Silicone rubber (SIR) shows superior performance when used outdoors, but its surface can be transformed frominherently hydrophobic to hydrophilic by the adsorption of contaminants. Al(OH)_3, Al_2O_3, quartz powder and active carbonwere selected as authentic contaminants. Hydrophobicity of the surface was determined using contact angle measurement.The results indicate that the adsorbability of the contaminants can strongly affect the hydrophobicity of contaminated SIRsurface. The increasing rate of contact angle of specimens contaminated by Al(OH)_3 was much faster than that by Al_2O_3 andquartz due to the adsorption of migrated low molecular weight (LMW) polydimethylsiloxanes. Specimens contaminated byactive carbon could achieve sunde hydrophobicity within 15 min because active carbon has high adsorbability. Surfaces ofcontaminated ultrapure SIR, polytetrafluoroethylene (PTFE) and glass remain hydrophilic because they contain no mobileLMW components. The addition of oligomeric polydimethylsiloxanes has little effect on the hydrophobicity of contaminantscovered on SIR surface. Silicone rubber (SIR) shows superior performance when used outdoors, but its surface can be transformed from inherently hydrophobic to hydrophilic by the adsorption of contaminants. Al (OH) _3, Al_2O_3, quartz powder and active carbonwere selected as authentic contaminants. Hydrophobicity of the surface was determined using contact angle measurement. The results rate that the adsorbability of the contaminants can strongly affect the hydrophobicity of contaminated SIRsurface. The increasing rate of contact angle of mortar contaminated by Al (OH) _3 was much faster than that by Al_2O_3 andquartz due to the adsorption of migrated low molecular weight (LMW) polydimethylsiloxanes. Specimens contaminated byactive carbon could achieve sunde hydrophobicity within 15 min because of the active carbon has high adsorbability. Surfaces of activated ultrapure SIR, polytetrafluoroethylene (PTFE) and glass remain hydrophilic as they contain no mobileLMW components. The addition of oligomeric polydime thylsiloxanes has little effect on the hydrophobicity of contaminantscovered on SIR surface.