Exploring Soft Materials for Realistic Skin: Creating Movable Animal Models for Filmmaking

Commonly Used Soft Materials

When creating movies featuring monster puppets or stop-motion dinosaur models, the choice of “skin material” becomes a critical challenge. If the focus is only on silhouette and movement, using entirely polyurethane materials is an option. For example, in my work Dark Demon Beast Wanigame-Eater, I used polyurethane for both the upper body monster puppet and full-body marionette, adding patches of textured skin and camouflaging the rest with paint.

However, for models like dinosaurs, the addition of realistic, molded skin textures like scales adds undeniable appeal. Achieving this requires soft materials that can capture intricate surface molds.

The most commonly used materials for soft skins are “foam rubber” and “latex.” Both are relatively easy to source.

That said, foam rubber requires mixing two chemicals, applying the foamed material to a plaster mold, and then baking it in an oven. This process demands large molds, and the size of the finished product is limited by oven capacity. Additionally, the material’s cost poses a challenge for me.

Latex, a liquid rubber, offers better workability. When poured into a plaster mold and air-dried, it sets into a texture similar to rubber bands. However, latex eventually deteriorates over time due to its organic nature.

Over 30 years ago, I repeatedly attempted to create stop-motion dinosaur movies while searching for a material to represent “soft skin.” Back then, the lack of accessible tools like video cameras and personal computers made the endeavor overwhelming, resulting in incomplete models. The only successful examples were the foam rubber dinosaur puppet head and latex stop-motion model featured in Wednesday Special THE MOVIE: Legend of the Crystal Skull. Both materials, however, had their drawbacks.

The Search for Affordable and Practical Materials

As of 2021, I’ve returned to my filmmaking roots by crafting miniature dinosaur models. This time, I’m not making unique, one-off pieces but developing blueprints and templates to enable mass production of identical models.

Having multiple models ensures backups for damaged ones during filming. Like Tim Burton’s approach of using several stop-motion models for a single character, this allows multiple scenes to be shot simultaneously in different locations.

As of July 2021, the “skeleton structure” prototypes are complete, and their blueprints are ready for mass production. Next comes tackling the “skin portion.”

This time, I plan to use a two-layer skin structure. First, I’ll create a fabric base by stitching detailed cloth pieces together to form a 3D underlayer, which will be placed over the skeleton. After adjusting the skin’s movement and folds, I’ll attach segmented skin pieces, complete with molded scales, onto the fabric.

The critical question now is: What material should I use for the “soft skin”?

The material must balance “workability” and “cost-effectiveness.” Among inexpensive options, construction fillers used for sealing wall gaps present a candidate. Silicone caulking, costing around 300 yen at hardware stores, remains rubbery when cured, but it’s unpaintable. Therefore, I’ve shortlisted special paintable silicone caulking (modified silicone) as a potential option.

Acrylic-based fillers, water-based wood glue, and thin films of hardened glue are also candidates.

Additionally, I’ll experiment by incorporating powders like starch into these materials. In sculpting, powders like talc are often added to liquid materials to bulk them up or improve workability. Substituting starch for talc is a common DIY practice, so I’ll also test “materials + starch” mixtures.

Beyond semi-liquid materials, I considered whether “lightweight clay” could be viable. Composed of hollow microspheres, lightweight clay hardens into a texture similar to polyurethane. Though not particularly durable, I’ll test reinforcing thin clay pieces by impregnating them with flexible drying agents like:

• Acrylic water-based varnish
• Wood glue

Experiment Results

For each material, I created 1–3mm thin pieces, dried them, and tested their flexibility and durability by bending and twisting them. Here are the results:

• All starch-blended materials became brittle and unsuitable for skin parts.
• Other materials demonstrated sufficient softness and seemed viable.
• However, filler-based materials with adhesive properties proved cumbersome, making it difficult to create thin membranes.
• Surprisingly, wood glue films exceeded expectations in flexibility, making it the most cost-effective material.

For highly textured sections, I plan to use “lightweight clay + water-based varnish,” while for smoother, thinner parts, I’ll rely on “wood glue.”

I hope these findings prove helpful for your projects.