Stone contains natural minerals and different deposits, which gives nutrients
to the mould spores when they try to establish growth on stone.
Stone surfaces differ in coarseness and therefore give different sized pores for the mould spores to gather in and to attach to. Mould is relatively easy to get rid of, but not that easy to stop the propagation of.
Mould spores spread easy and when they have become established and the affection is a fact, all pores, all old mould and all spores need to be cleaned and to be removed for the affection to stop. Sterilization
of the affections and disinfection of the surface is necessary.
Bensaltenside protects for four years, at least.