First, remove any loose plaster with a sharp knife or chisel. Next, use a metal wire brush to clean the surface of the plaster and remove any old paint or dirt. Then, apply a coat of bonding agent to the surface of the plaster. Finally, apply two coats of plaster over the bonding agent.

The first step is to identify the cause of the damage. Once you know what caused the plaster to crack or chip, you can take steps to fix it. Common causes of damage include water infiltration, thermal expansion and contraction, settling or seismic activity. If there is just a small area of damage, you can usually repair it with a patch. To do this, remove any loose material from the damaged area and then apply a coat of plaster primer. Allow the primer to dry completely, then apply a thin coat of plaster to the primed area. Wait for the plaster to dry completely before sanding it smooth. If necessary, you can then apply another coat of primer and plaster.