Moulding and casting is the process of taking a negative impression of a sculpted form and using it to produce copies — the only practical way to make identical puppet parts more than once.
Why bother
A troupe needs four matching puppets. A character gets destroyed on tour and needs replacing. A single face needs a dozen interchangeable expressions. In all three cases, sculptingSculpting in puppetry means shaping a three-dimensional form... More each one by hand guarantees they won’t match.
Mould types
Plaster moulds are cheap, rigid, absorbent and ideal for slush-cast latex. They are heavy and they do not tolerate undercuts. Silicone moulds are flexible, capture fine detail, release easily and handle undercuts a rigid mould can’t — but they cost considerably more. Two-part moulds let you cast a fully three-dimensional part rather than a face-only shell.
Casting materials
Liquid latex slush-cast in plaster gives a soft, flexible, paintable skin — the traditional choice for creature faces and rigid-featured heads. Foam latex is lighter and squashable but needs mixing equipment and heat curing. Urethane resin is hard, precise and right for eyes, teeth and mechanical parts.
The undercut
Any place where the form curves back on itself will lock a rigid mould onto the part. Flared nostrils, an overhanging brow, a curled ear. Design the sculpt to pull cleanly, or plan for a flexible mould, or split the mould — but decide before the plaster sets, not after.
The hack: mould release, every time, on every mould, even when the material claims it doesn’t need it. Losing a sculpt to a stuck mould costs a weekend.