Abstract: A process for rendering an inorganic substrate material hydrophobic includes the step of attaching a coating of hydrophobic silica to the substrate. The hydrophobic silica is preferably mixed initially with the substrate material. At least one bonding agent selected from the group consisting of siloxanes and functionalized silanes, and preferably siloxanes, is then mixed with the hydrophobic silica and substrate material. A dispersion agent can be provided to more evenly distribute the siloxanes and/or functionalized silanes over the hydrophobic silica and substrate material. Heat can be applied after mixing to remove any liquid dispersion agent and to chemically bond the bonding agent to the hydrophobic silica and to the substrate material. Hydrophobic inorganic materials including hydrophobic silica bonded to a substrate by a siloxane or functionalized silane bonding agent.