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1.
Microbial corrosion of glass causes problems on delicates antique glass samples. Until now, the effect of microbial activity on corrosion phenomena has not been well documented. Only a few studies have been published concerning the microflora growing on glass surfaces.The present study deals with the characterization of cultivable aerobic bacteria isolated from the historical glass window “Natività” in the Florence Cathedral, designed by Paolo Uccello and realized by Angelo Lippi between 1443 and 1444. Microbial strains were sampled from four of the 25 panels of the “Natività” in the occasion of a recent conservation treatment, due to the presence of various kinds of crusts. One hundred microorganisms were isolated, about 50% bacteria and 50% fungi. Bacteria were submitted to morphological characterization and classified in the Gram group. For twenty strains, from different glass panels, the 16S rDNA gene was amplified and sequenced. Sequence analysis showed genus Bacillus, Arthrobacter and Paenibacillus as the most representative. In particular Bacillus and Paenibacillus are crusts associated. Phylogenetic relationship among isolates was determined. Chemical analysis of the glass and crusts completed the study.  相似文献   

2.
The ablation of biofilms by excimer laser radiation was systematically examined in a series of model studies during which the biofilms originating from different historical panels were simulated on model glasses. The composition of these model glasses was modelled on that of the original historical glasses. Our studies have shown that glass composition, climatic conditions and biofilm formation are factors which interact synergetically. It could be observed that various biofilms grow differently on the same type of model glass and that the same type of biofilm shows a different development on various model glasses. The decisive factors for the effectiveness of biofilm ablation by laser irradiation is the formation of the biofilm on the one hand and its corrosive potential on account of its ability to accumulate moisture and to produce glass-damaging metabolites on the other. Glasses of low chemical stability promote the growth of dense biofilms and can be cleaned only with a high energy density, whereas glasses of high chemical stability merely allow for a slow growth of a biofilm spreading two-dimensionally on the glass surface which can be gently removed using low energy density.  相似文献   

3.
The conditions that led to the deterioration of the Madara Horseman sculpture, a relief carved in a sandy limestone cliff in north-east Bulgaria, were studied, with most emphasis on the chemical weathering at the stone–atmosphere interface. Total deposition sampled close to the monument contains high concentrations of NH4+ and K+, which shows the influence of the dense vegetation in the area, and Ca2+, which reflects the cliffˈs weathering products. Ca2+ is also one of the most important constituents (next to aluminosilicates) of the atmospheric particulate collected at the monument. S-rich particles are the most abundant particles in the size range < 0.5 μm. High amounts of biogenic particles (K-P-S-rich) were found, especially for particles < 1.0 μm. The chemical, mineralogical and petrographic characteristics of the stratum that holds the monument were studied down to a depth of 20 cm. Two distinctive processes are active at the stone–atmosphere interface. Firstly, a weathering crust (ca. 2 mm thickness), consisting mainly of calcite and gypsum and enriched with Cl–, K+ and NO3–, is formed in the rain-sheltered areas of the monument. Secondly, karstic dissolution in the interior of the rock substrate leads to the formation of a hard carbonate crust at the surface of the sculpture. This natural surface hardening leads to a state of ‘auto-conservationˈ of the monument. The atmospheric composition seems to have only a limited influence on the deterioration of the Madara Horseman. Far more important are the micro-climatic conditions and the action of lichens.  相似文献   

4.
Marble monuments and facades are susceptible to microbial colonization. Microbial growth on a marble surface can develop into unsightly red stains whose removal has proven problematic. The purpose of this study was to determine if the red-brown stains on Isamu Noguchi's marble sculpture Slide Mantra (1991) could be caused by pigment-producing microorganisms and to assess the potential of enzymatic stain remediation. Traditional cell culture methods were used to isolate a pigmented bacterium from a stained area of the sculpture. Sequencing and analysis of the 16S rRNA gene identified the organism as a strain of Serratia marcescens, and FT-IR spectroscopy demonstrated that the pigment produced by the bacteria was most likely a prodigiosin. Decolorization of the pigment in solution demonstrated that the enzyme laccase from the fungus Trametes versicolor has potential as a decolorizing agent. This study suggests that enzymatic decolorization may be applicable to stains on culturally significant marble caused by microbial colonization.  相似文献   

