| Abstrakt: | SUMMARIES. Extensive investigations of the deterioration of the romanesque painted wooden ceiling in the church of Saint Martin in Zillis (Switzerland) have revealed three major active deterioration phenomena: (1) tented flaking of paint layers; (2) flaking of the wheat starch fixative together with parts of the paint layer; and (3) fungal growth. These deterioration processes correlate with the dynamics of the prevailing room climate. Both forms of flaking are mainly driven by fluctuations of the relative humidity ( RH), whereas the fungal attack can be related to high average RH and stagnant air. Frequent daily fluctuations in RH of up to 20% in summer are due to visitors leaving the doors open, while fluctuations of up to 25% are related to heating in winter. Given the risks of new consolidation treatments, the aim is to slow the decay processes by influencing the climate in the room. Installation of automatic door-closers reduced fluctuations but led to a rise in RH and a reduction of air movement, causing greater fungal growth. Subsequently, an automatic air-exchange system triggered by absolute humidity values was installed to reduce excess humidity and to exchange stale air without producing major fluctuations in the relative humidity. This kind of 'climatisation ' has the advantage of being highly flexible, allowing variation of the rate and scale of exchange; it is, moreover, truly reversible.
CONCLUSIONS. The extensive investigations to determine and implement a sustainable conservation and care regime for the romanesque painted wooden ceiling in the church of Zillis led to a concept of indirect intervention by climatic regulation. These interven¬tions have been carried out step by step in order to perceive their actual effects, which are not suffi¬ciently predictable in such a complex system. The first step in 1994 was to install automatic door-closers to reduce the large and frequent daily humidity fluctuations caused by open doors in sum¬mer. However, side-effects included raised humidity and stagnant air. Since 1998, the PLC-controlled air-exchange system has allowed a controllable and moderate room ventilation to counteract these effects. Its great advantage is its flexibility: it can be varied over a very broad range, from gentle to strong ventilation or from drying to humidifying, simply by programming the conditions for activa¬tion. Furthermore, the system is completely reversible, as all installations are provisional and do not touch the historic materials themselves. Climatic regulation in the church will be contin¬ued, and will be improved by diminishing the steep variations during heating events. The aim is to reduce the risk of unacceptable loss, and to keep the state of the painted wooden ceiling under obser¬vation. This iterative procedure also provides the necessary time to undertake laboratory tests in order to address the unsolved problems such as how to reduce the wheat starch layers, how to per¬form consolidation treatments if these prove to be necessary, or how to determine the growth condi¬tions of the Aspergillus fungus in order to define appropriate climatic conditions. |
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