Half-ball eyes are hemispherical eye blanks — commercially made, or cut from ping pong balls — mounted to a puppet’s head and painted or fitted with a pupil.
They are the standard because a domed eye catches a highlight from almost any angle, and that highlight is what reads as life.
Sizing
Eyes are the fastest way to shift a character’s whole read. Large eyes relative to the head suggest youth, innocence and comedy. Small eyes suggest age, shrewdness or menace. Nothing else you build changes the character this much for this little effort.
Placement
Eye spacing and height do as much work as size. Set wide and low they read as gentle and slightly dim. Set close and high they read as sharp and intense. Pin them in position and look from ten feet before committing — this is not a decision to make at arm’s length.
The pupil, and the deliberate cross-eye
This is the technique that surprises everyone. Pupils placed dead centre leave a puppet with an unfocused, thousand-yard stare. Pupils angled slightly inward make the eyes converge at a point in front of the puppet — and that convergence is what an audience reads as looking at something. Most professional puppets are noticeably cross-eyed up close and perfectly focused from the house.
Mounting
A flat mounting surface carved or built into the foamFoam is the structural material most soft puppets are built ... More, then contact cementContact cement is a flexible solvent-based adhesive applied ... or a rigid adhesive. Eyes glued straight onto a curved surface tilt, and a tilted eye reads as a droop.
The hack: ping pong balls cut in half are free, take paint well, and are the right size for a mid-size puppet. Prototype with those before ordering.