5.
The exposure of historic stone to processes of lichen-induced surface biomodification is determined, first and foremost, by the bioreceptivity of those surfaces to lichen colonization. As an important component of surface bioreceptivity, spatiotemporal variation in stone surface temperature plays a critical role in the spatial distribution of saxicolous lichen on historic stone structures, especially within seasonally hot environments. The ornate limestone and tufa stairwell of the Monastery of Cartuja (1516), Granada, Spain, exhibits significant aspect-related differences in lichen distribution. Lichen coverage and diurnal fluctuations in stone surface temperature on the stairwell were monitored and mapped, under anticyclonic conditions in summer and winter, using an infrared thermometer and Geographical Information Systems approach. This research suggests that it is not extreme high surface temperatures that determine the presence or absence of lichen coverage on stonework. Instead, average stone surface temperatures over the course of the year seem to play a critical role in determining whether or not surfaces are receptive to lichen colonization and subsequent biomodification. It is inferred that lichen, capable of surviving extreme surface temperatures during the Mediterranean summer in an ametabolic state, require a respite period of lower temperatures within which they can metabolize, grow and reproduce. The higher the average annual temperature a surface experiences, the shorter the respite period for any lichen potentially inhabiting that surface. A critical average temperature threshold of approximately 21 °C has been identified on the stairwell, with average stone surface temperatures greater than this generally inhibiting lichen colonization. A brief visual condition assessment between lichen-covered and lichen-free surfaces on the limestone sections of the stairwell suggests relative bioprotection induced by lichen coverage, with stonework quality and sharpness remaining more defined beneath lichen-covered surfaces. The methodology employed in this paper may have further applications in the monitoring and mapping of thermal stress fatigue on historic building materials.  相似文献   

6.
The stained glass windows of the Pavia Carthusian Monastery are an important testimony of medieval glass making in which a wood-ash flushing component was used. Glass surfaces reveal alteration processes extending to depth, with evidence of microbial corrosion. Electron microprobe analyses coupled with EDS data allow the identification of different steps in the alteration process. Microbial attack occurs in an early stage and determines component leaching of the glass, with the development of reactions in which the crystallisation of gypsum is favoured.  相似文献   

7.
The microgravity method is one of the geophysical tools used in engineering and environmental and archaeological researches, where the detection of subsurface cavities or buried structures is essential. In this study, this technique has been revealed to be an efficient and respectful tool for use in Cultural Heritage restoration studies, such as those carried out in the restoration of historical sites in which the elements to be examined are beneath a shallow coating of material. Therefore, the aim of this microgravimetric survey is to define the exact position and dimensions of a subsurface structure (rainwater cistern) through microgravity response of the medium.For this purpose, the subsurface structure of San Gerónimo Cloister of the Vall de Crist Carthursian Monastery (14th century) has been researched. This monastery was known to be the largest Carthusian Monastery in the region of Valencia (Spain) and one of the most remarkable of the ancient Corona de Aragón. A rectangular grid of microgravity measurement station points was designed to cover the entire surface of the cloister. In addition, a microgravimetric profile was acquired along a hillside close to the Carthusian buildings in order to obtain the density value of the medium.The study was performed using a LaCoste&Romberg D203 gravimeter to detect and to map the shallow subsurface rainwater cistern that probably exits beneath it. This gravimeter has a sensitivity of approximately 1 μgal (μgal = 1.10−8 ms−2) and an accuracy of 3–5 μgal for relative gravity measurements.Two contour maps were calculated (observed gravity and Bouguer gravity values) in order to improve the interpretation results. On these maps we can observe the shape of the body that is causing the perturbation in gravity values. And what is more, it led us to deduce that the central area of the cavity is deeper than the border area. In addition, we can asses that the cavity is 8 m wide and 12 m long, and is symmetrical along its longitudinal axis, but not along its transversal axis.Also, a microgravimetric inversion was performed and the subsurface is split into 7 prisms and the depth and height of each is to be estimated separately. As a result of this inversion we can estimate that the ceiling of the cistern is located about 1 m under the cloister pavement and the cistern floor at a depth of 4 m. The cistern is slightly inclined towards one of its edges by about 20 cm.Finally, the 2D modelling derived by microgravimetric data has allowed us to determinate the shape, dimensions and location of the cistern accurately. In addition we have calculated the cistern capacity (288 m3, that is, 2880 Hl). This capacity was quite enough for the water necessities of 13 monks who lived there permanently, even for making it through the drought periods frequent in this kind of Mediterranean areas.  相似文献   

