Monitoring detaching murals in the convent of Müstair (Switzerland) by mirror micrometry
Konrad Zehnder|Alexander Voûte
In a parallel study, it has been shown by comparison of successive TV-holography campaigns that murals in the convent Müstair (Switzerland) have progressively detached from their substrate over time interval 5 years (J Cult Herit 2009). Here, we focus on dynamics ongoing detachment processes. order to regularly measure small surface displacements situ long duration several years, new method call Mirror Micrometry (MM) designed and implemented. This monitors reflection light beam mirror is mounted interest for experiment. The rotate about pivot as detaching occur, thus deflecting reflected beam. Measurements more than three Convent Church Holy Cross Chapel reveal various types displacement perpendicular wall surface. These are correlated with relative humidity (RH) changes room climate. Reversible short-term variations approximately ±5–10 μm occur periods one weeks relate primarily weather changes. long-term correspond averaged seasonal Irregular irreversible movements increments 20–30 record very localised progressive steps. A semi-quantitative correlation 1 per 1% RH change calculated. Based fact nearby measuring points can simultaneously move opposite directions, geometric model drawn explain deformation hygric swelling shrinking different shapes layers.
Journal of Cultural Heritage