Museum No 146 (Vol XXXVII, n° 2, 1985)
Museum, successor to Moueion, is published
by the United Nations Educational, Scientific and Cultural Organization in Paris. An international forum (quarterly) of information and reflection on museums of all kinds. No. 146, 1985
Percy Stulz EDITORIAL BOARD
Chairman: Syed A. Naqvi Editor: Yudhishthir Raj Isar Assistant Editor: Marie JosEe Thiel Editorial Assistant: Christine Wilkinson Design: MonikaJost ADVISORY BOARD
Om Prakash Agrawal, India Fernanda de Camargo e Almeida-Moro, Brazil Chira Chongkol, Thailand Joseph-Marie Essomba, President of OMMSA Gaë1 de Guichen, ICCROM Jan Jelinek, Czechoslovakia Luis Monreal, Secretary-Generalof ICOM, ex-oficio
Paul Perrot, United States of America Vitali Souslov, Union of Soviet Socialist Republics Correspondence concerning editonid matters should be addressed to the Editor (Division of Cultural Heritage, Unesco, 7 place de Fontenoy, 75700 Paris, France) who is always pleased to consider manuscripts for publication but cannot accept liability for their custody or return.' Authors are advised to write to the Editor first. Pub'ishedtexts may be f i e e h reproducedand translated (except dlustrations and when reproduction or translation rights are reserved), provided that mention is made of the author and source. Extracts may be quoted i f due acknodedgement zi given.
Authors are responsible for the choice and the presentation of the facts contained in their articles and for the opinions expressed therein, which are not necessarily those of Unesco or the Editorial Board of Museum. Titles, introductorytexts and captionsmay be written by the Editor. All correspondence concerning stlbscn$tions should be addressed to the Commercial Services Division, Office of the Unesco Press, Unesco, 7 place de Fontenoy, 75700 Paris, France. Each issue: 40 F. Subscription rates ( 4 issues or corresponding double issues per year): 128 F.
(dedicated to the k e m o r y of Grace McCann MorZey)
T r i h t e to Grace McCann Morley Editorid 63
Gaël de Guichen and Cengiz Kabaoglu Robert Organ and Brian Ramer István Eri George S. Gardner Claude Daniel Ardouin
How to make a rotten show-case 64 Some hard truths - interview 68 A brief histo9 o f the show-case 71 Old show-cases: discard or recycle? 74 Protection without encasement: an Afrikan argumewt
CLIMATE CONTROL, ACTIVE A N D PASSIVE
Bill Barrette Stefan Michalski Andrea Rothe and Bruce Metro Brian Ramer
The Egyptian Galleries at the Metropolitan Museum o f Art 81 A relative humidity control module 85 Climate controlled show-cases for paim5.g. 89 Showcases m o d y e d for climate control 91
Right: Bronzecharioteer from the Museum of
Qin ShiHuang TetracottaWarriors and Horses. An articleon this extraordinary site museum near Xian, in ShanxiProvince, China, will appear in the next issue,No. 147.
Gaël de Guichen and Vinicio Gai Alan Calmes Tim Padfield May Cassar
Controlling the atmosphere for 197 musical instruments 95 Charters of Freedom of the United States 99 A cooleddisplay case 102 Case design and climate confrol: a typological' anabsis 104 FLEXIBILITY
Wolfgang Selzer Ann Andrén
A n e w f l e d d e display system A Swedish paradox 112
SECURITY A N D STABILITY
Printed in the Netherlands
Smeets Offset (NBI) bv, 's-Hertogenbosch @ Unesco 1985 ISSN 0027-3996 N m e u m (Unesco, Paris), Vol. XXXVII, No. 2, 1985
Giinter S. Hilbert Protectiosz against thefi and wiqzl damage 115 Hiromitsu Washizuka Protection against earthquakes in Japan 119 Enrica Pozzi E a r t h q u a k e - r e s i t measures in Naples 122 Alexei Vyacheslavovich Bryantsev The Hermitage Museum's packing techniGues for paintings 123
TRIBUTE TO GRACE M c C A N N MORLEY (1900- 1985)
For thirty-seven years, she lavished upon Museum a constant maternal affection; her commitment to international cooperation was a lifelong dedication. As Head of Unesco’s fledgling Museums Division from 1946 to 1949, she was our magazine’sfirst editor, primus interpares on a Board of Editors comprising thirty other distinguished museum professionals. She was among those men and women who built the foundations of Unesco’s cultural heritage programme, bringing to this task an already broad intercultural vision, deepened during sixteen years of professional experience, first as General Curator of the Cincinnati Art Museum (1930-33) and then as Director of the San Francisco Museum of Art (1934-36).Once again Directorof the San Frahcisco Museum from 1949 to 1958, in 1960 she responded to the invitation of
productive professional exchange within Asia and between museum curators there and in the rest of the world. Like them, successive editors of a sure scientific footing. This unusual honour to a foreigner,particularlyin those Museum have all been deeply indebted to sensitive times, was fitting recognition of her wise and uncompromising guidance, her vast museum experience and, above her boundless attention. Shewas our most all, her abilityto share knowledgeand sen- constructive commentator, devoted to the sibility, to guide and inspire others. ‘Retir- pursuit of excellencein both broad princiing’ once again at 66 years of age, Dr ple and fine detail. We knew that each Morley was an adviser on museums to the issue would have to pass the test of her Government of India till, in 1968, she scrutiny, never indulgent, always at the founded the ICOM Regional Agency in cutting edge of good sense and profesAsia. As head of the agency till 1978 and sional relevance, and that she never ceased permanent adviser thereafter she played to care deeply about the present and a determining role in the Asian mu- future of the magazine. A rare friend is gone. It is by emulating seum movement. Indefatigable mentor, thoughtful counsellor and alert critic, she her example thar we can justify her trust encouraged dozens of budding vocations, and honour her memory. channelled intellectual energies throughout the continent and promoted the most Pandit Jawaharlal Nehru to become the
first Director of India’s new National Museum in New Delhi and launch it on
This is the second issue conceived and co-ordinated by our colleague Gaë1 de Guichen, Assistant to the Director of ICCROM. Like its predecessor (Vol. XXXIV, No. 1, 1982), it focuses on conservation, but on an even more exclusively technical level. We hope that it will be as well received by our readers, if not more so, and turn out to be as helpful and thought-provoking in professional terms. Our Advisory Board saw this special issue as one which would explore the ways in which show-caseshave been - or should be - designed so as to provide optimum protection for the objects they contain, exposing them to the visitor’s gaze yet at the same time shielding them from the potentially destructive effects of both nature and man. To use a clinical analogy, we were to look at a wide range of the prophylactic arrangements essential to protect artefacts on display from common factors of deterioration. These include inappropriate levels of relative humidity and temperature; pollution and dust; clumsy handling due to difficult access; in many regions, the rude and sudden shock of earthquake; and, of course, the unwelcome attentions of thieves and vandals. Stabilizing the immediate encased environment of the object is the fundamental objective. A substantial section on climate control presents innovative methods of doing so. These are both active and passhe: some complex (and costly), others simple (and within the reach of most museums). This section includes two exceptional American cases, one of which, in the National Archives in Washington, D.C., represents an extraordinary response to the twin needs of climate control and security. The latter subject is dealt with in a separate section, together with the problem of show-case construction for seismic areas. Reconciling the imperatives of conservation with those of aesthetics and adaptability also calls for much ingenuity on the part of ‘Homo fiber museorum ’, examples of which are proposed in the section on flexibility. The issue closes with a Soviet contribution on packing cases, a theme originally intended for treatment together with show-cases, but edged aside by a wealth of material on the latter alone. We hope that the sum of museographical imagination, resourcefulness and sheer common sense presented in these pages will testify once again to Maseam’s concern with an enduring challenge: neglect and/ or misunderstanding of the imperatives of conservation on the part of so many museum curators. In responding to that challengewe are also keeping faith with the aim set out for us thirty-seven years ago, that of ‘making instances of effective and useful museum work known quickly and clearly to museums everywhere, for the benefit of all’. 1 It is a sad irony that so deliberately practical an issue goes to press soon after the sudden death in New Delhi on 8January 1985 of the author of those lines: Grace McCann Morley. Museum’s most devoted adviser, how often did she reiterate a single plea: that the magazine concentrate on the sharing of practical technical and scientific information of direct and concrete usefulness to the daily work of museum professionals throughout the world. There must be a special corner of Heaven reserved for masters of the great museum tradition, P
1. Editorial, ‘~Wuxczrm and Museums’, in Muxesm, Vol. I, No. 112, 1948.
where Dr Morley now finds peaceful rest. This issue is dedicated to her memory; may it receive her blessings. A happier coincidence is the departure of Luis Monreal, ICOM’s SecretaryGeneral, who will have been installed as the founding director of the J. Paul Getty Conservation Institute in Los Angeles by the time this issue appears. His new appointment honours the qualities of the man and the worldwide significance of the organization he has served since 1974. It augurs particularly well for our common cause: better conservation in museums. An always constructive and discerning partner in the production of our magazine, Luis has also been determined and clearsighted in his commitment to conservation. He will bring this vitality and breadth of vision to the very considerable responsibilitieshe now shoulders, with their immense potential for the improvement of conservation practice everywhere.
Gaë1 de Guichen and Cengiz Kabaoglu
How to muhe u rotten show-cuse Make sure that the show-casewobbles. This way whenever anyone approaches it, all the exhibits will start vibrating: a good way to liven things up at a museum without having to bring in entertainers!
1. A Turkish architect, who drew the pictures.
How to make a rotten show-case
Be sure to display the locking mechanism prominently. 4 Leave a generous space between the sliding panels. This allows visitors to add (or subtract) new exhibits according to their taste. Another solution is to leave the showcase topless - aquarium style.
Avoid sealing the show-case too tightly because exhibits always look better when covered with a uniform coat of dust.
Gad de Guichen and Cenniz Kabaonh
Be sure to light up the area surrounding the show-case as brightly as possible. 7
Polish the glass of your show-case to a mirror finish.
Design an imaginative obstacle course or slalom run for the workers who change the burned-out lamps. Give a prize annually to the winner.
How to m d e a rotten showcase
Pay no attention to the fact that a welldesigned show-casestabilizes environmental variations and can replace an airconditioning system to great advantage. 11
Above all make absolutely sure your showcase is aestheticallypleasing!
An interview with Robert Organ and Brìan Ramer
Robert M. Organ Lectured in physics at the former College of Technology, Birmingham, United Kingdom. Research Laboratory, British Museum, 1951-65. Curator of Conservation, Royal Ontario Museum, 1965-67. At present Director of the Conservation Analytical Laboratory, Smithsonian Institution, Washington, D.C. Member, Institute of Physics, London. Fellow, Society of Antiquaries, London. Fellow of the International and American Institutes of Conservation. Author of Design for [email protected]
Conseruation of Antipities (London, Butterworths, for IIC, 1968).
Authorized staff should be able to Museum. 1 There is an increasing tendency among exhibition designers to show open a case when looking after a display free-standing objects without show-cases. without having to prop up a hinged door The theory behind it is direct contact be- so heavy that its weight pulls the case out tween the visitor and the object. What do of shape. If the door is attached by many screws these should be threaded into long you think of this? hard-metal sockets that will survive more Orgun. It certainly allows the visitor to than one or two screwings and will resist have direct contact with the object, as he cross-threading during any last-minute does with merchandise in a department rush to get the case closed in time for a store. Museum objects, however, should formal exhibition opening. A case should really be valued more than consumer not impose its own hazards on the object. A good case should not have ungoods. On open display they are subject not only to the exploring finger but also suspected crevices between sliding doors to risks from the janitor’s broom handle, or between frame and glass. These are from colliding passers-by, from the men- often present or develop with age. They tally deranged who seek publicity admit insects who are actively seeking a through vandalism, from invading in- comfortable home. They also admit dust which is carried by air currents: thrust insects, from leaks of water which &ict even the best of our buildings, from to the case by rising barometric pressure; blasts of either bitterly cold or hot, or moving in as the case cools down at the humid air released suddenly by a faulty end of the day. door or window, and so forth. Rumer. Too often show-cases are designMuseum. The show-caseis the last line of ed for their appearancerather than out of concern for their contents. There are protection for the object, is it not? technical requirements specific to muRamer. Yes indeed. Apart from the prob- seum show-cases. They need to be welllems listed by Robert Organ there are constructed units. Ideally they are lit others that are frequently less obvious. A from the outside because of the problems well-built show-caseinsulates its contents associated with overheating and the refrom vibrations in the building. It also sultant desiccation of humidity-sensitive provides protection from atmospheric objects. If the lighting source is internally pollutants, particularly dust, so that the mounted, it should be placed in a sepaneed for cleaning and maintenance is rate compartment and provision must be reduced. When cases are constructed made for proper ventilation. Shelving with ultraviolet-absorbing materials, within show-cases should be stable yet damage to light-sensitive objects is flexible enough so that it can be repositioned for objects of differing sizes. An lessened. important feature which should be incorMuseum. If a show-case must offer these porated in the initial design is a technical various kinds of protection, what are the area for the accommodationof humiditybuffering materials and security devices. characteristics of a good show-case? In cases which contain humidity-sensitive Organ. The case should be adequately objects, the climatic conditions should be designed, standing firmly on a solid monitored. Yet I also believe there is no floor. It should move as a unit if the floor reason why a show-case cannot be funcshifts under earth tremors, or by vibra- tional and aesthetically pleasing at the tion, or under change of load. (Have you same time. noticed how those long concrete beams in a parking garage vibrate under your feet Museum. Would you say that modern as cars pass by?) A good case should not show-cases are better than those prohave a resonance of its own at any fre- duced fifty years ago? quency to which the object could be sen1. This interview was conducted by Gaë1 de sitive. Guichen.
Some hard truths - interview
Organ. Not necessarily. Unfortunately, fifty years is more than one generation ago. Each generation seems to have to repeat the mistakes of the preceding one in order to learn and to make even more of them in order to 'express itself' and to show how much more it now knows. At least, the older cases tended to be made of traditional materials whose performances could be anticipated. They were often made in the same climatic region as the museum, so their materials had acclimatized fairly well to the same climate as had the objects. There were fewer demands for them, because there were fewer museums, so they tended to be custom made and very substantial and free from the weaknesses introduced with cost-cutting.2 Ramer. Remember also that fifty years ago the presentation of museum collections was based on a different philosophy. Temporary and loan exhibitions have created the need for a more flexible display unit, which is frequently moved and converted for each new exhibition. Greater flexibility has been achieved through the use of new and different construction materials making the cases of today unlike the heavy, traditional ones of the past. As a result, it is possible that some of the advantages associated with older show-cases have been compromised. For example, the joints between the frame and glazing of new cases are often not properly sealed, enabling the penetration of dust. In addition, as new show-cases frequently feature internal lighting, there is a greater risk of damage to artefacts due to heat and high levels of illumination. Maseum. What risks are involved in moving a collection from an old show-case to a modern one? Ramer. The risk to the collection is not the move from the old to the new or the new to the old, rather it is the move from a good-qualityshow-case to a poor-qualit y model and a change of environment which accompanies the move. Over time museum objects acclimatize to the environmental conditions within a showcase, and any abrupt change can create problems. Gradual adjustment to new conditions will prevent damage. It should also be pointed out that any showcase being prepared for a new installation can present risks: paints and adhesives which have not thoroughly dried can emit harmful fumes, as can certain fabrics
69 chosen to line case interiors. Methods of testing display materials have been published by Oddy, Blackshaw, Daniels and Ward of the British Museum.
Organ. Some materials used in show-case construction, or as mounts or backgrounds, also cause decay or corrosion of sensitive object material. Our only certain long-term protection against such losses is case ventilation, filtering the vent against intrusion of dust and insects. Ramer. With respect to climate control within show-cases, however, when the materials used to build them are chemically stable (metal, glass and sealant), or if they have been thoroughly tested, it is currently agreed to seal the show-case as tightly as possible.3 Miweam. Can you say a little more about mechanical stability? Ramer. Yes, there are a variety of sources of vibrations which can affect a showcase, ranging from the visitor trying to get a better look to the conscientious housekeeper who must remove the resultant fingerprints. Heavy traffk, construction work and even underground trains outside the museum can cause museum show-cases to vibrate and their contents to move and fall over. Organ. Yes! One can see objects in museums that have 'walked' to the edge of a shelf in a display case and then stay caught between the glass and the edge of the shelf. In a museum of my acquaintance the glass shelves happened to resonate with an air compressor, part of the engineering plant, three floors below. They bowed up and down on their supports with an amplitude of ten millimetres or more. The objects did not stay in place for long! Maseum. Earlier you mentioned the problems created by dust. Could you elaborate on this? 0rga;iz. Dust inside a case has many effects. On a shelf it is unsightly, so a conscientious curator asks for it to be cleaned. This means that the case must be opened. On an object, dust may soil a porous surface permanently. By attracting humidity 2. See article by George S. Gardner, on page 74 of this issue. - Ed. 3. See articles by Bill Barrette, Tim Padfield, Gael de Guichen and Vinicio Gai, and Brian Ramer in this issue. Ed.
Brian Ramer Born in Canada in 1947. B.A. (humanities) from Ohio State University in 1970 andB.Sc. in conservation of archaeological material from the Institute of Archaeology, University of London, in 1977. Assistant keeper (conservation) at the Sainsbury Centre for Visual Arts, 1977-83. Has been developing ICCROM teachihg materials for training programmes, especially in preventive conservation, and to provide technical assistance to Member States, from 1984 to present. Assistant co-ordinator of the Working Group on Climate and Lighting Control of ICOM's International Committee for Conservation.
Robert Organ and Brian Ramer
in the air, dust may stimulate corrosion of metals and accelerate deterioration. But the cleaning of a collection object cannot be undertaken lightly. Cleaning must be preceded by careful consideration of the risks involved. Every removal minutely shortens the life of an object. Thus treatments for soiling or corrosion should be avoided by eliminating the need by keeping dust out.
Musezlm. I also understood you to say that the installation of artificial lighting in modern show-cases is undesirable. Ramer. If the guidelines recommended for museum lighting are not followed, any artificial light source can cause damage to light-sensitive material.* To protect an object from adverse effects, both duration and level of intensity of the light source must be limited. The use of fluorescent tubes in a show-case also requires the elimination of ultraviolet radiation produced by this source of lighting. This can be accomplished by placing an ultraviolet-absorbing filter between the light source and the object. Because of the heat produced by the ballast unit of a fluorescent lamp, the unit must be mounted outside of the show-case. Heat is also produced by tungsten lamps - that is, ordinary light bulbs. Over 90 per cent of their energy is in the form of radiant heat, which must . be directed away from the object and out of a well-ventilated compartment. Museum. How is the heat generated by the use of artificial lighting especially harmful to objects? Organ. The amount of harm done by heat derived from absorbed light depends very much on the object. For any object the warming causes the film of air in contact with it to become drier. If the object is organic in nature (wood, textiles, paper, etc.) and therefore contains some moisture, some of this moisture evaporates into the drier air and the dimensionsof the object change slightly.
This change may be harmless if the object is free to move. If, however, the object is mounted under tension, or if neighbouring elements move against each other or move differently so that they pull or thrust or slide against each other, then the aged and weakened material may be pulled out of shape or be rubbed away or weakened. Furthermore, it can be shown experimentally that dark-coloured areas absorb more heat than their neighbouring light-coloured areas. As a result, neighbouring areas of the same material will dry at a different rate and shrink or twist differently, producing the same destructive stresses between neighbouring areas. Repeated cycles of such stress must shorten the life of old material. The best kind of artificial lighting comes from outside the display case. This avoids placing warm lamps and ballast units in with the objects.
Ramer. We should make it clear that an increase in temperature in itself does not damage the majority of museum objects. But temperature change does directly affect relative humidity. Particularly for humidity-sensitive material it is essential that a constant level of relative humidity be maintained. Museum. How does one maintain the relative humidity at a stable level? Organ. Use of a complete air-conditioning system comes to mind immediately. While a good working system can undoubtedly stabilize the general relative humidity in a case and eliminate major variations it does have its drawbacks. Most museums are not able to afford such a system. Furthermore, mechanical systems fail quite often or have to be turned off for maintenance. When this occurs, the humidity-sensitive objects in the museum are left unprotected. Stabilization of general relative humidity is probably achieved most gently by a system of humidity buffers within the case.
Ramer. Humidity buffers such as silica gel are capable of smoothing out variatipns in relative humidity within showcases. The benefits of passive (non-mechanical) methods of climate control such as humidity buffers are increasingly being recognized. They are less expensive than the installation and maintenance of active electrical systems such as air-conditioning. The buffers can be prepared and reused at a variety of humidity levels, making passive systems an appropriate and flexible choice for museum needs. Only if the case is to be held at a relative humidity very different from its surroundings need the cost of regularly reconditioning the buffer be considered. Museum. It is perfectly understandable that the public has no idea of all these problems. But what about museum curators? Ramer. Many show-cases are, in fact, designed and constructed without consideration of the particular requirements of the objects. Standard, commercially available models, for example, often provide little or no room to establish climate control. For this reason, show-cases sometimes have to be modified for a specific museum use once they have been purchased. This leads to extra costs in time and labour. It is far simpler and less expensive than many people realize to plan and construct good cases which provide, at no additional cost, features suited to the requirements of museum objects. It is desirable that a show-case contain three separate areas: one for access to lighting fixtures, one for artefacts, and one for security devices and environmental controls. Access to each area should be by means of a separate key. This will create a basic yet flexible case, which permits future modification with a minimum of effort and expense. 4. The four guidelines applied to natural and artificial lighting are: (a) eliminate ultraviolet radiation: (b) reduce infrared radiation; (c) reduce time of illumination; and (d) reduce intensity of illumination (illuminance).
