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The Principles of Conservation BERNARD M. FEILDEN The modem principles that govern the organization and application of conservation interventions have taken centuries of philosphical, aesthetic, and technical progress to articulate. The problem of con- serving architecture and the fine and decorative arts is not simple. Even in a scientific age that has developed the technology of space travel and atomic power, the solution to local environmental problems still presents a challenge to the present and the future. Only through understanding the mechanisms of decay and deterioration can con- servation skills be increased to prolong the life of cultural property for future generations. The conservation of cultural property demands wise management of resources and a good sense of proportion. Perhaps above all, it de- mands the desire and dedication to see that cultural property is pre- served. In this sense, two familiar maxims are pertinent: "Prevention is better then cure" and "A stitch in time saves nine." Modem long- term conservation policy concentrates on fighting the causes of decay. Natural disasters such as floods and earthquakes cannot be prevented, but by forethought the damage can be greatly reduced. Industrial life cannot and should not be halted) but damage can be minimized by combating waste, uncontrolled expansion, economic exploitation, and Bernard M. Feilden-is Director, Rome Center for Conservation, ICCROM, Rome. This essay is taken from Introduction to Conservation of Cultural Property {ICCROM~, 1979. 22

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Principles of Conservation pollution. Conservation is, therefore, primarily a process leading to the prolongation of the life of cultural property for its utilization now and in the future. 23 CONSERVATION METHODOLOGY The conservation of cultural property constitutes a single, interprofes- sional discipline coordinating a range of aesthetic, historic, scientific, and technical methods. It is a rapidly developing field that, by its very nature, is a multidisciplinary activity, with experts respecting each other's contributions and combining to form an effective team. Despite the difference in scale and extent of intervention, the under- lying principles and procedural methods remain the same for the con- servation of movable and immovable cultural property. There are, how- ever, important logistical differences. First, architectural work entails treatment of materials in an open and virtually uncontrollable environment. Whereas the museum con- servator/restorer can generally rely on good environmental control to ninimize further deterioration' the architectural conservator cannot. He must allow for the effects of time and weather. Second, the scale of architectural operations is much larger, and in many cases methods used by museum conservators/restorers may be found impracticable because of the size and complexity of the archi- tectural fabric. Third, and again because of the size and complexity of architectural conservation, contractors, technicians, and craftsmen must actually perform the various conservation functions, while the museum con- servator/restorer may do most of the treatment with his own hands. Communication and supervision, therefore, are important considera- tions for the architectural conservator. Lastly, because the architectural fabric has to function as a structure, resisting its own dead weight and applied live loadings, there are further differences between the practice of architectural and museum conser- vation. Architectural conservation must be within the context of his- toric structure, which also incorporates its site, setting, and physical environment. For both movable and immovable cultural property, the objects cho- sen for treatment and the degree of intervention are predicated upon the values that can be assigned to the property. These values help systematically to set priorities in scheduling interventions as well as programming the extent and nature of the individual treatments. The assignment of values or priorities; will inevitably reflect each different

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24 CONSERVATION OF HISTORIC STONE BUILDINGS cultural context. For example, a small wooden domestic structure from the beg~nrung of the nineteenth century in Australia would be con- sidered a national landmark because it dates from the founding of the nation and because so little Australian architecture had survived from this period. In Italy, on the other hand, with its thousands of ancient monuments, a comparable structure would have a relatively low prior- ity in the overall conservation needs of the community. The values assigned to cultural property come under three major headings: ~ Cultural Values: documentary value, historical value, archeolog- ical and age value, aesthetic value, architectural value, scientific value, symbolic or spiritual value, townscape value, landscape and ecological value. ~ Use Values: functional value, economic value, social value, po- litical value. Emo~ona] VaJu es: wonder, identity, continuity. For movable objects, the question of values is generally more easily defined. However, in architectural conservation, problems often arise because the utilization of the historic building, which is economically and functionally necessary, must also respect cultural values. The costs of conservation may have to be allocated partially to each of the above values in order to justify the total to the community. There may be conflicts between some of the values. In certain cases architectural values will predominate. In other cases artistic or his- torical considerations will prevail, while in yet others practical and economic considerations may modify the scope of conservation. Sound judgment based upon wide cultural preparation and mature sensitivity gives the ability to make correct value assessments. TREATMENTS When a treatment is being planned, the following three general con- cepts regarding an object or a structure's condition are considered, as exemplified by a minor seventeenth-century wooden polychromed sculpture damaged in the collapse of a church during an earthquake in Friuli, Italy: ~ Damage suffered by the object. The sculpture suffered multiple fractures during the church's collapse. The body was broken into three pieces the head, torso, and right leg. Both feet and arms were missing and presumed lost. The borders of the breaks were very abraded.

