Mask making for theater, film or costume play is fairly simple to perform at home. The process involves the application of techniques used in traditional art, and differs only in the casting medium. The mold-making process differs not at all from mold making for traditional sculpture. You can make a mold for any type of mask you would like, from a full-face monster mask to a partial character mask that changes only certain features.
Set up a head armature or lifecast that is large enough to fit the person for whom you are making the mask. Cover the structure with a plastic bag to protect it from the clay.
Cover the face of the head armature with a thin layer of plasticine clay. Cover a little more than the mask area, so that the armature will be protected during the molding process.
Layer clay onto the face areas you would like to build up for the mask. Form the clay into the basic shapes you need with your hands.
Sculpt the clay into the mask design you would like, using your sculpting tools. Add and remove clay as necessary.
Coat the entire clay design with Krylon Crystal Clear sealer spray. This will protect the clay surface during molding. Let the spray dry.
Pour a small amount of gypsum powder into a bucket. Add water until you have created a thick plaster soup. Stir well with a wooden dowel or other stirring tool.
Paint one layer of the plaster directly onto the clay mask design, covering only the clay areas of the armature. Make sure to get the plaster into all the nooks and crannies in your design.
Let the plaster layer dry for one hour, or until it is dry to the touch. In the meantime, cut your burlap into small strips with a pair of scissors.
Make another small plaster mixture. Paint another layer of plaster onto the mask design, then press a few burlap strips into the plaster. The burlap will make the mold structure stronger.
Paint over the burlap with plaster. Let the plaster dry.
Make another small plaster mixture. Paint a layer of plaster over the mask design and press more burlap strips into it. Layer plaster over the burlap.
Let the mold cure, or harden completely, for a full day.
Pull the plaster mold away from the armature, breaking the clay design. Pull all clay pieces out of the mold. If necessary, clean the inside of the mold with a small amount of water. Let the mold dry again if you use water.
This type of mold is best for latex masks, which are cast by filling the inside of the mold with latex and pouring out the excess.