'Ideal museum interior' by J. C. Neickel (published in 1727 in his Milseographia).
A bief history of István Eri Studied Hungarian literature and history at the University of Budapest, specialized in the archaeology of che Middle Ages at the National Museum of Hungary from 1952 to 1959, and has been head of the Institute for Conservation and Methodology in Budapest since 1974. He is Chairman of the ICOM-CIDOCworking group on Terminology.
Show-cases are without a doubt an essential part of museum display. Nowadays, curators and designers everywhere agree that the less conspicuous a show-case is, the better it will serve its true purpose, namely, to provide a safe place to conserve art objects while at the same time enabling them to be seen. This modern way of thinking contrasts radically, however, with the practice that prevailed in museums for several centuries. It may therefore be useful to look back briefly over the way in which show-cases have evolved, since they themselves reflect ideas on how objects should be exhibited, while at the same time exemplifying
e sbow-case styles of decorative art at different periods. Architecturally speaking, it is fairly easy to retrace the development of museums from their original settings in public buildings (former palaces, converted churches and so forth) to their later accommodation in purpose-built edifices, which are often objects of study in themselves. Museum furnishings, however, and particularly display cases, have seldom survived to the present day. Obsolete exhibition fittings, constantly being superseded by more modern installations, are usually discarded. Nevertheless, drawings and photographs
for storing them and the way in which they were arranged and displayed. Neickel’s Mzrseographia, published in 1727, gives the most detailed description of the ideal exhibition room, containing The beginnings in embryo virtually all the principles still The use of the term ‘show-case’ is itself applied today. The author states from the fairly recent. It was the product of an outset that the measurements of a room epoch-making change, when museum used to display museum pieces should be exhibits were separated from collections in a ratio of two to one; he indicates the kept in storage. From the beginnings of positioning of the windows, specifies that modern museum collections in the fif- the room must be insulated, etc. He also teenth and sixteenth centuries up until refers to the choice of a colour scheme for the nineteenth century, art objects were the room and its furnishings. He lays kept and exhibited in cabinets (Latin: down - according to the above-menalmarikm; French: amnoire) or on shelves tioned principle of classification - the (Latin: repositorikm). In the period number, order and positioning of the when collections of the ‘Kunst- und display cabinets and shelves. He takes Wunderhammer’ type (curio cabinet, care to point out that the distance besalle de curiosité, cabinet de curiosité) tween the shelves should become prowere taking shape and developing, we gressively smaller towards the upper find museum fittings of truly artistic de- shelves: in other words, that the exhibits sign. Very often the furniture - consist- should be clearly displayed and aping partly of fitted cupboards - of some propriately placed according to size. On of the rooms was used for presentation the subject of cabinets for numismatic and display purposes as well as for storage. collections, he observes that the system of In the inventory made in 1596 of the drawers and locking doors will safeguard treasures of Ferdinand I,’ one of the most small objects from theft and loss. Finally celebrated collections of the sixteenth - subscribing to the principle o€ study century, there are some references to the collections - he suggests that there furniture in which the collection was should be a large table in the middle of housed. The most valuable objects were the room, and possibly other, smaller, grouped together - by production tables near the windows, ‘so that objects technique, materials and intended use - can be placed on them for closer scrutiny’ in eighteen cabinets set back to back in (Fig. 12). The ‘heirloom’ cabinets of the sixthe curio room or grosse Kunsthammer. The principle that objects worth 1. King of Bohemia and Hungary (1526), King preserving should be divided into of the Romans (1531), Holy Roman Emperor separate groups is enunciated in Samuel (1556) after the abdication of his elder brother, Qkcheberg ’ Teatrum sapientiae , pub - Charles V. He grew up in Spain, but Charles V lished in 1565. It was a principle that recognized (by the Treaty of Worms) his possession of the five Habsburg states, and made applied not only to the collection of ob- him governor of southern Germany, the Tyrol jects but also to the kind of furniture used and Upper Alsace.
dating from the various periods provide us with a broad picture of the changes that have come about.
Nineteenth-century ‘studio cabinet’ (Graz, Joanneum). 14
Detail of an archaeological exhibition of 1909,at the Rheinisches Landesmuseum, Bonn.
A brief histoq of the show-case
teenth and seventeenth centuries were used both for storage and for display purposes. Although the quality of the workmanship may have varied according to their owners’ means, they were for the most part masterpieces of the cabinetmaking of their day. In keeping with contemporary principles of interior decoration, both the individual cabinets and their positions in the room were symmetrical. The same rule applied to the arrangement of objects on the shelves or on the walls, or even hanging from the ceiling. The infrequent visitors - the ‘initiates’ - could approach the objects placed either on the shelves or in the closed or partly glazed cabinets, which obviously meant that a careful watch had to be kept on the objects on display and that the number of visitors had to be restricted.
works of graphic art - as can be seen in certain kinds of show-cases in many museums). The old, almost exclusively wooden display cabinets were gradually replaced by metal-frame cases - mostly of iron and bronze - that could be massproduced and were easy to assemble. The primary function of these cases, which were used for both storage and display, was nevertheless security. They could be locked, and the objects could remain in them for decades, virtually dust-free, without being touched.
The total separation of museum collections from objects placed on display during exhibitions signalled the triumph of a new, modern, educational approach one still valid today - to exhibiting museum pieces. Like all innovations, it Changìng needs, new technodogies was able to gain ground only gradually. In the late eighteenth and early nine- This approach emerged in the United teenth centuries, the situation gradually States in the last decade of the nineteenth changed. With the opening of museums century and stemmed from a new concept to the public, the number of visitors in- of public education - on the one hand creased steadily, while at the same time a greater sense of responsibility towards the growth in the size of collections gave society (it was not state subsidies that prorise to storage problems. Larger and vided the bulk of museums’ financial larger museums were built, affording resources) and, on the other, a new apmore scope for selective display and for proach to the purpose of museums. separating exhibition and storage areas. This modern idea rapidly spread to Objects for display were housed in other continents, especially Europe, cabinets fitted with large glass panes - though even today obsolete conceptions the forerunners of today’s show-cases. of museum display persist, influenced by With the development of technology the antiquated interior fittings already in (increased production of plate glass for place. example), show-cases of increasingly With the expanding role of designers, varied shapes and models made their ap- interior decorators and advertising agenpearance. Akin in style to household fur- cies in the organization of museum exniture, museum furniture imperceptibly hibitions, curators have gradually found became more commercial in character. themselves taking a back seat, at least as Archaeological objects were grouped in far as the aesthetic presentation of exhibicategories in the same way as other tions is concerned, and it has therefore museum pieces, and found their way into become increasingly their responsibility collections, as did other categories of to ensure that the authentic scientific objects which had not previously been character of exhibitions is preserved. prized as collectors’ items (for example, As technology developed, designers items of folk art or industrial design). experimented with all the latest materials For over a century these wood-and- that could be used for display cases. glass cabinets were used for displaying These were superseded by huge glass objects and, for the most part, for storage tables, and display cabinets as such, servpurposes as well. The lower part of the ing practically no purpose other than as upright cabinets or tables were fitted with space-dividers, became almost superflusolid doors, the interior comprising ous. Aluminium-frame and plastic strucshelves and drawers, providing storage tures made their appearance. Lighting space for objects belonging to the same effects changed, as did methods of precategory as those displayed in the glazed sentation in general. A characteristic part, so as not to separate pieces belong- example is the study by J. F. McCabe of ing to the same set (for example pieces of Chicago on the layout of show-cases a dinner service, textiles or collections of in relation to visitor fatigue, which was
A row of show-cases at the exhibition of
goldsmiths’ work at the German National Museum (Germanisches Nazionalmuseum), Nuremberg, in 1920.
74 published in the review Mgseion (Vol. 19, No. III, 1932). His idea was that the size of show-cases should be geared to the visitor: in other words, chosen for the convenience of an average-sized adult without subjecting him or her to undue fatigue. Three major changes have occurred in the last thirty years: the replacement of wood by glass and plastics; the replacement of hermetic seals by sliding panels in glass which no longer ensure hermetic closure; the appearance of artificial light sources within the show-case itself and which are sometimes in contact with the objects. Each of these changes has brought about, unfortunately, a profound disruption of the equilibrium which previously ensured the stability of museum objects.
As a result, collections have been damaged irreparably. But the alarm has been sounded and studies are under way to test whether the new generation of showcases are a factor of destruction rather than of conservation. It is beyond question that, so as to augment the aesthetic appeal of exhibitions the primary museological imperative of conservation has been neglected. It is certain that the extraordinarily delicate balance between the curator, the conservator, the ‘museum engineer’, the designer and the architect is difficult to achieve when they join forces to prepare an exhibition. But without very close cooperation among diese different specialists we cannot hope to develop true professionalism in museology . [ Translatedfiom French]
recyde? George S. Gardner Graduated from Cooper Union and Pratt Institute in New York. Chairman of the Department of Exhibition and Graphics at the American Museum of Natural History since f973. Prior to that he spent twelve years as a partner in an independent design office specializingin exhibition and museum work. Currently on the editorial board of Curator, the quarterly journal of the American Museum of Natural History; adjunct professor in the Museum Studies Program at New York University. Cofounder and first president of the National Association of Museum Exhibition.
When an architect or museum planner is called in to update one of the older museums the tendency is to completely redesign the space available in an effort to present a more contemporary image. Dusty, antique show-cases are discarded, displays are redesigned, new lighting is installed and a newer, cleaner look is produced. However, there comes a time in many museums when serious thought is given to preserving some of the older exhibit cases or even an entire hall. Such a situation occurred some years ago at the American Museum of Natural History when a long, detailed look was given to the Northwest Coast Indian Hall, a dimly lighted, archaic gallery of magnificent ethnographic artefacts. Cases full of masks, pipes, shoes, bark costumes, baskets and tools had been installed in this hall from 1900 onwards. The space originally housed a variety of ethnographic objects when it was opened in 1896, so the large, handsome wood cases probably date from the turn of the century (Fig. 17). The Northwest Coast Indian material was added to from the Jessup North Pacific Expedition in 1909 and the display remained untouched for over fifty
years. A partial redesign of the graphics was completed in 1962. In the carefully crafted mahogany cases some artefacts were rearranged and new labels were prepared. But no new lighting was installed. To this day the majority of these 2.25-metre-high, glass-doored cases remain without interior lighting, almost ninety years after they were constructed! Needless to say, the scientific material on display is difficult to see and the interpretive labels are hard to read. Even in 1962 there seemed to be a conscious effort not to discard these boxy, old cases. But i n , our recent analysis, we decided that of all the halls in the American Museum of Natural History this one, the oldest, located in the oldest building (1877) of the museum complex, was indeed worth preserving.
Advantages and disadvantages What are the advantagesof keeping such a collection of antique, mahogany cases? First, they are well constructed, probably better than any we could purchase today. Second, they are virtually air-tight. With the replacement of some gasketing material they can probably offer protection to our collection of fragile objects as
Ol'dshow-cases: discard or recycl'e?
Pharmaceutical exhibit in recycled case, part of 1876: A Centenmal' Exhibition in the Arts and Industries Building.
George S. Gardner
View of the Northwest Coast Indian Hall in the American Museum of Natural History (G. 1900). Note daylight from both sides of the hall. These windows were filled in some years later.
good as many new cases. The third advantage is the cost factor, which obviously would save us thousands of dollars as opposed to building entirely new cases. Lastly, there is something noble and worth saving about these antiques, something that will show this and succeeding generations of museum visitors what a turn-of-the-century museum looked like. Retaining part of the heritage of a great natural history museum is an intangible but important factor in a decision of this kind. What are the disadvantages of keeping these cases? The dimensions of the cases put limitations on the flexibility of a redesign programme. There are just so many ways to put material into cases that are all the same and all measure 6 x 13 feet (1.9 x 4 metres) on the inside. However, the collections are at present being displayed in these cases, so it can be done. A second reason, and a very serious one already mentioned, is the total lack of lighting. A lighting system will have to be designed and retrofitted inside the existing framework and a means of dissipating the heat produced will have to be devised. A third disadvantage is the width of the stiles and the wooden door-framesin the cases and the fact that the visitor’s view is somewhat obstructed by them. However, this is probably offset by the acknowledged antique character of the cases and the recognition that they represent a nineteenth-century way of building.
major contribution to the United States Bicentennial Celebration of 1976, it canThe redesign programme of the North- vassed all the large old museums in the west Coast Indian Hall - which has country to find out what was available in been called a ‘museologicaldinosaur’ - the way of surplus nineteenth-century exis not yet under way in fact because other hibit cases. The reason for this search was high-priority design assignments have the re-creation of the Centennial Exhibiput this project in abeyance. However, tion held in Philadelphia in 1876. The result was 1876: A Centennial‘&some preliminary studies have been made to try to solve the lighting and hibition, a marvellous, nostalgic look at visibility problems and are shown here in what Americans were doing in 1876 in Figure 20. The initial step in the re- the field of exhibition and exposition design process is to slice the massive design. This was the official bicentennial case construction down the middle effort of the Smithsonian Institution, (presently there are thirty-six cases in though many branches of the Smithsoback-to-back pairs). To increase the ex- nian staged individual exhibitions in isting 127-mm depth to 380 mm the fine- their museums. The Arts and Industries ly detailed fronts will be separated and Building had previously housed exhibits new side-walls, floors and tops will be of the Air and Space Museum before its built. Mock-ups are planned - an early new premises were completed - many one is shown in Figure 20 - to try out visitors remember Lindbergh’s aeroplane different fluorescent fixtures and to Spirit of S t Louis when it was suspended determine lighting angles which provide from the ceiling of the old Arts and the least objectionable shadows below Industries Building. The interior was artefacts. Eventually new typography and completely gutted and all the walls, ceilgraphic layouts will be developed to ings and ornamental ironwork were reupgrade the exhibits visually and make furbished. Then a design team, under them more comprehensible to the mu- the direction of William F. Miner, inseum-visiting public. New, remote bal- stalled hundreds of exhibits on a variety lasts will help to keep the temperature in of subjects including applied technology, the cases down to an acceptable level. agriculture, science, state and foreign All lighting fixtures will be provided with governments,military and domestic arts. These were housed in hundred-yearultraviolet filters to keep the UV radiaold cases obtained from other Smithsotion down to a minimum. When the Smithsonian Institution nian branches as well as other American decided to build an ambitious new ex- museums. These handsome old glasshibition in the Arts and Industries and-mahogany or glass-and-walnutcases Building in Washington, D.C., as its were stripped, refurbished and refitted
old show-cases: Ascard or recycle? with ornate, gilt-lettered signs. In some Three storeys high, Hawaiian Hall has a instances new tables were fabricated for ground floor plus two balcony galleries glass specimen cases and new tops were surrounding an impressive open cenbuilt for large, free-standing glass cases. tral court. The building was completed in 1903 and has remained essentially un(Fig. 16). The cases had been carefully crafted by changed during the course of several the original cabinet-makers and boasted museum administrations over the ensutight-fitting doors and solid brass hard- ing years. In 1982 I was invited by the Bishop ware. The value of these cases was such that it represented a considerable saving Museum to act as a consultant to conduct on Bill Miner’s construction budget of a week-long study of existing condi$750,000. More important, however, is tions, particularly focusing on show-cases the effect created by the use of these and lighting, and to offer advice on how nineteenth-century cases in re-creating to upgrade exhibits by the application the mood and style of 1876. Potted palms of contemporary design techniques. I and red, white and blue bunting com- assured David B. Kemble, Chairman of pleted the picture and the resultant ex- the Department of Exhibits, that I was hibition, ‘a re-creation of a moment of just as concerned as he was that the apincredible pride in America’s history’, plication of these techniques be compatiwas one of the outstanding features of the ble with the Victorian architecture. The massive exhibit cases, elegantly bicentennial year. Originally scheduled for two years, 1876:A CentennialExhibi- crafted from prized native koa (Acacia. tion may remain on public view for ten koa) wood, were built into alcoves around the perimeter of Hawaiian Hall with winyears. dows spaced between the cases. In the 1960s these windows were partially covLìghìng without heut ered with panels on the lower half and The Bernice Pauahi Bishop Museum in louvres on the upper half. This elimiHonolulu, Hawaii, boasts a large exhibi- nated much of the daylight which was tion space called Hawaiian Hall which is gradually damaging the artefacts in the a masterpiece of late Victorian architec- collection. It also cut down on the natural ture. It is one of a very few remaining ventilation which had been the aim of the examples of this type of exhibition hall architects when designing windows into that have survived virtually unchanged. the building at the turn of the century.
An exhibit case in the Bishop Museum’s Hawaiian Hall in Honolulu illustrating glaring overhead light. 19
The sanie case after modificationswere made. Louvred lightbox and low-voltage spotlights were installed as well as a redesigned exhibit with new graphic treatment.
George S. Gardner
Elevation and section of existing casework and of proposed modification, Northwest Coast Indian Hall of the American Museum of Natural History. I
A section through a modified exhibit case in the Hawaiian Hall .of the Bishop
Museum. At the time of the window modification fluorescent fixtures were installed in the cases. This provided adequate lighting but caused glare which was evident to visitors standing in front of the exhibit cases as well as to visitors on the first floor as they looked up at the balconiés (Fig. 18).
One of the revisions I suggested is shown in Figure 2 1. Lightboxes were to be installed at a slightly lower level than before having parabolic, eggcrate diffusers on the bottom face. This would make the resultant light more directional and eliminate a great deal of the glare. In addition, installation of small, lowvoltage, incandescent spot-lights at the front of each case was suggested. This would permit highlighting of artefacts or specimentson the backwall or the floor of the case. Previously the lighting was essentially flat with little or no accent lighting. Ventilation could evacuate much of the heat out of the top of the case. A pair of cases on the second floor were modified to test the effectiveness of these recommendations.Before-and-afterphotographs (Figs. 18, 19), show the effects
of these lighting modifications. Lowvoltage fixtures mounted on ceiling tracks can be seen in the view of the new installation. The new graphic treatment obviously also improves and upgrades this exhibit. The problem of heat build-up was approached by experimenting with remote ballasts and transformers versus those left in the case. Dave Kemble reports that ‘monitoring revealed that the remote installation of the ballasts and transformers resulted in only a 1 “ C difference in the interior case temperatures. It wasn’t worth the expense and effort to install them in this manner.’ The conclusions drawn from this test installation indicate that the new system employing a mixture of warm fluorescent lamps and incandescent track lights constitutes a major improvement over the old system of straight fluorescents, particularly in terms of added flexibility. The exception is for cases with materials especially susceptible to the damaging effects of heat and light such as textiles.
Protection withoat encase an Afiican q g a Claude Daniel Ardouin, Director of the National Museum of Mali, Bamako, has c o n t n h t e d the following observations:
will suffice: a Dogon dance mask (singè):height 304 cm, width 18 cm; and an Arkila Jango carpet: 451 x 199 cm. This is also true of objects which have to be displayed with other items that normally accompany them so as to provide a more authentic idea of the setting in which they originated. What is essential is not the individual object as an artistic creation but the object as an integral part of a multi-faceted cultural phenomenon. In such cases - and they are quite common - special, extremely expensive show-cases would have to be used. Second, the difficulties in obtaining show-cases. Where the National Museum of Mali is concerned, these difficulties are twofold. To begin with, the funds of the museum are so limited that no cases can be bought; those that the museum does possess were all donated. Even. if the National Museum did have the necessary funds, it would still have difficulty in obtaining all the cases it needs. This is because there is little opportunity for obtaining display cases locally since there is no national glassmaking industry. Cases therefore have to be imported and this entails considerable difficulties (selection, transport, installation, etc.). For this reason it is well-nigh impossible to
The opening in 1982 of the National Museum took the activity of museums in Mali to a level far more complex and exacting than was previously the case. This was reflected, in particular, by the emergence or growth of problems that hitherto had not existed or had attracted only little attention. One such problem concerns the use of show-casesfor display. Is it possible or even absolutely essential to provide show-cases for all objects? The question may seem superfluous in an industrially developed country, but it is of relevance in the specific circumstances of countries such as Mali. The answer will depend on the type of collections, the local availability of materials, skills and financial resources and the expectations of the museum-going public. Bamako is in the Sudanic zone, where rainy and dry seasons alternate. The differences in relative humidity are, therefore, very pronounced, as may be seen from the minimum and maximum rates recorded in 1983 (Table 1). Since the museum has natural ventilation, these exterior variations are fully transmitted to the interior. Light intensity TABLE1. Relative humidity in Bamako, 1983 (percentages) and ultraviolet radiation likewise vary with the seasons. Month Since the exhibition rooms of the National Museum are not J F M A M J J A S O N D air-conditioned the advantages of using show-casesare obvious. Relative humidity But there are also, for a variety of reasons, certain practical limits Minimum 19 18 13 20 33 46 54 62 60 33 18 17 to their use. 40 42 34 59 75 89 97 98 98 87 73 45 First, the size of some objects or replicas makes it very difficult Maximum show-cases for them, for to find large masks, Source: Agence pour la Sécurité de la Navigation Aérienne (ASECNA), some statues, carpets, certain marionettes, etc. A few examples 22
MUSEENATIONAL DU MALI, Bamako. Dogon masks protected by glass panels. t
Claude Daniel Ardouin Ph.D. in Sociology. Consecutively Head of the Department of Ethnosociology at the Human SciencesInstitute, Director of the National Archives and (from 1981) Director of the National Museum of Mali. Research on blacksmiths and ironworking; Editor-in-chief of the periodical Etudes maliennes.
