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1.
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   

2.
Stained glass windows belong to the most precious pieces of art in many European countries. Examples of heavily endangered paint on glass are reported in the literature and mainly related to condensation effects and air pollution, as stained glass windows preferably remain in their original architectural surrounding. Several surface coatings and paint treatments have been proposed to consolidate and protect degraded paint. Very often, the selection of the materials is based more on practical aspects than on scientific research. This study concerns the comparison of some traditional, modern and newly developed consolidants for the preservation of historic glass paintings. Experiments have been carried out with model painted glass samples simulating weathering phenomena of originals. Traditional materials like Paraloid B72, modern ones like SZA (proposed by the Fraunhofer-Institut für Silicatforschung, ISC), and three new consolidants prepared by the sol–gel method and based on different hybrid organic–inorganic alkyl-alkoxysilane systems have been considered. The adhesion, penetration, stability, hydrophobicity, mechanical and chemical resistance are properties and requirements tested to prove their effectiveness and range of use. The three new materials developed in this study for the consolidation of paint on glass have the potential to offer alternatives to existing materials. Nevertheless, further research is necessary before their application in restoration workshops can be recommended. A strategic approach is requested to avoid risks for these valuable historical originals and to contribute to the long-term preservation of the paint on stained glass windows in their original sites.  相似文献   

3.
Microbial colonization of the surface of historic glass panels and the subsequent biodeteroration of glass are well documented phenomena. Yet little is known about the composition of this microflora that has to be adapted to low nutrient conditions and a dry environment. The microbial community growing on glass window panels from four different locations and ages ranging from 30 to 600 years was analyzed in situ using confocal laser scanning microscopy with nucleic acid stains and fluorescently labeled rRNA-targeted oligonucleotide probes for the domains Bacteria and Eucarya. A typical biofilm of the studied glasses displayed a total thickness of approximately 10–60 μm. Microbial colonization of the glass surface was heterogeneous at 0.8–7% areal coverage. The dominant microbial group belonged to the filamentous fungi. A different attached microflora was found only on one glass surface. This sample was sparsely colonized with areal coverage of 0.8% and a thickness of 10–20 μm; the biofilm consisted of single bacterial cells and microcolonies. Chemical composition and durability of the glass samples and availability of an additional organic layer were important factors influencing the extent of microbial growth. Information about the thickness and microbial composition of biofilms offer an essential background to optimize cleaning procedures or conservation strategies for stained glass windows.  相似文献   

4.
The methodology of protecting the European stained glass windows against environmental risk (e.g. meteorological factors, air pollution, microorganisms) by means of an external glazing is not new. In spite of many scientific studies carried out in the last 20 years, some questions were still up for discussion. The European VIDRIO (2002–2005) project gave an answer to these questions. The research carried out by the different project partners established a new multidisciplinary approach aimed at evaluating the efficiency of the protective glazing systems and their effects on stained glass windows conservation, and finally at assessing the most appropriate strategy to preserve stained glass windows. Scientific results showed that the so-called isothermal glazing (i.e. ventilation by the air coming from the inside of the building) protected efficiently the ancient stained glass window from environmental attack (i.e. rain, pollutants, condensation, thermal shocks) with very limited secondary effects. The scientific research highlighted that its efficiency was strongly related to the technical design of the protective system. In particular, the ventilation and the size of the interspace had to be carefully considered. The research developed within the VIDRIO project was turned into general recommendations to the owners and practitioners on the best practice for the stained glass windows future conservation.  相似文献   