8.
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9.
Acetic and formic acid vapors emitted from woodwork in historical organs are very important corrosive agents for lead pipes. These acids are slowly released from the wood both during playing and when the pipes are silent. To inhibit this emission process, the wood surface can be modified, by creating a protective layer with alkaline features. However, a coating of wood is not recommended since this could modify the appearance and create a layer not perfectly compatible with the substrate. For this reason, we propose to use some innovative nanotechnology that has been successfully applied for the deacidification of wood samples coming from the Vasa shipwreck. Application of calcium (or magnesium) hydroxide nanoparticles, with sizes ranging from 30–150 nm, allowed a homogeneous distribution of particles through the surface layer of wood simply by soaking (or spraying) it in a alcoholic (or mixed with less polar solvents) dispersion of nanoparticles. Nanoparticles do not modify the wood appearance and distribute randomly within the first layers of wood. The small size of particles accounts for the high reactivity with CO2 from the air, to give the alkaline reserve of carbonates that provide high efficacy in the neutralization of gaseous acids. The emission of volatile organic compounds (VOC) from the treated wood was determined by using an emission test cell, Field and Laboratory Emission Cell (FLEC). The results show that the emissions of acetic acid vapor from nanoparticles treated wood was very low (< 70 μg/m2 h) during the first 13 month. In contrast, untreated wood emitted high concentrations of acetic acid vapor (200–400 μg/m2 h).  相似文献   

10.
The Grotta of Buontalenti (GB) was built at the end of the 1500s during the Medicean period. One of the rooms that constitutes the Grotta is decorated with mosaics composed of tesserae of stained glass. The GB underwent several restorations, which took place between the end of the 1700s and 1980s, which are poorly described and documented, leading to some uncertainties about the extent and phase(s) of restorations of the mosaics. The original tesserae and mortars of the GB were analysed for their mineralogical and chemical composition. Results indicate that glass tesserae have a common sodic base composition. Cluster analyses, however, performed considering the glass base composition (i.e. SiO2, K2O, Na2O, MgO, CaO, and Al2O3), identify three groups of samples: A, B, and C. A and B are characterised by chromophores such as Se and Cr suggesting a recent age (50–150 years) of the tesserae. On the contrary, chromophores (Fe, Mn, Cu, Co) and opacifiers (mainly SnO2, Pb2Sb2O7, Ca2Sb2O7) of the third group (C) indicate a preparation procedure known since ancient times. Based on their mineralogy and petrography, four different types of mortars were recognised. The mortars cannot be precisely dated. However, by matching their composition with that of the glass tesserae, it can be concluded that one type of mortar may be of the Medicean period, whereas the others are relatively recent, probably of this century. This evidence, in accordance with historical data, points to a Medicean age of group C tesserae. Restorations of the GB involved partial substitution of the mortars whereas the glass tesserae were largely recycled with limited addition of new materials.  相似文献   

11.
The paper presents our results concerning a complex investigation by reflectance spectroscopy (RS) and Electron Paramagnetic Resonance (EPR) of the defects induced by gamma irradiation in 22 different historical pigments. Gamma irradiation is used to destroy microflora and insects which are involved in biodeterioration processes of art works such as paintings. At the same time, it can induce defects i.e. color centers which are likely to modify the original painting colors by altering the embedded pigments. Accordingly, RS was used to quantify, by means of CIELAB color space, the contribution of irradiation defects to the pigments color changes, while EPR spectroscopy, in view of paramagnetic properties of color centers, was used to confirm their presence after irradiation. Our investigations showed that, excepting marble dust whose color alteration was still observable after 3 months, color changes induced by irradiation in all other pigments disappeared after about 30–40 days. In addition, RS as well as EPR measurements suggest that color changes are related to irradiation color centers, this finding being confirmed by the coincidence, within experimental uncertainties, of the half-life time color changes as obtained by these methods.  相似文献   

