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1.
The elimination of spray paint using traditional (chemical and mechanical) methods inevitably entails altering surface characteristics. Hence, the impact and deterioration caused by graffiti in heritage buildings and monuments have led to the development and application of preventive systems in the form of antigraffiti coatings (which prevent paint from seeping into the pores of the surface material and facilitate cleaning). The effectiveness of two of these treatments, a commercial product (fluoroalkyl siloxane, protectosil, marketed by Degussa) and a hybrid organic-inorganic material (Ormosil), was evaluated in five construction materials (limestone, granite, cement mortar, lime mortar and brick), in terms of their penetration into the substrate. A number of techniques were used to determine the penetration depth (SEM/EDX, micro-Raman and LIBS), because a comparative analysis showed that none was universally valid for all types of treatments. The results show that the presence of the coating on the surface of less porous materials only ensures effective cleaning when the surface is fairly smooth. In granite, for instance, the CF3 terminals in the fluorinated treatment hinder spray paint bonding more effectively than Ormosil, but not efficiently enough to ensure complete removal of the paint from granite surfaces.  相似文献   

2.
This article demonstrates the importance of treatment application procedures on the consolidation effectiveness obtained by comparison of the results obtained using three different consolidants on four carbonate stone types, and proposes a general methodology for assessing the potential effectiveness of consolidants in laboratory conditions. It stresses the relevance of taking into account the treatment methodology, given the influence application protocols can have on the overall behaviour of the consolidated material. Several mechanical properties were assessed to demonstrate this influence on the performance of the consolidant. The results demonstrate that the strengthening action achieved with a specific product can only be defined in a strict relation to the treatment protocol used to produce it. The results also contribute towards the definition of standard testing protocols on stone consolidation. The application of a consolidant by direct contact capillary absorption is a reliable procedure and the results are easier to interpret than others obtained by brushing or by full immersion, thus making this procedure a good candidate for an eventual standard laboratory assessment method of the consolidation action of any specific stone/consolidant combination. This study also showed that the best test method to assess the strengthening action of stone consolidants in soft stones is DRMS (Drilling Resistance Measuring System). Moreover, the collection of longitudinal ultrasound velocity profiles determined in stones specimens treated by contact capillary absorption was shown to be a useful non-destructive method to assess the depth of the strengthening action achieved.  相似文献   

3.
The stele of Axum was brought to Rome in 1937, broken in five pieces. The erection of the stele in Rome, in Porta Capena square, required re-joining the pieces with mortar joints and bronze bolts. To give back the stele to the Ethiopian authorities, following an Italian/Etiopian agreement, it was impossible to send the stele as it was, it required separation into three pieces so that the load and dimension of each piece was compatible with the aircraft characteristics. This operation was very delicate, as for cultural reasons it was not acceptable to cut the stone (granite) of the stele with a saw; therefore the only option was to disarticulate the stele in two of the joints. To do that, as the material was weakened by microcracks and decay, it was foreseen to provisionally protect the stone with a carbon-fibre and epoxy fabric and then to apply tension forces to open the joints with a system of jacks.  相似文献   

4.
The paper presents the use of laser radiation for cleaning of beeswax treated granite stone. In the early sixties, prestigious restorers decided to apply molten beeswax on the granite surface of valuable monuments with the aim of preventing the erosive action of atmospheric agents. An interesting example of this treatment is the Renaissance Frieze in the Cloister of the Cathedral of Santiago de Compostela in Galicia (Northwest Spain). With time, salt accumulation beneath the beeswax layer has caused an intense surface disintegration of granite. Conventional cleaning methods can destroy sculptured details of these emblematic monuments. For this reason, excimer laser cleaning has been chosen as a promising non contact, selective and environmentally friendly cleaning technique to be studied.The cleaning tests have been carried out using an excimer laser (ArF, 193 nm), with fluences between 0.5 and 2 J cm−2 pulse−1 and a spot area of 0.025 cm2. Samples representing beeswax films over Roan granite have been irradiated and their degree of cleaning has been studied as a function of the number of pulses and the laser fluence.Cleaning efficiency has been evaluated by FT-Raman Spectroscopy, allowing to establish the beeswax ablation threshold and the ablation rate.Excimer laser cleaning allows a progressive and controlled removal of a few tenths of micrometers of beeswax per pulse without damaging the underlying granite stone.  相似文献   

5.
基于历史档案资料,追述了伦敦大火后英国圣保罗大教堂重建时期石材采运的历史,揭示了各类石材的开采与运输方式、建造中引发的问题,并首次对石材的供应情况进行了定量分析,呈现了石材采运如何成为圣保罗大教堂的重建历时35年之久的主要原因之一。圣保罗大教堂的石材采运问题并非独特案例,同类型的石材在同时期其他建筑中曾被广泛运用,因此对研究那个时代的砖石建筑具有更普遍的参考意义。  相似文献   

