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.

Rigid compounds form stiff, closed-cell foam, which prevents water and air from flowing through the part.

Machinable compounds are 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.

Before casting, apply a mold-release lubricant to prevent the part from sticking, stretching, and tearing. These wax-based lubricants won't cause the foam to collapse as it cures. Because they leave a residue, parts should be cleaned before painting or coating.