How to Repair Imperfections in Plaster Walls

Remove any debris around the cracks of the plaster. Put on some gloves and use your hands to pry up any loose plaster. Use a drywall knife to gently scrape away any debris from the area. Your patch will not work if debris gets into the new plaster.

Protect your lungs and your eyes. Plaster is a very dusty medium and it can be harmful if you breathe it in. Wear a rated respirator and safety glasses when mixing and applying plaster.

Mix together the plaster. Follow manufacturer instructions for your plaster medium. Most brands require simple mixing with water. Use a 5-gallon bucket for this if you have a large repair job; otherwise, mix in a smaller container. Remember, plaster sets quickly, and you don't want to have too much on hand. It is much easier to make up a second batch.

Smooth the plaster over the imperfection. Load up a hawk with a small dab of plaster and then transfer some to your trowel. Start below the crack or hole and sweep your trowel upward. You only need to put about a 1/4 inch coating of plaster over the area. Too much plaster creates a mess that will have to be sanded later. Feather in your edges by sweeping in different directions with each upstroke.

Sand down the spot if necessary. If you applied too much plaster, or if the edges are noticeable around your patch, use a hand block sander in a medium to fine grit and smooth this area out. Plaster is very hard; it may take quite a few tries until the wall is completely smooth. If the wall is painted, use the matching paint color to camouflage your patch.