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1.
ABSTRACT

This study examined the impact of relative humidity (RH) on the corrosion rate of 129 archaeological iron nails from two sites. Oxygen consumption of individual nails in controlled RH was used as a corrosion rate proxy to deliver quantitative data on corrosion rate as a function of RH. This was negligible at 20% RH, slow up to 40% RH for both sites, and increased rapidly at 60% RH for Roman nails from Caerleon (Wales) and at 70% RH for medieval nails from Billingsgate (London). The nails were digested and their chloride content was determined and related to their oxygen consumption at specific RH values. While a generic pattern of corrosion as a function of chloride was identified, for any single concentration of chloride corrosion rate was not predictable. Desiccation is in common use to control post-excavation corrosion of archaeological iron; quantifying how differing levels of desiccation changed corrosion rate provided a scaled tool for identifying corrosion risk, estimating object longevity, and calculating cost benefit for storage options.  相似文献   

2.
《文物保护研究》2013,58(2):88-94
Abstract

This paper examines the impact of relative humidity on jades by enclosing the samples under constant relative humidity (RH) of 32, 49, 61.5, and 81.7% at the same temperature of 40 ± 0.1°C for 160 days. The simulated samples were pure and dense tremolite jade and serpentine jade, impure tremolite jade and serpentine jade containing some calcite, and serpentinized calcite, which are all common materials of ancient jade found in archaeological excavations. All samples were characterized through particle-induced X-ray emission and a glossmeter. The degree of deterioration proved to be greater in impure materials than in pure ones. The best RH to conserve various kinds of materials differs: for pure tremolite and serpentine, all of the RH levels are equal; for impure tremolite with some calcite, 61.5 and 81.7% were superior; for impure serpentine with some calcite, the highest RH (81.7%) was best; and as to the serpentinized calcite, there is no clear conclusion as yet and further research is needed.  相似文献   

3.
《文物保护研究》2013,58(1):20-3
Abstract

Severe corrosion was found covering the brass beads on several beaded belts. The corrosion was a mixture of copper soaps and zinc soaps, and was so thick in some places that it completely buried the brass beads. One of these belts was chosen as a test case for cleaning. The details of the cleaning are described, as are the effects of the corrosion process on the beads and surrounding organic materials. Two supporting studies are also reported: tests of the solubility of the corrosion in a variety of organic solvents, including mixtures of ethanol and petroleum-based solvents; and tests of leather dressings and other coatings on brass, copper, and zinc coupons in various relative humidities (RH), to determine what values of RH could be recommended for storage.  相似文献   

4.
ABSTRACT

In the Mogao Grottoes of Dunhuang, China, the ambient relative humidity (RH) fluctuation in the caves is the main cause for the deterioration that has been observed, especially the deterioration of the earthen plaster and wall paintings linked to the presence of NaCl and Na2SO4 salt contaminants. To help identify the mechanism responsible for this salt-related deterioration and provide a theoretical basis for the development of a preventive conservation regime, this study addressed the basic moisture adsorption mechanisms of earthen plaster with soluble salts by taking an experimental approach. It is shown that, as ambient RH increases, the moisture adsorption process of the plaster containing the soluble salts can be regarded to have three basic stages, as evidenced by the results of the moisture adsorption tests performed on earthen plaster samples with different NaCl or Na2SO4 contents at various humidity levels. The moisture adsorption mechanism and its determining factors at each stage are also analysed. In addition, it is suggested that the hygroscopicity of the plaster structure and the interaction between the different kinds of salts in the plaster, which makes the dissolution or hydration of the salt in the plaster pores much easier, should be considered more seriously regarding increases in the ambient RH in the caves.  相似文献   