Claude Daniel Ardouin .
Figure of an N’domo dancer, with no protection.
-. .. -
, ..., .
,. . . .
- . -
Exhibition of a Tamasheg habitat, protected by stakes. ”.
acquire the large variety of show-cases that are needed to accommodate most of the items in the museum. Third, glass tends to create a barrier between the visitor and the objects. While this may seem to be of little importance for Europeans, who have a long tradition of visiting museums, it is significant for the large majority of the average Malian public, who are just beginning to discover the museum. Our visitors must find an environmentin which they feel at home, the more so since the museum they visit attempts to re-create for them their own culture by making them discover it. The use of showcases for all the items exhibited can have an adverse effect on the public, particularly if it creates a strange environment. It is, therefore, desirable to find the right proportion of show-cases to use so that the public does not shun the museum. Despite the obvious advantages of show-cases, therefore, their use in practice is a more complicated matter. To lessen the risk of damage to objects from physical and
human causes, there are surely several other means of protecting them such as: General measures in the exhibition halls, such as regular monitoring of climatic conditions and radiation, identification of potentially vulnerable areas during the mounting of exhibitions, protection of openings against radiation, etc. Use of glass panels to protect certain sections of the exhibition. Supervision of the public and their instruction in the use of the museum, although the attitude of visitors to the exhibition is generally one of care. There are thus many different ways of tackling the problem and they depend on the exhibitions and the objects being displayed, the primary objective being to ensure their maximum protection. [ Translazedfrom French]
CLIMATE CONTROL, ACTIVE AND PASSIVE The EgyptiuB GaZZenès ut the MetropoLtutz Mcsecm of Art In June 1983 the Department of Egyptian Art at the New York Metropolitan Museum of Art opened the third and final series of new galleries, concluding an eleven-year project to reinstall the entire Egyptian collection.* All the estimated 40,000 objects are now on view in thirty-two climate-controlled galleries, occupying nearly 7,000 square metres of exhibition space. Of the many problems facing the curatorial, conservation, architectural and engineering personnel in undertaking a project of this scale few were more formidable than the problem of climate control and show-case design. The new galleries were installed in three phases. In each phase a different approach to climate control was employed. The purpose of this article is to describe these three different approaches. I shall also try to shed a little light on some of the reasons for the gradual evolution away from air-conditioned cases towards the use of sealed cases within air-conditioned gallery spaces. Finally, I shall describe. the procedure used for testing these sealed cases.2
Phase I. Difficult to maintah The first of eleven galleries opened in 1976. In planning for this first phase of the installation, the Curator, Christine Lilyquist, decided to attempt to display all the objects - following a general recommendation by the architect, Kevin Roche - and to place them in chronological order. This meant displaying together objects with quite different environmental requirements - for example artefacts in ivory, bronze, linen and stone in the same case. It also meant that very large cases would be required to accommodate objects of greatly varying scale and to facilitate access to them. The resulting design scheme called for
large (380-7,300 m3) walk-in cases fronted by 2.3 x 2.3 m tempered glass lights butted one against the other with a 6 mm air space between each panel. In order to make these large display cases meet the museum staffs recommendation of 72 "F (22 OC), 50 per cent relative humidity (RH), our consulting engineers designed a separate air-conditioning system for the cases themselves. This was designed to provide a closely controlled (72 * 1 OF, 50 t- 5 % RH) temperature and humidity-treated supply of extraclean air to the cases. This air was to filter out through the joints between the glass panels into the public areas because of higher air pressure in the cases. The public areas were air-conditioned to comfort conditions by an existing system, and return air from this system was the source of supply air for the show-case air-conditioning. Low-voltage incandescent lighting fixtures were mounted in compartmentsinside the ceiling of the majority of the cases, providing 75 watts per linear foot of casework. This lighting, together with the transmission load from the surrounding spaces, constituted case-cooling load. Large load savings occurred when the lighting was turned off at night. Separate zoning was required for virtually each case, with temperature and humidity sensors within the cases varying the incoming air temperature and relative humidity and compensating for the case loads. This feature made it possible to modify the conditions inside the cases to suit special requirements of certain sensitive objects such as unstable bronzes or ivories. 1. See the article by Christine Lilyquist in Jfuxeum, No. 142, 1984. 2. I would like to thank John Alticri of John Altieri, P.E., Consulting Engineers, Norwalk, Connecticut, for providing much of the technical information contained in this article.
Bill Barrette A senior restorer with the Metropolitan Museum of Art, has worked in the Egyptian Department since 1975, participating in all three phases of its re-installation. Initially responsible for the conservation of the papyrus collection, he also worked on the treatment of polychrome wooden coffins and, beginning in 1977, was charged with the monitoring and assessment of climatic conditions in the newly constructed air-conditioned show-cases. These studies played a decisive role in the evolution of the department's approach to the problem of climate control, eventually leading to the use of sealed cases within air-conditioned galleries.
The volume of air required to maintain pressurization and proper temperatures and humidities resulted in approximately fifeen to thirty air exchanges per hour. Filters were provided in the inlet and outlet to each zone. These filters were 99.97 per cent HEPA filters normally used in controlling radioactive exhausts, screening out particulates to 0.3 of a micron in size. The effectiveness of these filters was somewhat lowered in several cases where the new case-supply ductwork was connected to existing riser ducts which were lined with accumulated dirt. The result was that loose duct lining and particulate matter could enter the air stream after filtration occurred, creating a maintenance and potential conservation problem in these cases. A system of continuously operating 35.6-ton-capacity dual reciprocating compressor machines provided 40 "F (4.5 "C) chilled water to coils located in each zone. A pneumatic control system maintained a saturated discharge temperature off the cooling coils in summer to maintain fixed humidity, with reheat coils maintaining temperature. In winter, humidity was provided by steam grid humidifiers with humidistats controlling steam flow. These steam grid humidifiers turned out to be the most troublesome feature of this system. On numerous occasions a humidifier would stick in the full-open position and quickly fill the case with air at 100 per cent RH, resulting in condensation on the objects and the in-
In the Phase III system the sealed casework and the hygroscopic materials within help to maintain stability even with fairly wide fluctuations in gallery temperature and relative humidity. The top chart records gallery space outside cases, the bottom chart records conditions inside a sealed case.
per cent inside a case the solenoid valve would then shut off the steam supply for the entire case system and sound an alarm in the engineers' office. Other modifications made at this time were the addition of a back-up chiller pump and a booster fan to improve air distribution in some of the cases and the addition of fibreglass insulation to the backs of cases that were situated against exterior walls. In general these measures were effective; however, this system will always require careful monitoring and extra maintenance to assure its stable operation.
terior surfaces of the casework. Some damage to objects resulted from these incidents. Conservators and curators soon found themselves in the uncomfortable position of having to protect the art from the system which had been installed to protect it in the first place! It was at this time that another conservator and myself were assigned to monitor conditions inside all the cases using recording hygrothermographs. This process was invaluable in determining the seriousness of system malfunctions, and provided a useful diagnostic tool which the engineers could eventually use in prescribing remedial work and in planning the design of the air-conditioning systems that were to follow for Phases II and III. We now have some thirty-six hygrothermographs in place throughout the wing, and while they present a considerable maintenance chore they remain the most reliable way of knowing with any certainty that conditions inside the cases are not presenting a danger to the objects. After about two years of operation it became obvious that substantial remedial work would be necessary to correct the shortcomings of this system. A number of modifications were made to provide for more stable operation and for better notification in the case of mechanical failures. These devices included a back-up shut-off solenoid valve in the feed of the steam humidifiers controlled by highlimit humidistats located in each case. In the event of the RH level exceeding 60 I
Phase II. Better cZìmate controd, bat more probdems Phase II consists of nine galleries opened in November 1978. The design of the show-case remains the same, but conditioned air is first passed into the case and then into the gallery through the 6-mm air space between tempered glass panels butted one against the other. This approach allowed us to improve the climate control design of Phase I. This design provides for dual chilling equipment with a complete system of electric / electronic controls. Fogging devices (cold water particles broken up by compressed air sprayed into the cooling coil) maintain a futed dew-point on all air supplied to cases. The case system and surrounding gallery system are conditioned to a futed-space dew-point of 52 "F (11 "C) combined with a fixed-space temperature of 72 "F (22 OC) resultingin .
The Egyptian Galleries a t the Metropolitan Museum of Art
26 Phase III: General view of the show-cases which are now sealed and no air space is left between adjacent glass panels.
Phases I and II: (1) pretreated air supplied directly into show-cases; (2) higher air pressure in show-cases causes air to exfiltrate through joints between glass panels into gallery space; (3) air-conditioningfor gallery space; ( 4 ) gallery. a constant relative humidity of 50 per cent. For each system a dew-point master controller (hygrometer) raises or lowers cooling-coil discharge dew-point to match space conditions as sensed. Should the gallery become heavily occupied, the rise in moisture is sensed as an increasing dew-point. The dew-point control acts to modulate the chilled water valve open, lowering supply air temperature (dehumidification). The various case and zone reheat coils modulate to maintain temperature. Should there be a reverse - a fall in sensed dew-point - the dew-point control acts to modulate the chilled water valve closed. In this manner, little or no dehumidification occurs, and warmer moisture-carrying air is supplied. Reheat is provided using silicon controlled rectifier (SCR) controlled electric heaters. The SCR provides closely controllable, infinitely variable power to the heaters. The Phase II system achieves a much more stable operation in comparison with Phase I. System problems were reduced due to a number of factors, including single control of moisture content inside all the cases; electronic rather than pneumatic controls; electric rather than water reheat; less dust in cases because the system used no outside air; better distribution of air to cases and, most significantly, in the event of mechanical failure, the foggers did not fill with excessive humidity. In spite of the obvious improvement of this rather elegant system over its predecessor, the first eighteen months of
operation were plagued by a host of mechanical and control problems. Some of these problems included impurities in the water supply to foggers which caused them to clog frequently and resulted in unacceptable RH fluctuations; difficulty in servicing the SCRs and some of the other sophisticated electronic control devices; difficulty in maintaining temperatures during peak load periods due to lack of adequate chilled water capacity; presence of dust in cases due to ongoing construction in the area. These problems were eventually resolved, and the system is now capable of providing 72 "F (22 "C)/50 per cent RH conditions in a reasonably stable manner. However, at the time we had to make a decision regarding the design of the Phase III system, the Phase II system was not operatingsatisfactorily.Togetherwith the ongoing problems of the Phase I system, these problems helped to create a consensus between the Egyptian, Objects Conservation and Textiles Conservation departments against another attempt at air-conditioned cases. By this time the museum staff also had enough experience with the various airconditioning problems to make the following basic assumptions about the longterm effects of air-conditioned casework. First, even under the best of circumstances, no air-conditioning system would be capable of providing constant temperature and relative humidity day in, day out, 365 days a year. Mechanical failures were inevitable, and deviations from mean temperature and RH - lasting
27(b) Phase III: (1) sealed showcases containing buffering material; (2) air-conditioning for gallery; (3) gallery.
84 anything from a few minutes to a few days - could be expected. Second, the Textile Conservation department observed that the constantly moving air physically disturbed the outer layers of the linens and expressed the concern that air constantly pumped into the cases was creating an oxygen-rich environment which could increase the rate of oxidation of the organic materials being housed therein. Also, the presence of particulate matter in the cases along with staining of the wall linen at air outlets suggested the possibility of pollutants being introduced with the air, steam, or both. Third, the increasing complexity of the systems and controls being installed required more maintenance, and in some cases more expertise than the museum’s Buildings Department could provide at that time. Even now the manpower needed just to keep the various controls, sensors and alarm devices properly calibrated exceeds what the museum’s staff can provide, with the result that outside contractors are hired to supplement their efforts. It was against this background that the decision to eliminate air conditioning from the Phase III cases was made.
P h s e III It was decided that temperature and relative humidity in the entire gallery space - in which sealed cases are constructed - would be controlled by an upgraded HVAC (heating, ventilation, and air-conditioning) system. To implement this, two new chillers and cooling towers were installed not only to run Phase III but also to add supplementary cooling capacity for Phases I and II. In addition, two new fans and an enthalpy control system with an economizer cycle were installed. The new system is rated at 200 tons of refrigeration to cool 2,140 m3 of air per minute to a sufficiently dry state so that moisture can be added continuously to maintain a constant relative humidity of 50 per cent. There are eighteen zones of temperature and humidity control, some located in the return air ducts above light attics of casework in order to respond quickly to varying lighting loads. In spite of these and other improvements, it was anticipated that there would be some daily variation in RH and occasional mechanical failures. The
casework was therefore designed to be measuring the rate of the tracer gas loss by sealed so that the RH in the cases would a Gow-Mac gas analyser fitted with a strip not be immediately affected in the event chart recorder. Further, in order to test of short-term fluctuations in the gallery the integrity of the seals, and to detect space (Fig. 26). specific points of leakage, a gas-leak It was felt that in order to be effective, detector with a probe attachment was the cases should at least be able to slow used, making it possible to improve seal down air exchange over a period of several integrity where needed until the case condays in order to maintain a stable RH en- formed to design criteria. vironment during periods when the On the basis of this prototype and this system was ‘down’. This would also make testing method, it was possible to avoid it possible for the cases to be retrofitted costly or irreparable mistakes during the with silica gel as an RH buffer should an final design construction and installation auxiliary humidity control be required. stages of Phase III. The contractor who inThe success of this approach hinged stalled the cases worked closely with consolely on whether or not sealed cases of servation staff and was able to modify and the size required (up to 180 m3) could be improve seals in response to test results. constructed to meet the conservation staff This resulted in even the largest of the criterion of 1.5 air exchangesper day. The finished cases being acceptable in their idea of sealed cases had been brought up ability to maintain RH stability over a by the conservation staff previously, considerable period of time. mainly in discussions concerning the It should be noted that this work was climate-control design of Phase II. The carried out well in advance of the actual concept was ultimately rejected as being installation of objects; almost a full year impractical if not impossible if curatorial was allowed for the testing of both the access to the cases was to be a factor. This air-conditioning system and the cases time, however, it was decided to assess before the installation of sensitive the feasibility of sealed casework by material. having the architect design. a full scale prototype case which would be rigor- ConcZusion ously tested by conservation staff prior to making final design decisions regarding On the basis of a year’s observation of the Phase III. Phase III system it is possible to state that A prototype case was constructed in air of constant temperature and humidity which all the movable elements were surrounding well-sealed and buffered carefully sealed. Access to the case con- cases does indeed result in quite stable sisted of pivot and sliding doors which, relative humidities inside the cases, even when closed, were sealed top and bottom during periods of instability in the gallery by a movable neoprene gasket which was system. The mass of the casework and the ratcheted into place. The problem of hygroscopic material within them help to dissipating heat load from the lighting maintain this stability even with fairly fixtures was solved by positioning them wide fluctuations in gallery temperature in a special chamber above the case and and relative humidity (Fig. 27(b)). directing return air through these It can be noted at the same time that chambers thereby removing the heat. To with in-case air-conditioning systems, test accurately whether the prototype case such as Phases I and II, operating costs met the design requirements, a method can be reduced when loading and was developed by Steve Weintraub of the operating of central air-conditioning museum’s Objects Conservation depart- systems are reduced (i.e. in case of an ment. emergency or for economic considerations, the case system can be run independently of the gallery system with Test procedure great savings in energy). However, the Briefly described, the testing procedure greater stability afforded by using tightly consisted of filling the cases with carbon sealed cases in conjunction with condioxide or helium (COz, because of its tinuously operated central air-condiweight, worked better for testing the tioning, and the increased safety of the lower parts of the case and, conversely, objects displayed in this manner, lead me helium worked best for testing the to strongly recommend this alternaleakage along ceiling joints) and then tive.
In 1934, J. McIntyre, a public works module. This could be either the engineer, published test results to show museum workshop or a local fabricator. that relative humidity (RH), in even a poorly sealed display case, is more stable Control modzcGe upphcation than the relative humidity in the room around it.1 He further demonstrated that One relative humidity control module the hygroscopic artefacts and lining of the can control many display cases. If they are case would improve this stability so that reasonably well sealed, it can control even with a one-millimetre gap around 100 m3, that is, 100 medium-size cases the glass base, relative humidity could be or twenty cases large enough for life-size rendered practically constant during the manikins. Typical tube diameters are inone week of monitoring. At the same dicated in Figure 29. Only one tube time, a patent appeared for additional enters each case. Exhaust is provided ‘regulating substances in cases and pic- simply by leakage through small gaps in ture frames’.Z These were salt hydrate the case. In the rare instance where the pairs. Later, saturated salt solutions3~* case is completely air-tight then a small were used and over the last two decades, 3-mm hole must be dlilled in the case silica gel has been popular.5 These addi- somewhere. Thus the’ modification to tional hygroscopic materials, or buffers, each case is minor, unlike the application were necessary if the relative humidity of of buffers that requires removal of all the case was to remain stable for more artefacts and the construction of a false than the few days’ grace offered by the bottom and access doors. Figure 28 shows artefacts and case lining themselves. a vinyl tube that supplies the controlled Unfortunately, if many cases are to be air through a hole in acrylic glazing. controlled by buffers the initial costs - Figure 30 shows a main branch of the silica gel, false bottoms, access doors - distribution system that supplies three and the maintenance - monitoring, large cases each having a volume of 8 m3. removal, calculating, reconditioning - Precise selection of tube diameters and all become deterrents. On the other lengths will be based on charts provided hand, environmental control of the en- in an installation manual. The main tire building is problematic if it is an supply tubes are large enough not to conhistoric building, especially with the cold strict the airflow and on the other hand winters that occur in Canada. the last tube to each case is small enough It is also fifty years since a professor of to control the airflow to that case. art history, W. G. Constable, published the suggestion that an alternative to buf1. J. Mdntyre, ‘Air Conditioning for fers was ‘feeding conditioned air into the Mantegna’s Cartoons at Hampton Court Palace’, frame (or case) by means of pipes’ .6 The Technical Studies in the Field of Fine Arts, Vol. 2, 1934, p. 171. idea was dismissed at the time on the 2. B. H. Wilson and L. W. Barridge, presumption of bulky and inconvenient ‘Improvement in Controlling the Humidity of in Enclosed Spacer Such 2s Containers, pipes. In 1979, Raymond Lafontaine, a Air Picture Frames and Rooms’, London, HMSO, scientist at the Canadian Conservation 1933 (British Patent 396439). 3. S. Sack, ‘A Case Study of Humidity Institute (CCI), proposed a solution: a Control’, BrookLyn Museum Annual, Vol. 5 , system that easily connects to each case by 1964, p. 99. small plastic tubing. In 1980, the author 4. T. Padfield, ‘The Control of Relative Humidity and Air Pollution in Show Cases and was hired to design the system. A Picture Frames’. Stztdies in Conservation. Vol. prototype was completed, tested and 11, 1966, p. 8. 5 . N. Stolow, ConservationStandards for installed in a museum. This has Works of Art in Transit gnd on Exhibitiin, operated successfully for almost two p. 126, Paris, Unesco, 1979, 55 illustrations. years. Blueprints, an assembly manual 6. W. G. Constable, ‘Appendix III: Framing and a maintenance manual have recently and the Control of Humidity’, Some Noter on Humidì0 in Relation to Works of been completed so that any good carpen- Atmospheric Art, p. 48, London, The Courtauld Institute of try workshop can produce the control Art, 1934.
Stefan Michalski Born in Birmingham, United Kingdom, moved to Canada in 1957. B.Sc. (Hons.) in physics, Queen’s University, Kingston, Canada, 1972.Research assistant in visual neurophysiology, 1972-76.Trained as artefacts conservator at Queen’s University, 197779. Internships in the Conservation Department, Royal Ontario Museum, Toronto; and Conservation Division, Parks Canada. Employed by the Canadian Conservation Institute, Ottawa since 1979; currently Senior Conservation Scientist. Has published articles on the development and assembly of a relative humidity control module and on history and theory of suction table use in conservation. Recently developed a poster and slide rule about light damage in museums. Consultant to Canadian museums on architectural, mechanical and display case aspects of environmental control.
Close-up of a four-millimetre-diameter plastic tube that supplies RH-controlled air to a wall display case in the National Museum of Man, Ottawa. The acrylic strip through which the hole is drilled was fitted during installation of the module to improve the air-tightness of the original glass front.
