EVA foamFoam is the structural material most soft puppets are built ... More is a rigid closed-cell sheet foam — the material craft foam sheets and interlocking floor mats are made from — used in puppet building for parts that must hold their shape rather than compress.
How it differs from puppet foam
Reticulated foamReticulated foam is open-cell polyurethane foam that has had... is open, airy and squashable. EVA is dense, closed and springy. Press it and it pushes back rather than collapsing. That makes it useless as a skull and excellent as a structural component.
Where it earns its place
Soft mouth plates, where you want a rounder mouth shape than rigid board gives but still need the plate to hold form. Tongues. Stiffeners inside floppy parts. Teeth. Beaks. Claws. Ears that need to stand up. Anywhere a shape must survive handling without a rigid former.
Thickness matters
Two millimetre craft sheet is for detail and small parts. Five to ten millimetre stock is structural and behaves almost like a rigid board while still flexing under load.
Heat forming
EVA’s useful trick. Warm it with a heat gun and it becomes pliable, then holds whatever curve it cools into. This is how a flat sheet becomes a curved mouth plateThe mouth plate is the rigid two-part structure inside a pup... More or a domed shell. Work in small areas and move constantly — it scorches.
Gluing
Contact cementContact cement is a flexible solvent-based adhesive applied ... works well. Hot glue bonds acceptably to EVA since it is not open-cell foam and will not pit, though the joint stays brittle.
Sealing before paint
Cut EVA edges are porous and drink paint unevenly. A coat of flexible sealant or watered PVA first gives a far better finish.
The hack: template in card first. EVA is cheap but not free, and heat-formed mistakes cannot be flattened out and reused.