West System 406 Colloidal Silica Filler – 10 lb
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High-Strength Thickening Filler for Epoxy Systems
Colloidal Silica (406) is a fine, fumed silica powder that thickens epoxy to control flow and prevent sag on vertical and overhead surfaces. At 10 lbs, this bulk container is well-suited for boatbuilding, structural repairs, and any project requiring consistent, high-volume filleting or bonding work.
When blended into epoxy resin and hardener, it produces a smooth, gap-filling mixture that bonds tenaciously to wood, fiberglass, and most marine substrates. It cures to an off-white colour and can be painted, faired, or finished once fully cured.
Key Features
- Controls epoxy viscosity — prevents runoff on vertical and overhead joints
- Creates a strong, smooth mixture ideal for structural bonding and filleting
- Most versatile filler in the 400-series lineup — works across a wide range of applications
- Frequently combined with other fillers to improve fairing compound strength and abrasion resistance
- Cures to an off-white colour; paintable and sandable
- 10 lb bulk container — suited for large-scale or ongoing projects
Common Applications
- Structural fillets along bulkheads, frames, and hull-to-deck joints
- Gap-filling bonds on wood and fiberglass assemblies
- Thickening base for custom fairing compounds when blended with low-density fillers
- Overhead and vertical epoxy work where sag control is critical
Recommended Pairings
Use with West System C105A Epoxy Resin and a compatible hardener. For large surface areas or warm-weather work, pair with the West System C209SB Extra Slow Hardener for extended working time. For lighter fairing work, consider blending with West System 407 Low Density Filler to reduce weight and improve sandability.
Parts Desk Insights
Best Use Case: 406 Colloidal Silica is the right call for customers doing structural bonding, filleting, or any epoxy work on vertical or overhead surfaces where runoff is a concern. It's the most versatile filler in the lineup — recommend it as a starting point for customers who aren't sure which filler to use. For customers building fillets along bulkheads or frames, suggest mixing to a peanut butter consistency. When a customer needs a fairing compound, suggest blending 406 with 407 Low Density Filler for a lighter, easier-to-sand result. The 10 lb size is best for boatbuilders or yards doing ongoing work — for smaller one-off repairs, a smaller size may be more appropriate if available.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.