Future climate-induced pressures on painted wood

A broad category of cultural heritage objects are multilayer structures composed of organic, humidity-sensitive materials – wood, animal glue, paper, leather, bone or paints. They respond to variations in relative humidity (RH) in their environment by cyclically gaining and losing moisture, and consequently swelling and shrinking. Differences in the moisture response of the materials induce internal stresses in the individual layers of the structures, which cause objects to deform and crack. Polychrome wood is examined in detail. The cumulative physical damage of the design layer on wood due to repeated RH variations is quantified in terms of their magnitude and number of times they occur. The climatological risk index for accumulated, ‘fatigue’ damage is established, using a procedure to reduce irregular real-world climate histories into simple RH cycles of known damage impact. Using output from the Hadley Model (HadCM3) and simple transfer functions predicting indoor temperature and RH from outdoor climate, changes in the indoor climate through to 2100 were forecast for unheated buildings. European maps highlighting the areas in which painted wood may be significantly affected by climate change are presented.     

Past,present and future effects of climate change on a wooden inlay bookcase cabinet: A new methodology inspired by the novel European Standard EN 15757:2010

This article illustrates a preventive conservation methodology for wooden collections and objects based on the respect of the historic climate, as established by the European standard EN 15757:2010. This requires the knowledge of the past indoor climate that should be kept unchanged in the present and the future, because discontinuities would be noxious for conservation. To this aim, a very vulnerable object, i.e. a wooden inlay bookcase cabinet built by G.M. Platina in 1477 AD has been considered. The paper illustrates the methodology used to reconstruct the historic climate, i.e. with proxy data from 1500 to 1715 and from 1716 to 2009 with instrumental observations. For the present, the indoor climate of the exhibition room and the cabinet response have been investigated to remove the perturbing factors that are damaging the cabinet. For the future, the ENSEMBLES model has been used for a probabilistic forecast of the temperature and humidity over the next century, the sustainability and the potential risk for conservation connected with the expected climate change. This research constitutes an example of a novel methodology based on the relevance of the Historic climate, and includes a synergistic effort of climatologists, material scientists and conservators, to be applied for preventive conservation and to evaluate and face the negative impact of the expected climate change.     

Control of indoor environments in heritage buildings: experimental measurements in an old Italian museum and proposal of a methodology

This paper describes some results from an experiment carried out regarding a procedure to be adopted for temperature and R.H. monitoring of indoor spaces designed for exhibiting events, such as museums and similar institutions. The monitored data employed in this study has been collected by the Department di Ricerche Energetiche ed Ambientali of the Università degli Studi di Palermo in co-operation with the Regional Gallery ''Palazzo Abatellis'' of Palermo. The study analyses a simple method for characterising the environmental quality of museums so as to ensure the optimal conservation of works of art. This methodology is based on the procedure (where thermal and hygrometry parameters are concerned) proposed by an Italian standard rule. A new technique, firstly applied to the industrial environment, based on the passive reactive monitoring of proper coupons is also proposed for monitoring air quality in museums. The methodology adopted, has been applied to two survey campaigns which were carried out at a distance of 5 years. This shows the two aspects of thermal-hygrometry and levels of indoor air quality aimed at preserving works of art. The future developments of this work are oriented towards the definition of guidelines in support of those responsible for the conservation of works of art and improvements in the quality of environments for artwork conservation and for the comfort of visitors through the use of proper HVAC systems.     

Using heritage risk maps as an approach to estimating the threat to materials of traditional buildings in Tainan (Taiwan)

