Aerosil (Fumed Silica) – Resin Thickener

Aerosil Fumed Silica is a high-performance thickening agent used to turn resin into a non-sagging adhesive, putty, or bonding compound. Often referred to as a Cabosil-type filler, this ultra-fine powder is widely used in fiberglass repair, marine applications, and composite construction.

Aerosil is added to polyester resin, vinyl ester, or epoxy resin to increase viscosity, prevent sagging on vertical surfaces, and improve bonding strength. It creates a smooth, strong mixture ideal for gap filling, fillets, and structural bonding applications.

What is Aerosil (Fumed Silica) Used For?

• Thickening resin into a non-sag putty or adhesive
• Creating strong bonding mixtures for fiberglass repair
• Preventing resin from running on vertical or overhead surfaces
• Making fillets and gap-filling compounds
• Improving strength and durability in composite builds

Key Features

• Cabosil-Type Filler: Comparable to Cabosil M-5, a commonly searched fumed silica thickener
• Non-Sag Performance: Keeps resin in place on vertical surfaces
• High Strength: Improves bonding and structural integrity
• Versatile Use: Compatible with polyester, vinyl ester, and epoxy resins
• Smooth Mixing: Creates consistent, workable paste or adhesive

How to Use

Add Aerosil to resin gradually while mixing until the desired consistency is reached. A thicker mix creates a strong adhesive or structural putty, while lighter mixes help control flow without sacrificing workability.

• Thin mix → controls resin flow
• Medium mix → gap filling and bonding
• Thick mix → structural putty or fillets (“peanut butter” consistency)

Custom Blends

Aerosil can be combined with other fillers to create custom performance blends:

• Mix with Q Cell for a lightweight, sandable fairing compound
• Mix with milled fibers for high-strength structural putty
• Mix with glass bubbles for easier sanding and shaping

Aerosil vs Q Cell

Aerosil is used for strength and bonding, while Q Cell is used for lightweight fairing and sanding. Many applications use both together to balance strength and workability.

Where This Fits in Your Filler System

• Use Q Cell for fairing and smoothing
• Use Aerosil for strength, bonding, and non-sag performance
• Use polyester fairing compounds like F206 for general surface prep
• Use Awlfair for high-end marine finishing

Need Help Choosing the Right Filler?

See our Fiberglass Fillers Guide comparing Aerosil, Q Cell, fairing compounds, and structural fillers →

Questions? Contact us at orders@fiberglassflorida.com and we’ll help you choose the right filler for your project.