Phenolic microballoons are lightweight, hollow spheres made from phenolic resin. They are commonly used as a filler material in boatbuilding and composite repair to create fairing compounds, lightweight putties, and to reduce resin density.

In boating, phenolic microballoons are often mixed with epoxy resin to create a fairing compound that is easy to sand and shape. This mixture is ideal for smoothing hulls, decks, and other surfaces before painting or finishing.

To use phenolic microballoons, mix them gradually into a two-part epoxy resin until you reach the desired consistency—typically a peanut butter-like texture for fairing applications. Always follow your epoxy manufacturer’s instructions for mixing ratios.

You can also use our Epoxy Calculator to help you determine the right quantities.

No, phenolic microballoons are designed for fairing and cosmetic work, not for structural bonding or load-bearing applications. For structural repairs, use a high-strength filler like colloidal silica.

• Extremely lightweight
• Easy to sand once cured
• Low density, which reduces overall weight of the project
• Excellent for fairing and cosmetic applications

They can be used with both epoxy and polyester resins, although they are more commonly paired with epoxy for superior bonding and moisture resistance.