5.
The impact of lighting, heating and people in re-using historical buildings are discussed for the case study concerning the ceremony room (i.e. the Giant Hall) of a mediaeval palace in Padova. The Hall has substantially four major problems for conservation: (i) the impact of heating, lighting and people when the room is used; (ii) many cracks on the oak panels of the coffered ceiling; (iii) the soiling by dust and soot particles deposited on the frescoes; (iv) the stained glass windows. A microclimate study was performed to know the impact of the environmental variables, and the use of the room, on the artworks preserved inside. The study has proved the impact of the lamps (both incandescence and compact fluorescent lamps) on the ceiling, the penetration of external air in the room, the heat and the moisture released by people, the impact of sunshine through windows and the scatter diagram of the daily cycles in temperature (T) and relative humidity (RH). During winter concerts, the strips of lead which are wrapped round the edge of the cut glass pieces in stained glass windows easily drop below the dew point and form condensation, starting corrosion. A discussion concerns the allowed variability, which should not exceed risk thresholds. A safe interval can be established within the area determined by the most frequent T and RH natural cycles. In fact, both of the cycles were compatible with the artefacts, or the artefacts were already damaged to allow the exceeding dimensional changes. Attention should be paid in the variability external to this area, especially approaching or exceeding a limit equal to twice the mode of the natural variability.  相似文献   

6.
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   

7.
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   

8.
The German Federal Foundation for the Environment (Deutsche Bundesstiftung Umwelt) is one of Europe's largest organizations of its kind. It supports innovative, exemplary projects for the protection of the environment and of national historic monuments and cultural landscapes. All projects are set up to provide a platform for researchers, craftsmen and restorers to find a common solution to difficult problems in conservation practice. More than 360 projects have been funded since 1990. Two recent projects deal with laser cleaning, one for stone and the other one for stained glass windows, the latter being presented here. This publication gives an overview on cleaning problems on stained glass windows and the project methodology. The interdisciplinary approach of the project provides the possibility of including experts in different fields to examine perspectives and limits of laser cleaning for stained glass windows. Two other publications in this issue (LACONA III) give selected results on cleaning experiments achieved within this project.  相似文献   

9.
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   

10.
The application of lasers for the removal of superficial deposits from historic stained glass is a comparatively new field of scientific interest. Experimental studies concerning the behaviour of glass substrates and the corresponding superficial deposits towards different laser wavelengths were carried out. The experiments were performed using wavelengths of λ = 193 nm (ArF-Excimer), 308 nm (XeCl-Excimer), 355 nm (Nd:YAG third harmonic) and 1 064 nm (Nd:YAG fundamental) in comparison to λ = 248 nm (KrF-Excimer). This comparison is due to the fact that the present knowledge is based on the 248 nm wavelength. Specially prepared model glass samples representing the original fragments and samples of organic polymers (formerly used as a protective material for historic stained glasses) were used to study the effects of laser radiation and were subsequently characterised by optical microscopy.  相似文献   

11.
Rescue archaeological excavations at an urban glass workshop of the 12th century AD in the city of Murcia (Spain) have provided one of the few evidences of glass production in the ancient Islamic territory of Al-Andalus. This paper reports the results derived from a chemical–physical characterisation study carried out on a representative sample set of glass fragments and industrial debris from that workshop. The main objectives of the research were to contribute to the knowledge of the type of glasses produced and provide some insights into the technology developed to obtain different colours in glasses. The resulting data indicated that both high-magnesia plant ash (HMG) soda-lime-silicate and soda-lime lead-silicate glasses were produced. They also indicated a deep knowledge of glass colouring techniques, which suggests that a careful control over the glass melting processes was achieved. Among others, the occurrence of bulk-coloured silver yellow and copper ruby red transparent glasses prove the skills reached by Murcian glassmakers. These results shed new light on the Islamic glass technology of a geographical area in which, up to now, little compositional and technological data from glass workshops were available.  相似文献   

12.
The study of the interaction between silica glass and saturated Ca(OH)2 solutions can be a useful approach to resolve the problem of the adhesion between lime-sand mortar and clay bricks. Since it is reasonable that the silica–calcium hydroxide system well simulates a brick–mortar system, experimental observations concerning the interaction of silica glass and this strong basic solution should be of value for the comprehension of the chemical reactions that could take place at the mortar–brick interface, maybe affecting the adhesion between the two building materials. We demonstrated the effects of saturated Ca(OH)2 solutions on commercial pure silica glass (fused silica) and on silica films obtained via a sol–gel process by means of dip-coating. Silica samples were dipped in the solutions at different temperatures (room temperature, 60 and 80 °C) and at different time intervals (1 and 21 h) and then they were analysed by means of surface techniques: X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM). It has been shown that Ca(OH)2 reacts with the silica glass network. The experimental results clearly show a very different behaviour of sol–gel silica with respect to fused silica, probably because of their different nanostructure. Many problems concerning the interaction of silica and Ca(OH)2 are still to be solved, but the results of this research strengthen the idea that adhesion between lime-sand mortar and clay bricks is caused not only by carbonation of calcium hydroxide contained in the mortar, but even by some chemical reactions involving the brick constituents and calcium hydroxide itself. The final products, calcium silicates, may induce a chemical continuity between lime-sand mortar and clay bricks.  相似文献   

