AIC's 46th Annual Meeting

Studies on the effects of vibrations on the condition of objects of cultural heritage often focus on paintings or unique objects with particular historical value. However, vibrations are also of concern for large collections of objects which serve as (inter)national reference collections. One such collection is the Naturalis Biodiversity Center, Leiden, The Netherlands, home to the fifth largest natural history collection in the world with over 37 million objects. The storage facilities are physically attached to the museum, offices and laboratories, which are undergoing major renovations. This collection cannot be moved elsewhere, so there are obvious concerns about the effect of vibrations due to heavy construction on the wide variety of objects in the collection. There is virtually no data in the literature on the effect of vibrations on natural history objects. Naturalis and RCE therefore conducted a limited set of vibration tests to obtain an initial impression of what could happen to representative objects under vibration loading. Of particular interest were object resonance, movement on the shelves (“wandering”), and the appearance of damage. The storage situation was simulated by placing objects on typical free-standing metal shelves used in the storage facilities, which were placed unfastened on a commercial vibration testing table. Objects included mounted fauna, small specimen boxes, wood and mineral samples, mounted insects, and bottled biological samples. In order to study the effect of vibrations on the objects alone, they were also tested directly on the vibration table. Testing was conducted at different vibration frequencies and levels. Members of the Naturalis collection care staff visually determined the resonant frequencies and wandering behavior of the objects. The results showed that object vibration behavior depends on a number of factors including their weight, geometry, and mounting, the vibration behavior of the shelves, and characteristics of the object/shelf contact surface. If objects were placed directly on the vibration table, they began to resonate visibly at their resonant frequencies above levels of around 5 mm/s, and began to wander at levels above 20 mm/s. No damage was found for the objects tested for short durations, except for a small loss of particles from a large historical tree branch, and from minerals which lay unpadded on the table. However, vibrations were amplified through the loose standing shelves, reaching levels up to 20 times that of the vibration table itself. This resulted in significant wandering of objects on the shelves, including small specimen boxes falling off of stacks of such boxes. These results indicate that the 2 mm/s low-risk limit suggested by Wei et al (2014) for collections for one construction project would be applicable as a low-risk limit for natural history objects. However, measures would are needed to prevent objects from wandering (see also Smyth et al 2016). Non-reactive padding would help, and would also prevent damage to objects in direct contact with hard shelving materials. Furthermore, monitoring would need to be performed directly on the shelves, as opposed to just on the floor near the shelves.