Proceedings e report - Firenze University Press

MOULD ON ORGANS AND CULTURAL HERITAGE OBJECTS. INVESTIGATIONS IN EIGHT CHURCHES IN SAXONY
Reichenbach, between March 2004 and June 2005 Cathedral, Zwickau, between April and August 2004
(measuring point: altar)
(measuring point: kneeler)
A more detailed climate curve of St. Marien Cathedral Zwickau from April to August 2004 is shown
in Fig. 5 (logger located behind a kneeler/prie-dieu, close to a wet exterior wall). A remarkable higher
humidity was determined comparing to the other hall of the church. The figure shows that relative
humidity changes more during the year than air temperature (despite of daily changes). During heating
phases, the humidity decreases typically with increasing temperature, but the general course of
humidity and temperature, influenced by seasons, follows a similar course (effect of outdoor climate).
The highest humidity of above 75% occurred at summer time, but 80% have never been reached.
If mould already exists, obviously short-time increases of humidity up to 65...70...75% are sufficient
to keep the mould alive. Possibly, the spore production is limited, but hyphae and mycelia are
growing. More dry periods – between that phases with higher humidity – may be survived easily.
In addition to the climate records, thermographs from critical areas were taken. Fig. 6 and 7 show
those areas: the organ (remarkable infected) is located above a cool, unheated room. Due to the
resulting higher humidity (up to 76%) over longer periods, the wooden flooring was getting wet; in
March 2004, the moisture content of the wood was between 17% and 19%.
To assess the microbial load, the content of airborne spores was determined in both objects.
Surprisingly, the – partly intensive – mould infection was reflected by an adequate spore concentration
of the air only in one case. Possibly, due to the very high room volume in relation to the moulded areas
the spores concentration in the air is low (thinning effect). The assessment of the airborne spore
sampling according to [8] resulted in a normal microbial load. From these results may be deduced no
increased health hazard for church servants, organists, visitors etc. in general. Instead, the special
hazard can only estimated by investigation of each individual case.
fig. 6: Interior view of the organ of Peter and Paul Reichenbach
fig. 7: Infrared thermograph of the area from fig. 6
The reasons for mould infection which were found out may be allocated to the following categories:
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