Academic studies concerning how climate influences Asian heritage are rare. The object of this study was to utilize the concept of heritage climatology together with a spatial analysis approach that includes respective climate parameter risks to cultural heritage sites. The study area, Tainan City, Taiwan, is in a subtropical zone south of the Tropic of Cancer. Tainan has nearly 300 hundred years of rich history and a multicultural background. This study used maps to gain information about potential climactic threats to Tainan's cultural-historical legacy. There are four kinds of map that use ArcGIS to analyse and demarcate regions not only by climate parameters but also by risk to heritage. These four types of map are climate maps, heritage climate maps, heritage maps and heritage risk maps. Climate maps give the short- to medium-term general status of the climate in Tainan City and thus served as the foundation of the other maps used in this study. Heritage climate maps give data concerning index factors that influence wood and stone materials. Heritage maps show locations of cultural heritage sites on an administrative map and categorize them according to their historic value. Heritage risk maps use accumulated calculations to superimpose the heritage climate map onto the heritage map in order to evaluate the risks to heritage sites in certain areas and categorize the levels of risk. Heritage sites in mountainous areas generally need to be protected from heavy rain, whereas downtown city environments, due to the urban heat island effect, require better protection against heat and cracking. By comparison of our field study results and climate risk maps, we found that in urban areas wooden materials have a higher risk of structural cracking, colour fading and bio-degradation, while coastal areas have a higher risk of weathering of stone materials.     

Efflorescence of mirabilite,epsomite and gypsum traced by automated monitoring on-site

Short crystallisation and deliquescence cycles of mirabilite, epsomite and gypsum are identified by using an automated monitoring system on-site. It consists of digital cameras and RH/T sensors which are computer-controlled and connected to the Internet. Digital images are processed to form a time-lapse movie, so that surface alterations are easily recognised. High resolution imaging (6 mega pixels) in combination with various lenses (12–24 mm zoom, 28–105 mm zoom, 20 mm inversed) results in a wide range of precise observation from 7 to 500 mm width of image. That is essential for discriminating phase transitions of single crystals at the same time as monitoring the evolution of the efflorescence as a whole. Crystallisation-deliquescence cycles are induced by small temperature and humidity variations. Mirabilite and epsomite undergo phase changes from crystallisation to deliquescence and vice versa at about 83% RH (15–20 °C). These equilibrium relative humidities are considerably reduced compared to the pure salt systems as a consequence of mixed salt solutions. Observations confirm predictions by ECOS simulation based on chemical analyses of water extracts from the site. Dehydration of mirabilite is observed when the relative humidity drops below 65% RH. Mirabilite exhibits the most pronounced and rapid phase changes in response to indoor climate variations. As an example, whisker crystals of 1–3 mm length grow within one up to some days. Epsomite responds fainter and slower. Crystallisation of gypsum is distinguished by the growth of new crystals on the stone surface. They have a size of about 10 μ – which is close to the image resolution – when they appear on the image. Crystallisation is associated with an increased granular disaggregation of the stone surface. Rhythmical crystallisation of gypsum appears to correlate with small relative humidity variations of ±2–5% within a band from 65 to 75% RH in the room. However, this needs to be clarified in detail.     

Daily natural heat convection in a historical hall

The use of numerical simulation methods for the Cultural Heritage is of increasing importance for the analysis, conservation, restoration and appreciation of works of art. This is particularly important when their preservation and planned maintenance is the primary aim. Today museums, and particularly historical buildings converted to museums, should be considered as places where precious artefacts should have first-rate protection and conservation. It is a question of solving the compromise between protection, conservation and comfort for works of art and/or visitors, with the consequence that preservation and planned maintenance criteria must prevail over use requirements. Refurbishment and conservation of a building, and requirements for visitor presence and works of art need different thermo-physical indoor parameter values. The present paper concerns the thermal and air velocity analysis of the Salone dei Duecento (the Hall of the Two Hundred of the Palazzo Vecchio (Old Palace)) in Florence. In this paper an appropriate transient 3D model by Computational Fluid Dynamics (CFD) software based on the finite element method (FEM) was used. Variations and interaction between indoor and outdoor microclimatic conditions, and thermo-physical behaviour of the building connected to lighting, visitor presence and cooling–heating fan coils system were considered. The 3D modelling method provided by the present paper can be applied to several situations where there is interaction between outdoor and indoor climate variations and the building structure. It can be very useful for defining measures to preserve tapestries, understanding deterioration processes, and developing new conservation techniques and strategies for care and exhibition.     