Typical tube diameters for the controlled air distribution network. Up to 100 one-cubicmetre cases can be controlled by a single module. There are no return air tubes, instead air continually flows out of each case. The module can be set for a relative humidity between 45 and 60 per cent RH. Optimal operation is at 50 per cent RH. Fluctuation about the set point is less than +. 3 per ,cent. There is no active temperature control - the module passively follows the room temperature. As with a building air-supply system, relative humidity control is only as good as temperature uniformity from point to point in a room. If a case is consistently warmer or cooler than the control module location, then its relative humidity will be lower or higher than the module output. Practically speaking, as long as none of the cases is illuminated excessively or is adjacent to a. cold wall, then the system works properly. The control module contains a particulate filter and space for an adsorption filter. In addition, separate groups of cases, whose contents demand removal of particular contaminants, such as silver artefacts, would have specific cartridge filters installed on their branch supply pipe. Unlike filtration of the total air in a building, filtration with the control module is cheap and can be tailored to individual artefact needs.
paper, then the case is reasonably airtight. Previous researchers have emphasized diffusion of water vapour through the case materials and through stagnant air in the gap^."'^' These slow mechanisms become important only for specially designed cases that are almost hermetic. In practice, the average display case leaks badly because of convection currents, i.e. slow draughts in and out of the case. Existing display cases can be rehabilitated by the same techniques one uses to weatherprodf a house or car, i.e. by carefully fitted trimmings, caulking, adhesive tape and foam weatherstripping. Some of these materials release gases that are harmful to some artefacts, indeed artefacts themselves may release such gases.8 Although the CCI has tested some products and can advise on their use, space does not permit their discussion here. A distinct advantage of the control module approach is that freshly controlled air is supplied to the cases at four air changes per day or more, so any contaminants are continually flushed out of the case. This flow also prevents infiltration of pollutants from outside the case.
Control modzde design Case qzcality What is meant by a ‘reasonably’ air-tight display case? Theoretical and experimental research at the CCI has shown that if gaps at the top and bottom seams of a case are smaller than 0.3 mm then the leakage rate of the case will be less than two air changes a day. In practical terms, if the gaps in the seams of a case do not allow easy insertion of a piece of stiff
Figure 3 1 shows the control module with its access cover removed and the 7. P. Brimblecome and B. Ramer, ‘Museum Display Cases and the Exchange of Water Vapours’, Studies in Conservation, Vol. 28, 1983, p. 179. 8 . T. Padfield, D. Erhardt and W. Hopwood, ‘Trouble in Store’, in N.S. Bromelle and G. Thomson (eds.), Science and Technology i f 2 the Service of Conservation,Prepnnts to the Washington Congress, 3-9 September 1982, p. 24, London, IIC.
A relative humidity control module
Pulled out from under one of the cases being controlled, this is a main-branch air pipe, 1.2 cm diameter. It uses inexpensive cold-water hose fittings - no sealant is necessary and the tube is flexible.
The RH control module with its front cover removed. The humidifier section is being witkidrawn to inspect the evaporator plates.
Diagram of the RH control module: (1) particulate filter, air intake; (2) cold coils of the refrigerant dehumidifier - C = compressor; (3) air blower; ( 4 ) evaporative humidifier; ( 5 ) heat exchanger; (6) silica gel buffer in heat exchanger; (7) humidistat; (8) adsorption filter. Solid arrows show the controlled air-stream; outlined arrows show the room air moved by two fans (F).
humidifier section pulled out. At the very top is a water reservoir to feed the humidifier and at the bottom is a tray for dehumidifier condensate. Each can have capacity for one week's operation in extreme dryness OT dampness. Both can be attached to plumbing systems for automatic operation if desired, or simply to larger reservoirs. The module is essen' tially a small-scale mechanical control system as shown schematically in Figure 32. The unusual components are: a blower, which is a three-stage centrifugal fan of modest speed and low noise, a heat exchanger, which passively keeps the controlled air at room temperature, and a silica gel buffer, which smooths out the RH of the output of the mechanical humidifier or dehumidifier. The silica gel buffer is itself in a heat exchanger that keeps the controlled air at room temperature. Further technical details have been published elsewhere.9 Routine maintenance, such as annual changes of adsorption filter, evaporator plates and dust filter, can be carried Out quickly once the access door is opened.
Conclusions Here is a relative humidity control module that can be built by competent craftsmen. Complete blueprints, instructions for assembly and use are all available from the CCI in both French and English. It can replace approximately C$20,000 worth of silica gel as well as eliminate the cost of installing silica gel compartments. The cost of the control module components is C$l,SOO. It requires about three months for a craftsman to fabricate it and then only a few days to install. The display cases must be made reasonably air tight as with any control of internal humidity. The module is appropriate for medium-scale museums and art galleries that cannot consider environmental control of the whole building yet have a sufficient number of cases to make the buffer approach costly and labour intensive. 9. S. Michalski, 'A Control Module for ~ ~Humidity l in ~~ i cases, ~ ~ini ibid., ~~ p. 28.
l ~ ~
Andrea Rothe Born in Bolzano, Italy in 1936. Studied conservation in Florence and Vienna, 1954-59. Assistant to Oskar Kokoschka at the Summer School of Vision in Salzburg, 1957-63.Private conservator for the Italian state, restoring works at museums and churches of cities and provinces of Naples, Urbino, Arezzo and Florence, 1959-81. Head of paintings conservation laboratory at the Pitti Palace in Florence, 1969-81. Since 1981 head of paintings conservation at the J. Paul Getty Museum, at Malibu, California.
Bruce Metro Born in 1950 in Michigan, United States. M.A. degree, 1976. Chief preparator, Los Angeles Institute of Contemporary Art, 1976-78.Now head of art preparation, J. Paul Getty Museum.
Because of their sensitivity to humidity changes., some museum objects may need climatic conditions that differ from the rest of the collection. In order to show these objects, special cases may be built for them that will keep climatic conditions constant. The J. Paul Getty Museum at Malibu, California, has a collection of thirteen Fayum mummy portraits that are displayed in the same galleries as the rest of the antiquities collection. The particular gallery was not designed as an exhibition space for such sensitive objects and has little climate control. Another object displayed in the museum’s painting gallery is a tempera painting on panel by Simone Martini. Dating from about 1330, the painting had shrunk before its’addition to the
museum’s collection. In order to reverse its tendency to shrink, it had to be placed in a special case with a higher humidity level than that normally maintained in the paintings galleries. The panel, showing St Luke, is made of poplar and belongs to a series of five. It measures 67.6 x 48.3 cm, and had been stored in a bank vault with no climate control. Consequently, the panel had shrunk 3.75 mm within the original frame. A large vertical crack formed on the left between the panel and the frame. That this had happened recently could be deduced by the fact that fills, inpainted by the Italian tratteggio method, had split, leaving part on the frame and part on the panel. Since this inpainting method was introduced by the Istituto
Cross-section of the show-case: (1) plexiglas bonnet; (2) plexiglas back plate; ( 3 ) ArtSorb in its container; ( 4 ) panel painting; ( 5 , 6 ) plexiglas rod mounts; (7) plexiglas support; (8) stainless-steelinsert; (9) ‘0’ring seal; (IO) metal wall mount; (1 1) wall.
The Simone Martini show-case in the gallery.
Andrea Rothe and Bmce Metro
90 35 Front and back of the show-case.
Central del Restauro in Rome in 1945 by Cesare Brandi and Laura Mora, the split must have occurred within the last forty years. By measuring the split over a period of time, it was observed that the panel was very sensitive to humidity changes which led to the belief that the panel would expand and minhize the crack if kept constantly in a highhumidity environment. A case had to be designed which was truly airtight and at the same time not too visually overpowering (Fig. 33). The museum staff and Helmut Guenschel together developed a design and the case was then built by Guenschel Inc., of Baltimore (Fig. 35)' This case is wallmounted and consists of three basic sections: a back panel, a front bonnet, or vitrine, and a silica gel container (Fig. 34). Partially embedded in the front surface of the back panel is a double row of Norton Tygon S-54-HL tubing around the outside perimeter.2 This tubing acts as a seal when the two halves of the cases are joined. Also on the back panel are mounts of 13-mm-diametercast plexiglas rods that hold both the silica gel container and the art object. The silica gel
container is constructed of plexiglas with a brass screen front and is removable. The front half of the show-case is a removable plexiglas bonnet constructed, like the back, of 6-mm-thick plexiglas using a Rohm & Hass PS-30 cement, a twocomponent reactive acrylic cement. The two parts of the case are sealed together with small bolts that are inserted through the back panel into stainless steel machine-threaded inserts in the plexiglas bonnet. As the bolts are tightened, the bonnet is drawn to the back panel and presses against the double seals. Selecting a sorbent for these two projects, we decided to use a new type of silica gel, produced by Fuji-Davison Chemical of Japan, which has recently become available.3 The gel, called ArtSorb, comes packed in propylenelpolyethylene sheet. Art-Sorb combines and exceeds the performance efficiency characteristics of both regular and intermediate density silica gels in the desired range. Ordinary silica gel is most efficient below 40 per cent RH and intermediate density silica gel is most efficient above 60 per cent RH. Art-Sorb is very efficient across this complete RH
range and in fact, papers presenting comparative performance statistics published by Steve Weintraub and Sadatoshi Mima4 indicate that Art-Sorb is superior to either ordinary or intermediate silica gel in the range of 40 to 70 per cent RH.5 For the Simone Martini panel 4 kg (dry weight) of Art-Sorb was put into the gel container and conditioned in a humidity chamber to 66 per cent RH. This amount 1. Helmut Guenschel, Inc., 10 Emala Avenue, Middle River, Baltimore, Maryland 21220, United States. 2. Available from the Norton Company, P.O. Box 350, Akron, Ohio 44309. 3. Available from: Fuji-Davision Chemical Ltd., Room 505, 5th Floor, Higashi-Kan, Dai-Ni Toyota Building, 11-27, 4-Chome. Meieki, Nakamura-Ku , Nagoya-Shi , Aichi-Ken ,Japan. Art-Sorb is also available from: Conservation Materials, 340 Freeport Boulevard, Sparks, Nevada 8943 1. 4. Steven Weintraub, A New Silica Gel and Recommendations, New York, Metropolitan Museum of Art; Sadatoshi Mima, Studies on the Behavior of RH Withitz an Exhibition Case. Part II: The Static and Dynamic Cbaracterirdics of sorbents to Control the RH of a Showcase, Ottawa, ICOM Committee for Conservation, 1981. 5 . Steven Weintraub, Stdies on tbe Bebavior of RH TVithin an Exhibition Case. Part I: Meusunhg the Efectiveness o f Sorbents for Use in un Enclosed Showcase, Ottawa, ICOM Committee for Conservation, 1981.
is four times that of Thomson’s recommendation for a case of this size.6 This show-case has been on display since March 1983, in a temperature- and humidity-controlled gallery. The RH in the gallery is a constant 14 to 16 per cent lower than the RH in the interior of the case. The painting has expanded for a total of 0.45 mm and we will continue to keep it in this condition for quite some time.
the RH during the period tested ranged from a low of 37 per cent to a high of 68 per cent. The temperature ranges from 20 o C to a maximum of 27 o C during the year, given the mild climate. The cases had to keep these mummy portraits in an ideal constant environmentof 50 per cent RH with little or no fluctuations. The Art-Sorb was preconditioned to this RH by placing it in the controlled environment of the museum storeroom and allowing it to come to equilibrium. After observing the hygrometers in the cases for ApplyìBg the same desìgB a period of time we were able to ascertain The Fayum portrait cases were con- that the RH never varied more than 2 per structed using the same design as the cent. The cases are sufficiently airtight as Simone Martini case. The back panel of to avoid having to open them to each case is of wood laminated with For- recalibrate the hygrometers and recondimica. On the front of this back panel is a tion the silica gel. stepped-out display board, also of lamAll the cases have been fitted with inated wood. The display board serves small thermohygrometers made by two purposes: the plexiglas rod mounts Pastorelli & Rapkin Ltd. of London. are bolted to it and it conceals the silica Though not as accurate as more sophistigel. The silica gel container is made out cated and much larger hygrothermoof birch with a silkscreen fabric stretched graphs, they were tested before being over the front and back. This container is mounted in the various cases. They also removable and slides in and out of proved to be reliable enough, even warnthe show-case from behind the display ing us when one of the cases was not comboard when the case is opened. The por- pletely airtight due to a loose stainlesstraits had to be exhibited on the first steel ‘insert. Their only disadvantage is floor where the antiquities collection is that they have to be monitored quite housed. In this gallery, open to the out- often, since there is no printout that can side environment during public hours, be read. Since the objects have been
Show-casesmo Brian Ramer The Sainsbury Centre for Visual Arts at Norwich, United Kingdom, houses a diverse collection of ethnographic objects, antiquities and modern works of art given to the University of East Anglia by Sir Robert and Lady Sainsbury.2 Opened in 1978, the building was erected by the university with the assistance of an endowment fund created by the Sainsburys. Designed by Foster Associates, the building is a long, open-ended structure in which both ends consist of large glass panels bonded together to form a continuous wall. Enclosing the ceiling and walls is a cladding system of interchangeable aluminium and glass panels. With all fixed services located in the skin, (the cavity between the external
mounted, the Simone Martini in March 1983 and the Fayum portraits in October 1983, there has been no need to open the cases and recondition the Art-Sorb. With the construction of airtight cases and the use of Art-Sorb as a sorbent, a constant RH can be maintained if the temperature changes are not too drastic. The long-term effectiveness of cases, due to their airtightness and very efficient silica gel, precludes the need for frequent openings to remove and recondition the silica gel. Being constructed of plexiglas, the objects are clearly visible and can be lit from the outside without any apparent temperature change. These cases have been in use at the J. Paul Getty Museum for over a year and have proved very satisfactory. 6. Garry Thomson, ‘Stabilization of RH in Exhibition Cases: Hygrometric Half-time’, Stlldies in Consemation, Vol. 22, No. 7, pp. 85-102.
ate controz and internal walls), the centre functions as an enormous, open-plan room. Within this room are exhibition and curatorial areas, the university’s School of Fine Arts, and reception and catering facilities (Fig. 36). Commissioned shortly after the oil crisis of 1973174, the building was de1. This article is an abridged version of ‘The Development of a Local Humidity Control System’, The Intemational Jounzal of Museum Management and Curatorship (London), Vol. III, NO. 2 , 1984, pp. 183-91. 2 . I wish to thank Dr Alan Borg, former keeper of the Sainsbury Centre, for his support during the development of the humidity control system and Mr Graham Beal, present keeper, for permission to publish this article. I also wish to thank Mr Piotr Stepien for drawing Figs. 37, 38 and 39 and Messrs Michael BrandonJones and Ben Taylor for their assistance with the photography.
The living area, the main gallery in the Sainsbury Centre.
37 Relative humidity readings taken within the Sainsbury Centre standard-sizeshow-case containing silica gel (proportional to 20 kg per m3 of display volume) compared with the ambient relative humidity recorded in the main gallery during 1979. (1) showcase RH; (2) ambient RH.
100 90 -
signed to be energy-efficient. To avoid standards,4 a localized system of climate the high installation and maintenance control was adopted. The system, concosts of air-conditioning, an innovative sidered essential for the preservation of scheme in building design was adopted. the humidity-sensitive material in the Integral features of the design are the collection, involves the establishment of height and shape of the spaces, and the predetermined levels of relative humidity thickness, reflectivity and insulation within individual show-cases. With the value of the enclosing walls. The absence use of silica gel, a humidity buffering of air-conditioning was seen by the agent, fluctuations in RH inside the cases architect to be in the spirit of a living- are controlled. The quantity of silica gel room environment rather than a climate- required is determined by the volume of the show-case, its leakage rate, and the controlled vault for works of art.3 The environmental conditions ex- estimated difference in RH between the perienced in the Sainsbury Centre,.how- case interior and its surroundings. ever, are not as stable as those associated with an air-conditioned space. The build- Choice of a method ing's fabric, consisting of metal and glass, does not possess any moisture-buffering In assessing the various systems of properties. During the winter heating humidity control employed within showperiod the relative humidity (RH) is con- cases, the use of a mechanical system of sistently low since the exhibition areas are control dependent on electricity was connot equipped with a humidification sys- sidered impracticable. The use of a satutem. In the summer during hot, sunny rated salt solution, most effective when spells the variation in relative humidity auxiliary support is provided by an eleccan be extreme. This is chiefly due to tric fan, presented the same drawbacks as the building's lightweight construction the fully mechanical system. The use of which responds quickly to changes in silica gel enabled the creation of a selftemperature. As the temperature in- sufficient system without the need for creases at midday, the RH drops in electrical support. This permitted unreresponse. With the lowering of the stricted placement of the show-cases temperature in the evening, the RH rises 3. N.Foster, 'Architects' Note', The again. Architectural Review (London), Vol. C W V , No. As the building is unable to maintain 982, 1978, pp. 347-53. 4. G. Thomson, The rMuJeum Environment. an appropriate level of environmental London, Butterworth, 1978, 270 pp., tables, control based on accepted conservation photos, bibliography.
Show-cases modified for climate control
within the open-plan exhibition space of the Sainsbury Centre. Regular density silica gel was chosen for these show-cases since it is readily available and comparatively inexpensive.5 Silica gel is an inert, clean, crystalline form of silicon dioxide. Having a very large internal network of pores through which water vapour can be absorbed or desorbed, silica gel is a particularly suitable humidity buffering agent. It compensates for changes in the watervapour content of the air within a case caused by variations in the environmental conditions surrounding the case. According to the nature of these variations, the silica gel either absorbs or releases water vapour to make the changes within the case less abrupt. In its state dispatched from the supplier, the water-vapour content of silica gel is too low to buffer humidity variation. Thus, before it is installed in a show-case, it is preconditioned, that is, it is prepared to a desired level of RH based on the humidity requirements of the objects to be exhibited. During precondi-, tioning, the water vapour content of the silica gel is increased to a predetermined percentage within a known constant environment.
Modificatìon of the display cares Approximately 130 show-cases were specially designed for the opening of the Sainsbury Centre.6 The majority were constructed to a standard size of 180 x 60 x 60 cm, thereby facilitating the adoption of a modular approach to local humidity control (Fig. 38). By exploiting the existing features of the show-cases, it has been possible to modify them to ac-
93 commodate a humidity buffer. Conversion could be undertaken because each free-standing show-case is a well-constructed unit. The plinths are made from mild steel with a stove-enamel paint finish.7 The tops, fabricated from high quality, 8-mm thick acrylic sheet, have mitred joints which are chemically welded.* Frequent exchange of air between the interior of the case and its surroundings is minimized by the impervious nature of these materials and their highquality construction. In 1980 the cost of constructing each standard-size show-casewas $275 ($305). An additional cost of approximately €10 ($11) in materials was incurred to modify each show-case. The materials included silica gel, a tray to contain it and a draught excluder to seal the case. The cost was low because the majority of the showcases were constructed to a standard size and the modification was made as simple as possible. Unfortunately, a particularly desirable feature, an independent access door to the silica gel, could not be included in the retrofit. The humidity buffer is contained in specially made polystyrene trays which are designed to rest snugly on an interior metal lip located at the top of the plinth (Figs. 39, 40). For maximum effect, the silica gel is distributed in a thin layer (3-4 cm) on the floor of the tray. The position 5. The silica gal, 2.5-6.0-mm particle site, was purchased from W. R. Grace Ltd, Northdale House, North Circular Road, London, United , Kingdom. 6. The show-cases for the opening of the Sainsbury Centre were designed by George Sexton Associates, Washington, D.C. 7. The plinths were built by Artisan Engineering Ltd, Seagrave, Luton, United Kingdom. 8. The acrylic tops were made by Isba AG, CH 4142, Miinchenstein, Switzerland.
Detail of cross-section of standard-size show-case before modification. (1) acrylic top; (2a) baseboard covered with display fabric; (3) interior lip; (4)security screw; ( 5 ) plinth. 39
Detail of cross-section of standard-size show-case after modification. (1)acrylic top; (2b) perforated baseboard covered with display fabric; (3) interior lip; (4) security screw; ( 5 ) plinth; (6) draught excluder; (7) polystyrene tray; (8) silica gel (3-4 cm depth) in muslin bag.
.. . ._
The muslin bag containing silica gel placed in the polystyrene tray. Holes are prepunched in the tray to accommodate the four metal protrusions located on the interior lip. The draught excluder is placed snugly against the edge of the tray.
94 of the tray beneath the baseboard brings the humidity buffer as close as possible to the exhibited objects and also reduces the volume of air in need of humidity control. To promote air circulation between the silica gel and the display volume above, the baseboard is drilled with a series of holes and trimmed along its edges before being covered with fabric. The baseboard rests on four metal protrusions situated at the corners of the interior lip of the plinth. To keep the contents of the case secure, a specially designed screw is passed through the plinth, acrylic top and baseboard into each protrusion. The air-change rate between the case interior and its surroundings is reduced by placing a draught excluder on the interior metal lip where the acrylic top rests on the plinth.
