West System 411 Microsphere Blend – 4L

West System 411 Microsphere Blend 4L — Lightweight Epoxy Filler

The go-to lightweight filler for fairing, filleting, and edge bonding.

West System 411 Microsphere Blend is a low density epoxy filler used with West System resin and hardener to create a lightweight filling putty with excellent filleting characteristics. When mixed into a cured epoxy system, it produces a cellular structure that stays flexible, spreads easily, and sands back cleanly. Furthermore, it’s the practical choice for fairing composite surfaces, filleting joints, and edge-gluing strip plank construction materials like cedar and DuraKore. Available in 4L, it works across the full West System epoxy range.

What 411 Microsphere Blend Actually Does

411 Microsphere Blend thickens a mixed epoxy batch into a workable putty without adding meaningful weight. Consequently, the filled compound stays lightweight — which matters enormously in marine and composite applications where fairing filler can add up quickly across a hull or panel.

Because the microsphere structure creates a cellular matrix within the cured epoxy, some tensile and compressive strength is traded for flexibility and low density. As a result, it performs best in non-structural filling, fairing, and adhesive applications rather than primary load-bearing bonds.

Furthermore, pot-life decreases when 411 is added to the epoxy mix. So working in smaller batches and adding filler gradually is the right approach — particularly in warmer conditions where pot-life is already reduced.

Mixing Guide

Always mix West System resin and hardener thoroughly before adding 411 Microsphere Blend.

This ratio produces a moderately low viscosity mix that spreads easily while retaining enough epoxy for soakage into timber in adhesive applications. However, adding too much filler produces a dry, doughy mix that reduces adhesion to the substrate — so add gradually and stop at the right consistency for the job.

Key Performance Advantages

• Low density filler — adds minimal weight to the epoxy mix, keeping filled laminates and fairing compounds as light as possible
• Excellent filleting characteristics — produces clean, consistent fillets on joints and corners without slumping or cracking
• Flexible cured compound — cellular structure retains flexibility after cure, resisting cracking under vibration and thermal movement
• Easy to spread — moderate viscosity at correct mix ratio allows smooth, controlled application across fairing and bonding surfaces
• Sands easily — low density cured compound sands back quickly and cleanly for smooth cosmetic results
• Odourless white powder — clean and easy to handle in workshop environments
• 2 year shelf life — stable in sealed plastic containers at room temperature between 15°C and 32°C

Typical Applications

• Surface Fairing — mixed to a smooth putty consistency for fairing composite hulls, decks, and panels before finishing
• Filleting — used to create structural and cosmetic fillets on internal joints and corners in composite and timber boat construction
• Edge Gluing — low density adhesive for edge-bonding cedar strip and DuraKore in strip plank boat construction
• Void Filling — filling surface voids, pinholes, and low spots on composite laminates before priming and painting
• Marine Boat Building — fairing and filleting throughout fibreglass, timber, and composite vessel construction
• General Composite Repair — lightweight filler compound for cosmetic and non-structural repairs on composite parts and structures

Technical Specifications

Health & Safety

• Use with good ventilation and adequate safety equipment including impervious gloves, safety glasses, and a dust mask
• Avoid skin and eye contact — wash skin thoroughly after handling
• If eye contact occurs, flush immediately with running water for at least 15 minutes and seek medical advice
• Moderate sensitising potential — avoid inhalation during mixing and application
• If swallowed, do not induce vomiting — give plenty of milk or water and contact a doctor or the Poisons Information Centre

Why Enhanced Composites

Enhanced Composites stocks West System 411 Microsphere Blend alongside the full West System epoxy range — so resin, hardener, and filler come from one account without splitting the order. Furthermore, the broader range covers composite fabrics, core materials, and laminating consumables. So whether this is a one-off fairing job or a regular production requirement, everything needed is available and ready to despatch across Australia.

Need larger quantities — 12L or 20L? Email info@enhancedcomposites.com.au

Data sheet: WEST SYSTEM 411 Microsphere Blend