5.
《文物保护研究》2013,58(4):229-240
Abstract

This paper describes a novel technique to stabilize the relative humidity (RH) of the air inside museum showcases by using a synthetic hydrophobic membrane coupled with a hygroscopic solution in a membrane contactor. RH-monitoring data for two identical test cases, one of them controlled by a set-up with a plane-plate membrane contactor crossed by forced air and lithium chloride (LiCl) solution flows, show a significant stabilizing effect on RH fluctuations. A theoretical model permits forecasts in close agreement with the experimental RH data. Further calculations carried out over a one-year period show that notable damping of external RH variations can be obtained by using a low air circulation rate, small membrane surface area and low solution mass per unit case volume. A more general analytical solution in harmonic conditions is derived and discussed.  相似文献   

6.
《文物保护研究》2013,58(4):269-277
Abstract

simple mathematical model is presented that predicts the decay time of the internal relative humidity (RH) of backboard-protected canvas paintings when subjected to external RH fluctuations. The model takes into account the permeance of the canvas and the hygroscopicity of the enclosed materials. Predictions from the model are tested experimentally. The wooden stretcher releases moisture more slowly than expected, providing less buffering than predicted by the model. The practical implications of these findings are discussed.  相似文献   

7.
ABSTRACT

Glass is often seen as a relatively stable material, unaffected by changes in environmental conditions, but recent studies indicate otherwise. Research on the atmospheric deterioration of glass has consistently shown a strong correlation between climate, especially relative humidity (RH), and the rate of deterioration. New studies by the authors have shown that even stable compositions are at risk, when the glasses are exposed to continuous broad fluctuations in RH and temperature. Letting standards slip for the long-term storage of glass can be devastating, eventually leading to irreversible damage that in the final stages can result in the complete destruction of an object. Current research and monitoring of collections at the Corning Museum of Glass indicates that the RH should be within the range of 40–50%. For already crizzled glasses, a tighter control to 40–42% is recommended. Analysis of compositions of already crizzled glasses is ongoing, and hopefully will lead to the identification of at least some groups of glasses that are more at risk. This will help in providing future environmental recommendations for identifiable compositions, selected glass types, or known manufacturers.  相似文献   

8.
《文物保护研究》2013,58(1):8-17
Abstract

Absorbent materials such as wood, paper and cotton stabilize the atmosphere of show-cases against the relative humidity changes caused by temperature variation and by exchange of air with the surroundings.

There are several exchange processes between the air in the case and the outside air: diffusion through porous COllstruction materials, air flow caused by temperature and pressure changes and airflow by convection in a show-case whose relative humidity differsfrom that of its environment. The air changes about once a day in show-cases made by conventional joinery techniques. The rate of exchange can be reduced to less than five volumes a year by sealing a show-case so that only one small hole is left for pressure equalization. A dust and sulphur dioxide filter can then be fitted to maintain a pure atmosphere within.

In heated rooms without air-conditioning the RH may fall dangerously low in winter. A static method of RH control for a show-case is described. This is a saturated solution of sodium bromide covered by a silicone rubber membrane.  相似文献   

9.
ABSTRACT

Samples of conserved archaeological wood of different ages, origins, and conservation histories were aged in a climate chamber for seven months, while the humidity alternated between 30% RH for 12 hours and 80% RH for 12 hours at a constant temperature of 30°C. Photographs were taken once every hour, which enabled the creation of a time-lapse movie. Some samples degraded visibly, whereas others were unaffected. Most of the samples were robust and would be able to survive well even in a very poor museum climate. Among the sensitive samples, three types of degradation were identified, namely disintegration, pyrite oxidation, and efflorescence of white crystals. Disintegration was ascribed to dimensional changes caused by the RH alternations in very fragile wood. The white efflorescence was interpreted as the recrystallization of an alum-associated substance, possibly mercallite (KHSO4). The pyrite oxidation was observed as the efflorescence of a thick yellow, grey, and green powder. Characterization of selected samples was performed using X-ray fluorescence spectrometry, X-ray diffraction spectrometry, scanning electron microscopy with energy dispersive X-ray spectroscopy, inductively coupled plasma – optical emission spectroscopy, Fourier transform infrared spectroscopy, ionic conductivity – liquid chromatography, and pyrolysis-gas chromatography-mass spectrometry with in situ silylation using hexamethyldisilazane.  相似文献   

