These photos are taken from a headcasting session I helped with in 2003. Thanks to the many talented folks there, Richard Halliday for being a victim and giving permission to use the photos, and Philip Burgess for providing the space.
Richard is getting a full headcast done that will extend down to the tops of his shoulders. The first step is to get him prepared for this process. We protect his hair by attaching a simple latex bald cap with spirit gum. The front edge is trimmed so that it just covers his hairline; otherwise, we would not get an accurate cast of his forehead area.
We keep the lower part of his body (relatively) clean using an apron. We improvise a disposable apron using masking tape and a garbage bag. Vaseline is applied to the eyebrows and eyelashes to ensure that the alginate will release easily from them. (People with beards or mustaches will need to fully protect them with masking tape.)
We begin mixing up a batch of alginate. This is a fluffy powder made from chemicals in seaweed which is mixed with water immediately prior to use. Our alginate is light blue, but it comes in a wide variety of colors. I'd recommend that you avoid flavored dental alginate unless you really want your entire head to feel "minty fresh".
The alginate is applied by hand to the top of the head. It should be about the consistency of waffle batter; it will begin to thicken almost immediately as you are applying it. Mixing it with cool or cold water can give you a little extra working time.
Apply alginate to the entire head and shoulder area. As the alginate drips down, scoop it up and pour it on the top of the head. The sitter will begin to look like the victim of some bizarre alien attack. The stuff also drips everywhere and will stick in fabric, so use work clothes and dropcloths.
Before doing the nose area, tell the person to take a deep breath in and hold. Daub some thick alginate around the nostrils and then have the person forcibly exhale to open air passages through the alginate. Some people prefer to use drinking straws but I don't recommend that. The alginate will soon get too thick to work with as it gels. Leave it alone as soon as it stops sliding off the person and let it set.
