited their highest abundance along the navigation routes. The smallest MPs (10–53 μm) accounted for 81.2% and for 62.2% of all MPs in S-SML and in bulk water among all sites, respectively. Polymethyl methacrylate (PMMA) was the major type of MPs identified while minor ones were polyethylene, polyesters, polystyrene, polypropylene, polyvinyl chloride, polyamide, etc. PMMA comprised 95.1% of total MPs in S-SML and 45.6% of total MPs in bulk water. In addition, PMMA accounted for 96.6% in S-SML and 49.5% in bulk water for the smallest MP category (10–53 μm). It can be assumed that the MP sources were marine paints—primarily APPs (antifouling paint particles)—as well as land coatings. Sea pollution due to microparticles from ship vessels should be given proper attention.
... Historical paint artworks may exhibit conservation issues due to degradation processes that may establish upon ageing, and that depend on several factors. Among them, a relevant role is played by the humidity conditions and/or exposure to moisture during certain conservation treatments [2][3][4][5][6][7][8][9]. Therefore, museums and galleries dedicate efforts into controlling relative humidity and temperature values at exposition sites, as well as in storage facilities, and optimal conditions are object of research [10,11]. ...
The role of water and hematite (Fe2O3) on the stability of ovalbumin-based model paint layers was investigated by means of DSC and FTIR. The aim of this research is to improve our understanding on the stability of paint layers based on proteinaceous media, assessing the water content and the pigment presence effects. Pigments may play a fundamental role in determining the structure of proteins in paint layers, thus affecting the possible interactions among proteins and the external environment, including humidity. Previous studies revealed that hematite affects the secondary structure of OVA in paint layers, although no experimental evidence of hematite/OVA covalent bonds has been reported in the literature. In this paper we investigate the synergic effect of water and hematite on OVA structure and stability. DSC analyses coupled with FTIR measures on protein hydration revealed that below 30 % of humidity the amount of water strongly influence the protein structure and stability: the less the water content, the higher the protein stability. Furthermore, our results suggest that a water phase separation occurs in the presence of hematite for which, in water-limiting condition, the hematite’s hydration shell becomes almost negligible if compared to the bulk water available for the protein hydration because of the high protein-water affinity. Accordingly, the protein phase humidity is higher than the sample’s nominal value. Paints at the same overall humidity exhibit different protein hydration state following the pigment/binder ratio, and in turn different resistance to damages throughout aging.
... Though a lot of work has been done on the ambient conditions (i.e. temperature and relative humidity) [3,4], not much work has taken place on the vibration and shock during transportation. Studies of early 1990s have recorded the impact of vibration and mishandling with photography and natural frequency measurements of canvas as well as acceleration measurements with attached accelerometers [5][6][7][8]. ...
A study is herein presented aiming to detect structure cohesion failure before its appearance in form of cracks on precious painted canvas surfaces subjected to transportation. Transportation is of prime importance for the deterioration mechanisms that disintegrate the structural condition of movable painted artworks. Cracking is most common result of intense transportation and most common cause of reduced state of conservation. Here two realistic conditions are encountered in the laboratory to simulate transportation effects: A transport simulator that reproduces transportation vibrations and a high resolution portable system based on optical coherent metrology technique that monitors in real time the surface response. The measurements were carried out on canvas samples with known defects. The known defects, existing and indications of new cracks. Their propagation effects were revealed. Preliminary results obtained in this study are encouraging for significant assessment of transportation effects in crack growth and propagation studies through real time monitoring of canvas surface.
... Knowledge of the mechanical properties for cultural objects, such as strength and stiffness, can help in understanding their response to changes in temperature and relative humidity as well as providing the range of allowable fluctuations in temperature and relative humidity before damage occurs. Such research has been accomplished in the past 10 to 15 years by scientists at the Smithsonian Institution for a large number of different materials such as wood, glue, and artists' paints (Mecklenburg 1991; Mecklenburg et al. 1992; Erlebacher and Brown 1992; Mecklenburg and Tumosa 1993, 1995). With the environment being maintained in an allowable RH range, the deformations and induced stress remain within the elastic range of the material and no permanent damage results. ...
As a caretaker of cultural and natural artifacts, the Field Museum of Natural History in Chicago, Illinois, contains irreplaceable objects. In situations where environments for artifacts are not correctly maintained and controlled, permanent damage to these objects can result. A longitudinal environmental survey was performed at the museum to assess the performance of the facility’s HVAC systems and controls. The primary objective was to develop and test a series of hypotheses to explain deterioration of a number of mammal mounts located in the museum’s exhibition halls. In this paper, the environmental factors affecting artifact lifetime are reviewed and recommendations are summarized. In addition, a method for evaluating the tightness of display cases using carbon dioxide as a tracer gas is presented. The survey indicated that the temperature in certain areas of the museum often exceeded a recommended upper limit of 77°F and humidity was uncontrolled in other areas.
