Expanded EVA / PE closed-cell foam or sponge is usually made out of a blend of Ethylene Vinyl Acetate copolymer (also known as EVA) and polyethylene. The product is a lightweight foam material which has a smooth surface and does not absorb water. Generally EVA sheeting is priced competitively, compared with other blown materials and is available in different densities, thicknesses and colours. It is one of the materials most popularly known as expanded rubber or foam rubber sheeting. EVA foam is used to produce - among others - mouse pads, flip flops and sports mats. Sheets of the material can be used for manufacturing Participatory 3D Models. Models made out of this material are well suited for humid tropical environments where carton board may deteriorate rapidly. Manufacturing a 3D model using 'expanded EVA / PE closed-cell foam' compared to carton board implies a slightly higher cost and non biodegradable debris, but ensures a more durable output and a consistent vertical scale/exaggeration of the 3D model. The 3D assembling process remains unchanged.
 

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Image courtesy PAFID

Image courtesy PAFID

Two of the most important skills for working with Expanded polyethylene closed cell sponge/foam are accurate marking and cutting of the sheets (layers in the case of a 3D model). The necessary tools include a foam board cutter and ultra-fine point permanent markers for tracing contour lines. The choice of the adhesive is important as well. In the case of model manufacturing, it is suggested to use a water based glue like office glue, to allow easy positioning of the cut-outs (the contour sheets). Using rapid contact cement would ensure a stronger adhesion, but would complicate superimposing of large and frequently windingly carved contour sheets. Distribute the glue evenly on the entire surface. Align the edges of the upper layer with the marks on the lower layer and press then firmly together staring from one edge to avoid air to be stuck in-between the two layers.