Rain and museum attendance: Are daily data fine enough?

I investigate the intraday effects of rain on the demand for indoor leisure. To do so, I use sub-daily museum attendance and weather data to reveal a dynamic response to precipitation that would be obscured using day-level data. I find that the magnitudes and signs of the effects of rainfall vary significantly throughout the day. In some hours, the predicted increase in visitors is nearly three times larger than would be expected from estimates using daily measures. Many individuals appear to actively adjust their plans throughout the day in response to rain, while others’ attendance depends upon prior weather forecasts of rain. Further analysis reveals that visit duration also increases during rainy periods, and visitors are more likely to attend pay-to-enter special exhibits. International visitors make up a greater share of total visitors during periods of observed precipitation. More broadly, this paper establishes the viability and value of working with widely available sub-daily rainfall data to uncover these dynamics.     

Effectiveness of crystallization inhibitors in preventing salt damage in building materials

Salt crystallization in porous materials constitutes one of the most frequent causes of decay of buildings in a wide range of environments. Up to now no definitive solution exists to limit salt crystallization damage, unless of removing either the salt or the moisture. The possibility of making the process of salt crystallization less harmful by means of crystallization inhibitors has only recently been considered. Crystallization inhibitors are known to delay nucleation and to modify the growth rate of the crystals in bulk solution, but their possible application for the prevention of salt decay in porous material is still controversial.The present paper reports a series of systematic investigations performed on three different materials (a limestone, a sandstone and a brick) contaminated with two types of salt (sodium chloride and sodium sulphate) and two types of inhibitors (sodium-ferrocyanide and diethylenetriaminepentakis methylphosphonic acid). Drying experiments have been performed to study the effect of the inhibitors on the salt solution transport. Accelerated crystallization experiments have investigated the possible consequences of the application of the inhibitor on salt crystallization damage (quantified as material loss).Environmental Scanning Electron Microscope (ESEM) has been used to study how the presence of inhibitors affects the crystallization morphology of salt in the material.The results show that the effect of the inhibitor strongly depends on the type of substrate. NaFeC, when applied on NaCl contaminated limestone and brick was able to enhance the drying and to favour the appearance of efflorescences, whereas the effect on the sandstone was very limited. DTPMP enhanced the drying of Na₂SO₄ laden sandstone, but had no influence on the drying of both brick and limestone. These different have been attributed to the properties of the materials, in particular pore size distribution and composition.The effects of the inhibitor on salt crystallization damage were less evident: no differences in surface damage, quantified as material loss, were observed between specimens with and without inhibitor.     

Assessment of seismic vulnerability of art objects: The “Galleria dei Prigioni” sculptures at the Accademia Gallery in Florence

The seismic assessment of art objects requires a multidisciplinary approach and the definition of a specific methodology for evaluating the level of safety and the possible interventions necessary for seismic risk prevention, finding a compromise between safety and conservation. This paper describes a first step in this direction, in which the different aspects of the procedure, from knowledge path of the art object to the structural analysis, were studied in the six Michelangelo's statues located in the “Galleria dei Prigioni” (Slaves’ Gallery) at the Accademia Gallery of Florence. We showed that the general principles and criteria expressed in the “Italian Guidelines for evaluation and mitigation of seismic-risk to cultural heritage”, which are specifically devoted to masonry constructions, could be profitably extended to other artworks, like statues, starting from historical research, geometrical survey and material characterization, up to the developing of specific methods of analysis. This research could be the base for future studies to be performed concerning the prevention of seismic damage of art objects, including both bare minimum interventions and specific devices, such as isolation systems.     

