Room temperature valcanizing (RTV) silicone rubber caoting has excellent leakage current suppression characteristics. It is used extensively on porcelain and glass insulators in pollution prone areas as an anti-pollution measure. A pollution aging chamber has been fabricated and an on line 4 channel personal computer (PC) based data acquistion system has been developed to conduct tests on RTV coated porcelain samples. A study of the floe rate, conductivity and pressure of the solution forming the fog is reported. It was observed that a higher charge and a highre average leakage current were obtained at a higher flow rate and a higher conductivity. The results with coated HV insulators are consistent with those published in the literature with RTV caoted fiber glass reinforced plastic (FRP) rods.