NOVELTY - Making coated article, comprises: providing inorganic substrate; coating the substrate with coating composition comprising many siloxane nanoparticles dispersed in organic solvent where a portion of nanoparticles comprise reaction product of first alkoxy silane compound having first organofunctional group and second organofunctional group of second compound and reaction between first and second organofunctional groups form organic linking group; drying coating composition; heating coated substrate to volatilize organic linking groups thus forming porous surface layer on inorganic substrate.    USE - The method is useful for making coated article, where the article is photovoltaic module (claimed).    ADVANTAGE - The coating composition: is free of organic polymer; and has no gelation after 1 month at 50 degrees C (all claimed). The method provides coated article that exhibits improved durability, excellent strength, weather resistance, UV resistance, and moisture barrier properties.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) article comprising an inorganic substrate and a porous inorganic surface layer having an average pore size of less than 30 nm, 25 nm, 20 nm, 15 nm, 10 nm, or 5 nm;    (2) coating composition comprising siloxane nanoparticles dispersed in organic solvent, where a portion of the siloxane nanoparticles are the reaction product of the alkoxy silane compound;    (3) article comprising a substrate and the dried coating composition or the dried and sintered coating composition disposed on a surface of the substrate; and    (4) making a nanoparticle coating composition comprising providing a mixture comprising organic solvent, first alkoxy silane compound having a first organofunctional group, second compound having a organofunctional group the reacts with the first organofunctional group forming an organic linking group no greater than 40 wt.% solids of alkoxy silane compound that lack organofunctional groups or partial hydrolysis products, combining the mixture with acid and water where the water to alkoxy silane molar ratio is no greater than 7:1, and hydrolyzing the mixture to form a coating composition.