evaporation processes and thereby may also influence the state of soluble salts.
The biofilm as a superficial layer reacts in a detrimental way comparable with
poor surface consolidation, e.g. casein which has not been applied in an appro-
priate way. Additionally, the application of surface consolidants, even cleaning,
procedures may be influenced and limited by the presence of biofilms.
Frequently, however, growth is not restricted to the surface. Even those
microorganisms that are dependent on photosynthesis, based on carbon dioxide
fixation in the light, may develop successfully just beneath the surface, e.g. in
renderings and fillings. Fungi often form more or less tissue-like mycelia beneath
the paint layer and have been detected in areas where casein was injected as
binder for consolidation treatment of plaster (see Figure 3).
250 Chapter 10
Figure 2SEM of biofilm on wall paintings, Kloster Altenburg, Austria
Figure 3SEM of microbial colonisation beneath plaster, Eilsum, Germany