Art Conservation and Restoration

I

Introduction

Art Conservation and Restoration, actions taken to examine, preserve, and restore to their original condition objects of historic and artistic merit. An art conservator examines an object to determine the materials of construction and the causes of their deterioration or alteration. The conservator preserves the object by preventing or retarding deterioration and restores it by correcting deterioration or any alteration made by someone other than the original artist.

From the moment an art object is completed by the artist it undergoes physical and chemical changes, such as the drying of oil paints, perhaps accompanied by color alteration, and the changes in dimension of materials containing moisture. When these changes become undesirably noticeable, deterioration is well under way. The principal causes of unwanted change are too much or too little humidity, light, heat and cold, polluted atmosphere, biological infestations, neglect, contact with contaminating objects, and inherent incompatibility of materials.

Excessive moisture makes wood swell, paper become limp, and organic substances develop mold. Insufficient moisture causes wood and ivory to warp and crack, and leather and paper to become brittle. Too bright light fades watercolors and textiles and accelerates their photochemical deterioration; it also discolors paper. Freezing and overheating may cause fracturing of stone, plaster, and glass. Insects, rodents, molds, and bacteria can destroy organic materials—textiles, leather, paper, and wood. Art objects placed in contact with chemically reactive materials can be damaged, as, for example, a drawing on good rag paper mounted under a wood-pulp mat, or colors in a collage, which darken as a result of the oxidation of poor-quality glue. Many materials change through oxidation, or reaction to air pollutants. For instance, in sulfur-laden air (resulting from the burning of fuel oil and coal) limestone, marble, and murals on lime plaster walls may all be changed from calcite to gypsum, which expands and flakes away.

Because all art objects are unique and give aesthetic pleasure to the beholder, they are much valued by the individual collector and by the art-minded public. Each country takes pride in its historic and artistic monuments. In recent years the public has become more aware of the need to preserve its past through the conservation of precious, brilliant pieces of art. Museums have set up conservation and scientific laboratories for the study, authentication, and preservation of their treasures. Universities have established graduate training programs in art conservation, which offer courses in art history and in the science and techniques of examination and treatment of art objects. National laboratories have been established in many countries, as have governmental agencies concerned with the preservation of the world's artistic heritage.

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Archaeologists have also become more aware of the need to preserve what they find. At many sites trained conservators examine and treat objects recovered from the earth or the sea. Some archaeologists employ architects and engineers to reconstruct monuments that were buried in antiquity.

II

Architecture

The architectural past has become a concern of governments, foundations, historical societies, and private citizens. Many old public buildings and noteworthy houses have been placed on registers of national monuments or have been designated as landmarks. Professional architectural preservationists study the materials and construction techniques used in old buildings. Many such structures may be preserved intact; the exteriors of others may be kept intact while the interiors are adapted to a new function, as, for example, the conversion of large private estates to museums. Houses are often furnished in keeping with their period to re-create a harmonious entity or a historic setting.

III

Decorative Arts and Sculpture

Furniture, ceramics, textiles, and many other types of artifacts require the attention of various specialists. Some study these objects to determine materials, methods and date of manufacture, and authenticity. Carbon-14 dating is frequently used to determine the age of organic materials. Thermoluminescent dating may be used to obtain the firing date of a ceramic object or, from its clay core material, the casting date of a bronze.

Conservators are taught to use adhesives to reassemble broken objects and the methods used to clean marble, ivory, and other materials. Conservators of metal objects learn to recognize genuine old patina or the effects of corrosion. They treat such problems as bronze disease—a chemical reaction involving bronze, the chloride ion found in most burials, water, and oxygen—that eventually may cause bronze to crumble. They also learn the treatment of silver objects and silver threads in textiles that have been tarnished by air pollution.

Textile conservators must be able to analyze fibers, weaves, and deterioration problems and be prepared to consolidate, clean, reweave, and mount fragile materials on auxiliary supports in preparation for storage or exhibition.

The specialist who conserves sculpture must understand the problems involved in preserving marble, limestone, granite, and other hard stones, and ceramics, metals, plastics, woods, papers, and fabrics.

IV

Art on Paper

The conservation of works of art containing paper—watercolors, drawings, prints, photographs, posters, documents, books, constructions, collages, and sculpture—presents special problems. Paper is fibrous material containing cellulose felted together in thin sheets. The cellulose can come from flax, cotton, jute, hemp, the inner bark of mulberry or other trees, and pulverized wood. The greater the amount of pure alpha cellulose present, the more permanent is the paper. Wood-pulp papers such as newsprint contain many impurities, which cause them to turn brown and become brittle and acidic. The paper conservator must analyze the types of fibers in a particular paper as well as diagnose the deterioration problems and treat them. Treatment may include deacidification, washing, bleaching, lining, laminating, matting, removing old restoration, and providing proper storage or exhibition conditions.