10.
《文物保护研究》2013,58(2):78-86
Abstract

Sensing devices used in museums for measuring relative humidity can be affected by pressure errors at altitudes over 900 m. The various instruments available for RH measurement are reviewed; an explanation of the pressure error is given and its significance for museums is evaluated; and information on avoidance of and correction for pressure errors is provided.  相似文献   

11.
ABSTRACT

Control of relative humidity (RH) for collections care is challenging in U.K. historic houses because they are often highly ventilated with poor heat retention, a porous building fabric and naturally tend to high (60–80%) RH if unheated. The significance of the building means that large-scale modifications and installation of air handling systems may be unfeasible and undesirable for the conservation of the building. In the late 1980s the National Trust, for English, Wales and Northern Ireland, investigated conservation heating as an RH control method that works with the natural environment of historic buildings, mimicking historic heating and requiring only modification of existing heating services or a light touch installation of new heating systems. The National Trust adopted conservation heating as its preferred method for environmental control in historic buildings from the 1990s. This method was presented at the IIC 1994 Ottawa congress on preventive conservation. Conservation heating has since been adopted by many historic house management organisations, particularly across north-west Europe, where it is well suited to the climate. This paper reviews conservation heating developments implemented by the National Trust since 1994, in response to a changing external context, new knowledge and developments in operational practice.  相似文献   

12.
ABSTRACT

The impact of relative humidity (RH) and temperature variation on the mechanical behaviour of paintings on canvas was investigated, based on the various environmental recommendations that are applied by museums and institutions worldwide. Paint samples were constructed based on the works of twentieth-century artists such as Soulages and Riopelle. The various samples are based on criteria such as paint media, additives, pigment type, canvas type, thickness, type of application, and drying time. Once they are fully dry, paint films behave as elastic, viscoelastic, or viscoplastic materials depending on the chemical nature of their components. These properties, as well as tensile strength, were determined by a series of tensile tests. Other samples were included, originating from discarded oil paintings on canvas from the seventeenth and nineteenth centuries. To carry out mechanical tests under controlled conditions of temperature and RH, a climatic chamber was built around the column of a universal testing machine. Samples were submitted to stress relaxation tests to observe their response to changes in environmental conditions. RH was increased from 20 to 90% and temperature from 15 to 60°C. Reactivity diagrams were drawn based on the results. The endurance limit under mechanical fatigue was determined from the diagrams and helped define the risks associated with each painting type when exposed to the accepted environmental recommendations.  相似文献   

13.
ABSTRACT

Panel paintings are essentially wooden boards painted on one side. Due to the vapor resistance of the paint layer, changing ambient conditions lead to exchange of moisture on only one surface. Subsequently, a non-uniform moisture content profile is formed across the thickness of the board. As a result, differential expansion causes the board to bend in case of no mechanical restriction, or it leads to a build-up of stresses inside the material if restrained. Experiments with oak boards sealed on one side and exposed to a change in the ambient relative humidity (RH) were performed. By scaling, the response of any board with different thickness can be predicted. Since the bending of the board can be described as a linear system behavior, the frequency response can be predicted based on the step response. In combination with critical strains for wood and gesso from the literature, this gives insight into allowable RH fluctuations in terms of frequency and amplitude for different board thicknesses.  相似文献   

