Muserm Management and Curutorsh~p (1990), 9,169-182 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJ Microclimate in the British Museum, London ADRIANA BERNARDI Introduction In the field of the conservation of works of art, a fundamental problem is that of establishing a ‘suitable environment’, i.e. one without any great or sudden changes in the main thermohygrometric parameters (in particular relative humidity) which cause structural alteration to works of art. Many studies have been carried out, ‘-’ in addition to those by the author, *-lo in order to demonstrate that an unsuitable microclimate is one of the important causes of damage, and they offer useful advice on how to improve the microclimatic conditions. It is not enough to use good techniques for restoration in order to preserve a precious work of art for the future, as each work of art can only be submitted to a severely limited number of ‘restorations’. In the present century, the physical condition of our cultural heritage has progressively and consistently deteriorated. In the past, much storage may have been worse, but the work of art was often surrounded by more stable microclimatic conditions. Then, for instance, there were no powerful space heating systems or direct artificial lighting, which are only two of the many factors now causing serious damage to the works of art displayed in exhibition galleries. During the course of this century, in order to give ever larger numbers of people the greatest possible enjoyment, many works of art have been transported from their original sites to new galleries, museums, and temporary exhibition rooms. But these new buildings do not always have suitable environments for the conservation of works of art. Indeed, these new buildings were often designed more for the comfort of the public, or the demands of aesthetics, than to provide a suitable microclimate for the conservation of works of art, which require a constant microclimate or very slow changes in the thermohygrometrical parameters. Such conditions are not impossible to attain, whilst at the same time providing adequate heating, air- conditioning, artificial lighting,” etc., for visitors. Experiments and environmental surveys can reveal whether a specific exhibition room has suitable microclimatic conditions, or not, and what are the main causes for any changes detected within it. The British Museum (amongst a number of investigations it then had in progress)‘* asked the present author to study the microclimates in two particular zones where works of art which are very sensitive to environmental changes are displayed and where it was observed that they were deteriorating. These were the First and Second Egyptian Rooms, where organic materials, in particular wood, are displayed, and the Special Exhibition Gallery, where no objects are placed on permanent display but where, during the field test, the exhibition Glass of the Caesar5 was on display. In neither of these areas were the works of art on show exhibited in hermetically sealed show-cases, and thus an analysis of the microclimates was essential in order to determine the optimum microclimatic conditions for the exhibits.13-l6 0260-4779/90/02 0169-14 0 1990 Butterworth-Heinemann Ltd