An unidentified white substance was observed on the exterior parts of the southern side of Hopperstad Stave Church, located in Vik in Sogn and Fjordane (Norway). One of the 28 remaining stave churches in the country, Hopperstad Stave Church was built between 1130 and 1150 and it constitutes an important part of Norwegian cultural heritage. Such a substance was observed for the first time in 2009 and serious concerns about its harmfulness and origin have been raised. A comprehensive study involving non-invasive (portable XRF) and micro-invasive analyses (SEM, ICP-OES, TOC) was undertaken to investigate the physico-chemical nature of this white substance. Tarring, salt migration from the nearby cemetery, atmospheric agents, leakages from the roof, biological infestation, previous treatments with pesticides are among the possible causes of the phenomenon. This work—employing a unique approach in conservation/conservation science—indicates that the white substance is mainly inorganic and crystalline. It was, therefore, possible to exclude some of the possible causes, hence, clarifying some of the conservation issues of the church.
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