An investigation into the effect of wavelength in the laser cleaning of parchment

An investigation has been undertaken into the effect of wavelength in the laser cleaning of parchment. Tests have been carried out using the fundamental (1 064 nm), second harmonic (532 nm) and fourth harmonic (266 nm) outputs from a Q-switched Nd:YAG laser (pulse length 10 ns). Initial testing was carried out on new parchment to characterise the damage caused by overcleaning. The fluence and wavelength of the laser beam were then optimised so that any damage to the parchment or loss of ink during dirt removal from a late eighteenth century parchment document were minimised. The cleaned surfaces were examined by optical and scanning electron microscopy and analysed by measurement of the shrinkage temperature of cleaned collagen fibres. The laser-cleaned areas were compared with uncleaned areas and areas cleaned by traditional techniques.     

Accelerated hydrothermal degradation of fibres of Phormium tenax (New Zealand flax)

Solid-phase microextraction (SPME)–gas chromatography (GC)–mass spectrometry (MS) has been applied to the analysis of acetic acid and furfural that are emitted from the fibres of Phormium tenax (Xanthorrhoeaceae) [New Zealand flax] during degradation. Accelerated hydrothermal ageing of fibres of the Ruawai cultivar of P. tenax for 55 days at 70 °C resulted in the production of acetic acid at a level greater or equal to 1.65 mg g^–1 fibre. This corresponds to only 8.5% of the acetyl groups present in the fibres. These groups are an important source of acetic acid, which is capable of damaging the fibres. The rate of production of acetic acid suggests that a heritage object made from the fibres of P. tenax, that was stored in damp ambient conditions, would undergo significant deterioration after a relatively short period. Other volatile products released during ageing included furfural, a series of short to medium chain aliphatic aldehydes that were derived from the oxidation of long chain unsaturated fatty acids on the fibres and a small group of products that were derived from carotenoids. The levels of furfural were determined to be approximately 0.75% of the potential production but at these levels, furfural could contribute to unpleasant odours from unventilated items. Fibres from six cultivars of P. tenax were found to release acetic acid and furfural all at the same rate. The levels of acetic acid that can be generated from these fibres are sufficiently high that low moisture levels and continuous change of air is required to minimize degradation of cultural objects that are made from these fibres and displayed in museum halls.     

Clothing as a source of fibres within museums

This paper examines the role of visitors’ clothing as a source of fibres and dust in museums. Some idealised experiments determined the mass of fibres and dust emitted from clothing and the range of particle sizes found. In chamber studies it was possible to examine the effect of different humidity and airflow on fibre release. Image analysis was used to determine particle size from sub-micron to giant particles including clothing fibre. Clothing was a significant contributor to fibre and dust generation and at low humidity winter garments composed largely of wool was especially large. High air velocity increased particle shedding from clothing. Clean clothing typically released a third to a tenth the weight of particulate material from dirty clothing. It is possible that the fibres and dust produced indoors from visitors could be reduced by an air-shower at the entrance, but less intrusive procedures such as keeping visitors at a distance from objects may be preferable.     

The Effects of Gender and Power Distance on Nonverbal Immediacy in Symmetrical and Asymmetrical Power Conditions: A Cross-Cultural Study of Classrooms and Friendships

Abstract

This essay examines the relationship between globalization and the diasporic movements of cultural groups as manifested in their communication practices of identity. I argue that diasporic groups dynamically reconstitute their understandings of cultural tradition, authenticity, and identity in line with their diasporic contexts and experiences. I frame my argument around two different diasporic Pacific Islander groups Tongans and Hawaiians—each situated in a particular kind of diasporic/global movement with specific historical, political, and economic dimensions. Qualitative in-depth interviews were conducted with each of these groups in this study.     

Particle-modified consolidants: A study on the effect of particles on sol–gel properties and consolidation effectiveness

In this paper, we have performed a systematic characterization of sol and gel properties for particle-modified silica consolidants filled with titania (TiO₂-PMC), alumina (Al₂O₃-PMC), and silica (SiO₂-PMC) particles. Viscosity of the sol is not increased much by loading with particles, especially for TiO₂-PMC and SiO₂-PMC. Composites show a strong reduction of silicate network shrinkage. Also, the incorporation of oxide particles into the matrix increases the elastic modulus while decreasing the thermal expansion. In agreement with the improvement of bulk gel properties, we observed better performance of PMCs against unfilled silicate upon consolidation of Ohio Massilian sandstone. Notably, the sulfate crystallization test has less effect on PMC-treated than on silica-treated samples.     