6.
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.  相似文献   

7.
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.  相似文献   

8.
Forty-six Streptomyces strains were isolated from paintings and stone surfaces from Tell Basta and Tanis tombs (80 km south-east Cairo, Egypt). Eight of these strains were selected to determine their sensitivity against 13 antibiotics. In general, high levels of resistance could be observed. Gentamycin, spiramycin and doxycycline were the most effective antibiotics against the majority of strains under study. Due to the observed antibiotic resistances, gamma irradiation was studied as a possible alternative to inhibit microbial growth. Isolated bacteria were exposed to different doses of gamma irradiation (5, 10, 15, 20 and 25 kGy). The growth of all Streptomyces isolates except S. canarius was completely inhibited at 25 kGy. The applied doses of gamma irradiation did not cause any observable alterations or colour changes to pigments and binding media (arabic gum, animal glue and egg-yolk) used in the paintings.  相似文献   

9.
Hybrid stone consolidants prepared from tetraethoxysilane (TEOS) and α,ω-hydroxyl-terminated polydimethylsiloxane (PDMS-OH) have been considered as one of the most promising approaches to improve the effectiveness of traditional alkoxysilane-based formulations. They have emerged as response to the negative reports commonly found in the literature: the resulting silica gel phase (SiO2) tends to develop fractures and fissures inside the stone as the gel shrinks during the drying stage. In this work, we employed SEM, solid-state 29Si NMR spectroscopy and compressive tests to characterize SiO2-PDMS hybrid gels. We report the morphological characteristics exhibited by gels prepared in vitro and in situ. It was found an appreciable reduction of gel fracture for hybrids prepared from 5% w/w of PDMS. As TEOS polycondenses, PDMS-OH is chemically incorporated into the gel matrix via Si-O-Si bonds. The inclusion of these elastic chains provides the necessary flexibility to resist the stress imposed by capillary pressure. Additionally, an important hydrophobic character is imparted to the stone.  相似文献   

10.
The growing interest in the conservation of historic buildings encourages the development of water-repellent materials and methodologies to consolidate and/or protect stones. Recently, particular attention was devoted to composites of inorganic oxides nanoparticles and hybrid siloxane or silicone polymers. Here we present a study on the water repellence of a thin protective coating obtained through sol-gel process starting from Glymo and Dynasylan 40®, and loading the silicate matrix with nano-sized silica particles (Aeroxide LE1® -Degussa-Evonik). The coatings were applied to limestone, sandstone and granite samples. The silica nanoparticles have been characterized by XRD, the siloxane matrix through micro-Raman spectroscopy, while the surface morphology was examined by SEM. The efficacy of the treatments has been evaluated through static contact angle measurements and capillary water absorption. The optical appearance of the coatings was evaluated by colorimetric measurements. Nanoparticles at suitable concentration gave high values for the static contact angle (up to ∼ 150°), for all stone species even for four months exposure to atmospheric conditions. The coatings, in the water capillary absorption tests, however, behave as expected only for granite even if the long-term water direct contact reduces the hydrophobicity.  相似文献   

11.
The quality of production (e.g. paper, typesetting, reproduction of illustrations, printing and bookbinding) of a book (reprint) is very important. The quality of a 1978 reprint of a book from 1921 was studied using standard and non-destructive testing methods such as microscopic and spectroscopic techniques. Chemical, physical and colorimetric properties of the papers, colour differences of the prints and typographic tonal density were analysed. Results showed that the reprint is not an identical copy of the original. Some of the differences in the reprint compared with the original (e.g. typographic tonal density) could easily have been avoided while others (e.g. structural and optical properties of paper, colour prints) are unavoidable, mainly because of the influence of internal and external factors on ageing. Ageing influences the properties of paper and colour print: optical and colour properties deteriorate and colour fades. It is concluded that precise and systematic evaluation of the properties of an old book should be carried out before a reprint is prepared. The results of the research, using non-destructive methods such as microscopy, spectroscopy and image analysis, are useful for characterising the properties of paper and printing ink, typography and reproduction of illustrations.  相似文献   

12.
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13.
Titanium dioxide (TiO2) can be used to realize transparent self-cleaning coatings on stone surfaces as an active and preventive protection system, limiting cleaning and maintenance actions, reducing their costs in Architectural Heritage. This self-cleaning ability is due to photo-induced hydrophilicity on treated surfaces. The aim of this investigation is to analyze this effect, since it could bring to a greater water absorption, a potential source of damage for stone surfaces. Titania sol, obtained by sol-gel and hydrothermal processes, was deposited on travertine by spray coating, in two different ways. Water absorption by capillarity, static contact angle and a specific surface water absorption analysis were assessed before and after the TiO2 treatments. The effects of deposited amount of titania on the characteristics of treated surfaces were evaluated. It was shown that there were no evident changes in the substrate reactivity without ultraviolet (UV) light exposure, while it seems that hydrophilicity due to UV light does not lead to higher water absorption, thus encouraging the use of TiO2 coatings in the field of Architectural Heritage. However, before widely applying this conservative treatment, some further researches are recommended in order to better assess its durability and sustainability.  相似文献   