Physical principles and efficiency of salt extraction by poulticing

The crystallization of soluble salts plays a significant role in the deterioration of porous cultural property. A common response to salt damage problems is to undertake treatments aimed at reducing the salt content of the affected object, most typically through the application of poultices. The process of poulticing is in theory relatively simple: the wet poultice material is applied to the surface of the object to be treated, and is kept in place for some period of time before being removed. However, in practice, the efficiency of the salt extraction, or even the location of salt accumulation post treatment is more difficult to predict. This paper examines the physical principles of salt ion and moisture transport by which poultices function, and shows how depending on the application methodology, these treatments can be divided into diffusion and advection-based methods. The maximum salt extraction efficiency, the depth to which this can be achieved, and the time scale required is estimated for each type of poulticing system, to gain a better understanding of their working properties and performance. Finally, the pros, cons and limitations of desalination treatments are discussed.     

Damage mechanism in Tournai limestone – The case of the tomb of Admiral Tromp in the Old Church of Delft (The Netherlands)

The funeral monument of Maarten Tromp, in the Old Church of Delft (the Netherlands), is partially built with Tournai stone, a grey-blackish limestone from the Wallonia region (Belgium). This stone is suffering a severe delamination and scaling, which has, in the course of the centuries, led to a considerable material loss from the surface of some of the stone elements. In order to identify the damage process and define a sound basis for the conservation of the monument, a research plan was set-up including, next to the tests and analyses on the stone, a 1-year monitoring of the microclimate in the church and the investigation of the structure of the monument as well as its connections to the adjacent walls. First of all, the stone type was identified by macroscopic features and by thin section microscopy. The moisture distribution in the monument and in the adjacent walls was gravimetrically determined on samples taken at different height and depths. The content and type of salt in the Tournai stone from the monument were determined by X-ray diffraction and ion chromatography, and the results compared to those obtained for the fresh stone. The analyses showed the presence of considerable amount of gypsum, together with a low content of soluble salts (chlorides and nitrates). The SEM-EDS observations showed that gypsum is mainly crystallizing in cracks between the layers of the material. The damage mechanism and the influence of salt on the decay were further investigated by combining hygroscopic moisture uptake, hygric dilation (RH cycles between 50% and 95% RH) measurements and SEM-EDS observations; all measurements were performed both on stone sampled from the monument and, as comparison, on fresh stone specimens. The results show that gypsum is the main salt present, but its role in the damage is not significant. The naturally thin laminated structure of the stone together with the considerable hygric dilation seem to be the main causes of the delamination observed in this stone.     

Non-destructive monitoring methods as indicators of damage cause on Cathedral of St. Lawrence in Trogir,Croatia

Durability is one of the most important engineering properties of cultural heritage monuments. For the purpose of the preservation of structures for future generations, the causes of damage should be determined for the proper choice of type and location of strengthening. The condition of the foundation is difficult to determine without an extensive investigation which is critical because most often the cause of damage is found in such foundations. Geotechnical investigation techniques require the damage and destruction of a building's surroundings or the damage of a foundation with a boring device. Non-destructive methods, such as geophysical methods, are less reliable and the results of such investigations must be combined with the results of subsurface exploration. This paper is a presentation of results achieved through the monitoring of the activity of a number of joints on the Cathedral of St. Lawrence in Trogir, Croatia, which is a cultural heritage monument protected by UNESCO. Excavations for the purpose of flagging replacement in the zone around the east frontage were made in 1979. A probe beneath the main apse uncovered a water cistern where the connection between the mid and north apses is located, and instead of a staggered foundation, a wall with a depth of more than 2.2 m beneath the flagging was discovered. With respect to the given that churches were built on existing ones, it is possible to assume that this is a wall of the late-antiquity church described by Constantin Porfirogenet in the 10th century, built on and later adapted to the foundation for the new structure. The displacement in time of the construction elements of the cathedral were measured and recorded using non-destructive methods. Fissure displacement behaviour, air temperature and air humidity were monitored. The monitoring of the air humidity did not lead to any useful conclusion, so it was quickly dismissed. Observations of data were performed during two periods with an interruption between the two caused by insufficient monetary resources. Data from almost 8 years of continuous measuring are available. The aim of this paper is to present the data of the measured fissure displacements which were correlated with air temperature changes and mathematical models which were based on statistical analysis. Correlation coefficients show that the analysed fissures react to the air temperature changes with different intensities. The obtained data lead to the conclusion that the causes of the structural damage are not found within a displacement or failure of the foundations. Instead, the causes of the damage were found in other parts of the structure.     

