406 Colloidal Silica is an epoxy thickening additive used to control the viscosity of the epoxy. It prevents epoxy runoff in vertical and overhead joints. This is a very strong filler. It creates a smooth mixture, ideal for general epoxy bonding and filleting. It is also our most versatile epoxy filler. Often used in combination with other fillers, 406 can be used to improve the strength, abrasion resistance, and consistency of epoxy fairing compounds. The result is a tougher, smoother surface. You can blend it into any WEST SYSTEM® 105 Epoxy Resin®/200 Series Hardener combination, G/flex® Epoxy 650, or G/5® Five-Minute Adhesive.
Modifying with fillers and additives makes WEST SYSTEM epoxy extremely versatile for a wide variety of bonding and coating applications. Epoxy can be thickened to the ideal consistency needed for a particular job. Epoxy thickened with adhesive (high-density) fillers strengthens structural bonds, bridges gaps, and fills voids. Epoxy thickened with fairing (low-density) fillers is easily sanded and shaped after it cures.
A fillet is a continuous bead of thickened epoxy mixture applied to the angle created between two parts. It increases the surface area of the bond and serves as a structural adhesive and brace. Because epoxy can be thickened with high-density fillers into a non-slumping consistency it can bridge large gaps in wood joints, without loss of strength, thus saving a great deal of time labor otherwise needed to create a strong joint.