Aerosil

Fumed Silica, used for altering the properties of resin to add viscosity or increase bond strength. May be referred to as a 'thixotropic' powder or addative. Use in combination with other fillers to improve working properties and minimize draining with polyester and epoxy resins. Cabosil/Aerosil (2 brand names) can make sanding more difficult. Can cause resin to harden slower, but as mixes of filler material + resin are usually laid on thicker than plain resin it usually hardens faster: use less catalyst. See Milled Fiber (used to add strength), micro balloons (easier sanding, light), Q Cell