Analysis of calcium acetate efflorescences formed on ceramic tiles in a museum environment

Salt crystallization is a major cause of damage in porous materials such as stone, brick and ceramics. The paper reports results of an analytical study on tiles of glazed ceramics that are seriously damaged by acetate salt crystallization. Measurements of the ionic composition of the salt mixture in the tiles and in the efflorescences were carried out. Based on the available information on the phase equilibria in the system comprising of the main constituents chloride, nitrate, acetate, calcium and sodium, the crystallization pathways of the various solid phases are traced. It is shown that a combination of qualitative XRD analysis of the phases present in the efflorescences together with a quantitative determination of the ionic composition is sufficient for the quantitative analysis of major crystalline species in the efflorescences, i.e. Ca₃(CH₃COO)₃Cl(NO₃)₂ · 7H₂O, thecotrichite, and NaCl, halite. The concentrations of these salts are obtained from a solution of the mass balance by least squares analysis. Their formation from the salt mixtures present in the tiles that are subject to acetic acid vapor attack is consistent with the solubility diagram of the above mentioned quinary system. Finally, the possibilities of preventive conservation of salt contaminated ceramics in typical museum environments are discussed.     

Valuing the Benefits of Cleaning Lincoln Cathedral

This paper summarises a contingent valuation study of willingness to pay forcleaning Lincoln Cathedral. A randomsample of the inhabitants of the city of Lincoln and the surrounding area wasquestioned as to their willingness topay for a change in the frequency of a hypothetical cleaning cycle from 40years to 10 years. This change wasillustrated by photographs which showed the same aspects of the Cathedralhalf-way through the two cleaning cycles.Individuals were also asked questions regarding their attitudes towards airpollution in general and its impact on theCathedral in particular. It was found that household willingness to pay isbest predicted by disposable income anda variable indicating distance from the site. Estimates of mean willingnessto pay range from £ 15 to £ 23 perhousehold per annum for those living Lincolnshire. Aggregating these valuesover the number of households inLincolnshire suggests that the annual damage inflicted by air pollution on theappearance of the building so far assoiling is concerned is valued between £ 0.4 m and £ 0.6 m.Different solutions to the problem of starting point biaswere explored and are shown to yield similar estimates of willingness to pay.     

气候变化适应型城市发展战略研究

世界上大部分经济活动和温室气体排放集中在城市,城市应该承担减缓气候变化的责任。城市人口与财产聚集使得气候变化及自然灾害的影响具有放大效应,城市必须在与之共存中做到趋利避害。为减缓和适应气候变化,建设气候变化适应型城市就成为可持续发展的客观要求。气候变化适应型城市以减缓与适应战略应对气候变化,即通过低碳发展战略减缓气候变化和适应战略来应对气候变化带来的极端事件以及气象灾害频度和强度日益提高的趋势,尽可能减轻气候变化所造成的各种不利影响。气候变化最不利的影响是气象及其衍生灾害,气候适应型城市通过灾害风险管理更好地减缓和适应气候变化及各种灾害风险。     

Approach to environmental risk analysis for the main monuments in a historical city

The analysis of environmental risk in historical cities facilitates the development of conservation strategies that can minimize the deterioration of historical heritage sites. Risk maps built with GIS software provide information about the probability of the main hazards in a region, and is a very useful tool to identify, evaluate and prioritize the restoration budget of a city in order to manage preventive conservation. In this paper, new methodologies are applied based on the vulnerability matrix and its relationship with static and structural factors, climate conditions, air quality and social agents. This technique has some obvious advantages in the application of risk analysis for cultural heritage conservation, such as the capability of simultaneous risk assessment and geographical references. The vulnerability study implies an on-site diagnosis analysis and requires an adapted protocol for archaeological heritage. The validation of this methodology was carried out in the historical town of Merida (Spain) with a GIS application (ArcGIS software), where the main monuments of this UNESCO World Heritage site were studied.     