Preconditioning of sikica geZ a d amount chosen Preconditioning of silica gel at the Sainsbury Centre is not a complex affair. The silica gel is preconditioned to 5 5 per cent RH for the exhibition of artefacts made from organic materials such as wood, ivory and leather. (This level of relative humidity was chosen since it was consistent with the one to which the artefacts had become acclimatized in the Sainsburys’house). Specific quantities of silica gel are distributed evenly within buffer trays stacked on table tops. Preconditioning is completed in approximately fourteen days in the art store in which the humidification system supplies a relative humidity of 5 5 per cent. In order to decrease this preconditioning period, increased air circulation is provided by way of a nearby fan. If a batch of silica gel is required at a different humidity level for other types of objects, an environmental chamber is used at the university. The amount of silica gel allocated to each show-case is stored inside a muslin
bag (Fig. 40). The use of a bag simplifies handling of the silica gel while the permeability of the muslin facilitates the exchange of water vapour between the silica gel and the air in the case. The dimensions of the bag are related to the standard-size show-case, and a tag attached to the bag is labelled with details concerning the preconditioning process. A pressure-sensitive fastener strip (Velcro) is sewn along one edge of the bag to allow easy access to the silica gel. To determine the amount of buffer required for effective humidity control, four standard-size show-cases were each installed with a different quantity of silica gel: 1, 2, 3 and 4.3 kg (dry weight before preconditioning). The last amount was designed to assess Thomson’s recommendation of 20 kg of silica gel per cubic metre of show-case volume.7 All quantities were preconditioned to 5 5 per cent RH. The environmental conditions within the show-cases were monitored with thermohygrometers which were read in the early morning and mid-afternoon, while the conditions in the gallery were continuously recorded on a thermohygrograph. The silica gel was not replaced during the period in which the monitoring took place. The relative humidity readings within the show-case containing 4.3 kg of silica gel were found to be most stable. The results of this monitoring are illustrated in Figure 37, demonstrating that Thomson’s recommendation serves as a good guide when initiating a system of local humidity control.
dardization of the storage units facilitates both the handling and preparation of the silica gel. To a large degree the success of the system was dependent on the physical properties and practical aspects associated with silica gel. The capability of being preconditioned to different relative humidity levels was of primary importance in creating a flexible yet inexpensive system. It is economical because of the comparative low cost of silica gel and its regeneration ability. The cases could be modified for humidity control because each metal plinth and acrylic top formed a closefitting, well-built unit. The impervious nature of the construction materials served to deter frequent air exchange between each case interior and its surroundings, an important feature permitting modification. Many museums could better preserve their collections by establishing a local humidity control system for their showcases. As has been discussed, this can be done in a straightforward and economical manner, provided the cases chosen for conversion are well-constructed units. At present the majority of commercially available show-cases are built without consideration of the various features of case design which facilitate climate control. Neither are many models sympathetic to modification or the creation of a local humidity control system. A well-constructed show-case can be aesthetically pleasing and functional at the same time. This underlines the importance of collaboration between designer, curator and conservator. This collaboration should take place at the beginning of a project - whether it be for a new show-case, temporary exhibition or new gallery.
In response to unacceptable levels of humidity in the Sainsbury Centre, a specially designed local humidity control system was developed for the show-cases 9. G. Thomson, ‘The Stabilization of RH in in which the humidity buffer is Exhibition Cases: Hygrometric Half-Time’ , prepackaged in permeable storage units StzldieJ in Consemfation(London), Vol. =II, determined by the size of the cases. Stan- NO. 2, 1977, pp. 85-102.
electric radiators. The largest room was 160 m2 in area and its ceiling was 12 m high. No recordings of environmental conditions were available for those rooms. The instruments were to be displayed in glass show-cases. The first thought was to install an air-conditioning system and a study was made by the de Micheli firm, which quickly decided against air-conditioning for the following reasons. First, the power supply of the Pitti Palace was not strong enough to handle the six air-conditioning units needed. It would have been necessary to install a more powerful transformer, and this was difficult to do in the historic centre of Florence. Second, the electricity company was planning to cut off the power supply for three hours every Wednesday morning as an energy-saving measure. Third, the minimum total inThe instruments stallation expense, which did not include The instruments were in a good state of operating costs, was estimated at around preservation. It was thus decided to 110 million lire.2 Finally, the windows of devote the utmost attention to maintain- the rooms looking out onto the Boboli ing conditions of stable RH while the col- Gardens surrounding the Palace could lection was being moved from the store- not be opened. For these four main reasons, it was rooms to the exhibition site, throughout the period of the exhibition and while the decided to study the possibility of controlling relative humidity by placing adcollection was being transported back. The group selected for exhibition con- sorbent materials inside the show-cases sisted of 197 instruments, including 84 only, allowing the atmospheric condistringed instruments. Among the latter tions in the rooms to fluctuate. Since the were the first upright pianoforte con- instruments had been maintained at a structed by Domenico del Mela in 1739, relative humidity of 53.5 per cent, it was the spinet constructed by Benedicti obvious that the relative humidity inside Floriani in 1568 and the cello and viola the show-cases had to be kept as close as medicea constructed by Antonio possible to that mark. An experimental show-case (Fig. 44) Stradivarius in 1690 for Prince Fernando de' Medici, son of Cosimo III. This last is with a double bottom was constructed by an exceptionally important instrument the Florentine firm of San Benedetto acbecause it escaped the modifications cording to the following specifications, which were made on almost all in- laid down by Professor Rossi: Length, struments of its type in the nineteenth 1.6 m; width, 0.8 m; height, 1.4 m plus 0.5 m for the legs; volume, 1.7 m3; century (Fig. 41). double-plated thermal-insulation glass, 5-mm plate glass plus 9-mm air space Research t o control rezative plus 5-mm plate glass; lighting, external; humidity
In 1979 a committee chaired by Professor Fernando Rossi and composed of representatives of the four Rotary Clubs of Florence decided to mount a temporary exhibition of the musical instruments of the Luigi Cherubini Conservatory of Music in Florence. Ever since the closing of the Conservatory Museum in 1964 for construction work, these instruments had been stored in three unheated store-rooms in the middle of an old building where atmospheric conditions vary gradually between 14 and 29 "C and between 45 and 59 per cent relative humidity (RH) each year. The most sensitive instruments were placed in a room where the RH varied between 50 and 55 per cent with an annual mean of 53.5 per cent.
The exhibition was to be held between February 1980 and February 1981 in four rooms on the third floor of the Pitti Palace, whose windows face the northwest. The rooms were not air-conditioned but were heated by a number of portable
1. The authors are most grateful to Mr Lucian0 Morgantini for all the information which he so kindly provided and without which it would not have been possible to write this article. Thanks are also due to Susan Inman for typing the text and to Piotr Stepien for his drawings. 2 . The exchange rate at that time was 900 lire to the dollar.
Gaë1 de Guichen' Chemical engineer, directo: of the studies relating to the conservation of the Grotte de Lascaux in 1968/69. Since then, member of the staff of ICCROM; appointed assistant to the Director for Special Programmes in 1983. Is particularly interested in preventive conservation, covering theft, fire, show-cases, reserves, destruction of insects, atmosphere and lighting, and has conducted courses on these subjectsat ICCROM and in twentyfive countries.
Vinicio Gai Born in Pistoia, Italy, in 1930. Studied liberal arts and music at the Luigi Cherubini Conservatory of Music in Florence, at whose museum he now holds the position of librarian and curator. A noted teacher of music history and scholar of the methodology of the conservation of ancient musical instruments. Has contributed to several periodicals and, more recently, to the Dizionario e~zciclopedico universafe derra musica J dei musicisti [Universal Encyclopedic Dictionary of Music and Musicians] (UTET).Author of several publications, including: Einige AspeIte der graphirchen undphotographischen Darstehzg von Ilfusìkinstrumenten in Museumshtafogen [Some Aspects of the Graphic and Photographic Representation of Musical Instruments in Museum Catalogues]. Nuremberg, 1969; and Decadmetito precoce degfì strumenti musicafie foropresePvszione[Premature Deterioration of Musical Instruments and their Conservation], Cremona, 1976.
41 The vio¿a medicea constructed by Stradivarius for Fernando de’ Medici.
Gat2 de Guichen and Knicio Gai
frame, yellow-gold coloured, enamel- the substance was sprayed with 250 g coated steel panel between the show-case of water vapour. The silica gel was then and the double bottom, holding the placed in an environmental room about silica gel,3 1.6 x 0.8 x 0.12 m; double 27 m3 in volume ( 3 x 3 x 3 m) which had bottom, masonite perforated with 84 been set at an RH of 53 per cent. It took holes 0.5 cm in diameter; cost of show- 96 hours for the silica gel to adsorb the case 1,028 million lire, two-thirds of water vapour in the surrounding air and which for the steel frame and one-third for its relative humidity to rise to 53 per for the double-plated glass. A special ef- cent. The silica gel, which now weighed fort was made to ensure that the show- around 600 g, was then placed in sealed case was airtight. The glass panels were containers, which were taken to the storeattached to the steel frame with screws rooms where the instruments were stored at 5 3 per cent. There the containers were (Fig. 45). The study directed by Professors Gai opened. At that point the instruments, and Rossi lasted four months, three of the air and the silica gel were all at the which were spent in the exhibition rooms same RH level. themselves.4 Environmental variations were recorded using three MT 1520 Transporting the instruments monthly thermohygrographers manufactured by SIAP of Bologna. One of the Eight days later and ten days before the instruments was placed outside the room, inauguration of the exhibition, 800 kg of one on top of the show-case and the third silica gel were taken from the storeinside the show-case. The 34 kg of silica rooms, transported in sealed containers gel were packed at 53 per cent RH in an to the Pitti Palace and placed inside the double bottom of each show-case, thereenvironmental room at SIEME. The silica gel was placed in the double by bringing the RH inside the show-cases bottom of the show-case. During the four to the 53 per cent mark that had prevailed months of the study, despite the ather- in the store-rooms. The show-cases were mal glass, the daily variations of now ready for the instruments. temperature of 4 “C recorded in the The transportation and installation of room were transmitted almost wholly to the instruments began seven days before the interior of the show-case in the space the inauguration of the exhibition. They of two or three hours. On the other hand, had to be transported from one end of the the relative humidity inside the show- city of Florence to the other across the two case remained remarkably stable, varying kilometres separating the Luigi Cheruat first at a rate of 6 per cent per week, bini Conservatory from the Pitti Palace. then at no more than 2 per cent when a Special wooden cases were constructed by silicon joint was installed to improve the the Scuola di Liuteria at Cremona.5These tight seal of the show-case. Outside the cases had also been previously placed in show-case, variations of as much as 30 per an environmental room €or three days to cent were recorded. set their RH at 53 per cent. The instruWith these unexpectedly good results, ments were placed in their respective it was decided to use the silica gel to cases with the 800 kg of silica gel which stabilize the relative humidity surround- remained in the store-rooms. The cases ing the instruments on display. Thirty- were then taken to the Pitti Palace, the seven additional show-cases were ordered instruments were rapidly placed in their at a total cost of 39 million lire. show-cases and the silica gel which had been used for transporting them was then added to the quantity already present in Setting the rezative humidity of the double bottom of the show-cases. the siZica geZ When the instruments were being transThe total volume of the thirty-eight ported, the mean relative humidity in the show-cases was about 60 m3. According- room was 57 per cent. ly, 1,230 kg of silica gel, which had to be set at 53 per cent RH were purchased at 3. The silica gel chosen as desiccant was manufactured by Grace Italiana S.p.A.: norm, a cost of 4.3 million lire. NATO MIL 3464; quantity, 34 kg in packets of Silica gel is sold dry at the factory, 480 g, or 20 kg per m3 of show-case; cost, i.e. at zero per cent RH. Its humidity 130,000 lire. See Garry Thomson, ‘Stabilization RH in Exhibition Cases: Hygrometric Halftherefore had to be brought up to 53 per of time‘, StzldieJ in Conservation, Vol. 22, No. 7, cent which, for the type of gel used, re- pp. 85-102. 4. The study was carried out by P. Desideri, E. quired the addition of around 300 g of Ferroni, V. Gai, G. de Guichen and L. Morgantini. water vapour per kg of dry silica gel. To 5. See A. Bergonzi, ‘I1trasporto degli strumenti accelerate the process, every kilogram of musicale’, Cremona, No. 1, 1980, p. 41.
Controlling the atmosphere for 197 musical instruments
Measuring atmospheric vkatiolzs during the exhì&itioiz A hygrometer and a thermometer were placed inside each of the thirty-eight show-cases. An SIAP MT 1520 monthly thermohygrographer was placed on top of a representative show-case and a similar instrument was placed inside (Fig. 4 2 ) . This particular show-case contained only brass instruments - such as trumpets and horns - which did not require the maintenance of a perfectly stable environment. It was thus possible to open it up once a month in order to reset the thermohygrographer. This show-case, to be sure, was situated near some windows in a passage where the atmospheric conditions were the least stable. The results obtained over the twelvemonth period of the exhibition are given in Table 1. Throughout the year, no daily variations of more than 2 per cent RH were ever recorded inside the show-cases. Of all the data recorded, only those taken outside the room, inside the room and inside a show-case during the month of October are presented here by way of example (Fig. 4 3 ) . In order to control the effect of the silica gel in stabilizing the relative
humidity over a one-month period (September), the silica gel removed from the double bottom of a show-case containing brass instruments, which are not very sensitive to hygrometric variations. All that month the windows were kept closed and the variations in relative humidity outside the show-case did not exceed 15 per cent. These variations, however, were almost wholly passed on to the show-case interior. This confirmed the role of the silica gel in stabilizing relative humidity inside the show-cases. In order to improve further
Representative show-casecontaining brass instruments, with recording instruments placed on top and inside.
36 " C 2.8.80
4 "C 13.1.81
32 "C 2.8.80
8 "C 10.1.81
31 "C 2.8.80
Temperature 7 " C RH 40%
18 " C
23 " C
365 days 1980
days Oct. 1980
Temperature - 7 "C Date 10.2.81 RH 4% Date 26.2.80
Gaël de Guichen and Vinicio Gai
43 Thermohygrometric variations in October 1980: (a) outside the Pitti Palace exhibition room; (b) inside the room; and (c) inside the representative show-case.
44 Plan of the experimental show-case. the results obtained, measures were taken to bring the silica gel into closer contact with the air inside the show-cases. To this end, the 5 mm holes of the double bottom were increased to 1 5 mm in diameter. This did not bring about any appreciable improvement.
E d: r-
Checks made on the stringed instruments E
/ . . . .
45 Detail of frame.
Before they were placed in the showcases, the stringed instruments were tuned in fifths to concert pitch diapason 440 Hertz at 20 "C. At the end of the ten-month exhibition period no damage was observed. None of the strings had slackened and none of the bridges had fallen. Moreover, all the instruments were still in tune with each other. Finally, their weight had not changed and no dust was to be found on them. The weight of a stringed instrument is naturally a function of the relative humidity of the air surrounding it. For example, Table 2 shows the recorded variations in the weight of a non-varnished violin and a varnished, but not exhibited, violin on 26 September 1983 as the relative humidity in Florence fell from 82 per cent to 20 per cent. TABLE 2 Time
10.00 11.o0 17.00
Weight of varnished violin (9)
Weight of non-varnished violin (g)
See in this regard the article by V.Gai in Legno ne/ restauro e restauro nellegno, Vol. 2.
After the exhibition When the exhibition was over the instruments were supposed to be returned to the store-room at the Luigi Cherubini Conservatory, but in view of the public interest which this collection had aroused, it was decided to place it on permanent exhibition at the Pdazzo VecChio, where it has now remained for more than three years. Silica gel is still used to control relative humidity and recordings are still being made on the thermohygrographer. The data sheets indicate that in these three years RH has fluctuated between 51 and 56 per cent and has never exceeded 1 per cent from one day to another. Silica gel has never had to be changed or added, hence there has never been any further manipulation of the cases.
ConcZusions The measurements recorded over the past four years indicate that the relative humidity surrounding the collection has been exceptionally stable. This was made possible by ensuring that the average RH at the different exhibition sites corresponded to that required by the collection. Relative humidity was maintained at a stable level inside the show-cases by making sure that the show-cases were tightly sealed and by adding an adsorbent material that had been set beforehand at the required RH and provided in sufficient quantity. These three conditions having been met, this method of stabilizing relative humidity has turned out to be particularly satisfactory and not very costly. [ Tmnslutedfrom French]
Alan Calmes Born in 1939 in Atlanta, Georgia, United States. Ph.D. in history from the University of South Carolina, 1968. Associate professor of history, Roanoke College, Salem, Virginia, 1968-74. Archivist, National Archives, Washington, D.C., 1974-79. Director, Federal Archives and Records Center for New England, Boston, Massachusetts, 1979-80. Preservation officer for the National Archives and Records Administration, Washington, D.C., from 1980. Publications in Southern American history, computer applications in historical research, and strategies for the preservation of permanently valuable information.
The encasement being filled with helium.
Each day of the year, except Christmas, in the National Archives Building in Washington, D.C., visitors file past the original parchment pages of the Declaration of Independence (1776), the United States Constitution (1787), and the Bill of Rights (written 1789; iatified 1791). No one notices that exceptional care has been taken to optimize the conditions of conservation of these documents known as the 'Charters of Freedom'. That exceptional care results from the National Archives' policy to keep the Charters of Freedom on permanent display yet protect them from deterioration and catastrophe. Because these goals are potentially contradictory, extraordinary measures have been taken to preserve the Charters: to prevent deterioration, the documents are hermetically sealed in helium; to prevent destruction by a catastrophe, the documents are provided with a mechanism that will lower them into a 55-ton vault in case of an emergency. The documents are encased inside glass containers filled with helium.' At the
end of each day, a huge scissors-jack lowers the encased documents into a room-sized, 55-ton vault 22 feet below the central rotunda floor. Each morning, the jack lifts the display into place, behind three inches of bulletproof glass and another glass with a laminated interlayer of yellow cellulose acetate to absorb ultraviolet radiation. In 1940, at the request of the Librarian of Congress, who at that time had custody of the documents, the National Bureau of Standards (NBS) started work on the project to enclose the Charters of Freedom in a protective case. The Second Wprld War interrupted the work. During tht war; the government stored the do,cuments under maximum security conditions at Fort Knox, Kentucky, the udderground repository of American gold reserves. After the war, NBS, with the assistance of the Libby-Owens-Ford Glass Company, developed seven herme1. Visitors in the exhibit area sometimes have difficulty reading the documents because the ligqt level is very low (50 to 100 lux).
tically sealed thermopane cases to house the seven precious parchment pages.
The choice of helium
47 A cross-section of the encasement. The document page rests on a sheer of pure cellulose - hand-made cotton-fibre paper. A cover glass rests on top of the document. An internal bronze bracket holds .the cover glass, document and paper matting in
place. Double-glazed,tempered plate glass, front and back, is hermetically sealed to a lead strip. The art of applying a metallic coating to glass took great skill.
Bronze f r a m e Plate glass
---Bronze bracket D o c u m e n t page
stitution and one transmittal or endorsement page associated with it were also encased. These three pages lie in a box within the vault. They are removed only under very special circumstances. On Constitution Day, 17 September, however, the Archives traditionally displays the full text of the Constitution. This requires the removal of the two middle pages of the Constitution, which are placed in special display cabinets at the centre of the Shrine rotunda in the National Archives Building.
In preference to air, which facilitates oxydization, NBS selected helium for the atmosphere inside the cases because it is inert and easy to obtain in a very pure oxygen-free state. The high thermal conductivity of helium provides a convenient method for detecting a leak. If air were to leak into a case, the electrical conductivit y of a tiny coil within the case would change and thereby indicate the presence MinimaZ risks and a spuce-age of oxygen. Shortly after installation in monitoring system 1952, the leak indicator of one of the cases registered a significant change in In spire of all precautions, some minimal conductivity. NBS resealed that case. risks remain. Although air will not leak Since then the leak detectors, which are into the encasement, helium may checked every three months, have not in- gradually penetrate the glass and leave the encasement, creating a vacuum. The dicated any leaks. (Figs. 46, 47.) Because too little moisture contributes leak detector can register the slightest into the deterioration of parchment, NBS filtration of air, but it cannot detect the mixed water vapour with the helium to loss of helium. The process of helium adproduce 25-30 per cent relative humidity sorption by glass is extremely slow and at normal room temperature. Parchment the resultant inward bowing of the glass is a stretched animal skin that tends to be may take a hundred years before it could dimensionally unstable when subjected press in on the document sufficiently to to fluctuations in relative humidity harm it. If that occufs, the encasements brought about by temperature changes. will have to be opened and refilled with A relative humidity of 25-30 per cent at humidified helium and resealed. In recent efforts to replicate the encase21 "C allows for some minor fluctuations in humidity as a result of temperature ment design for the Constitution of the changes. This prevents the moisture Commonwealth of Puerto Rico we exwithin the parchment from becoming so perienced great difficulty in re-establow as to dehydrate the protein mole- lishing the art of applying metal to glass cules - a condition that could lead for creating a hermetic seal. The considerable art and skill required for the to cracking. hermetic seal is no longer available in the United States. After about eighteen SpeciaZ design for conservation and months of experimentation, NBS security modified techniques used in the elecThe safe and lift mechanism as well as a tronics industry to develop a process of special vault designed to withstand fire, sealing glass to metal. The process conshock, temperature, water, and nuclear sists of coating the edge of the glass with explosions (at the magnitude known at silver which is fired on during the the time) were built in the early 1950s tempering process. The technique is con(Fig. 48). In 1952 an army armoured siderably dependent on the skill of the vehicle transported the Charters from the operator. Since there is a very limited deLibrary of Congress to the National Ar- mand for the application of this skill, it will probably have to be redeveloped the chives. Architects for the National Archives next time it is needed (Fig. 47). The daily movement of the cases by the Building took the basic design of the scissors-jack, as well as the annual manual display cases used for the Charters at the handling of the cases, prompted Archives Library and produced a shrine that consists of the' Declaration of Independence, officials to inspect the condition of the displayed vertically, and the first and last documents to determine if the current pages of the Constitution and the single- display practices might be causing page Bill of Rights - placed horizontal- damage to the documents. The cover ly and slightly tilted forward below and in glass directly over each document touches front of the Declaration of Indepen- the high spots of the slightly wrinkled dence. The two middle pages of the Con- sheet ofparchment. Some rubbing might
Charters o f Freedom o f the United States
cause ink-flaking. In 1982, a group of scientists and conservators from NBS (L. Smith), the New York University Institute of Fine Arts (N. Baer), Columbia University’s School of Library Services (P. Banks), and the Library of Congress (P. Waters) inspected the Charters. The group of examiners did not recommend a change in the present method of encasement, but did recommend improved documentation of the condition of the documents, and improvements in the mechanical system by which the documents are stored and displayed. The group found no evidence of deterioration beyond that which existed at the time of encasement. Observations derived by the comparison of past and present photographs, and examinationsof the actual documents, did not reveal sufficient data about slight changes such as inkflaking to provide the Archives with a comprehensive evaluation. Consequently, The Archivist of the United States
sought the assistance of image-analysis 100,000 picture elements (pixels) per experts in the United States space pro- square centimetre. Each pixel will record gramme - the National Aeronautics virtually all possible tonal variations and Space Administration (NASA). One digitally. Because the documents are perof NASA’s contractors, Jet Propulsion manently sealed under glass, scientists at Laboratory UPL) of the California In- JPL had to.design an imaging system that stitute of Technology, developed a con- would compensate for reflections coming ceptual model for an imaging system to off four surfaces. The target date for full analyse the Charters and to establish operation of the system is 1987, the precise pictures of the documents in bicentennial of the United States Conmachine-readable code. In future years stitution. Thus a space-age monitoring the same method of analysis may be used technique will keep watch over the to record pictures of the documents and, United States’ Charters of Freedom. with the assistance of a computer, the latter pictures will be compared with the former pictures. The system will be capable of detecting the subtlest changes in each document. JPL is now in the design stage of the document-imaging system that will use an electronic charge-couple device (CCD) 48 A model cross-sectionof the display case. camera similar to the earth-orbiting Documents are raised and lowered by a camera used by the Space Telescope. The scissors-jack. The vault is shown below the camera specifications call for a matrix of exhibition area floor.
