Gels formed by mixing line silica powders and poly(dimethylsiloxane) (PDMS) transform into viscous fluids over a period of a few days. By adding small amounts (a few weight percent) of surfactant-like block copolymers to the gel, we able to slow down the aging process significantly, increasing the aging time constant by more than 700-fold in some samples. This aging process is closely associated with the adsorption of PDMS onto silica surfaces. We propose a model in which surfactant and PDMS polymers compete for adsorption sites on silica after "poison" molecules desorb from these sites. This model predicts that the coating of silica by surfactants and PDMS grows with a characteristic time constant, and that this time constant depends on surfactant concentration with an equation that is similar to the Langmuir isotherm. This model gives an excellent lit for our experimental data. Our analysis indicates that the "poisons" are water molecules physically adsorbed on surface silanol groups on silica.