13.
On-line monitoring or even closed-loop control is necessary to avoid over-cleaning in case the ablation process is not self-limiting. Therefore, the laser-induced breakdown spectroscopy (LIBS) was used. Basic investigations were carried out on original sandstone samples (Elbsandstein) with strong encrustations as well as medieval stained glass samples (13th century from Cologne Cathedral). The spectroscopic study has shown that the plasma emission can be used for determination of the elemental composition of the ablated material. The plasma was initiated by 248-nm pulses of an KrF-excimer laser (30 ns FWHM). For the spectroscopic analysis, a grating spectrograph in combination with an optical multichannel analyser was used. For the glass and stone samples we obtained a continual alteration of the LIBS spectrum (vanishing of peaks and generating of new element peaks) during the removal process. Thus, certain element peaks can be used to distinguish between encrustation layer and valuable underlying material. To show the potential of LIBS we designed an experimental laser cleaning set-up including closed-loop LIBS control and demonstrated successful automatic cleaning of an original glass fragment.  相似文献   

14.
This work reports mainly the results of an X-ray Absorption Spectroscopy (XAS) study carried out on coloured glass tesserae from the palaeo-Christian mosaic which decorated the votive chapel of St. Prosdocimus (Padova) until its replacement with the current frescoes of Renaissance age, and which is one of the only two known mosaics in the Veneto region (Italy). The study aims at clarifying how the different local structure, oxidation state and quantity of copper influenced colour. Analysis of high-resolution Cu-K edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra showed that copper is present as cuprite (Cu2O) in orange samples and as metallic copper in red and brown ones. These phases are responsible for both the colour and opacity of the samples. In addition, Cu1+ ions linked to the oxygen atoms of the glass framework were identified in ratios of about 60% and 30% of total copper in orange and red/brown samples, respectively. In blue and green samples, copper is dispersed in the glass matrix as a mixture of Cu1+ and Cu2+ ions, and no crystalline phases are visible. In this context, the Cu1+ and Cu2+ contents in glass were also quantified thanks to suitable standards, demonstrating that, when Cu2+ is the main chromophorous ion, colour intensity is directly correlated to its content in the glass. In particular, in green and blue samples, coloured by copper, Cu2+ content varies from 26% to 56% of total copper, and the higher contents of Cu2+ are shown by more intensely coloured samples. It should be stressed here that the green colour of the analysed tesserae is given by the physical interaction of blue colour, due to Cu2+ ions, and yellow colour, due to Pb antimonates used as opacifiers.  相似文献   

15.
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   

16.
A significant number of archaeological finds of the 13th–16th century from the Tuscan sites of Germagnana and Gambassi in Valdelsa—FI, was studied by different physico-chemical investigations (SEM–EDS, ICP, Mössbauer spectroscopy, XRD, XRF, TG-DTA) in order to contribute to clarify the production methodology and the pre-industrial glass manufacture technology. The studied samples are mainly non-vitreous finds as production waste, refractory materials, crucibles and raw materials; also vitreous finds as frits, skims, glasses (glass masses, glass working waste and finished products) have been taken into consideration. The obtained petrographic and physico-chemical data strongly suggest that both Gambassi and Germagnana glass manufactures were strictly connected with the sources of vitrifiable materials, situated in Tuscan sand quarries. In particular a comparison between sands from the neighbouring quarries and appropriate finds of the two archaeological sites evidences that the employed vitrifiable materials possibly belong to La Casina La Cava resort. The archaeological classification, based on macroscopic observation and stratigraphic position, was compared and verified with the scientific classification of the examined finds of Germagnana and Gambassi sites based on their composition, morphology and physico-chemical properties.  相似文献   