The Charters Shrine, Washington, D.C. The Declaration of Independence in a vertical case above the Constitution and Bill of Rights in the central rotunda of the National Archives Building.
NATIONAL MUSEUM OF AMERICAN HISTORY,Washington, D.C. George Washington’s Commission on display.
Tim Padfield Supervisor of Conservation Science in the Conservation Analytical Laboratory, Smithsonian Institution, Washington, D.C. His research interest is in the effect of the environment on the deterioration of museum objects and historic buildings.
The display case illustrated in Figure 50 depends on two other factors - there was made for a vellum document, George must be hardly any variation in temWashington’s Commission as Com- perature within the enclosure and there mander in Chief of the Continental must be no leakage of air into the encloArmy, so that it could be shown in a sure. A sufficiently uniform temperature temporary exhibition at the National was attained by insulating the base and Museum of American History in sides of the case and by enclosing it in a Washington, D.C. The document is kept larger case so that the glass cover of the cooler than the exhibition room so that it airtight inner container was shielded remains in the condition it enjoyed in its from draughts. permanent home at the Library of Airtightness was obtained by using orCongress. thodox vacuum technology. The glass This cool, stable climate was achieved pressed against an ‘O’ ring which lay in a by enclosing the document in a closely groove in the metal sides of the box. The fitting airtight case which had a ther- glass was held in place by spring-steel moelectric cooler. The bottom and sides clips. were made of aluminium, the top was Only about 25 watts of cooling power in hardened glass. Figure 5 1shows the con- was needed to hold the case at 16 struction.1 an ambient temperature of about 2 1 “C. The relative humidity in such a case Two thermoelectric coolers were pressed need not be actively controlled. The ab- up against the aluminium base of the sorbent vellum and its card mat stabilize case. Thermoelectric coolers are solidtheir own moisture content in the sim- state devices with no moving parts. A plest possible way - there is nowhere cooling effect is produced by passing an for the water to go and there is no source electric current through the junction beof water that they can absorb. The reason tween two semiconductors. This is called for this is that the enclosure is small so the the Peltier effect. Heat is generated elsevolume of air within it holds a negligible where in the circuit and this must be amount of moisture in comparison with the vellum document and its mat. The 1. Further technical details about this care are walls of the container are of materials given in the preprints of the seventh triennial meeting of the ICOM Committee for which are impermeable to water. Con- Conservation held in Copenhagen, September, stancy of moisture content in the vellum 1984, pp. 17.38-42. O
dissipated, in our case by a stream of air from a fan. These devices are not very efficient but for small cooling loads they compare favourably with mechanical cooling units and are very reliable. Even the fan can in some applications be replaced by convective cooling. The technology used for this display case was entirely orthodox and, in principle, can be used to cool museum objects of other shapes and sizes. Thermoelectric devices, unlike other refrigeration systems, do not mind being turned upside down so they can also be used to keep objects cool during transport. There is a risk of condensation whenever a container is cooled and so it is very important to ensure uniformity of temperature within the enclosure. Stirring the air with a fan will do this, but it is a pity to complicate the system and it is risky to introduce electro-mechanical devices so close to the object; it is better to use convective stirring. Our show-case displayed a flat document, so the temperature gradient through the short vertical
distance was negligible. If we were asked to do a similar job for a tall object we would move the cooler to the top of the enclosure to ensure convective circulation of air. Leak detection is important. Any steady drift in relative humidity (RH) within the case indicates a leak. A cobaltsalt RH-indicating strip will therefore also serve as a leak detector. The salt is capable of changing colour as the RH changes, a property which enables the RH to be indicated. This cooling system with its need for an airtight insulated container also ensures protection for the document against air pollution, handling, fire and flood. On the other hand there is a danger of damage from pollutants released by materials within the enclosure which are very effectively trapped. It is important that only inert materials are used or displayed within an airtight case. The case illustrated contained only aluminium, glass acrylic sheet and archival paper besides the inked vellum of the document.
Cut-away diagram of the display case. The document (F) is enclosed by mat (E) and backboard (G). All this is sandwiched between Plexiglas sheets (D) and (H) and bound together with adhesive tape round the edges. This sealed assembly lies in the aluminium tray (K) and is covered by armoured glass (C). A viton ‘O’ ring lies in a groove round the edge of the tray. The glass is pressed down onto the ‘O’ ring by spring-steelclips. The tray is insulated by cork (L). All of this is supported within the show-case by four wooden blocks (T) so that it can be lifted out easily once the Plexiglas case top (A) has been removed. A frame (B) conceals the cork insulation and steel clips. The thermoelectriccoolers (M) and the heat dissipating fins (N) are pressed up against the aluminium tray by a spring (O). The duct (P) directs cooling air from the fan (Q) over the fins and eventually out through the holes (U) in the base of the case. Air comes into the case through holes (V) and is drawn up past the hinged plate (R), which operates switch (S) when it is pressed up by the flow of air.
Cuse design utzd cfimutecontrok u typozogìcuzu~u~sis May Cassar Born in Malta in 1955. B.A. (Hons.) in history, University of Malta, 1976. B.Sc in archaeological conservation, London Institute of Archaeology, 1982. Unesco research fellow at ICCROM, Rome, 1982183. Now assistant keeper (conservation), Sainsbury Centre for Visual Arts, University of East Anglia, Norwich, United Kingdom. Has published several articles in professional and scientific journals.
I I Type 3 n
Display cases have two obvious main functions: security and protection against dust. One function which is less evident but equally important, however, is the control of the stability of relative humidity. The climate within show-cases can be modified in two main ways. The first depends on a source of electric current and includes air-conditioners, humidifiers and dehumidifiers. These are all termed ‘active’ systems. The second method depends on the capacity of buffering materials such as wood, paper, textiles and silica gel to slow down the change in relative humidity. The use of humidity buffers is a ‘passive’method of climate modification. It is clear that the less exchange of air occurs between the interior and exterior of a display case, the less outside climatic conditions will affect those within the case. At present many articles describing the characteristics of display cases use terms such as ‘ventilated’, ‘sealed’ and ‘airtight’ without explaining their meaning. To establish a common ground for future discussion, this paper proposes typologies for display-case designs and various active and passive systems of climate control. The typologies, when combined, can be used to classify different methods used to modify the climate within display cases. This analysis and its diagrammatic representation refer to the control of relative humidity (RH) only, even though the control of temperature fluctuations and of both gaseous as well as particulate forms of pollution and dust are also of vital importance to the control of relative humidity. Furthermore, this scheme concentrates on a discussion of construction methods which reduce to a minimum leakage of air from the case. The typology of case designs therefore emphasizes ‘impermeable’ construction materials to promote RH control, of particular importance for artefacts made of organic materials. For certain metallic artefacts, however, this does not apply, and an adequate ventilation rate, rather than a minimal exchange of air between the inside and the outside of the case.
may be more desirable to dissipate harmful vapours which will cause metallic artefacts to deteriorate. Although these typologies of case construction and climate-control systems focus on the importance of stabilizing RH variations, a clear distinction should be made between the priorities for the display of organic materials and those for metals.
Basic display case construction designs in current use The following four basic types of display cases in current use in museums have been extrapolated from publications of experiments:
Type 1 Description: case in which there is free air exchange between the inside of the case and ambient gallery conditions. Example: commercially available standard stock in which no attempt has been made to lessen air exchange. Matenals: the frame is made of either metal or wood. In older cases, wood is the more likely material, painted or unpainted. The panes are more commonly made of glass, and would be in either doors on hinges with an ordinary lock for security, or in sliding-door type with a gap between the panes. Most museum display cases fall within this category. Advantage: protects against theft and vandalism. Disadvantages: does not modify adverse ambient environmental conditions. The climate inside the case will reflect, with a minimum time-lag, depending on the buffering capacity of the materials of the case itself, the climate surrounding it. It allows the free passage not only of air, but also of dust, dirt and pollutants. Type 2 Description: case in which a reduction of the exchange of air between the interior and exterior climate has been achieved.
Case design and climate control: a typological analysis
Example: commercially available or custom-built stock in which a conscious effort has been made to have a wellconstructed case that better isolates the interior environment. Matenah: the frame is made of painted or varnished wood, or metal. The panes are made either of glass or perspex, bearing in mind the diffusion capacity 'of this material. The number of joins are kept to a minimum to avoid air leakage, and where they are necessary, between the panes and the frame, sealants are used to minimize air exchange. Advantages: may be used to create a microclimate for the object, that is, a more stable climate than prevails outside the case. It protects against the entry of dust and pollution in particulate form. It can be undertaken without incurring too much expense and without it becoming labour-intensive. Disadvantages: through the reduction of air-exchange between the inside of the case and its ambience, there may be a build-up of acid vapours as breakdown products of degrading materials within the case. Unless these vapours are dispersed, they will cause the object to deteriorate. Type 3 Descn'ption: case in which an attempt has been made to reduce air leakage to a minimum. Example: owing to considerable cost in time and money, standard airtight museum cases do not exist. Since there will always be some diffusion through porous construction materials or through joins, this represents the type of case in which the air-exchange rate has been consciously reduced to a minimum. Cases described as 'hermetically sealed' in the literature, fall into this category. Matenals: every material is made of impermeable fabric such as metal for the frame and glass for the panes. The joins and closures are either fused, soldered or welded together permanently using such materials as lead solder. The case may contain either air or an inert gas. The possible inclusion of a leak detector would be evidence that the case is not airtight. Advantages: protects against fluctuating RH by isolating the object within a
microclimate within the case. It provides also the surest protection against the effects of dust, dirt, pollution and microorganisms.
Disadvantages: high cost in terms of time and money. It is therefore feasible only for individual and unique works of art. This type is more applicable to RH control for organic objects rather than for the display of vulnerable metals. The entry of small amounts of air may cause deterioration of materials, the acid breakdown products of which, finding no escape, will accumulatewithin the case and cause the degradation of the object. It should be stated that although attempts had been made in the past to use such cases under vacuum, it is difficult to maintain this, even over ashort period of time, and it has never actually been achieved with a museum case. Type 4 Description: case into which air is allowed to enter through one source, usually a hole into which a filter has been placed. Example: owing to the conscious decision to allow air-exchange between the interior and exterior of the case through one source, leakage of air through joins or porous construction materials is minimized. However, every effort should be made to construct a case similar to Type 3. Matenah: similar materials to the case described in Type 3 are used, including the fact that a hole, the diameter of which has been quoted differently by different authors, is constructed. A filter placed inside the hole to eliminate dust and sulphur dioxide allows only pure air to enter the case. Advantages: does not allow the entry into the case of corrosive vapours which could harm the object. Disadvantages: deliberate leakage must be taken into account when a microclimate is being set up, and allowance made for the change it may cause. Consequently it may complicate calculations of quantities of buffering materials. It may prevent entry of corrosive vapours, but it does nothing to actively dispel those vapours that have accumulated in the case from the materials used. It may be labour-intensive and expensive to construct.
In concluding this typology of basic display case construction designs, it can be stated that, for Type 1, the climate inside and outside the case would, at any one time, be similar. As regards Types 2 , 3 and 4 , however, the establishment of microclimates in these cases seems !o be more feasible than in Type 1. Taking into consideration such variables as ambient conditions, case materials, quantity of buffering agent and mass of object, the length of the life of the microclimate may be extended depending on the requirements of the display.
ControZZed climate systems for dispday cases in museums The macroclimatic and microclimatic systems described below have also been extracted from the literature and exemplify the more sought-after trends for the control of the environment within a display case:
I. MucrocZimute: mechunicd systems System I. A Description: air-conditioning plant to control the general gallery conditions. Advantages: this system should not only control RH and temperature, but should also filter gaseous pollutants and dirt. (Unfortunately, this is not always the case.) It is however the complete answer to environmental control. Disadvantages: the more obvious disadvantages of this system are cost, maintenance and that it is a measure which cannot be undertaken quickly.1 System I.B Descn$tion: air-conditioning plant which first forces conditioned air through a case before circulating it into the gallery. System 1.A
1. This system will not be covered extensively in this article, which concentrates primarily on microclimate control.
Advantages: ensures that conditioned air of cases to control the microclimate goes through the case and then outwards within the cases without affecting gallery under pressure. Dust, dirt and pollutants conditions. are unable to affect the object by entering the case. This system is better adapted for Advantages: can be installed quickly in case of emergency. It allows for flexible use with several wall cases. use with either one or several cases. It Disadvantages: has similar cost, main-. does not have high installation or maintenance and lack of reliability in terms of tenance costs. breakdown, as System I.A. It does not allow flexibility in display layout, which Disadvantages: subject to breakdown as a mechanical system. It may not be senhowever, System 1.A does have. sitive enough in the RH range required.
II. Microclimate: external control System II. C Description: dehumidifier or humidifier system attached to one or a small number System 1I.C
ttt System 1I.E
Microclimate: inteemal control System II. D Description: dynamic buffering system, using hygroscopic materials such as silica gel or saturated salt solutions, to ballast fluctuations in humidity. This system includes a fan to circulate the conditioned air which could either have had the moisture-content increased or reduced. Advantages: functions as an independent system within the case. This is a simple system which requires little maintenance. Inclusion of a fan prevents the formation of pockets of stagnant air within the case. Disadvantages: breakdown of the fan may cause the malfunction of the system especially if the buffering agent has not been well distributed within the case, by causing uneven humidity levels to form. System II. E Description: a simplified form of System 1I.D. Advantages: static system of control of humidity excludes the fan which is subject to malfunction. This is a simple and effective system of microclimate control which works independently of gallery conditions but takes them into consideration. It is inexpensive and can run itself with the minimum of attention. Disadvantages: unless all the variables are considered carefully before installing such a static system of microclimate control, the special climate established will soon drift towards gallery conditions.
Disczcssion Once the need for some form of climate control has been identified, a decision has to be made primarily between the use of either a macro- or a microclimatically controlled system. The choice depends
on a number of factors such as finance, available time, urgency of the.problem, size of the collection requiring attention, and the co-operation, knowledge and interest of the personnel recommending, approving and finally, undertaking the task. If microclimate control of individual caSes or groups of cases is decided upon, the choice of internal or external, static or dynamic control of climate should next be considered. Consequently, it is not only misleading but also dangerous to generalize by suggesting one system in preference to another, for given sets of circumstances. The climate systems listed above may be used either individually or in varied combination with any one of the four types of museum display caseswhich have also been described. The tabulation of the two typologies links these climatecontrol systems and display-case types in an effort to standardize terminology. The climate-control systems are listed in Table 1 along the vertical axis, while the different types of museum display cases are arranged along the horizontal axis. By reading along both axes, line diagrams of different climate/case combinations may be located. Each combination is illustrated by examples which have been reported after experiment, trial and use. These examples are listed opposite. Since not all methods of climate control can be effectively or even sensibly used wih every type of case construction design, only the more practical combinations have been tabulated, after a search through the literature. This does not mean that such an example has not been attempted. In fact any suggestions or information to modify or complete Table 1 would be appreciated.
ExampZes from pzcbZications in suflport of TabGe 1 1:A Vast majority of museums with airconditioned galleries have this type of case construction. 1:B Metropolitan Museum of Art Egyptian Galleries (Phase I). See article by Bill Barrette, p. 81. 1:c Combination of climate and case unlikely to exist. 1:D Combination of climate and case unlikely to exist. 1:E Most museum cases in which an attempt has been made to create a microclimate without actually understanding the limitations of the system.
Case design and climate control: a tvboloaical analvsis
2:A Large number of museums with air-conditioned galleries have this type of case construction. 2:B As presented by S. Michalski, p. 85. 2:c Museum of Mankind, The Ethnographic Department of the British Museum, London: Temporary Exhibition on Mexican Art, 1971. 2:D R. H. Organ, ‘The Safe Storage of Unstable Glass’, The Museum Jozrzal, Vol. 56, April 1956March 1957. 2:E B. L. Ramer, ‘Stabilising RH Variations within Display Cases: The Role of Silica Gel and Case Design’, in ICOM Committee for Conservation, 6th Triennial Meeting, Ottawa, 1981. See also article in this issue, p. 91. 3:A Metropolitan Museum of Art Egyptian Galleries (Phase III). See article in this issue, p. 81. 3:B Combination of climate and case unlikely to exist. 3:c British Museum cases for Unstable Metal Objects: G. Thomson, The Museum Environment, London, Buttenvorths, 1978. 3:D Literature or personal discussion have failed to reveal the use of this combination of climate and case. 3:E S. Miura, ‘Control of Climate in a Showcase by means of Zeolite: Report on the Exhibition of “La Joconde”,’ in ICCROM Conference on Museum Conservation Climate, Rome, 1978. 4:A Literature or personal discussion have failed to reveal the use of this combination of climate and case. 4:B Combination of climate and case unlikely to exist. 4:c Combination of climate and case unlikely to exist. 4:D Literature or personal discussion have failed to reveal the use of this combination of climate and case. 4:E Literature or personal discussion have failed to reveal the use of this combination of climate and case. From an examination of Table 1 and the examples which support it, it can be seen that microclimate control seems to have been attempted, not surprisingly, in museum cases in which a reduction of the exchange of air between the interior and exterior climate has been achieved (Type 2). The air-conditioning of museum galleries, however, is still a common feature in museum climate control (System I.A), and a variety of cases have
been used in these conditions (l:A, 2:A, 3:A). The creation of a microclimate within a case in which there is free exchange of air between the inside of the case and ambient gallery conditions (Type 1) is a waste of time, money and effort, yet it appears very likely that precisely this has been often attempted and is still being done. Unfortunately this shows a lack of understanding of the basic principles of microclimate control in museums.
TABLE1. Standardizing the use of museum display cases and climate control systems:
I 1 :B
‘!I “‘I l
FLEXIBILITY A newflem3Ze dis-Zay system Wolfgang Selzer Born in 1926. Studied archaeology, prehistory, protohistory, the history of art, history and German language, history and civilization at the University of Mainz. Doctoral thesis on ‘Franconian Ceramics in Rkenish Hesse and Starhenburg’, 1957. Has worked at the museum known today as the Mittelrheinisches Landesmuseum of Maim since 1963. He played a leading role in the redevelopment of the museum in 1960-62 and 1975-81 and is now Head Curator, Director of the Archaeological Section; also handles the museum’s public relations. Numerous publications in his scientific field and varied activities in the field of adult education.
