The Opportunities and Challenges of Preservation Technologies

The pace of technology development in fields other than historic preservation has generally outstripped that of historic preservation, resulting in a predominant flow from those fields into historic preservation practice. This chapter summarizes some of the major trends in technology transfer and explores some of the issues that the increased use of advanced technologies brings to the practice of historic preservation. It also examines the relationship of the development of technologies for historic preservation to public policy.     

Allowable microclimatic variations for painted wood

Abstract

Environmental standards for cultural heritage collections have been much debated in recent years. The interest in the issue has been driven by the growing movement towards green museums, that is, managing indoor museum environments in a responsible and efficient manner, especially in terms of reducing energy consumption and carbon emissions but at the same time maintaining high standards of collection care. Painted wood is among the category of heritage objects most vulnerable to relative humidity and temperature fluctuations. Therefore, scientific understanding of how changes in environmental conditions ultimately affect painted wood is crucial to the development of rational guidelines for the control of climate in museums and historic buildings. This review provides a systematic progression through two fundamental approaches to establish the allowable ranges of climatic variations – an analysis of the mechanical response of painted wood as a complex, multilayer system to climate variations, and an analysis of the historic climate to which the objects have acclimatized. The climate specifications and standards based on both these approaches are reviewed.     

The Cathedrals of England: Environmental Performance,Conservation and Exhibitions

ABSTRACT

English medieval cathedrals are a group of buildings of exceptional significance and they contain collections of equal importance. Both the historic building fabric and the artefacts are vulnerable to environmental deterioration. However, unlike buildings owned by heritage organisations, the primary purpose of cathedrals is to further the Christian mission, and the conservation of the building and collections is required to be conducted within these constraints. Increasing visitor numbers and the installation of sophisticated exhibitions makes the task of conservation all the more demanding. Next to mechanical damage, environmental factors are the greatest source of deterioration to sensitive fabric and collections. However, until recently, there has been little systematic study of English cathedral environments and the effects of different uses and control measures. Detailed studies undertaken on 20 cathedrals in the past two decades have provided an insight into their environmental performance and how they differ as a group from many other historic buildings, as well as the passive conservation measures that can be implemented within their primary function.     

Geographic Information Systems in Historic Preservation

Geographic Information Systems (GIS) are a rapidly developing suite of computer based technologies that allow the storage, manipulation, display and integration of a wide range of spatially based data. This chapter reviews some of the more significant applications of these technologies in archaeology and historic preservation and suggests future trends. It is arguably the case that space and time are the two central dimensions of our record of the past. Science has fundamentally influenced our understanding of this record through the development and improvement of ways to measure and understand time. GIS and related methodologies present methodologies that are improving our abilities to measure and understand space.     

Insect-Infested Wood Remediation by Microwave Heating and Its Effects on Wood Dehydration: A Case Study of Hylotrupes bajulus Larva

Wood artefacts are subject to damage by biologic infestations due to bacteria, insects, and fungal species. One of the worst feared attacks is due to the xylophagous insects whose larvae feed on wood by boring galleries, at the expense of building timbers and worked woods. These beetles are responsible for daily destruction of the world’s wooden cultural heritage, and their elimination has been always a big problem for conservation of wood. The need to avoid the use of chemical methods in conservation for pest control has led to the development of various non-chemical, non-toxic treatments. Among these, heating with microwaves (MW) seems to be one of the most promising, since it has already shown its high efficacy in destroying pests. Insect-infested wood remediation by MW heating in conservation is based on the larger thermal increment induced in larvae than in wood, due to their different dielectric permittivity in the GHz frequency range. However, the side effects that may occur due to MW heating of wood, such as dehydration, have never been discussed so far. Here we study the possible application of microwave heating as a remediation method for wood samples infested by the larvae of the insect Hylotrupes bajulus. We show that it is possible to set up exposure conditions able to achieve 100% of larvae death and that are sufficiently mild not to induce significant dehydration of the exposed wood from which shrinkage effects may derive. Indeed, under these conditions, MW-induced wood dehydration on cubic and parallelepiped sweetgum samples can be kept under control and to percentages as low as 0.4% (w/w).     