17.
A KrF-excimer laser operating at λ = 248 nm was used for basic studies in cleaning ancient glass surfaces. For irradiation a mask projection technique was applied. A modified optical set-up was designed using cylindrical lenses for large area removal by line scanning. Previous investigations revealed insufficient knowledge about interaction processes between UV-laser radiation and individual surface layers of encrusted historical glass. Thus, first detailed studies were carried out on special model glass samples simulating the behaviour of historical glass. The potential of removing crusts, bio layers as well as layers of different conservation materials (due to former conservation work) were examined. The avoidance of damaging material such as gel layers, paint layers or the bulk glass was of great importance. Removal rates and thresholds for the materials mentioned above were carried out. The collected data enables a comparison and evaluation of the feasibility for the removal of superficial layers from historical glass artefacts. The results indicate that in some cases a closed loop process control will be necessary to avoid over-cleaning.  相似文献   

18.
This paper reports results derived from a chemico-physical characterisation study undertaken on an important ensamble of early 20th century stained glass windows from Madrid and signed by the prestigious and well-known Maumejean Fréres company. The study is part of an on-going project of restoration and conservation carried out by the National Glass Centre Foundation (FCNV, La Granja de San Ildefonso, Segovia, Spain). The basic aim of the research was to assess their current state of conservation and to study the degree of damage suffered throughout the last century by different materials employed in their production, namely colourless and coloured glasses, grisailles, lead cames, and putties used to fix glass pieces into the lead cames. Selected samples from these materials were characterised through optical microscopy (OM), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), VIS spectrophotometry, and X-ray diffraction (XRD). As a general rule, most of them presented an acceptable state of conservation, without any of the known degradation phenomena of more ancient stained glasses (e.g. Medieval, Renaissance, etc.). However, some remarkable alterations were observed. Important deposits of soot and dirt particles coming from a polluted urban environment were detected, producing a slow blackening of the panels. Resulting data have been useful to design and optimise a combined conservation and restoration strategy in the recovery of this valuable legacy of early 20th century stained glass windows from Madrid.  相似文献   

19.
The experimental procedures and most important conclusions of the first on-site Raman study of the stained glass windows in the upper chapel of the Sainte-Chapelle, Paris are discussed. Some of the windows suffered damage during/after the French Revolution and were partly restored in the 19th century. Measurements were performed with a new portable Raman instrument on colourless, blue and green stained glasses. We illustrate how the Raman signature of the glass makes it possible to distinguish between medieval K/Ca or 19th century restored Na/Ca-based silicates and to determine their weathering degree. This is achieved by means of the extraction of vibrational parameters and then processing them, using chemometric approaches, principal components and cluster variation analyses with varying degrees of complexity. The Raman scattering intensity of weathered glasses is used to determine their relative age. The results differ from those presented in the Corpus Vitrearum Medii Aevi (obtained by visual inspection) and therefore demonstrate the need for updating these reports with modern methods such as in situ Raman spectroscopy.  相似文献   

20.
This articles reports new discoveries relating to ground glass and silica in European easel paintings from the 15th to the 17th centuries that were created by various German, Italian and Netherlandish artists. The earliest known additions of these extenders date to the early 1430s. Glass powder of varying fineness, prepared from vessel or window cullet, is often found in red lake glazes as well as in other colours or preparatory layers of paintings. SEM/EDX analyses of the glass particles reveal a variety of chemical compositions (soda ash, wood ash, wood ash-lime, wood ash-lead, mixed alkali), which are discussed with respect to the provenance of the paintings. Historical sources on painting techniques mention glass additions most frequently to accelerate drying of oil paints, but also occasionally to facilitate grinding of pigments. Another possible function of powdered glass and silica, especially in oil-bound red lake glazes, is that of a transparent filler, as will be here discussed based on paint trials.  相似文献   

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