How to Work With Fiberglass for Car Repair

by Jay Kurz

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Fiberglass is used for many purposes, including major construction, repairs or reinforcement, and will bond to almost any surface with the proper preparation. Auto-body repair shops often use fiberglass for repairs because it will bond to metal and offer a long-lasting, durable repair. Fiberglass is applied in layers of reinforced fiberglass material that's saturated with a catalyzed resin mixture. Fiberglass is easy to work with and very inexpensive to use as a repair material.

Step 1

Put on your safety glasses and grind the damaged area smooth using a dye grinder. For any cracks or fractures, grind directly on the crack, removing any rough or damaged material. Scuff the entire surface that will get fiberglass applied to it.

Step 2

Clean the surface of the affected area using a rag and acetone to remove any dirt or grease. This is crucial for a solid bond.

Step 3

Tear the fiberglass mat to size so it covers the damaged area. Tear the number of layers needed to bring the damaged area level with the surrounding surface. Tearing instead of cutting fiberglass mat eliminates visible edge lines on repair patches.

Step 4

Add catalyst to a small bucket of resin following the recommendations on the container. Thoroughly stir the catalyst into the resin using a stir stick.

Step 5

Wet the surface of the repair with the resin using a 4-inch felt roller. Apply the first layer of mat and saturate it with resin using the felt roller. When the entire layer is full of resin, roll out any air bubbles using an air roller. Repeat this process for each layer of mat until the repair is complete. Let the fiberglass harden.

Step 6

Sand the fiberglass repair using 100-grit sandpaper on a sanding block until it's smooth and level with the surrounding surface. Lightly sand the repair again with 300-grit sandpaper until the repair completely blends in with the rest of the surface.

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