The composite structure of most objects requires a deliberate choice of the physical conditions in which the object is exhibited or stored. Organic materials (e.g., leather and textiles) require a constant relative humidity of 50-55%, preferably with a constant temperature. Unavoidable fluctuations should be slow. Metals need specific protection against corrosion under these conditions. Contact with bare skin should be avoided. Light intensity should not exceed 150 lux; for textiles and ivory 50 lux is the limit. Ultraviolet light should be absent. Focused spotlights are to be avoided, because of high light intensities and heat radiation. To prevent too many cleaning treatments, metal objects should be given a layer of an appropriate lacquer; otherwise, a vapor phase inhibitor should be used in the showcase. The entrance of air pollutants into the museum is to be prevented by the use of suitable filters. A limited selection of materials is appropriate for use as a construction material for showcases; one should avoid the use of materials that give off vapors of acids and synthetic adhesives or may cause damage because of contact with the objects.