Science, Tech, Math › Science Prepping, Painting, and Finishing Composite Materials Tools and Tips to Get the Best Results Share Flipboard Email Print Ary6 / Getty Images Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Todd Johnson Science Expert B.S., Business Management, University of Colorado Boulder Todd Johnson has worked on the development, commercialization, and sales sides of the composites industry since 2004. He also writes about the industry. our editorial process Todd Johnson Updated January 08, 2020 Composite materials are mixtures of different fibers bound together by a hardening resin. Depending on the application, composite materials may or may not require painting when they're new, but painting is a good way to restore or modify color after the original finish has faded. The most effective method will depend on the type of materials the composite is made of. Before starting any painting project of this kind, it's best to check the manufacturer's recommendations. That said, the following step-by-step instructions should give you all the information you'll need to successfully paint some common composite materials. Fast Facts: Safety Tips for Painting Composite Materials As with any do-it-yourself project, thorough preparation is the key to a good-looking, long-lasting job, but even more important is making sure to follow all recommended safety precautions for the products you use and the tasks involved.Whenever you're working with fiberglass, wear gloves.Wear liquid-resistant gloves when using bleach or solvents.Wear eye protection when sanding, using bleach, or working with fiberglass.Make sure to have adequate ventilation when using bleach or solvents.Consult manufacturer's specifications prior to starting any project. Painting Fiber Cement Composites Use a pressure washer to clean the surface.Wait two to four hours for the cement composite to dry.Apply a primer.Wait for the primer to dry. Check the product instructions, but generally, it can take up to two hours. Primed surfaces should not be tacky to the touch.Apply the paint in the same manner as you applied the primer. Wait for the recommended amount of time for the paint to dry (generally about two hours). Painting Wood Composites For exterior wood composites, use a pressure washer with a low-pressure tip to clean.Wait two hours (minimum) for the composite to dry completely.For interior wood composites, dust with a broom. Use a tack cloth for tight spaces you can't reach with a broom.Using a roller, coat surfaces with an acrylic latex primer. Use a paintbrush for any areas you can't reach with a roller.Allow the primer to dry. (Again, this may take two hours or more.)You can use a satin or semi-gloss latex paint on interior wood composites, but be sure to use acrylic latex enamel on exterior wood composites. Apply the paint in the manner as you applied the primer. It should dry in about four hours. Painting Composite Decking Mix one part bleach with three parts water.Using rags, a roller, or a brush, apply the bleach solution liberally to all surfaces.After half an hour, scrub the surfaces.Rinse off any remaining bleach solution and residue.Using very fine sandpaper (220 grit), lightly sand all the surfaces.Wash off the dust and dirt with a household detergent or commercial cleaner made for cleaning composite decks.Rinse thoroughly.If you're going to paint the deck, prime with an exterior latex stain-blocking primer made for plastic materials. Do not prime if you're planning to stain the deck rather than painting it.For painting, use a high-quality latex floor and deck paint in a satin or semi-gloss finish. For staining, use a high-quality acrylic latex solid color deck stain recommended for composite decking. Painting Fiberglass Composites Fill holes or imperfections with fiberglass putty. Smooth the putty with a putty knife and let it cure completely.Sand with heavy sandpaper (100 grit) to remove any excess putty or paint. After the composite is fairly smooth, switch to 800 grit sandpaper and sand until the composite is very smooth. You can use an orbital sander or sand by hand.Use a dry rag and acetone to remove dust, grease, and debris.Apply a primer. (Most primers work on fiberglass, but it's a good idea to double-check the manufacturer's instructions or ask for advice at your local paint or hardware store on the best one to use.) Wait two hours or so until the primer is dry. The surface should not be tacky to the touch.Spray or use a brush to apply the first coat of paint. Wait until the paint is completely dry.Apply another coat of paint or apply a clear coat. Always use a clear coat after the final coat of paint. This seals the paint and helps protect it from the elements.