How Do I Bake Plaster of Paris?

by Richard Bigge; Updated September 26, 2017

Plaster of Paris is a plaster with a quick-drying quality. It is light, strong and soft enough to be sculpted into shapes. The substance does not have to be baked since it reacts with water to generate large amounts of heat that hardens it. This doesn’t however mean you cannot bake it; the process would require creating a mold out of the material, which you can then heat in your oven.

Items you will need

  • Rubber gloves
  • Goggles
  • Apron, sheet plastic or bin bag
  • Plaster of Paris powder
  • Water
  • Mixing bowl
  • Mold box
  • Oven
  • Petroleum jelly
  • Spoon
  • Hammer
  • Chisel
  • Waxed paper
  • Pliers
  • Baking pan
Step 1

Put on rubber gloves, goggles and apron, sheet plastic or bin bag to protect your clothing.

Step 2

Add a pint of water to a large mixing bowl. Add 8 cups of plaster of Paris powder to the water one cup at a time. Avoid stirring the mixture after each addition -- plaster of Paris powder is made by mixing calcium to gypsum, which is then treated to high pressure. The product is then scraped or ground to form powder that once mixed with water forms a plaster -- allow the mixture one minute to sit. Mixing the powder with water will enable you to create the material which you are supposed to create into a mold and bake.

Step 3

Apply a thin layer of petroleum jelly to your spoon to lubricate it. Use it to stir the mixture for three to four minutes or until it gains the consistency of oatmeal. This will create plaster. You may consider adding food flavor to change the coloring.

Step 4

Line the mold box with a plastic garbage bag to prevent your plaster of Paris from sticking to the box as it dries.

Step 5

Pour your plaster of Paris to the mold box immediately after mixing it to avoid drying. Allow it 25 to 30 minutes to set to the mold.

Step 6

Remove your plaster from the mold box. Allow it two hours to air dry and set it on your clean workbench.

Step 7

Make any necessary repairs to your mold before baking it. For instance, if you are considering adding artistic details to it, sculpt your plaster of Paris mold using a hammer. Also, use pliers to break of pieces of the plaster so as to shape it up. In case your mold chips or cracks, repair it with additional plaster.

Step 8

Lay your sheet of wax paper to your baking tray or baking pan and place your plaster of Paris mold over it. Ensure that your plaster of Paris mold is secured tightly to prevent it from falling over. This may interfere with the shape of your mold.

Step 9

Insert the tray into the oven and turn your oven on. Set it to 200 degrees Fahrenheit.

Step 10

Allow the oven to heat for 20 minutes before increasing the temperature to 250 degrees Fahrenheit. Allow it another 10 minutes and increase the temperature to 300 degrees Fahrenheit. Allow it another 10 minutes and increase the temperature to 350 degrees. Let it bake for 16 hours. This will enable the temperature to rise slowly and steadily in a way that will prevent your baked plaster from cracking or breaking.

Step 11

Remove your baked plaster of Paris mold from the oven.