The processes leading to the deterioration of building stone
have been the subject of numerous publications [11, 14-16,
21-23]. Therefore, stone deterioration is only briefly reviewed
herein for the purpose of providing a basis for understanding
the performances of stone consolidants. The factors considered
to be among the leading causes of building stone deterioration
include salt crystallization, aqueous dissolution, frost damage,
microbiological growth, human contact, and original
construction. In this review, however, only a few cases were
found in which the cause of stone deterioration was
unequivocally determined. All too often a speculative approach
was used in the analysis of stone deterioration, in place of a
more scientific diagnostic method.  2.1 Salt Crystallization
Crystallization of salts within the pores of stones can generate
sufficient stresses to cause the cracking of stone, often into
powder fragments. This process is considered to be the major
cause of stone deterioration in many parts of