12.
Red lake pigments and dyes used in works of art were characterized by microspectrofluorimetry, a new tool in the field of cultural heritage. Emission and excitation spectra were obtained with high spatial resolution (8–30 μm) in cross-sections from paintings by Vincent van Gogh and Lucien Pissarro and from millenary Andean textiles. The fluorophores were identified by comparing their spectra with those from historic reconstructions assembled in a database. In the paints, purpurin and eosin lakes were detected. In the Paracas and Nasca textiles, dated from 200 B.C. to A.D.1476, purpurin and pseudopurpurin were the red dyes used. Carminic acid was detected in textiles dated close to the Inca Empire, A.D. 1000–1476. The results obtained with this new technique were confirmed and are in agreement with those obtained with conventional methods, requiring microsampling, such as HPLC-DAD-MS and SEM-EDX.  相似文献   

13.
Leaves of common deciduous trees: the horse chestnut (Aesculus hippocastanum) and linden (Tilia spp.) from the park, near one of the most important cultural institutions, the National Library of Serbia, were studied as bioaccumulators of heavy metal (Cr, Fe, Ni, Zn, Pb, Cu, V, As and Cd) air pollution. The leaf samples were collected from the urban park exposed to the exhaust of heavy traffic. The May–September heavy metal accumulation in the leaves, and their temporal trends, were assayed in a multi-year period (2002–2006). Comparing the obtained concentration of the investigated elements from the beginning to the end of growing seasons, a significant rate of accumulation was determined for a majority of measured elements, and it was concluded that these tree species (horse chestnut and linden) can be used as bioaccumulators of the investigated heavy metals. The SEM-EDAX analysis of individual particles deposited on the leaves showed that the 50–60% belong to a class of fine particles (D < 2 μm), mainly of anthropogenic origin. Thus, the investigated tree species could be grown as a natural barrier against urban air pollution in the vicinity of libraries, museums and other buildings for cultural heritage storage.  相似文献   

14.
In a parallel study, it has been shown by comparison of successive TV-holography campaigns that murals in the convent of Müstair (Switzerland) have progressively detached from their substrate over a time interval of 5 years (J Cult Herit 2009). Here, we focus on the dynamics of the ongoing detachment processes. In order to regularly measure small surface displacements in situ over a long duration of several years, a new method that we call Mirror Micrometry (MM) has been designed and implemented. This method monitors the reflection of a light beam by a mirror that is mounted to the surface of interest for the duration of the experiment. The mirror is designed to rotate about a pivot as small displacements in the detaching surface occur, thus deflecting the reflected light beam. Measurements over more than three years in the Convent Church and in the Holy Cross Chapel reveal various types of surface displacement perpendicular to the wall surface. These are correlated with relative humidity (RH) changes in the room climate. Reversible short-term variations of approximately ±5–10 μm occur with periods of one to several weeks and relate primarily to weather changes. Reversible long-term variations of ±5–10 μm correspond to averaged seasonal humidity changes. Irregular and irreversible movements in increments of 20–30 μm record very localised progressive detachment steps. A semi-quantitative correlation of approximately 1 μm surface displacement per 1% RH change is calculated. Based on the fact that nearby measuring points can simultaneously move in opposite directions, a geometric model is drawn to explain deformation by hygric swelling and shrinking of different shapes of detached layers.  相似文献   