Thermographic study of the illuminations of a 15th century antiphonary

In this paper, we present an application of the infrared thermography to the study of illuminations. In particular, we analyze a 15th century antiphonary from the Biblioteca Angelica of Rome to characterize the conservation state and the structure of the illuminations on the occasion of its planned restoration. We show the results achieved from the stratigraphic investigation of the gilded surface, the parchment substrate and the underdrawing. The obtained information have been, then, used to direct the necessary restoration steps and also to assess the effectiveness of the treatments by a comparative analysis of the thermograms recorded before and after the restoration.     

An approach of a study of the interaction between collagen and sulphur dioxide by using ESI and MALDI-TOFMS

In order to further understand the interaction between pollutants and collagen, a study with two plain proteins, bovine serum albumin (BSA) and lysozyme, both exposed to SO₂ has been carried out. X-ray analysis of the samples using a scanning microscope spectrometer (SEM) was carried out. Samples were analysed by mass spectrometry using an electrospray source coupled to a time of flight analyser (ESI-TOFMS) and by Fourier transform infrared spectroscopy (FT-IR). A chemical cleavage using cyanogen bromide (CNBr) was carried out on BSA exposed to SO_2, the CNBr cleavage fragments were analysed by matrix-assisted laser desorption/ionization source coupling to a TOF analyser (MALDI-TOFMS). All these results allow us to determine a hypothesis for the mechanism of the reaction between SO₂ and BSA.     

Mapping air pollution effects on atmospheric degradation of cultural heritage

The costs for deterioration and soiling of different materials due to air pollution are huge and the damage to culture targets endangers seriously the rich European cultural heritage. Within the sixth Framework Programme of the EU, the overall aim of the CULT-STRAT project has been to assess and predict the effects of different pollutants on materials and objects of cultural heritage in a multipollutant scenario and to identify indicators and thresholds levels of pollutants. In particular, the present paper reports one of the studies carried out in the CULT-STRAT project at city level and focused on the town of Madrid (Spain). Different maps are shown for the past, present and possible future scenarios: inventory of stock of cultural heritage for each selected material, concentration of selected pollutants (SO₂, NO₂, O₃ and PM₁₀), corrosion (cast bronze) and recession (Portland limestone), exceedance of tolerable degradation thresholds for each material and corrosion-cultural heritage overlapped maps. The model and the methodology developed could be useful if apply it to towns, regions or countries in order to quantify the percentage of Cultural Heritage at risk or to quantify the percentage of the area where corrosion/recession exceeds the established tolerable levels.     

Environmental conditions controlling the chemical weathering of the Madara Horseman monument,NE Bulgaria

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.     

Microstructure,composition and processing of 15th century Vietnamese porcelains and celadons

Fifteenth century porcelains and celadons are the most interesting ancient Vietnamese ceramics, both from the material and aesthetic points of view. This paper reports on composition, microstructure and technological processing of the Chu Ðâu-My Xa (Hai Duong province) ceramics. Samples come either from the kiln site or from the Cù Lao Chàm (Hôi An) shipwreck. Chemical analysis, scanning electron microscopy, EDX analysis, X-ray diffraction, Raman spectroscopy, thermal expansion/shrinkage and open porosity measurements were systematically performed. The results show the Ca (+K)-based glaze, high-temperature-fired bodies, by one- or multi-step firings. Mullite phase (3Al₂O₃·2SiO₂) was formed in large amount indicating the true porcelain quality of the samples under study. The matrices used for overglaze colouring (e.g., the green, red and metallic-lustre) are lead-based low-firing-temperature glasses. Comparison was made for the structural elements and fluxing agents between the 15th century Vietnamese porcelains and the time-corresponding Chinese ones.     

Synthesis of Ca(OH)2 nanoparticles with the addition of Triton X-100. Protective treatments on natural stones: Preliminary results

Calcium hydroxide is typically used in Cultural Heritage conservation for superficial protective treatments thanks to its conversion into calcium carbonate. Calcium carbonate is, in fact, compatible with many carbonate-based architectonic surfaces, because its characteristics are similar to those of the restored materials. In order to improve calcium hydroxide treatments, Ca(OH)₂ particles with sub-micrometric dimensions (nanolimes), are synthesised by a chemical precipitation process: a sodium hydroxide solution, used as precipitator, is added, drop by drop, to a calcium chloride one. In this paper, a nanometric calcium hydroxide, to be used in stones treatment, is produced adding in the initial solutions a surfactant agent (Triton X-100); the solutions are then mixed together simultaneously, drastically reducing the time needful for preparation. Different contents of surfactant are employed, and the influence on particles dimension and carbonatation process is analysed too. The obtained Ca(OH)₂ nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction (ED). The Ca(OH)₂ nanoparticles are regularly shaped, hexagonally plated and with side dimensions less than 200 nm: in particular, increasing the surfactant content, the particle dimension reaches values until 20 nm. Comparing nanolime suspensions obtained without and with the addition of the surfactant agent, the last ones have comparable, if not better, performances in terms of average particle size and morphology, crystallinity and reactivity. Afterwards, the alcoholic nanolime suspension obtained by using Triton X-100 is applied on some natural stones; in fact, the aim of this section is to compare the obtained results with those achieved using a nanolime synthesised without the surfactant agent. To evaluate the treatment effectiveness in a preliminary way, standard tests are performed and compared with the same tests previously obtained by the nanolime synthesised without the surfactant agent: “Scotch Tape Test” and capillarity test.     

