While wood provides a rustic look to furniture, siding and decking, some homeowners prefer to paint over the wood to allow for colour selection and uniformity. Pine wood can easily be painted with proper preparation -- and with special consideration for the knots in the pine. Knots are the source of tar and tannins coming from the pine, and if not properly sealed during painting, they can lead to dark stains seeping through and staining the painted surface.
Wipe down the pine surface with a cloth dampened in white spirit to remove surface dirt, dust, oil and grease. For large pine surfaces, such as decks or siding, wash the wood with scrub brushes or hoses to remove surface contaminants.
Sand the entire pine surface lightly with 150-grit sandpaper. Sand in the direction of the pine grain to open the pores of the wood and make it more accepting of the primer and paint. Wipe down the surface with a dry tack cloth when finished to remove all sanding dust.
Seal the surface with oil-based wood sealer. Paint this sealer over the entire surface with a paintbrush or roller, applying it in a thin, even coat. This will prevent tannins or moisture from leaking out of the wood. Allow the sealer to dry overnight before continuing.
Sand the sealed surface with 220-grit sandpaper and wipe it down with a tack cloth. Paint the surface with oil-based primer, preferably in a colour matching the paint you intend to use. The primer will help reinforce the wood sealer. Allow the first coat to dry fully per product instructions before continuing.
Inspect the surface. If you can still see dark knots through the sealer and primer, apply a second layer of primer, sanding with the 220-grit paper and wiping with the tack cloth before painting. Allow the primer to dry overnight before continuing.
Sand the pine with 220-grit sandpaper, wipe away the dust with the tack cloth, and coat your pine in a thin layer of your chosen paint. Allow the first coat to dry, sand and wipe again, and apply a second thin coat. Allow the paint to dry overnight.
Inspect the surface. Apply a third coat of paint or touch-ups as necessary. For outdoor applications, consider applying clear polyurethane to better protect the surface from staining and fading. If you decide to use the polyurethane, apply at least two coats after the final coat of paint has dried completely.
Use oil-based sealer and primer for better penetration of the wood pores and a more moisture-resistant barrier. If you spot tannin stains on paint, wash the wood with deck cleaner, reseal and repaint.
Seal and paint your pine outdoors or in a well-ventilated area. The cleaning, sealing and staining products produce strong fumes that can be harmful if inhaled.