A method of treating porous particles, each porous particle having an external surface and a multiplicity of pores with interior pore surfaces, by contacting the external surface with a hydrophobic agent while causing the interior pore surfaces to remain substantially free of the hydrophobic agent. In certain illustrative embodiments, treating the external surfaces of the porous particles includes exposing the porous particles to at least one of water vapor, methanol vapor, or ethanol vapor； and subsequently exposing the porous particles to a second vapor comprising a reactive organosilane compound which reacts to form the hydrophobic agent. In some particular illustrative embodiments, at least a portion of the external surface of the treated porous particle includes hydrophobic groups, the hydrophobic groups selected from at least one of alkyl or aryl groups optionally substituted with fluorine, and siloxanes having alkyl groups, aryl groups, or combinations thereof.