The origin of syngenite in black crusts on the limestone monument King's Gate (Belgrade Fortress,Serbia) – the role of agriculture fertiliser

Black crusts formed on limestone built into the King's Gate represent the most important process in stone deterioration that is occurring in this part of the monumental complex of the Belgrade Fortress (Serbia). Of special importance is the association of salts (namely gypsum and syngenite). Syngenite is a common secondary deposit on granite monuments and on medieval stained glass (i.e., on K-containing materials). However, its appearance over calcareous substrates is not apparent, particularly in cases where cement mortar was not used for bounding. The origins of the potassium and sulphate ions required for syngenite formation are related to meteoritic water, which penetrates the soil above the arch of King's Gate. Water dissolves some soil components and becomes enriched with various ions before coming into contact with the limestone blocks. Enriched water contains two times more K⁺ and SO₄^2? ions than pristine meteoritic water does. The source of the required ions is potassium-sulphate that is present in agricultural fertilisers that are used above the monument. The proposed mechanism for syngenite formation was additionally supported with laboratory experiment. The results of X-ray diffractometry and SEM-EDS analyses of limestone treated with potassium-sulphate solution and sulphuric acid suggest the possibility that the syngenite was formed over calcite:CaCO₃ + K₂SO₄ + H₂SO₄ → K₂Ca(SO₄)₂ H₂O + CO₂↑However, the complex mechanisms of gypsum and syngenite formation under natural conditions (variable concentration of potassium and sulphate ions, intermediates phases, temperature changes, humidity, the amount of disposable water etc.) do not exclude the possibility of syngenite formation over gypsum.     

Comparison of hot-air and low-radiant pew heating systems on the distribution and transport of gaseous air pollutants in the mountain church of Rocca Pietore from artwork conservation points of view

The concentrations of CO₂, CO, formaldehyde (H₂CO) and water vapour were simultaneously monitored in various sections of a mountain church situated in the village of Rocca Pietore in the Italian Alps. The performance of a conventional, hot-air heating system and a novel design for heating the church, consisting of low-temperature heating elements, such as electrically heated pews and carpets, were compared for the supply, transport and removal of gases, the deposition and/or transformation of which may affect the preservation of displayed works of art. Experiments with sulphur hexafluoride (SF₆) tracer-gas showed a considerable influx of external air through the hot air carrier ducts of the old heating system, and also the leakage of the internal air mostly via the apertures of the doors. The ventilation rates for the total volume of the church with the hot-air heating system (on for 1.5 h), the new heating system (on for 2 h), and without heating were calculated to be 0.25, 0.18, and 0.13 h⁻¹, respectively. Without heating, a nearly homogeneous distribution of gases has been observed along both the horizontal and the vertical cross-sections of the church. Immediately after switching on the hot-air heating system, the levels of CO₂ and water vapour showed a sharp increase. After turning this system off, the levels of gases showed a slow fall and they developed a highly non-homogeneous spatial distribution indoors for many hours. In the upper region of the church, being airtight, higher concentrations of the pollutants could be detected. The low levels of CO and H₂CO, mostly originating from incense burning during services, were correlated to that of CO₂. The hot-air heating system has been proved to present a potential deterioration risk to artworks, as it increases the supply, transport and deposition probability of air pollutants. On the other hand, the novel, symmetrical heating system eliminates these undesirable effects, thus its application is advantageous to all churches involved in the preservation of works of art.     

