Mixing Plaster of Paris

Plaster of Paris is a great material to use for basic sculptures and craft projects because it is easy to prepare and sets in a few minutes. Mixing Plaster of Paris is easy but there are important steps to keep in mind to come up with a solid and sturdy sculpture.

Safety Tips

  • Plaster of Paris powder is extremely light and fine, thus easily dispersed through air. Caution should be taken to avoid getting the powder to the eyes and nose. Wearing a dust mask is highly recommended.
  • Never mix Plaster of Paris with your bare hands.
  • Kids mixing Plaster of Paris need adult supervision.
Mixing Plaster of Paris

Materials

  • Plaster of Paris powder
  • Water
  • Mixing container
  • Spoon or spatula
  • Measuring cup
  • Newspapers or plastic mat
  • Poster paint (optional)

Steps

Step 1 Mixing Plaster of Paris 1. Cover your work area with a plastic mat or with newspapers. Find a mixing container (preferably a disposable one) that could accommodate the amount of mixture intended.

The ideal ratio for a Plaster of Paris mixture is 2 parts Plaster of Paris powder to 1 part water. Measure out the water and pour it into your mixing container.
Step 2 Mixing Plaster of Paris 2. Measure out the Plaster of Paris on another container. Break up any lumps of powder with a spoon.

Remember that the ratio should be 2 parts powder to 1 part water. If you measured out 1 cup of water in Step 1, then you would need 2 cups Plaster of Paris powder.
Step 3 Mixing Plaster of Paris 3. Start adding the Plaster of Paris powder to the water in your mixing container by sprinkling or sifting the powder over the water. Do not add the powder in one spot, instead try to cover as much area as you can.
Step 4 Mixing Plaster of Paris 4. Do not mix yet. Instead, tap the side of your mixing container with a spoon to disperse the powder into the water and remove any air bubbles.
Step 5 Mixing Plaster of Paris 5. Continue adding the Plaster of Paris powder, tapping the sides of the container from time to time. The cue to stop is when you notice that the powder is almost covering the surface of the water and is not as easily absorbed by the water. Normally this point would be around the 2:1 ratio but could vary slightly depending on several factors, including your brand of Plaster of Paris and water temperature.
Step 6 Mixing Plaster of Paris 6. Gently mix the Plaster of Paris mixture until it reaches a uniform and smooth consistency. Do not stir vigorously to avoid any air bubbles from forming.
Step 6b Mixing Plaster of Paris *If colored Plaster of Paris mixture is desired, add some poster paint or acyrlic paint once the mixture is free of lumps and has a smooth consistency. Continue mixing from side to side until the color is uniformly dispersed.
Step 7 Mixing Plaster of Paris 7. Allow the mixture to stand for a minute before pouring it into your mold.

Earth Friendly Tips

  • Do not throw Plaster of Paris into the drain, it will clog the pipes. If you have any leftover mixture, let it harden, then throw it into a garbage can.
  • If you want to save spoons or containers used for mixing Plaster of Paris, scrape off the hardened plaster and wipe the utensils with a damp cloth.

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