The Advanced Art of Stop-Motion Animation: Building Puppets: Part 3
Another important thing to understand about silicone is there are some types that are better for molding (creating a negative impression of a sculpt) and others better for casting (creating the replica of the sculpt that comes out of the mold). Within these two categories, there will be different brands and varieties, each with their own characteristics. Molding silicone is generally much denser and harder, so if you use it for puppet skin over the armature, you won’t be able to bend it easily. It also typically comes in specific colors like pink, purple, orange, blue, or green, which are not very convenient base colors for a puppet. Certain brands of molding silicone include Mold Max, RTV, and many others. Most types of silicone that work well for molding are of the tin-cure variety, but others that are platinum-cure can be used as well.
For casting a silicone puppet, the best silicone products are of the special effects variety. These are mostly platinum-cure, much softer, and will easily bend and flex over an armature like real skin. Casting silicone typically becomes transparent or milky translucent when it cures, and you want to make sure the activator that mixes with the base says it’s translucent on the bottle. For this reason, if you want a specific color for your puppet, an acrylic tint must be added to the base while mixing. This step has traditionally been important because silicone does not respond well to being painted afterward. In more recent years, however, there have been new developments made in certain silicone products that enable them to be painted. In those cases, tinting may not be necessary. All the same, tinting in the actual mixing process creates one less step later and ensures a smooth surface in the color you want, and you do not need to worry about hiding brush strokes in applying paint. For skin tones, you can alternatively use just a few drops of oil-based foundation from your local drug store’s make-up department. Some popular brands of casting silicones include DragonSkin, Plastil, and EcoFlex. There is also a product by Smooth-On called Soma-Foma, a silicone foam that bonds well with other brands and can help to create extremely lightweight puppets. (It also has an extremely fast pot life, about 30 seconds, so it must be worked with very quickly before concealing it into a mold for curing.)
Many different kinds of silicone, both for molding and casting, can be browsed and acquired through Smooth-On (http://www.smooth-on.com), the Compleat Sculptor (http://www.sculpt.com), Sculpture Supply Canada (http://www.sculpturesupply.com), and other special effects/sculpture service companies that sell these kinds of products, depending on your country of residence.
Casting a Silicone Puppet
The general rule for molding and casting, because the mold needs to come apart, is that if your cast is meant to be soft and flexible (like foam latex or silicone), its mold should be created in a hard material (like plaster). If your cast is meant to be a hard material that does not bend (like plastic or resin), its mold should be created in a soft material (like silicone). There are some methods for using silicone in both molding and casting simultaneously, which are mentioned later in this chapter, but for the time being, let’s say you need to cast flexible silicone around the armature of your puppet using a plaster mold. A basic overview of this process, using pictures from the creation of Charlie’s hands from Ava, is provided below. (All photos in these molding/casting sections are courtesy of Bronwen Kyffin and Melanie Vachon.)
The first step is to create the sculpt, which can be of the entire puppet or just part of it (Figure 3.58). When creating a sculpt for eventual casting in silicone, it is important to use a modeling clay that is not sulfur based. Silicone is generally sensitive to sulfur materials, which can cause it not to cure properly. Some brands of clay that can be used include Chavant NSP and Prima Plastalina. Before creating a mold for the sculpt, it should be lacquered with Krylon Crystal Clear spray to create a barrier that keeps it from getting damaged or reacting with any other substances to which you’ll be subjecting it.