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Article

Harold Meek and Marion Meek

The stabilization, repair or reconstruction of buildings of historic, cultural or architectural significance. The history of building conservation is beset with ideological and aesthetic problems, including whether it should be practised at all and, if so, to what extent restoration should supervene in the original structure. Modern conservation principles, as set out in the Venice Charter (1964; see §3 below), are based on specific alternative approaches. Preservation involves minimal intervention, ensuring the stabilization and maintenance of remains in their existing state and retarding further deterioration. Restoration involves returning the fabric to a known earlier state of greater significance by removing accretions or by reassembling existing components, but without the introduction of new material. Reconstruction involves returning the fabric as nearly as possible to a known earlier state and is distinguished by the introduction of materials—new or old—to the fabric. Architectural conservation may include any of these approaches or a combination of more than one, as well as the adaptation or modification of a building to suit proposed new and compatible uses....

Article

Susan Buys

revised by Beky Davies

See also Ceramics

The nature of the deterioration and damage to which ceramics are subject varies with the physical and chemical properties of the different types of ware. Although ceramics are among the most stable materials used in art objects, they are very susceptible to mechanical shock caused not only by accidental knocking and dropping, but also by failing previous repairs, vibration from visitor footfall in busy galleries, or inappropriate storage and display cases. Lower-fired wares are porous to liquids, which may cause staining and contamination of the body or soluble salts that can be destructive to the body. If these wares are soaked in water for extended periods, for example during burial, soluble fractions of the original composition can leach out. Higher-fired wares become partially or completely vitrified during firing, so their porosity is low, and they are not susceptible to damage in this manner.

Unlike high-fired ceramics, such as hard-paste porcelain and stonewares, where the glaze and body fuse together during firing, the attachment of the glaze to low-fired wares, such as earthenware, may be weak, and the glaze may be easily scratched or chipped off. Minor damage of this type may be accepted as natural wear and tear, characteristic of the ceramic type. Decoration that is applied over a high-fired glaze, such as overglaze enamel or gilding, is also fired at lower temperatures, making its attachment to the glaze weak and liable to flake off. Gilding is easily scratched and may be damaged by adhesive tapes or labels. Damage or disfigurement can also be caused by the use of unsuitable conservation materials and techniques. Damage caused by mechanical shock can be avoided by careful handling and storage. In addition, display conditions should be dry and dust-free and inert, lighting that has a strong heating effect should not be used, and the substitution of LED lighting instead of tungsten or halogen lights will mitigate the problem of strong heating effect. Plate-hangers should be avoided and stands used with care....

Article

Beril Bicer-Simsir and Simeon Wilkie

One of the most significant transformations in the construction industry began with the invention of Portland cement at the beginning of the 19th century. This transformation continued by the subsequent developments of Portland cements (e.g. specialty and blended Portland cements) and concretes (e.g. reinforced, pre-stressed, post-stressed, prefabricated, etc.), and resulted in an extensive collection of historically significant concrete architecture. Similarly, Portland-cement based material developments also influenced art and artistic works, and many examples of concrete art including decorative elements, wall paintings, and sculptures became an important part of our built heritage. In many cases, the lack of understanding of the relationships between the properties of concrete and its performance (e.g. the use of improper mix constituents and proportions, mixing, curing, and design criteria) and the lack of established quality control have also become the main sources of deterioration and durability issues, which historically significant concrete art and architecture face today and therefore require conservation. In other cases, the change of use, function, and significance of the concrete architecture as well as the intent to extend the design life of the concrete art and architecture necessitate the conservation of concrete....

Article

Mike Howden

Most commonly the conservation treatment of a gilded object will involve cleaning and consolidation, the purpose being to preserve and prevent deterioration rather than restore. If the object serves a presentational function—such as a gilded picture frame—it may also be important to minimize the visual distraction of damage or loss, so the painting or ceramic displayed remains the main object for the viewer rather than frame or stand. The care and preservation of a historic object, with a full or partial covering of applied gold or metal leaf, should only be undertaken with a clear understanding of the process and materials by which that decoration has been applied (see Gilding, §I.). The leaf itself is extremely thin and fragile, and many of the materials that make up the surface onto which the leaf is applied are soluble in many solvents and so can be easily damaged unintentionally. Any contact with the metal leaf will cause some form of abrasion and loss of original material, and with some metal leaf, such as silver, removal of the protective seal coating is likely to lead to irreversible discoloration by oxidation or similar if not replaced....