Egyptian Sarcophagi and Mummies in the San Diego Museum of Man: Some Technical Studies

Nine ancient Egyptian sarcophagi of the twenty-fifth to twenty-sixth dynasty, one Ptolemaic Hawk Mummy, and one Amarna fresco were examined in the collections of the San Diego Museum of Man. Binding media, pigments, wood identification, deterioration and alteration products were identified. The pigment palette represents the basic suite of ancient Egyptian pigments: charcoal black, red ochre, yellow ochre, Egyptian blue, green earth, calcite, and gypsum. In the case of the Hawk mummy, oxammite was identified as a degradation product, together with magnesium phosphate, the first identification of oxammite in ancient artefacts. In a child’s coffin, realgar and orpiment were additionally identified. The binding media for practically all of the coffins studied was confirmed as gum Arabic with only one example of gum tragacanth found from a wall plaque from Amarna. Wood identification showed that Ficus sycomorus had been used, rather than the assumed cedar of Lebanon for coffin manufacture. One unidentified species of shrubby wood was also found. Some of the coffins had been restored, with one having a completely repainted face, in rutile, and the child’s coffin has an attached foot-box with modern screws. Possible indications of ancient reuse were found during the study.     

Expand Reference Resources

Summary

The Internet opens a wide range of possibilities for accessing materials from both traditional sources and more volatile areas-personal homepages, e-mail and discussion groups archives. Though the role of reference librarians to find the most relevant information for our users seems monumental in this medium, it is an area that needs the objective, ethical expertise of the librarian and archivist. In this 50th year of remembrance of the Holocaust, the Internet is especially active with information on that historic tragedy. Excerpts from accounts by one Hungarian and one Norwegian political prisoner interned in the camps are included as illustrations of material which may not have been found using more traditional research tools.     

Conserving contemporary artworks: perspectives of artists and curators at the National Art Gallery of Zimbabwe

In fine arts, contemporary artists seek to showcase their artistic skills and concepts. There is very little awareness by most artists on the quality of materials they use in art production and the conservation needs of contemporary artworks which pose conservation challenges as materials used and the physical quality of artworks produced are secondary to what the artists seek to express. Of prime interest to them is the expression of concepts through various genres of art creation. However, the quality of material used by most artists is largely affected by their financial situation and inadequate knowledge on the durability of such materials. Artworks created using recycled materials such as found objects and cheap materials like poor quality paint on paintings, low grade paper in artworks, or poor quality wood present conservation challenges to professionals in galleries. The end product are artworks made from composite materials, some stable and unstable. Thus professionals are faced with a dilemma to reconcile the conservation needs of these artworks and the artists’ expression of their concepts. Moreover, in the absence of remedial conservation measures, artworks are prone to deterioration. This is worsened by dwindling donor and government funding which negatively impacts on the gallery's capacity to conserve the art. Additionally, conceptual expression, artistic creativity, and commercialisation of the art are of priority over conservation. Therefore there is need to maintain a balance between the need to express concepts and commercialise the art on one hand and to conserve the contemporary artworks on the other hand.     

Study of the deterioration products,gilding, and polychromy of the stones of the Scuola Grande Di San Marco's façade in Venice

The Scuola Grande di San Marco is one of the most outstanding Renaissance buildings in Venice. Destroyed by fire in 1485, the Scuola was reconstructed between 1487 and 1495 by Pietro Lombardi (and sons), together with Giovanni Buora and Mauro Codussi. The façade is considered one of the finest and most original exteriors of Venetian buildings and in particular features refined sculptural and painted decorations and a remarkable pictorial effect created by the extensive use of polychrome marbles and the false perspective view between the pilasters of the lower order. Most of the stone materials (Istrian and Verona red limestones, nero di Roveré, pavonazzetto toscano, Carrara marble and various reused antique marbles) present evident decay phenomena such as scaling, exfoliation, powdering, fissuring, salt efflorescence, black crusts, and artificial patinas of various kinds. The present study reports the results of petrographic and chemical laboratory analyses carried out in preparation for the conservation treatment of the building, in order to characterize the main micro- and macro-morphologies of decay and to identify the causes and mechanisms of deterioration as well as the nature and application technique of the polychromy, gilding, and patinas present on parts of the monumental Renaissance façade.     