What do plastics emit? HS-SPME-GC/MS analyses of new standard plastics and plastic objects in museum collections

In recent years, plastics are designated as a source of indoor pollution and particular attention has thus been devoted to the identification of emitting low molecular weight compounds. Headspace-solid phase microextraction-gas chromatography coupled with mass spectrometry (HS-SPME-GC/MS) has been already successfully applied for screening emissions from synthetic materials. This analytical tool being also non-invasive, it has been already successfully applied in the field of cultural heritage science for the identification of volatile organic compounds (VOCs) emitted from various museum objects made of natural materials. In this research, we aimed at assessing the use of HS-SPME-GC/MS as an in situ non-invasive analytical tool for a better knowledge of the volatile organic compounds emitted by plastics in collections. The possibility of characterizing plastics based on their emission signatures was also evaluated. Twelve new standard plastic samples, belonging to seven main polymer families widely present in museum collections as well as three naturally aged museum objects, were investigated. In this paper, we provide a survey of the VOCs emitted, and the use of HS-SPME-GC/MS for identifying volatile marker compounds, degradation products, additives, and monomer residues of the plastic synthesis is evaluated. More than 200 different VOCs were identified from the new standard samples. Two categories of VOCs were distinguished: “non-specific” and “specific” ones. We showed that based on the “specific” VOCs, it was possible to identify the nature of the polymeric matrix itself or at least to unambiguously distinguish a plastic by family. Emissions from the museum objects were then characterised, and main volatile degradation compounds considered as degradation markers of the natural deterioration of polymeric matrices, were identified. This identification procedure could be further exploited for the characterization of VOCs emitted by objects made of multiple synthetic polymers. Complementary to other techniques, this analytical tool is an interesting way to assess the risk for the objects stored in the vicinity of emitting plastics.     

Mapping the impact of climate change on biomass accumulation on stone

Several climate parameters affect the growth of organisms and, hence, their capacity to accumulate biomass. In the present research, we analyse the influence of two parameters, temperature and precipitation, on biomass accumulation on stone substrate, and propose a function to estimate it in temperate areas. The expression is subsequently used for the first time to evaluate the impact that climate change would have in biomass accumulation in Europe. The models on climate change predict an increase in temperature and precipitation in northern areas of Europe for the far future (2070–2099), which would lead to a higher accumulation of biomass. Otherwise, a significant reduction in precipitation is expected in southern areas of Europe, associated with a lower biomass accumulation in such areas.     

Environmentally-induced stone decay: the cumulative effects of crystallization–hydration cycles on a Lincolnshire oopelsparite limestone

An investigation has been undertaken at St Andrew’s church, Walpole St Andrew, Norfolk, to establish the underlying causes of the observed stone decay to the upper parts of the six stone piers. The stone decay was first recorded in the early 1930s. The salt-contaminated masonry within the church has been shown to undergo severe salt decay during the summer, with little damage occurring over the winter months. The south aisle piers have been shown to decay 2.5 times faster than the north aisle piers. Although crystallization–hydration cycles have been identified, the rate of decay is at its greatest when the cycling is relatively infrequent. This was not the expected trend. Furthermore, it has been shown that during extended periods where the ambient relative humidity is less than 75%, the rate of decay reaches a maximum. It is the length of this ‘drying’ period that apparently has the greatest influence on the rate of decay and could explain the significant difference in the rate of decay between the south and north aisle piers. The results have serious implications for passive conservation, where it is often recommended to lower the ambient relative humidity to well below the equilibrium relative humidity of the salt contaminant, to avoid crystallization–hydration cycles. Since, at the time of building, the church was situated on the coast, it is possible that the sodium chloride contamination occurred during the building process (1440–1520), particularly since the area was prone to sea-flooding at this time. Alternatively, the salt could have been applied as a treatment during the general restoration of 1897. Whatever the source of the salt, it seems likely that the ambient environment was changed by the insertion of a sealed floor in 1897, which could account for the onset of the salt decay.