The paper presents the results of measurements of the L*, a*, and b* color coordinates in the CIEL*a*b*76 (D65/10) space of paint layers of zinc white and ultramarine with several primers and binders. The coordinates are measured for naturally aged reference samples and test samples that underwent two thermal shocks. The color differences of samples obtained using three binders and three primers are quantitatively characterized. It is shown that thermally induced changes in the L* coordinate, as distinct from the a* and b* coordinates, are significantly greater than the changes predicted by the artificial aging protocol. However, during subsequent storage, L* partially relaxes to its original values, and the resulting changes in this coordinate can be considered insignificant. The relaxation effect is also characteristic of the a* and b* coordinates for most samples. Specific results are obtained for paint layers with resin-containing binder on glue–chalk primers. When zinc white is used, such samples have greater L* coordinate and smaller b* coordinate, i.e. appear to be lighter and less yellow in comparison with the remaining samples. When ultramarine is used as a pigment, the resin-containing binder and glue–chalk primers provide the maximum depth of blue color (minimum b* value), which remains almost unchanged with aging. However, the crimson hue characteristic of such samples (greater value of the a* coordinate) is intensified due to heating. The results show that two thermal effects on paint layers separated in time can lead to opposite changes in color coordinates.
Acrylic polymers, commonly used in paints, can degrade over time by several different chemical and physical mechanisms, depending on structure and exposure conditions. While exposure to UV light and temperature results in irreversible chemical damage, acrylic paint surfaces in museums can also accumulate pollutants, such as volatile organic compounds (VOCs) and moisture, that affect their material properties and stability. In this work, we studied the effects of different degradation mechanisms and agents on properties of acrylic polymers found in artists' acrylic paints for the first time using atomistic molecular dynamics simulations. Through the use of enhanced sampling methods, we investigated how pollutants are absorbed into thin acrylic polymer films from the environment around the glass transition temperature. Our simulations suggest that the absorption of VOCs is favorable (-4 to -7 kJ/mol depending on VOCs), and the pollutants can easily diffuse and be emitted back into the environment slightly above glass transition temperature when the polymer is soft. However, typical environmental fluctuations in temperature (<16 °C) can lead for these acrylic polymers to transition to glassy state, in which case the trapped pollutants act as plasticizers and cause a loss of mechanical stability in the material. This type of degradation results in disruption of polymer morphology, which we investigate through calculation of structural and mechanical properties. In addition, we also investigate the effects of chemical damage, such as backbone bond scission and side-chain cross-linking reactions on polymer properties.
Most of the artwork and cultural heritage objects are stored in museums under conditions that are difficult to monitor. While advanced technologies aim to control and prevent the degradation of cultural heritage objects in line with preventive conservation measures, there is much to be learned in terms of the physical processes that lead to the degradation of the synthetic polymers that form the basis of acrylic paints largely used in contemporary art. In museums, stored objects are often exposed to temperature and relative humidity fluctuations as well as airborne pollutants such as volatile organic compounds (VOCs). The glass transition of acrylic paints is below room temperature; while low temperatures may cause cracking, at high temperatures the sticky surface of the paint becomes vulnerable to pollutants. Here we develop fully atomistic models to understand the structure of two types of acrylic copolymers and their interactions with VOCs and water. The structure and properties of acrylic copolymers are slighlty modified by incorporation of a monomer with a longer side chain. With favorable solvation free energies, once absorbed, VOCs and water interact with the polymer side chains to form hydrogen bonds. The cagelike structure of the polymers prevents the VOCs and water to diffuse freely below the glass transition temperature. In addition, our model forms the foundation for developing mesoscopic and continuum models that will allow us to access longer time and length scales to further our understanding of the degradation of artwork.
The quartz crystal microbalance (QCM) was used to measure the time-dependent mechanical properties of an alkyd resin throughout the transition from its application as a liquid to the formation of a solid film. Three different regions of curing were observed, corresponding to solvent evaporation; early stage curing, where the mass increases as oxygen is incorporated into the film; and long-term curing, where the mass decreases as volatile compounds are released. Mechanical property changes obtained at 15 MHz with the QCM were correlated with measurements at much lower frequencies utilizing traditional dynamic mechanical analysis. These mechanical property changes were in turn correlated to chemical changes tracked with Raman spectroscopy. From the temperature dependence of the curing process we obtain an effective activation energy of 4.1 kcal/mol.
