How is a Purple Rock Puppet Head Made from a Mold?
Molds are made when you need several versions of one character. I like to make molds even when I plan to make only one puppet, since I can have the option of making it again if I wish.
After a great deal of planning, a sculpture is made out of clay.
This is a sculpture that just came out of the plaster mold, so the face is a little smooshed.
Plaster comes in a powder.
I pour the powdery plaster into a bucket with water. I make sure I have enough water to fill at least half the box mold.
Plaster reacts with the water, becoming thicker and thicker. I mix it up with my hands so I know the exact time to pour it into the box. Also, I am able to get any of the lumps out with my hands.
One half of the plaster mold is 
made first. After I make sure there are no lumps or bubbles, I press the sculpture into the still- wet plaster. Then I made "keys" in the plaster so that the two parts of the mold will fit tightly together. You can see the marks I've made in the plaster above and in the close-up below.
The object in this mold is sculpted out of a polyurethane foam. It may soon be the body of another puppet.
Why Plaster?
Plaster is mixed up and poured around the sculpture so that it's details can be seen inside the mold. Most of my head molds are in two parts, front and back. It's called a "box mold" since the sculpture is set into a box and the plaster poured into it. The box prevents the plaster from spilling over. When you make a two part box mold, you need to make one half and then the other half, making sure to spray a "separator" element between the halves so that the plaster doesn't stick to itself.
Plaster is fairly inexpensive, and easy to use.
After the mold is made and cleaned, I put the mold back together tightly. I then use a product called neoprene, which is a kind of liquid that you buy especially for pouring into molds.
Neoprene comes in different "densities". Some kinds of neoprene is used in wetsuits, or the soles of shoes. One kind is used in making engine parts! The kind I use is especially made for puppets and dolls and masks. It is not latex, but looks like latex.
Like latex, it also looks like milk, but smells strange, since there is amonia in the mix.The amonia smell dissipates when the product dries.
After pouring it inside the mold, I wait several hours for it to set. During this time, I can write or rehearse or sew or work on other things. When about three to five hours have passed, I pour the excess neoprene out of the mold and wait several more hours so that the inside of the mold can dry well. No matter how neat I try to be, there's always a big mess that I have to clean up!
When I pry the mold apart, I have a neoprene head. What you see in the above photo is the two part mold showing the negative half of the front of the face and the positive neoprene cast still within the back part. Here is another point of view:
It takes three to five days for the neoprene head to "cure". This means that the air will work on the neoprene. It will shrink a little -- about 15 to 20% -- and become a deeper shade of yellow. 
It will also be hard so that I can drill or glue things to it.
Next I prepare the head for painting. I sand the neoprene and clean it with rubbing alcohol to get the dust off.
I use acrylic paint, so the head must be painted first with a product called gesso, which makes the paint stick to the head.
Acrylic paint does not stick to neoprene. 
This character is from The Comedy of Errors.
I sculpted the head and hands and prepared
them for painting. My friend Elizabeth Wadsworth
painted and costumed the figures, just as she did with
all the puppets in the play.
