Things You'll Need
Electric buffer (optional)
Whether you accidentally dropped a candle in your fiberglass bath tub or accidentally held a welding torch too close to your boat hull, you'll have to deal with the resulting burn or scorch mark. Fiberglass is a composite material consisting of glass fibers which is similar to plastic in look and feel. Though it's highly resistant to corrosion, cracking and heat, a direct flame can easily burn the surface of fiberglass. Depending on the severity of the burn, it can either be erased with an abrasive material or coated with epoxy resin.
Don your safety goggles, mouth mask and work gloves. Fiberglass may emit tiny fibers of glass that can irritate the eyes, skin or respiratory system.
Clean the burned area of the fiberglass using a scouring pad a solution of warm water and several drops of dish soap. The fiberglass should be free of all grease, dirt and other residue prior to treatment.
Sand the burned area with a pad of fine-grit sandpaper. If the burn mark begins to dissipate, continue sanding and then wipe the fiberglass clean with a damp cloth.
If the mark still shows, open your container of two-part epoxy and mix according to the instructions on the container. Apply the epoxy over the burn mark using your plastic spreader. If the burn mark has any depth to it, pack the recess with epoxy and scrape the area until it's completely flush with the rest of the surface.
Drag the spreader over the area until the epoxy is as smooth as possible. Allow the epoxy to cure for the time suggested on the container.
Sand the epoxy smooth using a pad of fine-grit sandpaper. To restore shine to the fiberglass, follow with an electric buffer. If the fiberglass was painted, coat the epoxy patch with a matching shade.
Allow the epoxy to cure completely before using, storing or reinstalling the fiberglass item. If you're sanding or patching a large burn mark, use a belt sander for faster results.
Work in a well-lit, ventilated area to avoid hazardous fumes from the epoxy and fiberglass dust.