Plaster is a wall and ceiling covering material. It can be smooth, rough or textured. In order to paint a plaster wall, you will want to sand it down to the bare plaster for the most effective and lasting paint application. In order to sand a plaster wall, you will need to use coarse sandpaper on rough textured surfaces and finer grit sandpaper on smooth surfaces. It is important to take your time when sanding plaster because you could crack or damage the wall if you sand too vigorously. Sanding plaster is not difficult, but it is messy and time consuming.
Assess the surface of the wall or ceiling. Note whether it is smooth, rough or textured.
Attach a 60-grit sandpaper to a sanding block to sand rough or textured plaster surfaces. Sand the wall lightly with the sanding block.
Remove the 60-grit paper and attach 80-grit sandpaper. Continue sanding the wall until you are satisfied with the surface of the wall. Smooth the texture with the sandpaper until the wall can be painted with a brush or roller, depending on your preference.
Attach 120-grit sandpaper to the sanding block and sand a smooth-surfaced wall or ceiling until the surface is completely smooth and free of imperfections.