Mix these two-part foam casting compounds and pour into your mold—they expand to fill every hole and cavity. Because they're foam, they're lighter weight than other casting compounds.

The foam's expansion is related to its density. Denser foam expands less; lighter foam expands more.

Before casting, apply petroleum jelly (not included) to prevent the part from sticking, stretching, and tearing. It won't cause the foam to collapse as it cures. Because it leaves a residue, parts should be cleaned before painting or coating.

Flexible compounds cure into soft foam; use them to cast gaskets, cushions, and other bendable objects. The foam is open cell, which means it will absorb water, air, and gases.

Rigid compounds form stiff, closed-cell foam, which prevents water and air from flowing through the part. Machinable, they’re dense enough to create prototype modeling blocks, so you can make mockups and test out tooling setups with little cost and less wear on your tools.