15.
Although Venice is regarded as being one of the most important centres of glass manufacture and trade in Western Europe, little is known about the origins of the Venetian glassmaking. Some archaeologists suggest there is a continuity in the history of glass making, in its transplantation from the Roman centres of the mainland (Altino and Aquileia), first to some islands of the lagoon, and later to the town. Some others, instead, think that there was no continuity at all and that the art of glassmaking was imported in Venice from the Islamic glass factories of the Middle East. Of great help in answering this and other technological questions is the information about the composition of ancient glass from well-dated excavations that allows to conclude on the early technology, sources of raw materials and long-distance trade. Some significant glass findings, including fragments of pots used for glass melting, were found on the island of Torcello and, more recently, in two emergency excavations in the historic centre of Venice. In this paper, the chemical composition of a large set of glass findings (and related materials) from the Venetian lagoon dating from the 7th to the 13th centuries is determined by X-ray microanalysis in order to throw new light on the glassmaking technology in the early centuries of the Venetian tradition. The results show that in this period there occurred a gradual transition from the Roman technique (a two-ingredient formulation with silica-lime sand and natron as a fluxer), towards the use of silica sand and soda plant ash. There is evidence, therefore, for a production continuity with the Roman period (melting pots and glass scraps with a natron-based composition), yet restricted to transparent blown items. No evidence was found for a local production of glass tesserae for the mosaics of the church of St. Maria Assunta in Torcello.  相似文献   

16.
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.  相似文献   

17.
Zinc oxide nanoparticles were prepared and used for surface treatment of oil paintings painted on paper supports. The prepared coating mixture containing 2% of ZnO nanoparticles showed excellent transparency. The effect of coating on protecting the paper support and paintings against microbial attack by Trichoderma reesei and Aspergillus niger, dirt accumulation, and UV aging was studied. Coatings containing ZnO nanoparticles enhanced the durability of linseed oil-based paintings toward UV aging regarding the change in color. Coatings containing ZnO nanoparticles improved resistance to microbial attack when subjected to inoculums containing T. reesei or A. niger fungi. In addition, coatings containing ZnO nanoparticles reduced accumulation of dirt on oil paintings when left in open air for 6 months; cleaning of paintings was quite easy compared to the non-coated paintings or those coated with the varnish without ZnO nanoparticles.  相似文献   

18.
The aim of this study is practically to establish a chemical strategy for cleaning soiled deposits and encrustations on archaeological glasses. Investigations were performed on a series of Roman glass samples (Fragments and complete objects) coming from different excavations in northern Jordan. The chemical composition of the glass samples was determined by X-ray fluorescence spectrometer (XRF) analysis technique, whereas X-ray powder diffractometer (XRD) and Energy dispersive X-ray (EDX) methods were used to determine the mineralogical and elemental composition of the soiled deposits and encrustations on the glass surfaces. Furthermore, Scanning Electron Microscopy (SEM) examination and optical assessment were performed before and after cleaning glass. The glass samples were subjected to different cleaning protocols such as Calgon (Sodium hexametaphosphate), ethylenediaminetetraacetic acid (EDTA) at different pH values, citric and tartaric acids and piranha solution (a solution of sulphuric acid and hydrogen peroxide). Sepiolite poultices soaked by chemical agents were the most suitable methods used for applying chemical solutions on the glass surface. It can be concluded that EDTA is generally accepted as the most effective chelating agents recommended for cleaning encrustations on durable glass. It was more effective and safe at neutral pH with low concentrations around 5 to 7%. The calcareous crusts can safely be removed by using a piranha solution. Citric and tartaric acids appeared a moderate efficiency on cleaning weathered and stable glass. Calgon has a tendency to damage corroded and iridescent surfaces, and should be avoided when cleaning weathered glass.  相似文献   

19.
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20.
Two multivariate statistical tools – principal components analysis and cluster analysis – were applied to aid in the interpretation of the historical development of St. John the Baptist's church (?i?e, Slovenia). With these methods it was possible to distinguish between the types of mortar used in the Romanesque and Gothic time periods. The investigated structure is a ruin with poorly preserved fragments of historical mortars, so tracing the individual stages of its construction proved to be a demanding task. Its chemical composition was determined by inductively coupled plasma mass spectrometry (ICP-MS) and the results of the content of various oxides were statistically evaluated to interpret the age of the southern wall of the church.  相似文献   

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