Plastered walls are made up of three layers: a base coat, a thick coat of plaster for durability, and a finishing coat for appearance. These may be placed over wood lath, metal mesh, special gypsum wallboard, or masonry.
1. When patching a fine or small crack in a plastered wall, widen the crack to 1/8 inch with the tip of a lever-type can opener. Once the crack is about 1/8 inch, blow out dust and debris (make sure to wear safety goggles). Fill the crack with speckle using your finger or putty knife.
2. Once dry, sand down the speckle, using a block wrapped with fine-grade sandpaper; sand in a circular motion. Make sure to prime the patch with sealer before painting.
Tip: Go to your local paint store and give them the name of your home builder and in what community you live in. They should have on recorded what color paint the builder used.