Humidity Control in Historic Buildings in Denmark

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.     

向伐区剩余物二次挑选要效益

随着天保工程的实施,木材产量不断调减,天保二期工程东北、内蒙古重点林区木材产量由天保一期的1058万立方米调到618．4万立方米,产量下调了42％。木材减产将造成木材生产季节作业,采运机械闲置,木材生产劳力过剩,木材产品收入和职工收入降低,工业原料不足,木材生产组织形式不适合等问题,为了解决这些问题,临江林业局2009年至2012年两年时间对枝桠材及刨花板原料进行了二次挑选,实践证明时伐区剩余物二次挑选,是企业创效增收、提高伐区利用率的有效途径之一。伐区剩余物二次挑选一是可节约木材,提高森林资源的利用率。二是可增加企业效益。三是可安置生产富余职工,增加职工收入。     

Conservation Heating 24 Years On

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.     

Long-term changes in climate and insect damage in historic houses

Abstract

Insect pests are an important source of concern in historic houses as the larval stages in particular can feed on a variety of important heritage materials, causing significant and sometimes irreparable damage to collections. Damage to wood and textiles is a special problem. The lifecycles of insects are sensitive to climate and require relatively warm conditions. There has been a significant increase in the presence of insect pests within historic houses in the early twenty-first century. The reasons may include: warmer winters, widespread use of natural fibres, less potent insecticides, and occupation of new niches indoors. The interior climate, especially increasing warmth, offers the potential for greater insect growth and survivability. Modelling changes in the temperature and humidity within the Cartoon Gallery at Knole, southern England, for the period 1770–2100 suggests a dramatic increase in favourable temperature conditions through the current century.     

Methods and Techniques Used in Significant Restoration Projects in Qatar

The large number of conservation and restoration works recently completed in Qatar show that there exists a need to enhance appreciation of the local architectural and building traditions, as a way of bringing to light the historical memory of these local places, using local techniques and materials to conserve existing buildings and to typologically integrate them. This paper offers an update on the status of some recent conservation projects in Qatar, analysing and comparing a number of completed restorations of historic buildings on the basis of the categories into which they can be organised; the extent to which they had deteriorated before restoration; the methods that were adopted; the construction materials and techniques used; the philosophical approach taken to restoration; and the various proposals for reusing the restored buildings. Comparison and analysis of the data make it possible to classify these methods and techniques in ways that could be applied to other conservation projects in future. The aim is to define a philosophy and methodologies that are consistent, and will be able to give expression to the specific local culture in matters of conservation, while respecting shared international rules.     

Environmental conditions for the safeguarding of collections: A background to the current debate on the control of relative humidity and temperature

Conditions of relative humidity (RH) and temperature within museums and buildings holding collections of cultural heritage objects are often maintained around a strictly controlled set point of about 50 ± 5% RH and 20 or 21 ± 2°C to provide safe, stable conditions for hygroscopic artifacts. It has recently been proposed that these ranges should be relaxed to values that are less energy-intensive to maintain while still being safe for the objects in the collection, with the aim of reducing both carbon footprint and energy use. It is also suggested that conditions should be determined by the needs of individual objects and by the local climate of the region, rather than applying overall values across the museum as a whole. This proposal has led to much discussion within the conservation community. The suggested values, a stable humidity within the range 40–60% RH and a stable temperature within the range 16–25°C for most objects, apart from the most vulnerable, are derived from the results of experimental research on the responses of individual materials to particular conditions of RH and temperature, as well as observations of the behaviour of cultural heritage objects in their own environments and on loan. This paper describes briefly the historical and scientific background to the present discussion.     