52 Modular system, Type 1: 80 x 80 x 250; free-standing, connected at right angles to a Type 2 module. Roman section.
All museums possess show-cases, which serve, as we all know, both for the display of objects and for their conservation and security. In the not so distant past, showcases were pieces of furniture, often regarded as objects to be displayed in their own right. But more recently they have adopted a lower profile. Consisting entirely of glass, in most instances, all that is asked of them today is that they protect the object contained within while displaying it to the best advantage. Despite the efforts made by well-known designers, the production of standardized models has resulted in a certain degree ofsterility. It is, therefore, hardlysurprising that museums have for some time been demanding, with increasing insistence, the development of more flexible display systems. During the large-scale extension and redevelopment work carried out at the Mittelrheinisches Landesmuseum in Mainz between 1975 and 1981, the museum completely replaced its stock of show-cases. Its large collection includes an archaeological section, with exhibits extending from Palaeolithic times to the Middle Ages and where the best represented period is the Roman. Its section on the history of civilizations covers the entire period from the Middle Ages to the twentieth century: it contains a collection of porcelain and a very important collection of Jzgendstil glass objects. Because of the large number and variety of the exhibits it was apparent right from the planning stage that the display system would have. to offer maximum flexibility and, bearing in mind the new style of display which it was hoped to adopt - maximum capacity. As none of the modular systems then available on the market satisfied the criteria adopted during the redevelopment of the museum, the author himself designed a new type of modular display case which is described below.
A prototype is devehped Our point of departure was the consideration that it is no longer sufficient today
merely to exhibit an object: it must be presented in a clear, objective and up-todate way in keeping with its character which at the same time situates it in a wider context. This meant the complete rejection of the traditional type of showcase in favour of ‘display units’ which allowed maximum space, a separate position for each object, complete transparency, optimal lighting, high security, flexibility and ease of assembly and dismantling. All of these requirements, which at first sight appeared practically impossible to satisfy on the basis of a single system, nevertheless led to the development of two types of display unit which could be interconnected in a variet y of ways. The museum itself produced the first design (Fig. 53) together with the following specifications: Large-capacity modules for the reequipment of the Mittelrheinisches Landesmuseum in Mainz; two formats (bases of 80 x 80 cm and 160 x 80 cm with a single height of 250 cm); interconnection (end to end or at right angles) or separate use; materials: glass and metal; enclosed base and upper casing containing the lighting system (fluorescent tubes and low-voltage spots beneath diffusers); each module to have a two-way sliding front panel; inside, arrangements for mounting one or more glass shelves of different sizes at varying heights. After a series of improvements to the original design several specialist firms were approached to undertake the technical execution of the project. The negotiations were long and many technical problems had to be resolved as they arose. Finally, the Glasbau-Hahn company of Frankfurt developed for mass production the Hahn modular system, which meets the requirements of the museum in every respect. After a few prototypes had been produced, series production for the Mainz museum began in 1978/79. The system has the following advantages over other well-known models of the same type:
There is no frame or external system of attachment. The absence of supporting or connecting members means that the cases are easy to assemble and dismantle and also eliminates the ‘forest’ of uprights produced by a row of traditional display cases, which obstructs the view. Effective protection against dust due to the perfect fit of the glass panels and the practically invisible felt-lined joints between them. The cases may be connected in several ways, with or without a dividing panel. Ease of access to the cases by means of ‘Monorail’ three-way sliding doors. Great stability of all components due to the utilization of 10-mm thick panels of transparent glass. The design of the corner connections reduces to a minimum the number of components required to form a module with a base either 80 or 160 cm long: the 80 x 80 cm panels can form three sides of a case with a base of 80 x 80 cm or the side walls of a case with a base measuring 160 x 80 cm; thus, the entire system requires only four types of panel (including the two sliding panels, 80 and 160 cm wide respectively).
of their size and the practically limitless number of combinations, the modules provide enough light even for rooms that receive no natural light, thus enabling objects, such as glassware for example, to be displayed to their best advantage. The modular system also has a number of specific features already mentioned but which deserve to be described more fully. The wider advantages of the assembZy and di”nding It makes moduZar system quick and easy, operations that can be This system has now been in use for over carried out by the museum staff without five years at the Mainz museum and it has recourse to technical aid from the not only made the museum’s ideal of a manufacturer, as is necessary with other flexible and modern display system a systems. As the module has a door that slides reality but has generally proved its worth in the day-to-daywork of the museum. It both ways and can be pushed back, if so can be used to display all types of objects, desired, the entire length of the adjacent allowing each the space that a modern ap- case (whether integral with, or merely proach requires, and in keeping with the adjacent to, the module), its iizterior instructional and educational role of to- organization raises no problems. All day’s museum. Its success is due to several points inside the case can be reached easifactors: the large capacity of the display ly, which is particularly convenient when cases makes it possible to ..achieve displays consisting of small items have to aesthetically satisfactory results; their be assembled within the actual case. Although the panels have no fixed complete transparency is not impaired by the presence of any supports; and the joints, the modules are dust-proof to a lighting system, which is practically in- remarkable degree. This is achieved by visible to the observer, is extremely effec- glued-on bristle-and-felt strips which tive and casts no shadows even when contact with the adjacent panel. The several shelves have been fitted. Because movable front panels of the display cases
Shelves of different sizesmay be mounted one above the other. The fluorescent tubes provide excellent general lighting inside the case which is supplemented by concentrated low-voltage spots focusing on the objects.
Vertical and horizontal views of the Hahn modular system, Types 1 and 2, with various possible combinations and types of assembly. U
First sketch of the new system of modular display cases produced by the author.
Type 1 : 1.60 x 250 x 80 cm
80 cm Type 2: 80 x 250 x 80 cm
Hahn module, Type 1 : base 700 x 700 rqm Hahn m.odule, Type 2: base 700 x 1400 mm
Accessories: one or more glass shelves of various sizes can be mounted a t various heights at any point of the module
Assembly a t right angles in L, T and Z shapes
Modular system, Types 1 and 2: various combinations. Roman section.
have the same form of da~tprotection (Figs. 56, 57). Experience has shown that the interior of the cases need be cleaned only once every four or five years and, even then, only the glass shelves require cleaning. The system is maintenance-free, In particular, there is no need to open or empty the case in order to change a fluorescent tube as the lighting system is accessible through an easy-to-open overhead flap. Secarity is unfortunately very important today. The thickness (10 mm) of the glass alone provides considerable protection for the object on display; this is augmented by four cylinder safety locks which secure each sliding door and are practically invisible and inaccessible to unauthorized persons as they are internally mounted. Each display case can, of course, be linked to an alarm system incorporating a movement detector or glass-breaking detector. The size of the components and the transparency of the material used facilitate the surveillanceof
the entire room at all times so that the number of staff allocated to these duties may be reduced. At the Mainz museum, one individual can maintain surveillance over a room of 600 square metres. Thus, the new module can save money for the museum which adopts it. Because of the variety of forms that can be assembled using the two types of module this is, to the best of our knowledge, the most $exilde system available at the present time: it offers flexibility in terms of assembly and, thus, in terms of the exhibition in general. All of the uses envisaged at the time of the original project are now possible from the freestanding display case to the series of interconnected cases placed end-to-end or at right-angles to each other. Museum officials and exhibition organizers will particularly appreciate the opportunity to construct vast continuous display cases by removingthe side walls of modules in juxtaposition. Experience at the Mainz museum has shown that every conceivable combination is possible. It
A new flexibh d%--Laysystem
111 SG The two-way sliding front panels of glass in the open position. They are sealed against dust by means of bristle-and-felt strips.
Example of the seal between panels of glass with no rigid joints. Bristle-and-feltstrips are glued to the edges of the panels.
should be added that each panel of glass may be replaced by a solid (wood or plastic) panel which can serve as a backdrop, a partition, a display surface or a board on which information can be presented.
Conchsion Finally, it may be said that the modular display cases with which the Mainz museum was entirely re-equipped during its re-development have provided complete satisfaction. The only difference between the first serial model and the one now commercially available is that it is slightly smaller: 70 x 70 cm, with 140 x 170 cm bases, and a single height of 213 cm. Their adaptability and flexibility are unchanged. For further ease of operation, the system has been supplemented by specially designed fork-lift trucks, by means of which assembled display cases
may be moved and connected to any other group without being dismantled. Experience has shown that the flexibility of the new system enables it to meet present-day requirements. It has been adopted by other museums in the Federal Republic of Germany (for example, at Kassel and Hanover), Japan and the United States. It is particularly pleasing that, since its adoption by the Maim museum five years ago,. its advantages have been recognized not only by many museologists, both German and foreign, but also by the visitors themselves which is much more important for a modern museum. Needless to say, it is also a pleasure for scientists and museum st& to use the system in their work and creative activity. [Translatedfrom Geman]
NATIONAL MUSEUM OF ETHNOGRAPHY, Stockholm. A basic display idea - the creation of open exhibition areas comprising a number of miniature theatres which could be viewed from the outside, ‘like walking across a square’.
This is the story of some of Sweden’smost controversial show-cases, which started well but finished badly. The moral of the story almost certainly applies to many other fields as well and should be discussed much more widely. But let’s start at the beginning. Once it had been decided to build a new museum of ethnography out on the beautiful Stockholm island of Djurgirden, the National Board of Public Building signed up a team of architects, landscape gardeners and interior designers to begin work on the 40-millionkronor project. The building itself was attractively designed. The architects Jan Gezelius and Gunnar Mattsson described it as follows: We tried to make the building both light and unpretentious as it was to be a typical park building which would fit in with the free imaginative style so typical of Djurgirden. We also wanted to set it apart as being something outside the ordinary daily round, as indeed, people would expect it to be.
A speciakly designed show-case system Planning the interior architecture began in the autumn of 1974. It was based on a
room function programme. The designers, Erik Karlström, KjellJensfelt and Gunnar Rydberg, sought to create an interior that was both functional and timeless, where the museum’s collections - some of them irreplaceable - could be stored, conserved and displayed. The collection brought home by Swedish researchers and explorers over the decades was to be displayed to the schoolchildren of today in an entirely new light. Erik Karlström describes the basic requirements and design of the show-case system specially planned for the new museum. Objects of great value must naturally be properly conserved if we and future generations are to be able to study the cultures they represent. As the museum management has chosen to display the original artefacts and not dummies or copies, priority must be given to protection. The display system is therefore not based on individual show-cases but on a tubular steel framework and a few assembly components which can be interconnected to form large or small units of any shape desired, and so, after glazing, provide the requisite protection for the artefacts. In our view, the message of an exhibition and the ob-
jects which help communicate that message are more important than the setting of the exhibition itself. The exhibition system should be so unobtrusive as to be unnoticeable. The arranger of the exhibition, who should have the skills of a set designer, himself decides how wide and how deep the show-cases should be to protect the objects on show. In addition, we know from experience that much of the material is often thrown out whenever the exhibition is taken down or in some way modified, so it was important that the components of our system could be used again after they had been dismantled. The large, two-storey exhibition space called for a system permitting the creation of individual rooms. We therefore developed a system based on a kit, the components of which afford the set designer a wide range of alternatives in adapting and protecting the various dioramas, scenes and collections of artefacts. The basic elements can also be used as exhibition screens. The components of the system are made of durable materials and can be reused after the exhibition has been taken down.
A Swedish paradox
Karl Erik Larsson, who was then director of the museum, had also envisaged the creation of open exhibition areas comprising ‘miniature theatres’ which could be viewed from outside. It was a matter of trying to provide an open environment for the visitors while at the same time enabling the research workers at the museum to work in peace and quiet in their own rooms. In the two exhibition halls on the ground floor of the museum, which were not divided into rooms or compartments, there was to be space for large temporary exhibitions, while the permanent exhibitions were to be designed so that schoolteachers and others could return to the museum over a number of years and find the basic framework unchanged.
Co-operation Interior planning, carried out in stages over a period of four years, was combined with a comprehensive study programme which included visits to a number of European museums for the purpose of
gathering first-hand experience. At an early stage co-operation was initiated with senior museum staffwho, for the entire planning period, followed and participated in the detailed design of the storage and exhibition systems. Both the designer and the museum director agree that work proceeded in the form of a dialogue between the architects and the museum staff, with drawings and models being submitted to the latter on a continuous basis.
The storm gathers All this sounds too good to be true. Indeed, when the show-case system first came into use the storm clouds immediately began to gather! Brita Kleen, the exhibition architect, and Björn Ranung, who had previously been the exhibition keeper at the museum, commenced working with the system in the spring of 1981. Onlyayearlater, in 1982, they declared: In our opinion, the show-case system works badly. It is too heavy and is far too unstable when an exhibition has
Ann Andrén Freelance photographer and exhibition designer, previously editor of Fomm Nämdjö, a journal for interior architects. Her work has been shown at collective exhibitions at the Liljevalch Art Gallery, the Stockholm Cultural Centre and the Malmö Art Gallery, and in oneman shows at schools and libraries following trips to India and Africa.
59 The basic elements of the show-case system can also be used as exhibition screens, as here in the exhibition The Chukchi - A people of Siberia.
One of the first exhibitions constructed with the present system was Sep&-Art from New Guinea. The basic model comprises chromium-platedsteel frames, wooden beams and glazed sides: 2 . 1 and 2.7 m respectively.
to be taken down. The positioning of holes and slots makes it very inflexible. In addition, the glass is only 2 . 1 metres high, which is insufficient we have been able to raise it to 2.7 metres, but this means we are unable to cover the show-case. And if you want to provide a glass roof, there is no grid or screen from which to suspend the objects. The transverse wooden beams, which are supposed to act as stays, are extremely clumsy and the external lighting sets up reflections in the glass. That was straight talking if you like! How could something which had started so well turn out so badly? In 1782 I put the question to Björn Ed, who was then acting keeper of the exhibitions. He thought it would be wrong to blame the show-case system in itself. Where the real difficulty lay was in designing for an extremely tricky exhibition hall which, with its false ceiling, light-colouredfloor and incoming daylight, has a character all of its own. Although the system as it is now may be clumsy to work with, it would still be quite possible to continue developing it and find new solutions to the problems it raises by using its components in new ways.
The trouble lay, therefore, not so much in the ambitiously designed show-case system itself as with the way the purchaser and museum management had handled the affair: they had not test- built the system and had not sought advice from those whose job it would be to put the exhibitions together!
I recently put the same questions to the designer, Brita Kleen, who over the course of the years has more than anyone else been obliged to learn how the system works, and, after much sketching and drawing, to try to come up with the best solutions possible under the circumstances. She is still critical: Although we’ve worked with the show-case system and put together a number of exhibitions, I can’t say I feel happy with the results. It’s highly unsatisfactory aesthetically always having to put up with makeshift solutions. I still maintain that the showcases are the wrong height, too heavy, hard to illuminate properly and difficult to hang things in. And in addition to the basic problems of height, covering and weight, I also question the value of spending lots of money manufacturing a new static show-case
system which is supposed to be suitable for all the different artefacts in the museum. It just does not work. I would have preferred designs of our own, glazed cases adapted to the objects we wanted to exhibit. Where things went wrong was that no work at all was done on exhibitions during the planning period. It was therefore impossible to test the system. And the much-vaunted dialogue never reached the members of the staffwho would be responsible for the exhibitions in practical and artistic terms. If ever there was bad financial planning, this was it. The paradoxical end result is that the museum’s storage area, which potentially produced the largest number of difficulties, and wich called for a special design, is the most successful of all. Here the interior architects have found excellent solutions. B L ~these will unfortunately remain hidden from the public. Visitors will have to make do with viewing the collectionsin traditionally designed show-cases in which the illumination is far from satisfactory.
S E C U R I T Y A N D STABILITY Protection against During opening hours on 3 June 1981, a thief broke open a show-case in the exhibition room of the Staatsbibliothek Preussischer Kulturbesitt (National Library of Prussian Cultural Heritage, West Berlin) (see Fig. 61). There were only a few visitors in the room at the time, and the attendants were no longer at full strength, so that he was able to operate unnoticed. With a short-bladed knife he prised up the lid of a table-top show-case and took two illustrated Japanese manuscripts. The inquiry revealed that the relatively new show-case glass had been fued not with the usual glass cement but with a silicon rubber. Now, this substance unless spread very thinly can easily be cut with a knife. The thief would probably have given up if the seal had been strong enough or if there had been an attendant or visitors near by; any deficiency in physical protection devices can to some extent be offset by increased surveillance, and vice-versa. TABLE I . Comparativeproperties of ordinary
glass and organic glass1
Unbreakable Non-flammable Drill-proof Scratch-resistant Colourless Antistatic Lightweight
Yes Yes Yes
No No No
1. Known under various trademarks (e.g. Plexiglas). 2. Some types of polycarbonate glass (Lexam or Makrolon) are completely unbreakable. 3 . ‘White’ glass exists for special uses.
This theft highlights a fundamental principle: all security measures, whether for the museum as a whole or for a single show-case, must be mutually complementary so as to provide a system without loopholes. Such a system is always a twofold one consisting of both physical protection and surveillance attendants or an alarm device. These two components
must be so connected that in the event of theft or damage the alarm is given before the physical protection gives way. This principle of two-tier protection is relatively easy to applywhen the museum possesses an alarm device, but where surveillance is exercised solely by attendants, they will be able to act in time only if the show-cases cannot be broken into rapidly, easily or silently. We need therefore to take a look at a few aspects of physical protection.
GZazing The glass of a show-casemust protect the exhibits without aesthetic impairment. What, then, is the best material ordinary silicate glass or acrylic ‘glass’? Table 1 gives the essential properties of these two materials but is less than complete for purposes of comparison in that laminated safety glass is not mentioned.’ Laminated glass is not entirely unbreakable but cannot be shattered by a single hammer blow. And double glass, 8 to 9 mm thick in all with the further inclusion of a sheet of strengthened plastic, offers fairly good security. It must be used as a matter of course if the exhibition cannot be surveyed at a glance, or is inadequately supervised because of a shortage of attendants and if it contains particularly tempting objects. As a general rule, however, ordinary glass at least 6 mm thick will do. The same thickness is required for organic glass. For protection, ordinary, laminated and organic glass are just about equivalent. Preference thus generally goes to ordinary glass, either laminated or single, especially for permanent exhibitions, because it scratches less easily and cleans better. It can also be given anti-reflection treatment and, in the laminated version, be treated to absorb ultraviolet rays. In temporaryexhibitions organic glass is more frequently used, no doubt because it enables show1. A sheet of cellulose acetate between two panes of ordinary glass (e.g. ’triplex’ glass).
Giinter S. Hilbert Born in Leipzig in 1923. Studied mechanical engineering and thermodynamics at the Berlin Technical University, graduating as an engineer in 1953. Between 1953 and 1971 he was engaged in design and project engineering, marketing and sales activities in various firms. Since 1971 he has been Director of Technical Services for the Staatliche Museum Preussischer Kulturbesitz (National Museum of Prussian Cultural Heritage). Consultant on museum security, a subject on which he has written a number of articles, he is also a member of the ICOM International Committee on Museum Security.
KULTURBESITZ, West Berlin. Table-top show-casesin the exhibition of the National Library of Prussian Cultural Heritage.
Ratchet locking device, of dubious reliability. cases of a great variety of dimensions and forms to be set up rapidly. Whatever the type of glass used, it is important to assemble the various parts of the showcase properly and firmly.
Locking systems I
I I I
I I I
Front pane of a wall show-case in the Museum of Antiquities, National Museum of Prussian Cultural Heritage: (1) glass pane; ( 2 ) bolt; (3) groove; ( 4 ) cover of lighting element; ( 5 ) safety lock; ( 6 ) fluorescent lamp. 63
The more reliable push-button security lock: (1) sliding panes; (2) pane 'shoes'; (3) lock; (t) travel.
F U R T H E RR E A D I N G TIUOTSON,R. G.; MENIES, D.D. (eds.). Museum Security. Paris, ICOM, 1977. STROIK,John (ed.). Bzddng Security. Philadelphia, ASTM, 1981. HILBERT,Giinter S. Samhhngsgut in Sicherheit. Part I: Berl'iner Schn$en zur Museumskunde. Berlin, Gebr. Mann, 1981. BLAIR, C. D.Protecting your Exhibits. Nashville, Tenn., American Association for State and Local History. 1977. (Technical leaflet, 99.)
Even the best glass is no use if the showcase can be opened easily, hence the importance of the locking system. Many free-standing vertical display cases are fastened by means of a ratchet lock (see Fig. 62). This device is more symbolic than anything else since it can be opened without difficulty, and no key is needed. All that can be said for it is that it is quick and easy to operate. But a museum is not a jeweller's shop, and a certain loss of time when opening show-cases has to be accepted if security is thereby improved. Figure 63 shows a much more satisfactory device. Although it disregards the principle that the fastener should be concealed, it does at least enable a safety lock to be used, one that cannot be opened with a skeleton key and for which additional keys can be supplied only by the manufacturer. Show-casGa w l m undivided panes of glass look better and offer more security. To open the case a pane is raised and slid to one side; and the safety lock can be placed in an inconspicuousposition. The system represented in Figure 64 is excellent. To open the case the movable pane has to be lifted out of the lower groove by means of a suction grip (Fig. 66). This method constitutes in itself a
Protection against tbefz and [email protected]
Exhibition of the Egyptian Museum at the National Museum of Prussian Cultural Heritage. Showcase opening system.
guarantee, for it would be difficult to It is essential, then, to fasten all the walk into an exhibition with such an im- component parts of a show-casetogether. plement and use it without attracting at- If screws are chosen, care must be taken to tention. Security is further increased grind the heads smooth once the screws when the glass is too large and heavy to be have been inserted, since, as we know, manipulated by one person so that it quite a few people go around nowadays takes two to open the case. Furthermore, with a screwdriver on them. as Figure 64 shows, the pane can only be raised once the safety lock and lamp cover Adarm systems have been opened. The show-casesshown in Figure 65 are secured by means of a A security system also requires attendants similar system: to open them, several or, failing that, automatic surveillance, panes have to be raised and then slid. which means an alarm device. A profesDesigners and manufacturers can thus sional alarm system comprises warning give full rein to their ingenuity - devices (sensors and triggering mechaespecially for all-glass cloche-type show- nisms), a central unit with an indepencases, in which it is not easy to reconcile dent power supply, and a communicagood looks with security. As Figure 67 tion system enabling the speediest counshows, holes have to be drilled through teraction to be taken. Those who can the glass. This in itself presents no step in most promptly are, during openproblem, but with ordinary glass the ing hours, the attendants; at other times, edges are liable not to withstand fre- as a rule, the police. Unfortunately, quent handling; it is therefore wise to there is not always a direct link between use a metal-framed cover (Fig. 68). the museum and a police station, in which case the museum should have its own surveillance station. Rather than Assembly connect the alarm to the guardian’s Several years ago, a valuable statuette was premises, it is better from the point of stolen in Hamburg from its locked table view of reliability and prompt action that show-case. Since, inadvertently, the bot- the alert go straight to a specialized firm, tom had not been screwed down on to the if possible one equipped with radio cars. corner iron, the thief had only to lift up Failing that, there is the audible alarm, one side to slip the statuette out of the with a siren alerting the neighbourhood. case. In 1977 a deft ‘visitor’ managed to Whatever the system chosen, it must unscrew a show-case in an understaffed function rapidly and give the alert before museum. He calmly removed one of the the thief has had time to operate. This ofglass panes and filled his pockets before fers the only hope of preventing the disappearing. In both instances there was theft. While the various types of central unit nobody near by.