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Principles of Conservation 25 Insecurity of the object. The wood was weakened from wormwood infestation, which had reduced the wood to frass in many areas. The wooden support and glue preparation for the polychrome were further weakened by mold growth resulting from exposure following the church's collapse. The remaining original polychrome had detached once tended to fan off. Green mold hyphae were evident, and there seemed to be dry rot as well. Disfigurement suffered by the object. Much of the remaining orig- inal paint was covered by unsightly overprint. The entire sculpture was very dusty and in some areas was encrusted with mud. By taking the above criteria into consideration, a judiciously selected intervention was programmed in this case. Because the sculpture had relatively minor artistic and historical value, and would remain in- definitely in storage rather than on view, treatment priorities focused on conservation methods needed only to ensure the sculpture's sur- vival: fixation of polychrome, securing of breaks, removal of surface dirt, disinfection, fumigation, and controlled cIrying. Restoration mea- sures, such as the removal of the overpaint and the reintegration of lac~,nae, were held for some future date. During this treatment, and during all conservation treatments, the following standards of ethics must be rigorously followed: The condition of the object, and all methods and materials used during treatment, must be clearly documented. Historical evidence should be fully recorded; it must not be de- stroyed, falsified, or removed. Any intervention must be the minimum necessary. Any intervention must be governed by unswerving respect for the aesthetic, historical, and physical integrity of cultural property. Interventions should: Be reversible, if technically possible. Not prejudice a future intervention whenever this may become necessary. Not hinder the possibility of later access to all evidence incor- porated in the object. Allow the maximum amount of existing material to be retained. Be harmonious in color, tone, texture, form, and scale, if additions are necessary, but be less noticeable than original material, while at the same time being identifiable.

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26 CONSERVATION OF HISTORIC STONE BUILDINGS Not be undertaken by conservators/restorers who are insuffi- ciently trained or experienced, unless they obtain competent advice. However, it must be recognized that some problems are unique and have to be solved from first principles on a trial-and-error basis. Preparatory Procedures Prior to conservation interventions, preparatory operations are re- quired: Inventories At the national level, conservation procedures consist first of making -an inventory of aU cultural property in the country. This is a major a~Tninistrative task for the government. It involves establishing ap- propriate categories of cultural property and recording them as thor- oughly as possible, graphically and descriptively. Computers and mi- crofilm records are valuable aids. A preliminary written study of each object or building is necessary in order to know and define it as a whole, which, in the case of ar- chitecture, includes its setting and environment. The present condition of the building or object must also be recorded. Documentation of these studies must be full and conscientious. Records and archives must be searched. In some countries, reliance may have to be placed on oral traditions, which should be recorded verbatim and included in the dossier created for each object or building. Documentation Complete recording is essential before, during, and after any interven- tion. In all works of preservation, repair, or excavation of cultural property there must always be precise documentation in the form of analytical and critical reports, illustrated with photographs and draw- ings. Every stage of the work of cleaning, consolidation, reassembly, and reintegration, including all materials and techniques used, must be recorded. Technical and formal features identified during the course of the work should also be included in the documentation. This record should then be placed in the archives of a public institution and made available to research workers. Finally, if the intervention can in any way serve to broaden general knowledge, a report must be published. Often in large projects it may take several years to write a scholarly

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Principles of Conservation 27 report, so a preliminary report or series is desirable to inform the public and to maintain popular support. Documentation is essential because it must be remembered that the building or work of art will outlive the individuals who perform the interventions. To ensure the maximum survival of cultural property, future conservators/restorers must know and understand what has occurred in the past. Interventions The intervention should be the minimum necessary. The techniques used depend upon the conditions of climate to which cultural property is likely to be subjected. These fall into three groups: Natural climatic and microclimatic conditions, which vary greatly and are virtually uncontrollable. Modified climatic conditions, such as those found in a normal building that forms an environmental spatial system with a partially self-adjusting modified climate. Conditions where humidity and temperature are controlled arti- ficially to minimize dangerous variations. Ideally, the climatic control has been designed for the safety of the objects, rather than the comfort of the visitor. Interventions practically always involve some Toss of a "value" in cultural property, but are justified in order to preserve the objects for the future. Conservation involves making interventions at various scales and levels of intensity that are determined by the physical condition, the causes of deterioration, and the probable future environment of the cultural property under treatment. Each case must be considered individually and as a whole, taking all factors into account. Always bearing in mind the final aim, principles, and rules of con- servation, seven degrees of intervention can be identified. However, in any individual conservation treatment, several degrees may take place simultaneously in various parts of the whole. The seven degrees are: i- Prevention of deterioration Preservation Consolidation Restoration Rehabilitation Reproduction Reconstruction