14.
The protective performances of two new fluorinated acrylic copolymers (based on the monomers 1H,1H,2H,2H-perfluorodecyl methacrylate (XFDM) and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFIM) are evaluated and compared with Paraloid B72, a commercial copolymer ethyl methacrylate/methyl acrylate (EM/MA) and its partially fluorinated homologous 2,2,2-trifluoroethyl methacrylate/MA (TFEM/MA). The polymeric materials have been tested on Candoglia marble, a very low open porosity stone (<1%) used in Italian historical architecture (Milan Cathedral). The copolymers were tested according to UNI-Normal protocol. Measurements of capillary water absorption, static contact angles, colour variation and water vapour permeability were made before and after accelerated photo-ageing. FTIR spectroscopy and size exclusion chromatography (SEC) analyses were carried out on samples aged on inert substrate to assess the photostability of the copolymers themselves. The relationship between the protection efficacy and the fluorine content and distribution has been investigated. The results obtained show that the addition of a partially fluorinated co-monomer to the Paraloid B72 copolymer structure did not result in the expected improvement of the coating properties, while the fluorination of the copolymer side chain gave rise to encouraging performance.  相似文献   

15.
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.  相似文献   

16.
This study shows that the sandstone used in the construction of the Church of San Mateo in Tarifa (Cádiz, Spain) is highly sensitive to processes of decay because of a combination of factors that are intrinsic and extrinsic to the material. The mineralogy, texture and porous system of the sandstone and the proximity of the church to the sea all play a part in these processes. X-ray diffraction reveals that there are interstratified chlorite/smectite clays among the minerals that make up the rock. These mixed layer clays have been shown to undergo hydric expansion. This phenomenon may be accompanied and augmented by the presence of NaCl which acts as an electrolyte in osmotic swelling processes. Two varieties of sandstone were used in the construction of the church, namely grey sandstone and brown sandstone. The latter is more porous and undergoes greater hydric expansion, showing a higher degree of deterioration. Ultrasound analysis has demonstrated that both varieties are anisotropic because they contain bedding planes and are affected by the preferred orientation of the phyllosilicates in the rock. The anisotropic nature of these stones was confirmed by capillary suction tests. The capillary front reaches a relatively low height which means that when water is absorbed, the anisotropic textural properties combined with the presence of chlorite–smectite mixed layers in the sandstone result in mechanical (shear) stress between the first few centimetres of the wet stone and the dry area behind. The latter effect favours the development of flakes, so causing the decay of the ornamental stone and the church façade.  相似文献   

17.
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18.
Production of Egyptian blue and green frit was obtained by pure chemicals and natural raw Egyptian materials in different experimental conditions. Changes in stoichiometric ratios and in melting temperatures were tested to synthesize the expected pigments. Obtained products were examined under the polarizing microscope and characterized by XRD analysis; in addition, absolute colour measurements were taken in CIE 1931 and CIE 1976 coordinates to evaluate colour changes. Correlations among chemical composition, melting conditions and recorded colours were discussed.  相似文献   

19.
Ceramic samples made with a mixture of 70% ball clay and 30% quartz sand were moulded and then fired at 900 °C in an electric kiln. Samples were then treated with different products and analyses and tests were performed to evaluate the physical changes induced by the application of these products and their effects on the quality of the ceramics. A petrographic study indicated that the ceramics were composed of quartz, small amounts of mullite and sanidine and traces of hematite. Mineral clays (i.e. kaolinite) disappeared during firing. Two consolidating products (Paraloid B72 and Tegovakon V) and one water repellent (Silo 111) were applied to samples by capillarity, and physical changes (colour, water flow, porosity and pore size distribution) were measured. Finally, we carried out salt crystallization tests in order to determine which product improved the quality of the ceramics. Treated samples registered a decrease in porosity and a general increase in pore size. The application of Silo 111 drastically reduced water absorption by immersion and by capillarity. This product was also responsible for a decrease in pore interconnection. Samples treated with Tegovakon V performed better in terms of their overall hydric behaviour. Silo 111 was the only product that did not modify the colour of samples when compared with untreated ones, and after accelerated aging tests, samples treated with this product hindered the absorption of saline solution into ceramic pores and prevented their decay. Paraloid B72 did not improve any of the properties of the ceramics.  相似文献   

20.
The utilization of laser light to produce fine and selective cleaning of superficial deposits and encrustation from stones was originally proposed more than 20 years ago by John Asmus who performed pioneering trials of laser cleaning on stone façades in Venice, Cremona and Padua. The opportunity to collect stone samples from these sites allowed us to carry out an original study aimed at evaluating the conservation state of stone surfaces cleaned 10–20 years ago by means of three different techniques: Nd:YAG laser radiation, micron sandblasting and chemical pads. Samples of various stone types, as Istria limestone, Botticino limestone and Nanto sandstone were collected and examined by means of optical and SEM microscopy, FT/IR, and EDAX analyses. The results provided preliminary indications that the state of conservation of stone surfaces previously subjected to laser cleaning is generally better in comparison with those which concurrently underwent mechanical and chemical cleaning.  相似文献   

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