The imperfect nature of fiberglass makes it notoriously difficult to paint: with insufficient preparation, blemishes such as pinholes, spider webs and cracks appear in the final painted finish. Although the painting process is similar to the practices used on metal car body panels, poor preparation can prevent the hobbyist painter from achieving a topcoat resembling those applied by automotive professionals.
Items you will need
- Masking Tape and Paper
- 240-grit Abrasive Paper
- 800-grit Abrasive Paper
- Compressed Air Source
- Fiberglass Paste and Hardeners
- Plastic Spreader
- HVLP Spray Gun
- High Build Primer and Hardeners
- Automotive Paint and Hardeners
Apply two strips of two-inch masking tape to the edges of adjacent body panels to prevent the sandpaper from scratching nearby paintwork. Wipe over the panel thoroughly with degreaser to remove oil, dirt and traffic film residues.
Rub over the surface of the fiberglass panel thoroughly using 240-grit sandpaper. Carry out regular visual checks to ensure that the glossy surface of the fiberglass has dulled. Ensure that any texture, such as orange peel, flattens out to a smooth and even finish.
Use compressed air to blow excess dust from the fiberglass before wiping the panel clean with degreaser and drying it with a piece of clean cloth. Study the panel for pinholes, small cracks and other imperfections. Mix a small quantity of fiberglass paste with hardener and apply to the imperfections with a plastic spreader. Leave the paste to dry for 15 minutes.
Rub down the dried fiberglass paste with 240-grit sandpaper until all applications level down to the flat surface of the panel. Blow excess dust off and carry out a final check for imperfections. Add more activated fiberglass paste where required and rub down again.
Wipe the panel clean and mask it out using tape and paper. Make sure the rest of the vehicle is isolated to prevent the risk of overspray. Apply two coats of high build primer, leaving a short curing period of 10 minutes between the first and second coat. Leave the primer to dry overnight.
Rub down the primer using 800-grit sandpaper until a flat, smooth finish remains. Remove all masking, wipe the panel clean and mask the vehicle again using clean tape and paper. Move the vehicle into a well-ventilated area before painting begins.
Apply one medium-volume coat of paint to the fiberglass panel using an HVLP spray gun. Make sure the first coat covers the primer entirely, and ensure that hidden areas such as door edges also receive a similar application. Leave it to cure for five minutes.
Apply a second, full and final application of paint over the entire panel. Carry out a visual check to ensure paint coverage is even and uniform. Leave the paint to dry overnight before unmasking, cutting and polishing.
- Always wear suitable respiratory equipment when applying automotive paint.
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