Cab-o-sil HS-5 Fumed silica Cabot Rheology Modifiers / Thickeners >> Mineral >> Synthetic Silica Rheology Modifiers / Thickeners >> Mineral >> Fumed Silica SEALANT ADHESIVE CAB-O-SIL® HS-5 untreated fumed silica is a synthetic, amorphous, colloidal silicon dioxide that is generally regarded as unique in industry because of its unusual particle characteristics. CAB-O-SIL fumed silica’s extremely small particle size, its enormous surface area, its high purity, and its chain forming tendencies set it apart in a class of its own. CAB-O-SIL fumed silica is a light, fluffy powder that is white in appearance and is used in many applications and a variety of industries. Synthetic, amorphous, colloidal silica. Used as rheology controler for adhesives and sealants in a variety of industries. Possesses small particle size, big surface area and a high purity.