14.
ABSTRACT

Historic buildings in Denmark have a high relative humidity (RH) all year, so the interiors are exposed to biological degradation. The acceptable range for RH is 60–70%, which is higher than the usual recommendations for museums and galleries. There are two options for humidity control: conservation heating or mechanical dehumidification. Calculation of the energy performance of a generic building was used to determine which method is the most efficient. Studies of a cottage in Liselund Park, and of two medieval churches in Hellerup and Vemb have confirmed these predictions: dehumidification is less energy consuming than conservation heating in buildings with poor thermal insulation and a moderate air infiltration rate (AER?<?0.6?h?1). Dehumidification is suitable for historic buildings, where heating is not needed for human comfort. A condensing dehumidifier uses less than half the energy per kg water compared to an absorption dehumidifier. But it does not work at temperatures below 2°C. The combination of a condensing dehumidifier and a little heating to prevent frost is the most energy efficient solution for humidity control. These results are only valid in mild and humid climatic conditions similar to Denmark.  相似文献   

15.
《文物保护研究》2013,58(2):47-52
Abstract

An environmentally controlled case is described for conserving a Fayum panel painting on loan to the Brooklyn Museum which exhibited a high degree of sensitivity to changes in relative humidity. The case was constructed of aluminium with a glass front, sealed in an air-tight fashion with a gasketted metal frame. It was intended to maintain a level of 50% RH in order to relax the panel painting from its high degree of warping, returning it to its original contour, and to conserve it permanently in this micro-climate. The humidity control agent found very satisfactory for this purpose was silica gel pre-conditioned to produce the 50% RH environment. The method of preparation of the gel was by exposure over a saturated solution of magnesium nitrate hexahydrate. The authors have detailed the construction of the case and method of installation of the Fayum portrait, as well as the technique of silica gel maintenance. The interior climate has been controlled satisfactorily since November 1974.  相似文献   

16.
ABSTRACT

The National Museum of Ethnology, Osaka, Japan, collects a vast amount of materials and information related to peoples’ life and culture, and makes them available to society through exhibitions and other activities. The number of collected items is increasing every year: 343581 objects have been collected from Japan and abroad as of March 2017. The continuous efforts have been necessary to improve storage conditions and to save space for both general and special storerooms. The former, which account for 90% of the storage capacity of the museum, are air-conditioned during working hours, with temperature and relative humidity (RH) settings varying with the seasons. The latter, which house objects for which strict conservation conditions are required, are air-conditioned for 24 hours with fixed settings of temperature/RH throughout the year determined by the nature of the materials from which the objects have been made or formed. Storage re-organization began with special storerooms, for which the number of objects and the storage area are far more limited in comparison with the general storerooms. The storage shelves for fur/skin/feather (almost 1000 objects) and for carpets (almost 550 objects) were all renewed in FY2007/2008. Then two large-scale innovation projects for general storerooms were conducted: construction of storage areas for ships equipped with a CO2-based and anoxic pest treatment facility (FY2015), and a complete refurbishing of the general storeroom for large objects (FY2016). Windows were set in the corner of this storeroom to provide visitors an opportunity to view and learn about the museum activities. In parallel to the above projects, daily storage improvement efforts have been undertaken. Storeroom No. 3, chosen as an example for general storerooms for small and medium-sized objects, was used to investigate the range of issues related to the shelving arrangement and storage conditions. Guidelines for storage re-organization were formulated according to the results of the investigation and according to the experiences gained through the renewal of special storerooms. Storage re-organization undertaken in storeroom No. 3 was conducted for 6 years at the rate of around 2000–4000 objects per year with a low budget and with reuse of existing shelves. In FY2016, all objects in storeroom No. 3 were properly redistributed. About 40% of the storage space was saved. Over these 10 years of storage re-organization, preventive measures have been taken for sustainable collection management. As early as FY1992, pest trap investigations have been carried out seasonally. Since FY2004, the results of investigations have been analyzed using a customized computer program. Subsequently, appropriate integrated pest management measures have been taken. In addition, since FY2014, energy-efficient air-condition control has been adopted for general storerooms. It consists of switching off air-conditioning in spring and autumn, and of starting it only when the temperature or RH values become too high in summer or too low in winter. Because the turning-off of air-conditioning causes comparable or even less climatic fluctuation, it was considered acceptable both economically and from a conservation perspective. It is estimated that turning the air-conditioning off during transitional seasons brings cost savings of about 3000000–4000000 JPY (about 26800–35700 USD as of 23 September 2017) per annum, which accounts for almost 30% of the electricity expenditures for all general storerooms.  相似文献   