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28 Prevention of Deterioration CONSERVATION OF HISTORIC STONE BUILDINGS Prevention entails protecting cultural property by controlling its en- vironment, thus keeping agents of decay and damage from becoming active. Neglect must also be prevented. Therefore, prevention includes control of humidity, temperature, and light, as well as measures for preventing fire, arson, theft, and vandalism. In the industrial and urban environment, it includes mea- sures for reducing atmospheric pollution, traffic vibrations, and ground subsidence from many causes, particularly abstraction of water. Preservation Preservation deals directly with cultural property. Its object is to keep it in the same state. Damage and destruction caused by humidity, chemical agents, and all types of pests and microorganisms must be stopped in order to preserve the object or structure. Maintenance, cleaning schedules, good housekeeping and good management aid preservation. Repairs must be carried out when nec- essary to prevent further decay and to keep cultural property in the same state. Regular inspections of cultural property are the basis of prevention. When the property is subjected to an uncontrollable en- vironment, such inspections are the first step in preventive mainte- nance and repair. Consolidation Consolidation is the physical addition or application of adhesive or supportive materials into the actual fabric of cultural property in order to ensure its continued durability or structural integrity. In the case of immovable cultural property, consolidation may entail, for example, the injection of adhesives to secure a detached mural painting to the wall. Movable cultural property, such as weakened canvas paintings and works on paper, are open backed with new supportive materials. With buildings, when the strength of structural elements has been so reduced that it is no longer sufficient to meet future hazards, the consolidation of the existing material is necessary, and new material may have to be added. However, the integrity of the structural system must be respected and its form preserved. No historical evidence should be destroyed. Only by first understanding how a historical building as a whole acts as a "spatial environment system" is it possible to make adjustments in favor of a new use, introduce new techniques satisfac- torily, or provide a suitable environment for objects of art.

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Principles of Conservation The utilization of traditional skills and materials is of essential im- portance, as these were employed to create the object or building. However, where traditional methods are inadequate, the conservation of cultural property may be achieved by the use of modem techniques that should be reversible, proven by experience, and applicable to the scale of the project and its climatic environment. In buildings made of perishable materials, such as wood, mud, brick, or rammed earth, traditional materials and skills should be used for the repair or res- toration of wom or decayed parts. Finally, in many cases it is wise to buy time with temporary mea- sures in the hope that some better technique will evolve, especially if consolidation may prejudice future works of conservation. 29 Restoration The object of restoration is to revive the original concept or legibility of the object. Restoration and reintegration of details and features occur frequently and are based upon respect for original material, archeolog- ical evidence, original design, and authentic documents. Replacement of missing or decayed parts must integrate harmoniously with the whole, but on close inspection must be distinguishable from the orig- inal so that the restoration does not falsify artistic or historical evi- dence. Contributions from all periods must be respected. All later additions that can be considered as historical documents, rather than merely previous restorations, must be preserved. When a building includes superimposed work of different periods, revealing the Underlying state can be justified only in exceptional circumstances: when the part re- moved is widely agreed to be of little interest, when it is certain that the material brought to light will be of great historical or archeological value, and when it is clear that its state of preservation is good enough to justify the action. Restoration also entails superficial cleaning, but with full respect for the patina of age. Rehabilitation The best way of preserving buildings is to keep them in use, a practice that may involve what the French call "rnise en vaTeur," or modern- ization and adaptive alteration. Adaptive reuse of buildings, such as utilizing a medieval convent in Venice to house a school and laboratory for stone conservation or fuming an eighteenth-century barn into a domestic dwelling, is often the only way that historic and aesthetic values can be made econom-

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30 CONSERVATION OF HISTORIC STONE BUILDINGS ically viable. It- is also often the only way that historic buildings can be brought up to contemporary standards by providing modem amen- tles. Reproduction Reproduction entails copying an extant artifact, often in order to re- place some missing or decayed, generally decorative, parts to maintain its aesthetic harmony. If valuable cultural property is being damaged irretrievably or is threatened by its environment,- it may have to be moved to a more suitable environment. A reproduction is thus often substituted in order to maintain the unity of a site or building. For example, Michelangelo's sculpture of David was moved from the Pi- azza delIa Signoria, Florence, into a museum to protect it from the weather. A good reproduction took its place. Similar interventions were undertaken for the s-cuipture of the cathedrals of Strasbourg and Wells. Reconstruction Reconstruction of historic buildings and historic town centers using new materials may be necessitated by disasters such as fire, earth- quake, or war, but reconstructions cannot have the patina of age. As in restoration, reconstruction must be based upon accurate documen- tation and evidence, never upon conjecture. In the case of a work of art, a stolen pane] from the Ghent Altarpiece (ca. 14321 was replaced with an exact reproduction. The reerection of fallen stones to create an accurate and compre- hensive version of the original structure is a special type of reconstruc- tion called "anastylosis." Moving entire buildings to new sites is another form of reconstruc- tion that is justified only by overriding national interest. However, it entails some loss of essential cultural values and the generation of new envirorunental risks. The classic example is the temple complex of Abu Simbel (XIX Dynasty, EgyptI, moved to prevent its inundation by the Aswan High Dam.