Mapping the corrosion impact of air pollution on the historical peninsula of Istanbul

This paper presents the most comprehensive study conducted so far for evaluating the corrosion levels related to air quality and the seasonal pollutant (NO₂, SO₂, and O₃) exposure levels over 50 monitoring stations distributed on the historical peninsula of Istanbul. Istanbul has been one of the most important as well as most populated major cities in the world during all the ages. Today, owing to its historical and cultural structures, the historical peninsula of Istanbul has become an attraction point of tourism and is one of the most unique and ancient urban settlement areas in the world. However, the cultural heritage stocks in the peninsula are under the risk of corrosion and critical air pollution level exposure caused by chemical reactions under the multi-pollutant situation of the air pollutants, principally SO₂, NO₂, and O₃, as well as meteorological factors, e.g. humidity and temperature. In the present study, seasonal exposure of NO₂, SO₂, and O₃ pollutants were monitored using passive samplers, and corrosion attack values were calculated using dose-response functions. The geostatistical analyst tool of ArcGIS^® 9.1 was then used for generating GIS-based surface pollution and corrosion distribution maps. Subsequently, two hotspots were clearly identified, the tip of the peninsula and the area around the Ataturk Bridge, which fall under serious corrosion risks for copper, cast bronze, and carbon steel materials. However, no significant risk was identified for cultural heritage materials made of limestone in the peninsula.     

Quantitative modeling of blistering zones by active thermography for deterioration evaluation of stone monuments

Infrared thermography for stone monuments to date has primarily focused on qualitative analysis to judge the location of defect zones using relative temperature differences, but there are difficulties in mapping a blistering zone and quantitatively calculating its area. Therefore, this study used quantitative modeling to map blistering zones with graduated heating thermography. To achieve this goal, the following steps were performed: acquisition of thermographic images by passive and active methods, construction of a temperature distribution curve, establishment of the critical temperature and transitional zone, classification of the relative deterioration grades of the blistering zone, monochrome processing, vectorization, and deterioration evaluation of the blistering zone. After evaluating the blistering degree of the specimen through modeling, the total areas and rates were calculated as 359.3 cm² and 80.1%, respectively. This study was very useful for identifying the location, area, and relative degree of deterioration of blistering zones that were not easily detectable with the naked eye. In the future, if quantitative modeling of blistering zones is actively applied to deterioration maps, the reliability of deterioration evaluation for stone monuments will be improved, and additional deterioration, such as scaling, may be prevented.     

Mineralogical and microstructural characteristics of historic Roman cement renders from Budapest,Hungary

Roman cements, one of the most extensively produced types of hydraulic binders of the second half of the 19th century, played an important role in the architecture of many European countries. This paper deals with the chemical-mineralogical and microstructural characterisation of historic Roman cement renders from Budapest, Hungary. Different microscopic techniques were used on polished thin sections and fracture surfaces in order to understand the method of producing these renders and the effect of urban pollution on them. The renders exhibited characteristics typical to a Roman cement mortar, such as high binder to aggregate ratios (b/a), mostly fine-grained aggregates and high capillary porosity, but without the shrinkage cracks that are also normally present. This research suggests that coarse residual cement grains may have acted in a manner similar to aggregates by absorbing stress and thereby reducing the formation of shrinkage cracks. Based on the mineral characteristics of residual cement grains, the samples could be divided into two groups, which correspond to either a higher or lower temperature of calcination of the original source material of the cement. Chemical characteristics of the binders suggest the presence of intermixed CaCO₃ originating from the carbonation of hydration products and partly from residual calcium carbonate of the raw material. Despite dense and often impermeable coats applied in later renovations and exposure to a polluted urban environment, which resulted in formation of gypsum on the surface of the renders, the samples show good to excellent state of preservation after more than a century. The strong “house of cards”-like arrangement of the complex C-(A)-S-H-type phases is responsible for both the high capillary porosity and the good resistance of Roman cement renders to atmospheric pollution and potentially damaging salts such as Na- and K-chlorides which are found near the base of the building due to sidewalk de-icing. These results help to better understand the behaviour of historic Roman cement renders, which in turn assists in making good decisions in choosing a repair material to future restorations of 19th century façades built with this material.     

Nanolime suspensions applied on natural lithotypes: The influence of concentration and residual water content on carbonatation process and on treatment effectiveness

Ca(OH)2 particles with submicrometric dimensions (nanolimes) are recently introduced in cultural heritage conservation, in order to improve lime treatments. Lime nanoparticles are typically produced by a chemical precipitation process in supersaturated aqueous solutions of the reactants (calcium chloride [CaCl₂] and sodium hydroxide [NaOH]); water is then partially substituted with 2-propanol in order to improve stability and to reduce a random orientation of the particles. Aim of the present work is to analyse the influence of the nanolime suspensions concentration on the carbonatation process, in relation to the residual water content too. The obtained lime nanoparticles are characterised by X-rays diffraction (XRD) and profile analysis. Afterwards, the influence of the suspension concentration on stones protective treatments is evaluated: alcoholic nanolime suspensions, characterised by different concentration values, are applied on several natural lithotypes. Standard tests are performed to estimate the superficial consolidation and the protective treatment effectiveness: “Scotch tape test” (STT) and capillarity test. Porosimetric investigations are performed too.