Contemporary artworks are often realized with multi-component mixtures with unknown compositions, which may be subjected to an unforeseeable degradation. A detailed characterization of these materials provides relevant information both to plan proper restoration strategies and to prevent damages. In particular, binders identification represents one of the major problems in the conservation of the contemporary works of art. In this paper, five binders routinely employed in contemporary paintings, i.e. acrylic resins, ethylene vinyl acetate, dammar varnish and linseed oil, were studied by Time Resolved Laser Induced Fluorescence Spectroscopy (TR-LIF). Experimental results confirm the TR-LIF analysis capability to isolate specific contributions from the investigated constituents. The spectral features of ten commercial paints containing the above mentioned binders were analyzed as well. In this latter case, additional diagnostic techniques, such as X-Ray Fluorescence Spectroscopy and Fiber Optics Reflectance Spectroscopy, were demonstrated to provide useful complementary information to integrate TR-LIF results.
Acrylic artist paints are viscoelastic composites containing a high molecular weight copolymer, pigment and a variety of additives.
The glass transition temperature of the latex binder is typically slightly below ambient conditions, giving mechanical properties that are strongly dependent on strain rate and temperature. In previous work, the viscoelastic behaviour of custom-formulated latex artist paints was reported for films with known volume fractions of pigment using data from uniaxial tensile tests at different strain rates and temperatures.
Secant Young’s modulus and failure strain master curves were constructed for each film through time-temperature superposition, allowing predictions beyond the experimental timescale at a selected reference temperature.
A similar analysis is now presented for a small set of commercial artist paints tested at ages of 1 and 27 years. Experimental shift factor values are reported with fits to the Arrhenius, WLF and Vogel Fulcher equations, along with a comparison with published data for acrylic polymers. The tensile results highlight a spectrum of properties that acrylic paints may exhibit—brittle glass to hyperelastic—depending on the conditions during deformation. Strong similarities are shown between products from different manufacturers, and the findings suggest a high degree of stability with age. A method for predicting failure as a function of strain rate and temperature is also presented, and the methodology gives a framework for investigating other artist materials and the factors influencing their mechanical properties.
The presence of zinc oxide oil paint and the condition problems observed in a group of paintings from the collection of the Hirshhorn Museum and Sculpture Garden prompted analytical examination of the museum's mid-20th century holdings. Results reveal a link between upper layer deterioration and underlying zinc oxide paint layers, and suggest that certain visible signs of deterioration may signal the presence of more serious and widespread condition problems. The popularity of zinc oxide house paint among mid-century artists creates a higher probability of this type of deterioration in works from this period.
Acrylic emulsion (or more accurately dispersion) paints present major challenges to paintings' conservators, yet remarkably few studies of these materials have been published. The intent in this paper is to present the conservation information that does exist in a concise format to expedite much needed further discussion and research by conservators, paint manufacturers and artists. Brief descriptions of the development and analysis of acrylic emulsion paints are given, but the focus of this review is on conservation concerns, in particular issues surrounding the paints' properties, ageing and cleaning.
The tensile properties of latex coatings were investigated with a set of custom formulated artist-type paints at an age of 1 year. All films in the study contained a poly(methyl methacrylate-cobutyl acrylate) binder exhibiting a glass-transition at approximately 10°C. The viscoelastic behaviour of the latex matrix is first highlighted through a series of experiments involving different strain histories and temperatures. Influence of the inorganic particle concentration and geometry is then illustrated using TiO2 and calcined kaolin for the secondary phase. Experimental data from a wide range of conditions are summarised through master curves of secant modulus and failure strains using time–temperature superposition. The results indicate that the latex films behave in a rheologically simple manner and it is possible to predict the response outside of the experimental time-scale. An analysis by similar methods is also given for TiO2 pigmented films with/without surfactant removed by immersion in water. Differential scanning calorimetry and atomic force microscopy were also used in conjunction with mechanical tests. The combined findings suggest that a fraction of surfactant migrates to the TiO2 interface during film formation, where it interferes with adhesion of the acrylic matrix.
There is little information in the conservation literature with respect to artists' alkyd paints; thus, artists and conservators are somewhat at a loss about how to use and treat alkyds. Recently, analytical methods have been developed to identify the components in these polymers (oil modified polyesters), rates of cross-linking and mechanical properties. Presented in this paper are some of the characterization results of artists' alkyd paints using THM (thermally assisted hydrolysis and methylation) gas chromatographye mass spectrometry (THMeGC/MS) and Fourier transform infrared spectroscopyeattenuated total reflectance (FTIReATR). Four brands of artists' alkyd paints containing alkyd resin have been analysed; one containing a phthalic anhydride and pentaerythritol based alkyd resin, two containing isophthalic acid and pentaerythritol based alkyd resins, and the final one containing both phthalic anhydride and isophthalic acid and pentaerythritol based resins among the colours studied.
Typescript. Thesis (M.S.)--University of Wisconsin--Madison, 2000. Includes bibliographical references (leaves 151-155).
An Introduction Into the Mechanical Behavior of Paintings Under Rapid Loading Conditions
- M F Mecklenburg
- C S Tumosa
Mechanical Behavior of Paintings Subjected to Changes in Temperature and RelativeHumidity
- M F Mecklenburg
- C S Tumosa