Sand, fill and seal MDF properly, then apply primer and two topcoats for a smooth, durable finish.
PM-01Set up your workspaceWork in a well-ventilated room, or a garage with the door open, away from draughts that can blow dust onto wet paint. Lay a dust sheet down and rest the MDF on a workbench or trestles at a comfortable height. Wear a dust mask while sanding, and gloves if you're using an oil-based product.
PM-02Fill holes, joints and gapsFill any screw holes, joints or gaps with a filler labelled suitable for MDF, pushing it in firmly with a filling knife so there are no air pockets. Ordinary filler can soak into MDF edges and swell, so avoid plain interior filler on exposed edges. Leave it to dry fully, following the time on the tub, before you touch it again.
PM-03Sand the whole pieceSand the flat faces with 120-grit sandpaper, then move to the cut edges — these are the roughest part and need the most work. Sand any dried filler flush with the surrounding surface. Finish with 180-grit for an even smoother feel before you prime.
PM-04Remove all the dustBrush off loose dust, then wipe the whole piece with a tack cloth or a cloth lightly dampened with water. Any dust left behind will show up as a gritty texture once painted. If you used a damp cloth, let the surface dry fully before moving on.
PM-05Seal the MDF with primerApply a proper MDF primer/sealer with a brush or foam roller, working it well into the cut edges — these soak up moisture fastest and will swell if left unsealed. A water-based MDF primer is quicker-drying and lower-odour; an oil-based one gives a tougher seal. Apply one full, even coat and leave to dry as stated on the tin, usually 2-4 hours.
PM-06Sand the primer coatOnce the primer is completely dry, sand lightly with 240-grit sandpaper to knock back any raised grain or brush marks. Wipe away the dust with a tack cloth. This gives the topcoat a smooth, even surface to grip.
PM-07Apply the first topcoatUse a mini foam roller for a smooth finish, or a good-quality synthetic brush for edges and mouldings. Apply a thin, even coat of a water-based eggshell or satin paint, which is durable and easy to wipe clean. Leave to dry fully, checking the tin for recoat times.
PM-08Sand lightly between coatsOnce the first topcoat is dry, sand very lightly with 320-grit sandpaper to remove any nibs or roller texture. Wipe off the dust with a tack cloth. Sand gently so you don't cut through to the primer underneath.
PM-09Apply the second topcoatApply a second thin, even coat the same way as the first, paying attention to edges and corners where paint runs and pools easily. Leave to dry fully before handling — most paints are touch-dry within a few hours but need 24-48 hours to harden before heavy use. Clean your brush and roller straight away with water or white spirit, depending on the paint type.
PM-10Tidy upFold away the dust sheet and let any settled dust clear before sweeping the floor. Seal opened tins of paint and filler tightly and store them upright somewhere frost-free. Wash brushes and rollers thoroughly so they're ready for next time.
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