How to Make Wall Plaster

Plaster of Paris is a mixture of water and powdered gypsum which hardens on its own without heating. It can be used to patch walls or to make molded and cast objects for home decoration, including picture frames, ceiling medallions, ash trays and serving pieces. Here's how you can make wall plaster.

Things You'll Need

  • 10-lb. package of powdered gypsum
  • 1 tsp. powdered alum
  • 1-lb. package powdered wall sizing
  • Painter's mask
  • Eye protection
  • Rubber gloves or plastic "lunch lady" gloves
  • Wooden spoon or paint stick
  • Metal wash tub for mixing
  • Bakery bags
  • Packing tape
  • Modeling clay
  • Non stick cooking spray or petroleum jelly
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Instructions

    • 1

      Don a mask, gloves and eye protection before working with powdered ingredients. Mix all dry ingredients together in a large metal tub. Use a wooden spoon or paint stick to ensure that all ingredients are well mixed.

    • 2

      Fill bakers' bags with about 2 lbs. of plaster mix. Roll top of bag down and seal with packing tape. Store in a cool, dry place out of reach of pets and children.

    • 3

      Mix one bag at a time with just enough water to make a thick, creamy and easily mounded slurry. Use less water to make wall plaster and slightly more water for plaster casts. Be sure to use eye protection, masks and gloves when working with plaster, whether wet or dry (see Resources below for a video tutorials).

    • 4

      To make a plaster cast, take a ball of clay a little larger than the object you wish to cast. Roll flat, but make sure the clay is at least 3/4 the thickness of the object you wish to cast. Spray clay surface with non-stick cooking spray or smear with petroleum jelly. Press object into clay and remove.

    • 5

      Fill depression with plaster mix and allow to set. Carefully remove clay mold from plaster cast. Paint your plaster cast as desired or leave it plain. Display your collection in a shadow box or on a shelf.