In other recent work, Heiling compared the suitability of bread or sponges
(Wishab) for cleaning wall paintings. The results turned out to be completely
unexpected.Although most of the microbial isolates from the paintings under
investigation were able to grow on starch (from bread), enhanced microbial
infestation at the treated sites could not be observed. Although starch could be
shown to remain upon the surface in some cases, microbial infestation using
starch at site was not seen by scanningelectron microscopy, even at sites
which were infested in untreated areas. It could be shown that the amount and
form of copper in the dough influenced the rate of microbial turnover in labora-
tory experiments. Moreover, extracts of “Wish up”were demonstrated to serve
as nutrient source for the microbes frequently isolated from wall paintings. In
relation to water repellent capacity, “Wish up” resulted in a partly enhanced
repellence as compared to areas treated with bread. Obviously, these results are
being confirmed by a more intensive survey.
5 Conclusions
It is clear that there are many different factors that induce, or at least influence,
deterioration processes in wall paintings, most of them somehow linked with
humidity. Attempts to maintain humidity control are difficult and restricted by
the fact, that different parts of the room, like furniture and organs, may demand
a different climate to that of the painting. For the painting, deterioration pro-
cesses due to salt crystallisation attracts higher moisture, while, biodeterioration
is enhanced by humidity. Consolidation treatments may also induce other detri-
mental processes that, on the one hand, may result in flaking due to climatic
changes, and on the other, may serve as a carbon source for microorganisms.
Methodologies and materials that have been used for a long time are better
understood than those that are recently developed. Therefore new approaches
should only be tested in controlled circumstances and afterwards be carefully
monitored for an appropriate time, before the methodology can be accepted
for safeguarding the paintings. Wall paintings should not become a testing
ground or field of experimentation for factories producing materials for
building maintenance. Moreover the different parameters that lead to deteri-
oration at different places will never allow one mode of intervention, since
every situation demands intensive investigations of the detrimental processes
and an approach that is specifically adapted to the situation at site, includ-
ing the state of the building itself, climatic situation, the mode of specific use
of the objects, any salt problems and possibly the biodeterioration taking
place.
To summarise the problems, one has to consider that any material introduced
into wall paintings for consolidation, cleaning or any other purpose may react
with ions already present at site and cause new, and even worse, problems.
Wall Paintings: Aspects of Deterioration and Restoration 263