Things You'll Need
Acrylic latex primer
Acrylic latex semi-gloss or gloss paint
Masonite was invented in 1924 by William H. Mason. Masonite is the original hardboard. Hardboard is made of wood fibers broken down during the manufacturing process into their base components: cellulose and lignin. Lignin is the natural "glue" that holds wood together. There are three construction processes -- wet, wet-dry and dry -- but all result in a hardboard made of cellulose fibers glued together by lignin. The paintability of Masonite, or hardboard, varies by manufacturer and manufacturing process even if the hardboard panels are in the same class. Painting Masonite requires using basic painting techniques for a long-wearing finish.
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Spread drop cloths over the flooring and furniture. Tape around the outer edges of the Masonite wall and the ceiling with painter's tape. Also apply painter's tape around all elements such as light fixtures and baseboards that will not be painted.
Scrape and sand any peeling paint or damaged areas on a previously painted Masonite wall. It is not necessary to sand unfinished surfaces unless the Masonite has sun or water damage.
Fill nail holes and any small damaged areas with caulk or spackling paste. Allow the caulk to dry completely before priming and painting the wall.
Roll a coat of water-repellent preservative over unfinished Masonite. Use a paintbrush in corners and along edges. If the Masonite has not been installed on the walls, apply preservative to all edges. Allow the preservative to dry according to the manufacturer's directions.
Apply two coats of primer to the Masonite wall, allowing drying time between coats per the manufacturer's directions. Use a roller made for a smooth surfaces. Touch up around the edges with a paintbrush.
Roll a coat of a good-quality latex paint over the entire wall. Allow the paint to dry, then add a second coat.
Two light coats provide a better surface than one heavy coat of paint.
Paint when the temperature is above 50 degrees Fahrenheit, and at least two hours before dew is expected to form.
Use a 5-gallon bucket and a metal roller grid instead of a paint tray if painting large surfaces.
Avoid painting exterior walls when the sun is shining directly on the walls.
Wear gloves and safety glasses when working with Masonite and painting.
Severely damaged Masonite or hardboard should be replaced. Repairing swollen or peeling hardboard may delay replacement, but your results may not be satisfactory.