{"product_id":"west-system-colloidal-silica-epoxy-thickener-406-off-white-paste-for-fillets-fairing","title":"West System Colloidal Silica Epoxy Thickener 406 — Off-White Paste for Fillets \u0026 Fairing","description":"\u003cstrong\u003eWEST SYSTEM 406 Colloidal Silica is a finely powdered epoxy thickening additive that turns liquid epoxy into a stable, creamy paste for improved handling and fairing.\u003c\/strong\u003e\n\n\u003cp\u003eWhen working with WEST SYSTEM resins and hardeners, controlling flow and body is essential for vertical fills, fillets, and fairing compounds. 406 Colloidal Silica is formulated in the USA as a high-performance fumed silica that increases viscosity without undermining the cured epoxy's integrity. It helps you tailor epoxy consistency so you can place material exactly where it’s needed—on faces, edges, and overhead surfaces—while producing a smooth, sandable finish suitable for structural and fairing applications.\u003c\/p\u003e\n\n\u003ch3\u003eHow does 406 Colloidal Silica change epoxy handling?\u003c\/h3\u003e\n\u003cp\u003eAdding a small amount of 406 transforms thin epoxy into a thixotropic paste that resists sagging and dripping. You can easily control how thick or spreadable the mix becomes by adjusting the amount of powder, giving you predictable placement on vertical or angled surfaces.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eCreate non-sag fillets and edge fills for joinery and laminates.\u003c\/li\u003e\n  \u003cli\u003eConvert laminating epoxy into a brushable or trowelable fairing compound.\u003c\/li\u003e\n  \u003cli\u003eMaintain workability long enough to shape and finish before cure.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat performance changes occur after cure?\u003c\/h3\u003e\n\u003cp\u003e406 Colloidal Silica principally modifies the uncured epoxy's rheology; once cured it forms a uniform, creamy off-white paste that remains structurally stable. While it thickens the mixed epoxy, it does not change the fundamental cured strength of properly mixed WEST SYSTEM resin and hardener systems when used in typical fairing and filleting ratios.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eCures to a sandable, abrasion-resistant surface suitable for finishing.\u003c\/li\u003e\n  \u003cli\u003eAdds bulk and body without significantly reducing bond performance when used correctly.\u003c\/li\u003e\n  \u003cli\u003eStable color and texture for cosmetic and structural touch-ups.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow much should I use and how do I mix it for best results?\u003c\/h3\u003e\n\u003cp\u003eStart with small increments: add powder a little at a time until you reach the desired body. Thoroughly blend the silica into a fully mixed resin\/hardener blend to avoid streaks; using a stirring paddle or disposable mixing stick helps achieve an even, lump-free paste.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eAdd in measured spoonfuls to control viscosity precisely.\u003c\/li\u003e\n  \u003cli\u003eMix until homogenous—no visible streaks or clumps remain.\u003c\/li\u003e\n  \u003cli\u003eUse within the epoxy’s working pot life; don’t extend cure time by excessive cooling or dilution.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat projects benefit most from 406 Colloidal Silica?\u003c\/h3\u003e\n\u003cp\u003eUse 406 wherever you need epoxy to stay put: building fillets, fairing hulls, filling gaps, or applying a trowelable filler before sanding and finishing. Its creamy cured texture makes it ideal for cosmetic fairing as well as reinforcing structural joins where sag-free placement is critical.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eVertical and overhead repairs where runoff needs to be prevented.\u003c\/li\u003e\n  \u003cli\u003eCreating smooth fairing layers that are easy to sand and shape.\u003c\/li\u003e\n  \u003cli\u003eMixing into epoxy putties and bulkers for improved consistency.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for? 406 Colloidal Silica is for boatbuilders, composite technicians, woodworkers, and DIYers who use WEST SYSTEM epoxy and need precise viscosity control. If your work involves vertical bonding, fairing, or any application where drip-free application, smooth finishing, and compatibility with WEST SYSTEM resins matter, this additive gives you predictable handling and a sandable finish without compromising the system’s established performance.\u003c\/p\u003e\n\u003csection class=\"product-faq-snippet\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Can I use 406 Colloidal Silica with all WEST SYSTEM epoxies?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Yes. 406 is formulated for use with WEST SYSTEM resins and hardeners to adjust viscosity without altering core cure properties.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Will adding 406 affect cure time?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: Used in typical amounts for fairing and filleting, 406 changes body but has minimal effect on normal cure schedules.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"West System","offers":[{"title":"Default Title","offer_id":48087362830494,"sku":"B0000AY1OC","price":37.82,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/2041\/9486\/files\/west-system-406-front-bottle.jpg?v=1785921714","url":"https:\/\/northtrailauto.ca\/products\/west-system-colloidal-silica-epoxy-thickener-406-off-white-paste-for-fillets-fairing","provider":"North Trail Auto","version":"1.0","type":"link"}