Gunter S. Hilbert
Cloche-type show-casefitted with a security lock.
Cloche-type show-casewith metal frame secured by means of screws with nonstandard heads.
Example of alarm glass (System: VEGLAAachen). A metal wire under closed-circuit current is fued, in one corner only, to the inner surface of the pane of toughened laminated glass.
and communication system on the market are more or less of equal worth, the same cannot be said for detection devices. We shall briefly review these in the chronologicalsequence of an attempted theft.
Detectors The thief with his eye on an exhibit in a show-casefirst checks to find out whether it is actually locked. Therefore opening detectors (i.e. mechanical or magnetic contacts) are required to give a positive indication that the show-case is properly locked. Such detectors operate automatically whenever the show-case is opened or closed. Glass-breakage detectors are microphones sensitive to specific frequencies, attached to the various panes of the show-case so as to record acoustic vibrations directly. Unfortunately, they are often so sensitive that they set off the alarm at the slightest sound. These false alerts are very much less frequent with ‘alarm glass’, a double sandwich pane with an incorporated electrical circuit carrying a low current. Whenever the glass is broken, the current is cut off and the alarm automatically given; hence the
system is highly reliable. However, although the circuit wire is only O. 1 mm in diameter and the wires are 5 cm apart this device is often regarded as an inconvenience and therefore seldom used. Another type of sandwich glass (Fig. 69) does not present this drawback since the electrical device is placed in a corner and connected to a tempered glass pane (of the Securit type). On impact such glass shatters, as we know, into very small pieces. We can thus be sure that the pilot current will be cut off if anyone damages the glass. Motion detectors, admittedly less reliable, provide another means of protecting a show-case without installing glass-breakage detectors. Motion detectors, generally, activated by infra-red radiation, signal any movement inside the case, such as that of a thief‘s hand. Unfortunately, they do not always go unnoticed. In free-standing illuminated display cases they are placed in the upper lighting device, which is fitted with a ‘window’ enabling them to ‘survey’ the space inside. Removal detectors offer the advantage of being discreet. They exist in two types: one sort sets off a signal when a hand approaches the object and the other when
the object is removed. The former relies on a capacitive principle and the latter on a mechanical principle, such as a switch or simply a pilot current. Installation is rapid and inexpensive for both types, but they do not offer absolute protection since the al&m signal is set off only when the thief s hand is already inside the case.
Conchsion If precious objects are to be protected against theft and vandalism when on display in show-cases, the latter must be equipped with a reliable locking system and its various components firmly fured together. Supervision is also needed -in the form of attendants or, an alarm system - for a thief will utimately, if he has the time, get the better of any physical protection device, however sophisticated. In a good security system, the alarm should be given as soon as the thief tries to get past the physical protection. To ensure security outside opening hours, an alarm system should be installed that surveys not only each of thewindows but also the entire museum or, at any rate, the exhibition rooms. [ Translatedfrom German]
Hiromitsu Washizuka Senior Research OfFicer for Cultural Objects, Arts and Crafts Section, ConservationDivision, Department of Culture.
Documentary photographs of damage caused by the recent earthquake at Tokachi, Japan: (a) the panes of a display-cabinetare shattered and its contents overturned; (b) books falling from an overhanging shelf broke these restored potsherds in a conservation laboratory. a
for example by sandbags concealed behind panels. This is the ideal solution. In recent times, however, there has been a general trend towards show-cases on legs, which are more pleasing to the eye but which rule out this solution. In exhibition rooms, cases are often moved about and legs of this type tend to become distorted, with the result that the cases become unstable. There is a danger Improving stability: the basic that visitors bumping into them might principk accidentally make them wobble. To preWe shall discuss in detail below the vent them from wobbling or sliding, it is measures to be taken, but the basic prin- best to fix them to the floor and the comciple is to lower the centre of gravity so as monest way of doing this is to fuc metal to improve stability. Accordingly, show- angle brackets at the four corners. cases should not be too high and, above Cabinets placed against a wall can be faall, they should have a large enough base ed at the top by the same kind of bracket. in relation to their height. In the case of When two free-standing show-cases are free-standing show-cases, our experience placed back to back, they can be fmed to shows, though this is not backed up by the floor and, in addition, fuced to each any law of physics, that if the height is other at the top with metal ‘T’ or inverted more than three times the smallest ‘U’ brackets so as to increase the area of dimension of the base, the case is the base. Storeroom and library shelving must be joined at the top. It is quite easy unstable. Show-cases for the display of objets to fasten two show-cases together, but if d’art usually have from three to five sides they are moved often the fuctures unformade of glass. As the density of glass is tunately leave marks if the floor surface is 2.6 to 2.7, it is obvious that the more of marble, wood or rubber. To improve glass there is, the more top-heavy the case the adherence of a show-case to the floor will be. It is even more top-heavy if there without leaving marks, pieces of hard is a lighting system in the upper part. rubber or felt can, of course, be stuck on Plexiglas has a lower density than or- the bottom. Recently, a new type of frameless freedinary glass but has the disadvantage of scratching easily and attracting dust standing show-case has come into use, because of static electricity, so therefore made of five sheets of glass stuck together cannot be recommended. One way of with silicon resin and topped by Plexiglas reducing the top heaviness of show-cases attached with polymeric resin. This type is to increase the weight at the bottom, of display case has to be ruled out in a b Earthquakesproduce two types of tremor - vertical and horizontal - which can combine in highly complex ways. They begin by making show-cases as well as the objects displayed within vibrate and slide about and may, if continuous, cause objects to topple over or the show-case as a whole to collapse.
Paper, silk and wood, common media forJapanese works of art, are not very robust and can easily fade when in direct contact with the air or light if the precaution of covering them with a protective film has not been taken. Varnishes are extremely sensitive to ultraviolet rays. For these reason our works of art cannot generally be shown for more than one month in the year. Changing them entails frequent re-arrangement of the gallery and hence the shifting of show-cases. This is why ours are equipped with castors. However, because they are small, they cannot support the weight and break easily. As a rule, once the exact spot for the show-cases has been chosen, we block the castors with wedges, but this is not always enough. For perfect stability without damaging the floor, it is preferable for all the weight to be borne by the cross-pieces on which the castors are futed and for the castors to be blocked by means of a screw. When this is impossible, piano castors can be used, which are then placed in protective cups. As we have just seen, there are certain drawbacks to using castors as an easy way of moving show-cases. In recent years, manually operated hydraulic fork-lift trucks have come into use. The recommended method is to cut the bottom part of the
Side view of inclined display table, shc)wing plat.ic bar to arrest sliding, and plastic pins and stoppers to hold objects in place. 1
show-case lengthwise so that the forks of the truck can pass through. In this way the whole of the show-case can be moved without it being subjected to extra weight or jolting. This method has the obvious advantage of avoiding distortion, and stability is good as all the weight of the show-case, once it is in position, rests on the floor. Gallery floors are supposed to be level, but in an old building they rarely are. One way of curing this is to cut out a segment in the form of threequarters of a circle from each corner of the show-case and to let in adjusters. Another solution, but one we have not tried, is to fur angle plates to the bottom of the show-case, which could be an effective way of ,preventing it from tipping over. To prevent show-cases from squeaking, braces and struts can be put in between the members of the frame, or cross-piecescan be added, but squeaking can never be completely eliminated because of the glass. It is vital to fit braces and strengtheners between the main members in the base and the top of the show-case, though this is not so necessary when the frame is made of brazed brass.
Proteetion against earthquakes in Japan
Show-cases joined together for stability.
country like Japan, where earthquakes are frequent. Earthquakes are not the only danger, however, since, with this 'cloche' type of display case, the objects must first be placed in position and then covered, an operation involving the risk of accident and damage. Materials such as wood, metal or synthetic resins, may be used for the frame and exterior of the show-cases but for both strength and safety, steel is best. We have concentratedon free-standing cases, but the same applies to large fuced display cabinets or cases desipned for exhibiting scrolls. Display stands for modern or contemporary sculptures such as busts or heads are usually about thirty centimetres wide at the bottom and about one metre high, giving them a high centre of gravity which is bad for stability., The stand therefore has to be weighted inside with sandbags and held in place by metal angle-brackets.
the object is) and this, should the glass break, protects the object inside from falling splinters. When earthquakes occur, the glass is broken by objects falling from the walls or ceiling or by the fall of other objects on show. Accordingly, objects that might fall should not be placed near show-cases or, if that is not possible, they should be firmly fixed to the walls or ceiling. In some countries, objects are often placed on shelves inside the showcase, but in Japan, for reasons already mentioned, this is never done. Wall shelving is generally held in place by angle-brackets beneath the shelves, but after a number of years the shelves tend to sag. If there then happens to be an earthquake, the vibrations cause the objects to slide towards the lowest point of the shelf and eventually to fall. It is therefore essential to fix the shelves at all four corners to avoid sagging. When, to improve visibility, shelves are tipped forward, the objects on them must naturally be fixed in place, but to make doubly sure there should be a rim along the outer Resistance to Knocks and vibrations edge of the shelf. Glass shelves are not The glass used for the show-cases may be only slippery but can also steam up if ordinary soda glass, double glazed or metal objects are placed directly on them. toughened glass. Toughened glass is It is therefore essential to put a stand, clearly the best for strength but unfor- with anti-slip felt or cloth stuck on its tunately it sometimes shatters explosively underside, between the glass shelf and when knocked by sharp objects such as the work of art. tacks or diamond rings. It therefore canWe shall now turn to some specific not be used for low show-cases with display techniques and methods used in horizontal glass surfaces. To resist knocks Japan. Characteristically, Japanese oband vibration, the glass generally used is jects - in metal, lacquer or pottery, at least 8 mm thick for the vertical sur- fabrics, armour and arms - are rarely faces and over 10 mm for the horizontal placed directly on the floor of the display ones. When there is a large horizontal case but almost always on a stand, usually glass surface, an anti-shatter film is stuck made of wood covered with felt or fabric. on its inside surface (i.e. the side where When there is an earthquake, this fibre
Cylindrical show-case, weighted on the inside with sandbags.
covering stops the object or its base from slipping. If the stand is rather high, it is recommended that its centre of gravity should be lowered in the same way as for the show-cases. An effective measure to Prevent a stand tipping over is to give it a shape that is slightly trapezoidal or like a truncated cone so as to increase the surface in contact with the floor. Thin objects, such as mirrors for example, can be seen more easily if placed on an inclined stand either hollowed to fit the shape of the object or with little plastic clips to hold it in place. The same technique is used for objects with a narrow base, such as small vases. These may also be held by nylon threads tied round the neck of the vase, but in the case of pottery fired at low temperatures, care must be taken that the threads, which are sometimestoo stiff, do not damage the object.. We try to improve the stability of larger vases, such as flower vases, by placing small bags of dry sand inside to lower the centre of gravity. To display receptacles with spherical or protruding bases, we use plastic tripods,
which are stable because of their open base, but which can be made even more stable by joining the legs together with a hoop. To prevent damage to the object, it is preferable to cover the inner surface of the upper hoop with fabric or with transparent silicon resin. To display costumes, the legs of the stands used should be sufficiently wide apart and should be weighted with metal discs. Stands for draped clothes and swords should be so arranged that their centre of gravity is not too high. The hooks used for hanging paintings should preferably be the kind that fit into a rail. Failing that, hooks with locking screws are recommended. Finally, I would like to touch on a subject related to the general theme of protection against earthquakesrather than to show-cases in particular: the care of objects buried as the result of earthquakes. In Japan, archaeological excavations have brought to light building timbers, wooden receptacles or Indian ink inscriptions on wood, called mokkan. Before
their excavation, these objects had spent a very long time in a humid environment and had become thoroughly waterlogged. They are therefore subjected to treatment with a polyethylene-glycol solution, which of course is done by submerging the object in a container filled with an aqueous solution.' When there is an earthquake, oscillations occur in this liquid, which, if the earthquake continues, become more and more pronounced through the effect of resonance until all the liquid overflows, with possible damage to the object immersed in it. To avoid this, a fairly thick perforated plaque of wood or plastic should be placed in the container. The holes break the surface of the liquid and halve the effects of resonance. [ Translatedfrom Japanese]
1. See Muream, No. 137, 1983, in particular the article by David Grattan, 'Recent Progress in Conserving Waterlogged Wood'. -Ed.
Eurtbqauke-resistuatmeasares i .Nuples Ms Ennia Pozzi, superintendent of the archaeological' department in the regions of Naples and Caserta, Italy, has kindlyprovided us with the following information on the Archaeological Museum o f Naples: The need to adopt special protective measures in the Archaeological Museum of Naples arose as a matter of urgency following the earthquake of 2 3 November 1980, which struck the city and much of Campania. During the earthquake, tremors caused considerable structural damage to the building, which led in turn to damage to part of the collection - the terracottas and the vases both in storage and on display. Items of sculpture, on the other hand, were completely undamaged. The damage consisted in the breakage of items on shelves that collapsed or overturned. As the possibility of the repetition of earth tremors must be envisaged, since the city of Naples is- regarded as a high-risk earthquake area, we have considered it essential to adopt the following measures.
The vase collection. Each individual shelf has been equipped with side-pieces of varying height which can, however, retain the items in the event of a fall. The shelving, joined in lots of two, has been made to stand free of the walls so that it will not be affected by any distortion and will be better able to absorb the shocks caused by an earthquake. Studies are under way on
producing spacers of soft, elastic material to deaden the shock in the event of an earthquake.
Exhibition rooms. In association with the work of strengthening the whole building and carrying out earthquake-resistant structural changes, it has been necessary to alter the ways in which the museum is fitted out. With regard to the new display cases, methods of preventing objects from falling from the upper shelves and also mountings specially designed to prevent the collapse of the items on display are now being tried out. Studies are also under way on the production of earthquakeresistant display cases which would remain in a stable position independently of movements of the walls and floor vibrations, and which would therefore be affected to a negligible extent by movements caused to the building by seismic waves. Collection of scu4ture. These objects were hardly affected by the translatory movements caused by the earthquake. Only in connection with particularly unstable objects (because they are fragmentary) are studies being carried out so as to develop special mountings which would be able to absorb any shocks which might upset the static equilibrium of the sculptures. This system was first tried out for the exhibition of sculptures from Punta Epitaffio (Baia) which opened on 20 October 1984. [ Translatedfrom Italian]
The itage Masezc 5 pgcking techniuztes for baintings 1
Every year the Hermitage Museum sends fifteen to twenty exhibitions to various towns in the Soviet Union and abroad. A great many of the exhibits are paintings. In 1984, for instance, the Hermitage Museum supplied over 100 canvases for various exhibitions. The preservation of pictures during transport and display away from the Hermitage is one of the museum’s main conservation activities. Transportingpictures always entails risk; jolting and vibration are inevitable, whatever the means of transport. Sudden changes in humidity and temperature and reductions in atmospheric pressure during air transport have disastrous effects on the backings, priming coats, and paint and varnish layers. There are also biological factors that cause damage. When works are transported, therefore, it is not only essential to wedge the pictures securely into their chests, in order to prevent the paint surface from coming into contact with the packaging and with other canvases, but steps must also be taken to protect them from humidity, mildew and, above all, insects. The safety of paintings during transport thus depends largely on their packaging. For about thirty years now the Hermitage has been using a packaging system devised by two restorers, N. D. Mikheevand A. M. Gashkov.Theessential
feature of the system is a chest comprising a set of standard wooden holders, the size of which is determined by the measurements of the largest of the canvases to be packed. The holders are made from square sections of pine with bevelled grooves, joined with nails and sheetmetal strips, and can be divided into compartments to suit the dimensions of the smallest pictures. Each picture is laid in its compartment, face downwards, on the levels of the pinewood grooves and held in place on the upper side by swivelling wooden catches secured with screws. In this way the edges of the pictures come into minimum contact with the packaging. All the Hermitage’s pictures are completely surrounded with small protective slats so that the painting at the edges of the pictures does not touch the packing frame. The base and lid of the chest are made of plywood about five to six millimetres thick. The inside of the chest is lined with oilcloth (with the shiny side outermost). The chest is fitted with wooden guiderails in order to prevent holders, which are stacked on top of one another, from moving. The distance between the holders is adjusted by means of short, square-section pine spacers nailed to the lower or upper surface of the strips surrounding the frames. Once the holders containing the pictures have been placed
Alexei Vyacheslavovich Bryantsev Born in 1922. From 1948 to 1954 a student at the Faculty of Theory and History of Art at the I. E. Repin Institute of Painting, Sculpture and Architecture inleningrad. Specialist in the restoration of pictures by old masters and canvases dating from the late nineteenth and early twentieth centuries. At the Hermitage Museum since 1954 and now chief restorer. He has often accompanied exhibitions to Sweden, the Federal Republic of Germany, the United States of America and Japan. Since 1959 he has lectured on the technical aspects of painting and restoration at the I. E. Repin Institute. Since 1971 he has taught at the Faculty of the History of Art at Leningrad University.
Model of the packaging system used at the Hermitage Museum, general view.
Holders containing pictures placed in the compartments, rear view.
Alexei Vyachesluvovich Bryantsev
Holders containing pictures placed in the compartments, front view.
Packing the holders into the chest- general view. in the chest, they are held in position by tury) require individual packaging. For I pieces of wood or by the lid. Each picture example, to transport Matisse's pictures holder is marked to show the number of La masique and La dame special chests its chest and the 'level' it occupies. Each had to be made with a flannel base line4 compartment also bears the inventory with mica paper. The canvases were put number of the picture. In addition, this into position face downwards and very , , number always appears on the picture firmly secured. The packaging for these itself in the lower right-hand corner of canvases was tailored to their specific ' the holder base and is also marked on the characteristics (their large size and the wood of the holder or compartment, so fragile condition of the paint). The picture frames are transported that when the canvases are placed in the compartments the numbers are visible separately - not only because they come one above the other. This enables each in a variety of shapes but also because if ' picture to be placed in the correct the frames were to be broken they would compartment without any possibility of not damage the paintings. In such a case error. Pasted on the inside of the lid of it is important to fix the canvas securely to each chest is a list of the pictures it its frame and the frame into its contains. This list bears the name of the compartment. Care must also be taken to artist, the title of the work and its ensure that the shape of the frame does not constitute a danger to the other , inventory number. Another advantage of this packaging pictures packed in the same chest. The Hermitage Museum continues to arrangement is that the pictures can be removed from the chest, still in their observe with attention and interest the holders, and inspected on both sides to methods of packing pictures adopted in ' check them against the description of Soviet and foreign museums. We hope that our experience may in turn prove their condition. I Nevertheless, some canvases (mainly useful to our colleagues elsewhere. works belonging to the latter half of the [ Tradateedfrom Rzcssian] ! nineteenth century or the twentieth cen-
Photo credits Frontispiece: Kinsey Bros. New Delhi; 2-11: Cengiz Kabaoglu; 12-15: István Eri; 16: Lautman Photography, Washington, D.C.; 17, 20: American Museum of Natural History; 18. 19, 21: Bernice Pauahi Bishop Museum; 22-24: National Museum of Mali; 25-27a and b: Bill Barrette, The Metropolitan Museum of Art; 28-32: Stefan Michalski; 33: Bogdan Rodziewicz; 34, 35: J. Paul Getty Mu-
seum; 36: Brian Ramer; 37-39: Piotr Stepien; 40: Michael Brandon-Jones, University of East Anglia; 41-45: ICCROM; 46-49: Alan Calmes; 50-51: Tim Padfield; 52, 55, 56, 57: Annegret Koffmane; 53, 54: Wolfgang Selzer; 58-60: Ann Andrén; 61: R. Schacht; 62-64, 67-69: Günter S. Hilbert; 65-66: Kgyptisches MuseumlM. Büsing; 70-73: Hiromitsu Washituka; 74-77: Hermitage hluseum.
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