Acoustic emission monitoring of an eighteenth-century wardrobe to support a strategy for indoor climate management

Abstract

The on-site monitoring of acoustic emission (AE) has allowed the direct tracing of climate-induced crack propagation in an eighteenth-century wardrobe displayed in the Gallery of Decorative Art in the National Museum in Krakow, Poland. The anti-correlation measuring scheme and frequency filtering allowed very low levels of physical damage to the wardrobe to be detected in spite of the high background noise typical of the museum environment. The total AE energy recorded during two years of monitoring corresponded to a fractured area of 12 mm² or a total crack propagation of 1.2 mm for two10-mm-thick panels. Although the total damage recorded was minute, correlation between the events of fracturing and falls in indoor relative humidity (RH) in winter due to insufficient humidification was evident. The risk of damage, expressed in terms of crack propagation, was quantified as a function of the magnitude of the RH falls of the duration compatible with the response time of the object. The data allow acceptable RH falls to be identified if a conservation professional or a curator selects a ‘tolerable’ yearly propagation of the fracture, in other words the progress of damage considered insignificant.

Keywords:

• Acoustic emission
• Monitoring
• Physical damage
• Cracking
• Furniture
• Relative humidity
• Indoor climate
• Management strategy

Acknowledgements

The research was supported by a grant from the Polish Ministry of Science and Higher Education supporting activities of COST Action IE0601, ‘Wood science for conservation of cultural heritage’. Further support by Grant N N105 278536 funded by the same Ministry is acknowledged.