Article

Christopher Calnan

revised by Rosie Bolton

Leather is a complex organic material made up of skin proteins, tanning compounds, and lubricants (see also Leather). The character and, to a large extent, the type of deterioration is determined by the nature of the tanning compounds.

Historically, leather across Europe has most commonly been made using various vegetable tannins. This leather is to be found on saddlery and harness, military accoutrements, upholstery, and items that require tooling and embossing, for example screens and panels for wall hangings. Other common types of tannage found in Europe include alum tawing, which produces a white leather used principally for items such as gloves and furs; and oil tanning, which produces buff leather from which gloves and jerkins were made. Oil tanning (brain tanning) was also historically the primary tannage throughout the Americas.

Common tanning processes throughout Asia used alum, oil, and smoke. Natural lacquers, native to Eastern Asia, were commonly applied to the leather to provide a hard-wearing finish (...

Article

Catherine Rickman and Tanya Millard

As in other conservation areas, the preservation of works on paper is an attempt to stabilize their condition by arresting active deterioration. This is achieved through chemical or physical intervention, including the modification of display and storage environments. The emphasis across the field of paper conservation is that of preservation, although remedial treatment amounting to restoration is often carried out by paper conservators specializing in prints, drawings, and watercolors.

See also Paper.

The permanence of a paper-based object depends on its initial formation as well as the conditions of storage and use.

The materials and processes used in the manufacture of paper can significantly contribute to its deterioration. Innovations in the paper making industry (see Paper, §I), including the “Hollander” beater (17th century), the introduction of alum-rosin sizes, and the addition of chlorine bleaches (18th century), led to much European and American paper being inherently weaker than earlier types. Papers made from mechanical wood pulp, in use since the mid-19th century, are particularly unstable. Wood pulp contains lignin, which, like the acid products of chlorine bleaches and alum, leads to the breakdown of the cellulose that gives paper its strength. In a normal environment, papers made from mechanical wood pulp, such as newsprint, will only last a limited number of years before becoming brittle, more vulnerable to mechanical damage, and discolored. When chemically treated, wood pulp can make a paper almost as stable as cotton or linen rag papers, which in contrast, in a normal environment, will age at a significantly slower rate. Other additives in the paper making process that can contribute to the deterioration of papers include vegetable oils, traditionally used to make translucent tracing paper, some colored dyes, and metallic particles....

Article

Yvonne Shashoua

Until the late 1970s, plastics were widely believed to last forever. However, degradation of plastic artworks and objects is often detectable by appearance, odor, or feel within five to twenty-five years of acquisition. The challenges posed by the deterioration and conservation of plastics in heritage collections were recognized formally in 1991, largely as a result of the international conference “Saving the Twentieth Century: The Conservation of Modern Materials” organized by the Canadian Conservation Institute. The major causes of degradation are attributed to physical, chemical, and biological factors. Exposure to physical agents of degradation often occurs during use prior to collection by museums and results in mechanical damage. Chemical causes include reaction with oxygen, ozone, water, metals, light, and heat. Biological degradation results from attack by insects, microorganisms, and fungi but is rare in heritage collections of plastics.

In order to select the most appropriate conservation strategy for artifacts, it is essential to identify first the polymer, plasticizers which for some polymers can be major additives included to control physical and chemical properties, stability, and cosmetic agents. These materials determine the sensitivity to agents of deterioration, primary pathways, and deterioration rates of an artwork or object. The appearance of a piece, however, does not always provide reliable information that it ...

Article

Ksynia Marko

See also Tapestry

For the purposes of conservation, it is necessary to place tapestries in a category of their own. There are several reasons for this. Tapestries have always been expensive and highly valued, especially since they often incorporate fine silk and metal threads. The skill of manufacture and pictorial subject matter, together with the fact that they were designed by such well-known artists as David Teniers (ii) and William Morris, have given them a cultural significance and monetary value more commonly associated with paintings than with textiles. From a practical point of view, certain characteristics of the tapestry-weaving technique, along with the great size and weight of many hangings, give rise to specific problems that need to be dealt with by specialist conservators. In addition, the space, equipment, and skill required in handling a delicate object that can measure as much as 4–6 m high and 10 m long, and the difficulties of maintaining a consistent standard of workmanship throughout a single treatment that might last many months or even years, mean that tapestry conservation has to some extent evolved as a separate discipline....