SOME ASPECTS OF THE CONSERVATION OF WORKS OF ART IN BUILDINGS OF NEW CONCRETE

Abstract

This paper deals with the materials used in conservation treatments in the first half of the twentieth century for the preservation and consolidation of wooden art objects from the Saxony region in Germany. The use of such materials must be seen as early attempts to find a conservation treatment for wood. The documentation of conservation treatments provides a reference to the application of oils and oil–resin mixtures. The results from the chemical analysis of samples of historic preservatives from the beginning to the middle of the twentieth century (so-called 'Puckelin') carried out by gas chromatography–mass spectrometry (GC-MS) and Fourier transform infrared (FTIR) analysis confirm the use of tung oil as a drying oil, whereas the use of linseed oil cannot be excluded. Colophony and, probably, amber varnish were used as resinous constituents. There are indications that a conservation material dating from the second half of the twentieth century most likely contained rapeseed oil.     

Changing research trends in the field of archaeological wood at the Conservation Department,Faculty of Archaeology,Cairo University

Abstract

Since 1980, much research in the field of treatment and conservation of archaeological wood has been carried out at the Conservation Department, Faculty of Archaeology, Cairo University. Materials and methods used in conservation have been changing gradually over the years worldwide. It was necessary to study critically previous masters and doctoral dissertations on Egyptian archaeological and historic wood, all written in Arabic. This review of them includes a brief history of the Conservation Department at Cairo University and five main focal points of past research: types of wood used throughout Egyptian history, assessment of wood decay, wood properties and composition, treatment and conservation of decorated wood, and the evaluation of chemicals and polymers used in the treatment of archaeological wood and composite objects containing wood.     

FTIR Measurement of Cellulose Microfibril Angle in Historic Scots Pine Wood and Its Use to Detect Fungal Decay

Microfibril angle (MFA) – the orientation of cellulose fibres in the S2 layer of the secondary cell wall – is a key determinant of the stiffness and strength of timber. The microfibril angle depends on the way in which the timber was grown and its position within the tree. Microfibril angle can be measured by X-ray diffraction and other methods, but the methods in current use are slow or require advanced instrumentation. The aim of this study was to explore the use of polarised Fourier transform infrared (FTIR) microscopy as a relatively fast and inexpensive method for measuring MFA in historic Scots pine (Pinus sylvestris L.). The FTIR measurements were calibrated against X-ray measurements of MFA in modern Scots pine. We observed a wide range in MFA values and a radial pattern of MFA similar to modern Scots pine in undecayed Scots pine heartwood from sixteenth and seventeenth century beams in Scottish secular buildings. The density of the heartwood was also similar to modern plantation-grown Scots pine despite the much slower growth rate recorded in the ring widths of the historic timber. The sapwood, which had been attacked by both insect pests and fungi, showed an erratic reduction in density and a large increase in MFA compared to the modern material. The increased sapwood MFA was attributed to selective destruction of the S2 layer of the wood cell walls by fungal decay. Using MFA measurements in conjunction with density offers the possibility to estimate the mechanical properties of sound historic pine timber, to detect fungal decay more sensitively than by density alone, and to distinguish between pest and fungal attack in a way that relates directly to the remaining mechanical performance of the timber.     

浅析电梯导轨对轿厢振动的影响

随着我田房地产的快速发展,城市建设的脚步不断加快,高层建筑的不断增多,电梯作为高屡建筑中垂直运行的交通工具已与人们的日常生活密不可分。无论是去商场、超市、酒店、办公接还是公寓楼都要用到电梯,电梯已经成为人们用的最多的变通工具。正因为如此,电梯导轨对轿厢振动的影响已经成为人们曩关心的话题,文章就此问题进行了研究和分析。