17.
《文物保护研究》2013,58(4):251-268
Abstract

Extensive investigations of the deterioration of the romanesque painted wooden ceiling in the church of Saint Martin in Zillis (Switzerland) have revealed three major active deterioration phenomena: (1) tented flaking of paint layers; (2) flaking of the wheat starch fixative together with parts of the paint layer; and (3) fungal growth. These deterioration processes correlate with the dynamics of the prevailing room climate. Both forms of flaking are mainly driven by fluctuations of the relative humidity (RH), whereas the fungal attack can be related to high average RH and stagnant air. Frequent daily fluctuations in RH of up to 20% in summer are due to visitors leaving the doors open, while fluctuations of up to 25% are related to heating in winter. Given the risks of new consolidation treatments, the aim is to slow the decay processes by influencing the climate in the room. Installation of automatic door-closers reduced fluctuations but led to a rise in RH and a reduction of air movement, causing greater fungal growth. Subsequently, an automatic air-exchange system triggered by absolute humidity values was installed to reduce excess humidity and to exchange stale air without producing major fluctuations in the relative humidity. This kind of 'climatisation' has the advantage of being highly flexible, allowing variation of the rate and scale of exchange; it is, moreover, truly reversible.  相似文献   

18.
《文物保护研究》2013,58(2):104-112
Abstract

An exhibition case displaying ancient bronzes was found to have a high leak-rate and was subject to a variety of environmental factors. Because of the original case design, passive means of control were not proving effective. A simple, low-output (below 28l.min?1) drying system based on hollow fibre (polysulfone) technology was tested and installed in the case to maintain the microenvironment below 43% relative humidity (RH). The membrane was tested below industrially-specified pressure parameters (less than 4 bar) and found to produce a range of consistent RH outputs suited to museum use. After some years in service, the system has proved reliable and simple to operate; optimum performance was achieved with more continuous operation.  相似文献   

19.
ABSTRACT

The need to keep things cool for durability should be the single most powerful influence on storage design. The simplest temperature control is to moderate the outside temperature by a combination of thermal insulation and heat capacity. The low energy storage building is a lightweight, thermally insulated, airtight building put on top of an uninsulated floor slab laid directly on the ground. The thermal insulation is calculated to even out the daily temperature cycle but to allow an annual temperature cycle which is about half the amplitude, but much smoother, than the annual temperature cycle outside. The winter temperature inside will nearly always be above ambient and so will maintain a moderate RH without need for either humidification or dehumidification. The temperature inside in summer will be below ambient and thus will force dehumidification of the infiltrating air. However, the airtightness of the building allows intermittent dehumidification with low energy consumption, less than one kWh/m3 per year. There now exist enough buildings designed on this principle to reassure curators that highly valued collections can be stored in a space with a gentle temperature cycle and with an RH stability as good as air-conditioning usually achieves.  相似文献   

20.
ABSTRACT

This experimental program, implemented by the Managing Collection Environment Initiative at the Getty Conservation Institute, has provided data about the response of historic objects to changes in relative humidity (RH). Alongside other less sensitive documentation techniques (visual observation, physical measurements, photography, and 3D scanning), acoustic emission (AE) was monitored for six historic, museum-like wooden objects exposed to gradually increasing RH variations. Quantitative calibration of AE sensors and an anti-correlation measuring scheme to reduce environmental noise allowed the AE system to effectively trace micro-damage development caused by environmentally induced stress. Using an epidemiological approach, with respect to sample selection and experimental protocol, the obtained results can be used to explore the acceptable range of climate fluctuations for museum collections. The study’s well-controlled environmental protocol also allowed for the examination of the concept of ‘proofed fluctuation’ by the analysis of object response to reoccurring conditions.  相似文献   

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