A dart is a wedge of material removed from a flat piece and closed up, turning something flat into something curved. It is the fundamental move in both puppet fabricFabric is the outer surface of a puppet — the skin, the cl... More work and foamFoam is the structural material most soft puppets are built ... More construction.
The principle
Flat material cannot wrap a sphere without wrinkling — the excess has to go somewhere. Cutting a narrow V from the edge and joining the cut sides removes that excess. The piece pulls into a curve. Repeat around a circumference and a flat disc becomes a dome.
Depth and spacing control the curve
Deeper darts and more of them give a tighter curve. Shallower and fewer give a gentler one. This is the entire vocabulary of shaping a puppet skull from sheet material, and it is why contouringContouring is the practice of turning flat foam sheet into a... beats carving a solid block: same shape, a fraction of the weight, and room inside for a hand.
In foam
Cut the wedge, skive both cut edges to a matching bevel, then glue with contact cementContact cement is a flexible solvent-based adhesive applied .... A square-cut dart leaves a ridge exactly where the curve is tightest — the worst possible place for one, because fleeceFleece is the knit fabric used as the outer skin on most mod... More follows it exactly.
In fabric
Darts are sewn rather than butted, stitched from the wide end to a point that must be tapered to nothing. A blunt dart point produces a visible dimple that no amount of pressing removes.
Placement is a design decision
Put darts where seams hide — the back of the head, under the jawThe jaw is the lower half of a puppet's mouth — the plate ..., behind a hairline. A dart across the front of a face is permanent.
The hack: cut shallow first. You can always deepen a dart to tighten the curve. You cannot un-cut it.