How Do You Mix Plaster and Joint Compound?

Make a plaster coating that sticks to almost anything by combining equal parts of plaster of Paris and joint compound, and slowly stirring in enough water to give it a spreading consistency. This process requires a large container and a 4-inch plaster knife for stirring.

  1. Add joint compound to a large container

    Pour joint compound around the edge of the bottom of a container that is large enough to hold your finished plaster mixture. Leave an indentation in the middle of the joint compound.

  2. Pour an equal amount of plaster into the center of the container

    Add the plaster of Paris to the indentation in the center of the joint compound. Using the same amount of plaster as joint compound assures a finished product that sticks well to most surfaces.

  3. Pour water into the plaster and stir

    Pour a stream of water into the center of the plaster. Slowly stir the plaster and water together with a 4-inch putty knife to form a smooth texture. Add more water as necessary.

  4. Incorporate the joint compound

    When most of the plaster is moist, start moving some of the joint compound into the center of the container. Keep expanding the area that you are stirring until all the joint compound is incorporated with the plaster. Add water as necessary to create a final texture similar to frosting.