This study discusses the assessment of the role of bats excretions (guano, blood and urine) in
physiochemical degradation of historical stone surfaces for conservation purposes. The study
was applied on the wall painting from Mohamed Ali palace (1812) located in Suez, Egypt.
Certain parts of the inside walls of the palace suffer from the accumulation of bats excretions
that lead to deformation, exfoliation and detachment of a large area of the paintings. The
assessment was performed through characterization of the degradation products and the
microbial activities. The study was carried out using various analytical methods such as optical
microscope, scanning electron microscopy equipped with the energy dispersive X-ray (SEMEDX)
system and X-ray diffraction (XRD). These complementary analytical techniques allowed
the identification of the wall painting components and the degradation products accumulated on
the wall painting surface. The data showed the presence of phosphates minerals: Brushite
(CaHPO4.2H2O), Whitlockite (Ca,(Mg, Fe)[PO3OH/(PO4)6]) and Newberyite MgHPO4·3H2O).
These minerals are most probably derived from bat guano (excrements).The microbiological
study of accumulation excretions allowed the identification of some fungi such as: Aspergillus
niger, Aspergillus flavus, Acremonium cerealis, Morterilla subtilssina and one kind of Gram+ve
bacillus sp. (mono-dibble-strepto bacillus). Their metabolic activities play an important role in the
physiochemical disruption of paint layers.