The Advanced Art of Stop-Motion Animation: Building Puppets: Part 3
Once the wall is complete, plaster (Ultracal or Hydrocal 30, not art-store plaster of paris varieties) is mixed and poured in to create the first half of the mold (Figure 3.62). After this hardens, the Lego wall is taken away, the clay bed removed, and all clay remnants washed away with water. The sculpt remains inside the plaster mold, which is coated with Vaseline to aid in eventually prying it apart from the next mold half. The process with the Lego wall can now be repeated as another layer of plaster is poured on top of the first mold half inside. When this is complete, there will be a two-part hard plaster mold for the original sculpt (Figure 3.63), which can now be removed. As an alternative to plaster, you can also create molds for a silicone puppet from a two-part plastic or resin. This would involve mixing and pouring it over the sculpt in a manner similar to this method.
Now, it’s time to get the mold ready to cast some silicone! First, the armature is laid inside the mold, and it needs a way to stay suspended right in the middle because everything around it will be eventually filled in with sticky, gooey liquid silicone. There are a few ways to do this, which may vary depending on the design of what you are casting. It also depends on how you plan to get the silicone into the mold. For Charlie’s hands, the armature was held in place by a lump of Klean Klay placed within the entrance hole where the silicone was poured in. Both halves of the mold should be clamped shut as tightly as possible to avoid leakage and to ensure that the mold will be filled up properly (Figure 3.64). As the mixed silicone batch is poured into the entrance hole, the mold cavity surrounding the armature, which is being suspended upside-down, fills up. When pouring the silicone into or onto any space, it’s important to avoid the creation of air bubbles as it collects and starts to cure. Bubbles can create unwanted warping in the surface of your puppet. To alleviate bubbles, it helps to first tap the container (with the silicone inside it) firmly onto a flat surface after mixing it; this forces the bubbles out. When applying it or pouring it out, you can also drizzle the silicone in a thin, high pour, raising it slowly about 1 foot above the mold (Figure 3.65). These methods will work well if you’re doing this on your own at home, and if you have the means or space, following this process in a specially built vacuum chamber will help to suck any air bubbles out of the silicone as you work with it.