This material is also referred to as colloidal or fumed silica, and is an excellent thixotropic agent which is used to control the viscosity of mixed epoxy systems. Silica can be used alone for a very smooth, non-sagging, high strength mixture or combined with fillers or fibers to make them non-sagging. A 5-quart quantity of Silica Thickener when combined with 1 gallon of mixed epoxy/hardener, will produce about 1.75 gallons of a non-sagging firm paste.