Article

Sheila Landi

The fragments of ancient textiles recovered from bogs and burials around the world are among the first signs of the technological developments that are the basis of modern civilization. However, they have not always been treated with the respect they deserve, and much information has been lost through indifference on the part of archaeologists and dealers, and even some museum curators who were blind to the cultural significance of textiles. Increasing industrial pollution created by that very same civilization put at risk objects that were at last being recognized as of great historical interest when most museums were short of space and money, and provision for textiles was often particularly poor and overcrowded. As we advance into the 21st century, attitudes towards textiles have changed for the better, but there is still much to be done to encourage investment in the preservation of artifacts that are especially vulnerable to environmental fluctuations, the wear and tear of ordinary use, and poor storage conditions....

Article

Rupert Featherstone

Article

Jill Dunkerton

Painting on a wooden support. This article treats the construction and conservation of panel supports from a technical point of view; for the application of the ground and paint layers in a panel painting see Ground, Encaustic painting, Oil painting, and Tempera.

Wood was used in ancient Greece and Rome as a support for encaustic painting, and the first Byzantine icons, of the 6th century, are executed in this technique (see Early Christian and Byzantine art, §VI). In the late 20th century the Greek and Russian Orthodox churches were still using wood for their icons (see Icon), though encaustic painting has long been replaced by tempera. In western and northern Europe wood was not widely used as a support until the Gothic period (see Gothic, §IV, 2, (ii)). The painted altarpieces and altar frontals of the 13th and 14th centuries are on wood, as are the more complex altarpieces that evolved at this period, for which wood was the only suitable support. Most surviving works from the 15th century are on wooden supports, but during this period ...

Article

Catherine Hassall

Process of conveying an image from one surface to another. Preparatory drawings or designs can be transferred to another support by several methods: see Cartoon, Counterproof, Pouncing, Squaring up, Stylus and Tracing. For the history of transfer printing in the decoration of ceramics (a process in which an engraved copperplate is printed on to paper, which is then pressed while still wet against the ceramic surface to be decorated) see Ceramics §I 4.. The article below discusses the conservation technique of transferring paint layers on to a new backing following the complete removal of an irretrievably deteriorated support. It concentrates on the use of transfer for panel and canvas supports; for information on the detachment of frescoes see Fresco §2.

The process of transfer was developed in France in the mid-18th century by Robert Picault, a restorer who worked on many of the large altarpieces brought to Paris from Italy. Since then, it has been a regular part of conservation practice, though it is now used only in extreme circumstances, when all other courses of treatment have been tried and found to fail. The transfer of a painting is a long and laborious task, but a relatively straightforward one. The reluctance to carry it out is partly due to the fact that it goes against the conservation principle that all treatment should be reversible. A transfer is clearly not reversible: the panel, board, paper or canvas is removed in little pieces, and an important part of the historical record of the painting is lost. Another reason for caution is that the appearance of the painting is inevitably slightly altered, however carefully the process is carried out. Paintings transferred from wooden supports are worst affected. Old ...

Article

Peter L. Laurence

Although the theory and practice of renovating cities is ancient, and although the term is still used to refer to similar practices today, “urban renewal” typically refers to the large-scale, federally funded redevelopment projects that took place in US cities in the 1950s and 1960s. Such projects wrought dramatic physical transformations and caused controversial social upheaval. Urban renewal in this sense came into being with the US Housing Act of 1954, although it evolved out of a history of government-funded slum clearance and housing project construction dating back to the 1930s. Following two decades of slum clearance and model housing projects including First Houses (1935), Williamsburg Houses (1937) and Stuyvesant Town (1947), all in New York, the US Housing Act of 1949 was signed into law with broad political support due to a national postwar housing shortage. As the immediate legislative predecessor of urban renewal legislation, the Housing Act of ...