What filler should I use for a fiberglass repair?

The correct fiberglass filler depends on whether you need to thicken resin, reinforce a repair, bond parts together or smooth a surface before painting.

• Aerosil: Thickens resin and helps prevent it from running or sagging. It is commonly used when making bonding mixtures, fillets and non-sag repair pastes.
• Q-Cell: Creates a lightweight filler that is easier to shape and sand. It is primarily used for fairing and filling low areas rather than structural bonding.
• Milled fibers: Add short glass fibers to resin for increased strength. They are useful for reinforced putties, filling small gaps and repairing damaged fiberglass.
• Chopped strand: Uses longer fiberglass strands to add bulk and reinforcement to larger or deeper repairs. The finished mixture is generally rougher and more difficult to sand.
• Bonding putty: A premixed product made for joining fiberglass panels, stringers, decks and other components.
• Fairing putty: A lightweight, sandable material used to smooth low spots and prepare a repaired surface for primer or paint.
• Duraglass: A fiber-reinforced polyester filler commonly used for strong fills and smaller fiberglass repairs. It is stronger and harder to sand than a finishing putty.

Powder fillers let you adjust the thickness and strength of your resin mixture. Premixed bonding and fairing putties are more convenient and provide a more consistent result. Always confirm that the filler or putty is compatible with the resin system and application.

If you are unsure which material your repair requires, contact Fiberglass Florida with pictures of the damaged area and a description of what you are repairing.