New Colloidal Silica west System 4062 17 oz : A thickening additive used to control the viscosity of the epoxy and prevent epoxy runoff in vertical and overhead joints Very strong filler that creates a smooth mixture ideal for general bonding and filleting It is also our most versatile filler Often used in combination with other fillers it can be used to improve the strength abrasion resistance and consistency of fairing compounds resulting in a tougher smoother surface Cures to an off-white color