Method for preserving porous inorganic substrates

A porous inorganic substrate protected against damage by salt water, gaseous pollutants, graffiti, and erosion consisting of the substrate coated by a gas and vapor permeable preservative composition consisting of an aqueous solution or dispersion of a carboxylated hydrophilic acrylic copolymer containing monomer units from at least one C.sub.1 -C.sub.4 alkyl acrylate or methacrylate and from about 5% to about 20% by weight of at least one carboxylic monomer, a cross-linking agent for the carboxylated hydrophilic acrylic copolymer constituting from about 1.0 to about 10% by weight of the aqueous solution or dispersion and from about 0.1 to about 2.0% by weight of said aqueous solution or dispersion of an ultra-violet absorbing agent.